PythonQ 248-8XX Specifications

The DENX U-Boot and Linux Guide (DULG) for
m28
Table of contents:
• 1. Abstract
• 2. Introduction
♦ 2.1. Copyright
♦ 2.2. Disclaimer
♦ 2.3. Availability
♦ 2.4. Credits
♦ 2.5. Translations
♦ 2.6. Feedback
♦ 2.7. Conventions
• 3. Embedded Linux Development Kit
♦ 3.1. ELDK Availability
♦ 3.2. ELDK Getting Help
♦ 3.3. Supported Host Systems
♦ 3.4. Supported Target Architectures
♦ 3.5. Installation
◊ 3.5.1. Product Packaging
◊ 3.5.2. Downloading the ELDK
◊ 3.5.3. Initial Installation
◊ 3.5.4. Installation and Removal of Individual Packages
◊ 3.5.5. Removal of the Entire Installation
♦ 3.6. Working with ELDK
◊ 3.6.1. Switching Between Multiple Installations
♦ 3.7. Mounting Target Components via NFS
♦ 3.8. Rebuilding ELDK Components
◊ 3.8.1. ELDK Source Distribution
◊ 3.8.2. Rebuilding Target Packages
◊ 3.8.3. Rebuilding ELDT Packages
♦ 3.9. ELDK Packages
◊ 3.9.1. List of ELDT Packages
◊ 3.9.2. List of Target Packages
♦ 3.10. Rebuilding the ELDK from Scratch
◊ 3.10.1. ELDK Build Process Overview
◊ 3.10.2. Setting Up ELDK Build Environment
◊ 3.10.3. build.sh Usage
◊ 3.10.4. Format of the cpkgs.lst and tpkgs.lst Files
• 4. System Setup
♦ 4.1. Serial Console Access
♦ 4.2. Configuring the "cu" command
♦ 4.3. Configuring the "kermit" command
♦ 4.4. Using the "minicom" program
♦ 4.5. Permission Denied Problems
♦ 4.6. Configuration of a TFTP Server
♦ 4.7. Configuration of a BOOTP / DHCP Server
♦ 4.8. Configuring a NFS Server
• 5. Das U-Boot
♦ 5.1. Current Versions
♦ 5.2. Unpacking the Source Code
♦ 5.3. Configuration
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♦ 5.4. Installation
◊ 5.4.1. Before You Begin
⋅ 5.4.1.1. Installation Requirements
⋅ 5.4.1.2. Board Identification Data
◊ 5.4.2. Installation Using a BDM/JTAG Debugger
◊ 5.4.3. Installation using U-Boot
♦ 5.5. Tool Installation
♦ 5.6. Initialization
♦ 5.7. Initial Steps
♦ 5.8. The First Power-On
♦ 5.9. U-Boot Command Line Interface
◊ 5.9.1. Information Commands
⋅ 5.9.1.1. bdinfo - print Board Info structure
⋅ 5.9.1.2. coninfo - print console devices and informations
⋅ 5.9.1.3. flinfo - print FLASH memory information
⋅ 5.9.1.4. iminfo - print header information for application image
⋅ 5.9.1.5. help - print online help
◊ 5.9.2. Memory Commands
⋅ 5.9.2.1. base - print or set address offset
⋅ 5.9.2.2. crc32 - checksum calculation
⋅ 5.9.2.3. cmp - memory compare
⋅ 5.9.2.4. cp - memory copy
⋅ 5.9.2.5. md - memory display
⋅ 5.9.2.6. mm - memory modify (auto-incrementing)
⋅ 5.9.2.7. mtest - simple RAM test
⋅ 5.9.2.8. mw - memory write (fill)
⋅ 5.9.2.9. nm - memory modify (constant address)
⋅ 5.9.2.10. loop - infinite loop on address range
◊ 5.9.3. Flash Memory Commands
⋅ 5.9.3.1. cp - memory copy
⋅ 5.9.3.2. flinfo - print FLASH memory information
⋅ 5.9.3.3. erase - erase FLASH memory
⋅ 5.9.3.4. protect - enable or disable FLASH write protection
⋅ 5.9.3.5. mtdparts - define a Linux compatible MTD partition scheme
⋅ 5.9.3.6. UBI Usage in U-Boot
◊ 5.9.4. Execution Control Commands
⋅ 5.9.4.1. source - run script from memory
⋅ 5.9.4.2. bootm - boot application image from memory
⋅ 5.9.4.3. go - start application at address 'addr'
◊ 5.9.5. Download Commands
⋅ 5.9.5.1. bootp - boot image via network using BOOTP/TFTP protocol
⋅ 5.9.5.2. dhcp - invoke DHCP client to obtain IP/boot params
⋅ 5.9.5.3. loadb - load binary file over serial line (kermit mode)
⋅ 5.9.5.4. loads - load S-Record file over serial line
⋅ 5.9.5.5. tftpboot- boot image via network using TFTP protocol
◊ 5.9.6. Environment Variables Commands
⋅ 5.9.6.1. printenv- print environment variables
⋅ 5.9.6.2. saveenv - save environment variables to persistent storage
⋅ 5.9.6.3. setenv - set environment variables
⋅ 5.9.6.4. run - run commands in an environment variable
⋅ 5.9.6.5. bootd - boot default, i.e., run 'bootcmd'
◊ 5.9.7. Flattened Device Tree support
⋅ 5.9.7.1. fdt addr - select FDT to work on
⋅ 5.9.7.2. fdt list - print one level
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⋅ 5.9.7.3. fdt print - recursive print
⋅ 5.9.7.4. fdt mknode - create new nodes
⋅ 5.9.7.5. fdt set - set node properties
⋅ 5.9.7.6. fdt rm - remove nodes or properties
⋅ 5.9.7.7. fdt move - move FDT blob to new address
⋅ 5.9.7.8. fdt chosen - fixup dynamic info
◊ 5.9.8. Special Commands
⋅ 5.9.8.1. i2c - I2C sub-system
◊ 5.9.9. Storage devices
⋅ 5.9.9.1. MMC devices
⋅ 5.9.9.2. NAND devices
• 5.9.9.2.1. nand bad - show bad block information
• 5.9.9.2.2. nand erase - erase region
• 5.9.9.2.3. nand write - write to NAND device
• 5.9.9.2.4. nand read - read from NAND device
◊ 5.9.10. Miscellaneous Commands
⋅ 5.9.10.1. date - get/set/reset date & time
⋅ 5.9.10.2. echo - echo args to console
⋅ 5.9.10.3. reset - Perform RESET of the CPU
⋅ 5.9.10.4. sleep - delay execution for some time
⋅ 5.9.10.5. version - print monitor version
⋅ 5.9.10.6. ? - alias for 'help'
♦ 5.10. U-Boot Environment Variables
♦ 5.11. U-Boot Scripting Capabilities
♦ 5.12. U-Boot Standalone Applications
◊ 5.12.1. "Hello World" Demo
◊ 5.12.2. Timer Demo
♦ 5.13. U-Boot Image Formats
♦ 5.14. U-Boot Advanced Features
◊ 5.14.1. Boot Count Limit
• 6. Embedded Linux Configuration
♦ 6.1. Download and Unpack the Linux Kernel Sources
♦ 6.2. Kernel Configuration and Compilation
♦ 6.3. Installation
• 7. Booting Embedded Linux
♦ 7.1. Introduction
♦ 7.2. Flattened Device Tree Blob
♦ 7.3. Passing Kernel Arguments
♦ 7.4. Boot Arguments Unleashed
♦ 7.5. Networked Operation with Root Filesystem over NFS
◊ 7.5.1. Bootlog of tftp'd Linux kernel with Root Filesystem over NFS
♦ 7.6. Boot from NAND Flash Memory
♦ 7.7. Standalone Operation with Ramdisk Image
• 8. Building and Using Modules
• 9. Advanced Topics
♦ 9.1. Flash Filesystems
◊ 9.1.1. Memory Technology Devices
◊ 9.1.2. Journalling Flash File System
◊ 9.1.3. Second Version of JFFS
◊ 9.1.4. Compressed ROM Filesystem
◊ 9.1.5. UBI and UBIFS file systems
⋅ 9.1.5.1. Create Device Files
⋅ 9.1.5.2. Using UBI on NAND Flash:
⋅ 9.1.5.3. Creating UBIFS File System Images
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• 9.1.5.3.1. Determining the Parameters of the used Flash Types:
• 9.1.5.3.2. Create some Test File System Hierarchy
• 9.1.5.3.3. Installing UBIFS images into existing UBI Volume:
• 9.1.5.3.4. Installing UBI images (if no UBI Volumes exist):
♦ 9.2. The TMPFS Virtual Memory Filesystem
◊ 9.2.1. Mount Parameters
◊ 9.2.2. Kernel Support for tmpfs
◊ 9.2.3. Usage of tmpfs in Embedded Systems
♦ 9.3. Using MultiMediaCards in Linux"
♦ 9.4. Splash Screen Support in Linux
♦ 9.5. Root File System: Design and Building
◊ 9.5.1. Root File System on a Ramdisk
◊ 9.5.2. Root File System on a JFFS2 File System
◊ 9.5.3. Root File System on a cramfs File System
◊ 9.5.4. Root File System on a Read-Only ext2 File System
◊ 9.5.5. Root File System on a Flash Card
◊ 9.5.6. Root File System in a Read-Only File in a FAT File System
♦ 9.6. Root File System Selection
♦ 9.7. Overlay File Systems
♦ 9.8. The Persistent RAM File system (PRAMFS)
◊ 9.8.1. Mount Parameters
◊ 9.8.2. Example
• 10. Debugging
♦ 10.1. Debugging of U-Boot
◊ 10.1.1. Debugging of U-Boot Before Relocation
◊ 10.1.2. Debugging of U-Boot After Relocation
♦ 10.2. Linux Kernel Debugging
◊ 10.2.1. Linux Kernel and Statically Linked Device Drivers
◊ 10.2.2. Dynamically Loaded Device Drivers (Modules)
◊ 10.2.3. GDB Macros to Simplify Module Loading
♦ 10.3. GDB Startup File and Utility Scripts
♦ 10.4. Tips and Tricks
♦ 10.5. Application Debugging
◊ 10.5.1. Local Debugging
◊ 10.5.2. Remote Debugging
♦ 10.6. Debugging with Graphical User Interfaces
• 11. Simple Embedded Linux Framework
• 12. Books, Mailing Lists, Links, etc.
♦ 12.1. Application Notes
♦ 12.2. Further Reading
◊ 12.2.1. License Issues
◊ 12.2.2. Linux kernel
◊ 12.2.3. General Linux / Unix programming
◊ 12.2.4. Network Programming
◊ 12.2.5. C++ programming
◊ 12.2.6. Java programming
◊ 12.2.7. Internationalization And Character Sets
◊ 12.2.8. ARM Architecture Programming
◊ 12.2.9. Power Architecture® Programming
◊ 12.2.10. Embedded Topics
♦ 12.3. Mailing Lists
♦ 12.4. Links
♦ 12.5. Tools
• 13. Appendix
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♦ 13.1. Flat Device Tree
♦ 13.2. BDI2000 Configuration file
• 14. FAQ - Frequently Asked Questions
♦ 14.1. ELDK
◊ 14.1.1. ELDK Installation under FreeBSD
◊ 14.1.2. ELDK Installation Hangs
◊ 14.1.3. .gvfs: Permission Denied
◊ 14.1.4. Installation on Local Harddisk
◊ 14.1.5. System Include Files Missing
◊ 14.1.6. patch: command not found
◊ 14.1.7. ELDK Include Files Missing
◊ 14.1.8. Using the ELDK on a 64 bit platform
◊ 14.1.9. How can I check if Floating Point support is working?
◊ 14.1.10. ELDK 2.x Installation Aborts
◊ 14.1.11. Enable SSH Access
♦ 14.2. U-Boot
◊ 14.2.1. Can U-Boot be configured such that it can be started in RAM?
◊ 14.2.2. Relocation cannot be done when using -mrelocatable
◊ 14.2.3. Source object has EABI version 4, but target has EABI version 0
◊ 14.2.4. U-Boot crashes after relocation to RAM
◊ 14.2.5. Warning - bad CRC, using default environment
◊ 14.2.6. Net: No ethernet found
◊ 14.2.7. Wrong debug symbols after relocation
◊ 14.2.8. Decoding U-Boot Crash Dumps
◊ 14.2.9. Porting Problem: cannot move location counter backwards
◊ 14.2.10. U-Boot Doesn't Run after Upgrading my Compiler
◊ 14.2.11. How Can I Reduce The Image Size?
◊ 14.2.12. Erasing Flash Fails
◊ 14.2.13. Ethernet Does Not Work
◊ 14.2.14. Where Can I Get a Valid MAC Address from?
◊ 14.2.15. Why do I get TFTP timeouts?
◊ 14.2.16. Why is my Ethernet operation not reliable?
◊ 14.2.17. How the Command Line Parsing Works
⋅ 14.2.17.1. Old, simple command line parser
⋅ 14.2.17.2. Hush shell
⋅ 14.2.17.3. Hush shell scripts
⋅ 14.2.17.4. General rules
◊ 14.2.18. How can I load and uncompress a compressed image
◊ 14.2.19. How can I create an uImage from a ELF file
◊ 14.2.20. My standalone program does not work
◊ 14.2.21. Linux hangs after uncompressing the kernel
◊ 14.2.22. How can I implement automatic software updates?
♦ 14.3. Linux
◊ 14.3.1. Linux crashes randomly
◊ 14.3.2. Linux crashes when uncompressing the kernel
◊ 14.3.3. Linux Post Mortem Analysis
◊ 14.3.4. Linux kernel register usage
◊ 14.3.5. Linux Kernel Ignores my bootargs
◊ 14.3.6. Cannot configure Root Filesystem over NFS
◊ 14.3.7. Linux Kernel Panics because "init" process dies
◊ 14.3.8. Unable to open an initial console
◊ 14.3.9. System hangs when entering User Space (ARM)
◊ 14.3.10. Mounting a Filesystem over NFS hangs forever
◊ 14.3.11. Ethernet does not work in Linux
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◊ 14.3.12. Loopback interface does not work
◊ 14.3.13. Linux kernel messages are not printed on the console
◊ 14.3.14. Linux ignores input when using the framebuffer driver
◊ 14.3.15. How to switch off the screen saver and the blinking cursor?
◊ 14.3.16. BogoMIPS Value too low
◊ 14.3.17. Linux Kernel crashes when using a ramdisk image
◊ 14.3.18. Ramdisk Greater than 4 MB Causes Problems
◊ 14.3.19. Combining a Kernel and a Ramdisk into a Multi-File Image
◊ 14.3.20. Adding Files to Ramdisk is Non Persistent
◊ 14.3.21. Kernel Configuration for PCMCIA
◊ 14.3.22. Configure Linux for PCMCIA Cards using the Card Services package
◊ 14.3.23. Configure Linux for PCMCIA Cards without the Card Services package
⋅ 14.3.23.1. Using a MacOS Partition Table
⋅ 14.3.23.2. Using a MS-DOS Partition Table
◊ 14.3.24. Boot-Time Configuration of MTD Partitions
◊ 14.3.25. Use NTP to synchronize system time against RTC
◊ 14.3.26. Configure Linux for XIP (Execution In Place)
⋅ 14.3.26.1. XIP Kernel
⋅ 14.3.26.2. Cramfs Filesystem
⋅ 14.3.26.3. Hints and Notes
⋅ 14.3.26.4. Space requirements and RAM saving, an example
◊ 14.3.27. Use SCC UART with Hardware Handshake
◊ 14.3.28. How can I access U-Boot environment variables in Linux?
◊ 14.3.29. The =appWeb= server hangs *OR* /dev/random hangs
◊ 14.3.30. Swapping over NFS
◊ 14.3.31. Using NFSv3 for NFS Root Filesystem
◊ 14.3.32. Using and Configuring the SocketCAN Driver
◊ 14.3.33. Telnet / SSH (dropbear) server not working
♦ 14.4. Self
◊ 14.4.1. How to Add Files to a SELF Ramdisk
◊ 14.4.2. How to Increase the Size of the Ramdisk
♦ 14.5. RTAI
◊ 14.5.1. Conflicts with asm clobber list
♦ 14.6. BDI2000
◊ 14.6.1. Where can I find BDI2000 Configuration Files?
◊ 14.6.2. How to Debug Linux Exceptions
◊ 14.6.3. How to single step through "RFI" instruction
◊ 14.6.4. Setting a breakpoint doesn't work
◊ 14.6.5. Remote 'g' packet reply is too long
♦ 14.7. Motorola LITE5200 Board
◊ 14.7.1. LITE5200 Installation Howto
◊ 14.7.2. USB does not work on Lite5200 board
• 15. Glossary
1. Abstract
This is the DENX U-Boot and Linux Guide to Embedded PowerPC, ARM and MIPS Systems.
The document describes how to configure, build and use the firmware Das U-Boot (typically abbreviated as
just "U-Boot") and the operating system Linux for Embedded PowerPC, ARM and MIPS Systems.
The focus of this version of the document is on m28 boards.
This document was generated at 10 Dec 2012 - 06:19.
1. Abstract
6
• 2. Introduction
♦ 2.1. Copyright
♦ 2.2. Disclaimer
♦ 2.3. Availability
♦ 2.4. Credits
♦ 2.5. Translations
♦ 2.6. Feedback
♦ 2.7. Conventions
2. Introduction
This document describes how to use the firmware U-Boot and the operating system Linux in Embedded
Power Architecture®, ARM and MIPS Systems.
There are many steps along the way, and it is nearly impossible to cover them all in depth, but we will try to
provide all necessary information to get an embedded system running from scratch. This includes all the tools
you will probably need to configure, build and run U-Boot and Linux.
First, we describe how to install the Cross Development Tools Embedded Linux Development Kit which you
probably need - at least when you use a standard x86 PC running Linux or a Sun Solaris 2.6 system as build
environment.
Then we describe what needs to be done to connect to the serial console port of your target: you will have to
configure a terminal emulation program like cu or kermit.
In most cases you will want to load images into your target using ethernet; for this purpose you need TFTP
and DHCP / BOOTP servers. A short description of their configuration is given.
A description follows of what needs to be done to configure and build the U-Boot for a specific board, and
how to install it and get it working on that board.
The configuration, building and installing of Linux in an embedded configuration is the next step. We use
SELF, our Simple Embedded Linux Framework, to demonstrate how to set up both a development system
(with the root filesystem mounted over NFS) and an embedded target configuration (running from a ramdisk
image based on busybox).
This document does not describe what needs to be done to port U-Boot or Linux to a new hardware platform.
Instead, it is silently assumed that your board is already supported by U-Boot and Linux.
The focus of this document is on m28 boards.
2.1. Copyright
Copyright (C) 2001 - 2011 by Wolfgang Denk, DENX Software Engineering.
Copyright (C) 2003 - 2011 by Detlev Zundel, DENX Software Engineering.
Copyright (C) 2003 - 2011 by contributing authors
You have the freedom to distribute copies of this document in any format or to create a derivative work of it
and distribute it provided that you:
• Distribute this document or the derivative work at no charge at all. It is not permitted to sell this
document or the derivative work or to include it into any package or distribution that is not freely
available to everybody.
2. Introduction
7
• Send your derivative work (in the most suitable format such as sgml) to the author.
• License the derivative work with this same license or use GPL. Include a copyright notice and at least
a pointer to the license used.
• Give due credit to previous authors and major contributors.
It is requested that corrections and/or comments be forwarded to the author.
If you are considering to create a derived work other than a translation, it is requested that you discuss your
plans with the author.
2.2. Disclaimer
Use the information in this document at your own risk. DENX disavows any potential liability for the contents
of this document. Use of the concepts, examples, and/or other content of this document is entirely at your own
risk. All copyrights are owned by their owners, unless specifically noted otherwise. Use of a term in this
document should not be regarded as affecting the validity of any trademark or service mark. Naming of
particular products or brands should not be seen as endorsements.
2.3. Availability
The latest version of this document is available in a number of formats:
• HTML http://www.denx.de/wiki/publish/DULG/DULG-m28.html
• plain ASCII text http://www.denx.de/wiki/publish/DULG/DULG-m28.txt
• PostScript European A4 format http://www.denx.de/wiki/publish/DULG/DULG-m28.ps
• PDF European A4 format http://www.denx.de/wiki/publish/DULG/DULG-m28.pdf
2.4. Credits
A lot of the information contained in this document was collected from several mailing lists. Thanks to
anybody who contributed in one form or another.
2.5. Translations
None yet.
2.6. Feedback
Any comments or suggestions can be mailed to the author: Wolfgang Denk at wd@denx.de.
2.7. Conventions
Descriptions
Warnings
Hint
Notes
Information requiring special attention
File Names
2.1. Copyright
Appearance
Note.
Warning
file.extension
8
Directory Names
Commands to be typed
Applications Names
Prompt of users command under bash shell
Prompt of root users command under bash shell
Prompt of users command under tcsh shell
Environment Variables
Emphasized word
Code Example
directory
a command
another
application
bash$
bash#
tcsh$
VARIABLE
word
ls -l
• 3. Embedded Linux Development Kit
♦ 3.1. ELDK Availability
♦ 3.2. ELDK Getting Help
♦ 3.3. Supported Host Systems
♦ 3.4. Supported Target Architectures
♦ 3.5. Installation
◊ 3.5.1. Product Packaging
◊ 3.5.2. Downloading the ELDK
◊ 3.5.3. Initial Installation
◊ 3.5.4. Installation and Removal of Individual Packages
◊ 3.5.5. Removal of the Entire Installation
♦ 3.6. Working with ELDK
◊ 3.6.1. Switching Between Multiple Installations
♦ 3.7. Mounting Target Components via NFS
♦ 3.8. Rebuilding ELDK Components
◊ 3.8.1. ELDK Source Distribution
◊ 3.8.2. Rebuilding Target Packages
◊ 3.8.3. Rebuilding ELDT Packages
♦ 3.9. ELDK Packages
◊ 3.9.1. List of ELDT Packages
◊ 3.9.2. List of Target Packages
♦ 3.10. Rebuilding the ELDK from Scratch
◊ 3.10.1. ELDK Build Process Overview
◊ 3.10.2. Setting Up ELDK Build Environment
◊ 3.10.3. build.sh Usage
◊ 3.10.4. Format of the cpkgs.lst and tpkgs.lst Files
3. Embedded Linux Development Kit
The Embedded Linux Development Kit (ELDK) includes the GNU cross development tools, such as the
compilers, binutils, gdb, etc., and a number of pre-built target tools and libraries necessary to provide some
functionality on the target system.
It is provided for free with full source code, including all patches, extensions, programs and scripts used to
build the tools.
Some versions of ELDK (4.1) are available in two versions, which use Glibc resp. uClibc as the main C
library for the target packages.
Packaging and installation is based on the RPM package manager.
3. Embedded Linux Development Kit
9
3.1. ELDK Availability
The ELDK is available
• on DVD-ROM from DENX Computer Systems
• for download on the following server:
FTP
HTTP
ftp://ftp.denx.de/pub/eldk/
http://www.denx.de/ftp/pub/eldk/
• for download on the following mirrors:
FTP
HTTP
ftp://ftp-stud.hs-esslingen.de/pub/Mirrors/eldk/
http://ftp-stud.hs-esslingen.de/pub/Mirrors/eldk/
ftp://mirror.switch.ch/mirror/eldk/
http://mirror.switch.ch/ftp/mirror/eldk/
not available
http://mira.sunsite.utk.edu/eldk/
ftp://ftp.sunet.se/pub/Linux/distributions/eldk/
http://ftp.sunet.se/pub/Linux/distributions/eldk/
3.2. ELDK Getting Help
Community support for the ELDK is available through the ELDK Mailing List.
Previous postings to this mailing list are available from the ELDK archives.
Commercial support is also available; please feel free to contact DENX Software Engineering GmbH.
3.3. Supported Host Systems
The ELDK can be installed onto and operate with the following operating systems:
• Fedora Core 4, 5, 6 Fedora 7, 8, 9, 10, 11, 12
• Red Hat Linux 7.3, 8.0, 9
• SuSE Linux 8.x, 9.0, 9.1, 9.2, 9.3, 10.0
• OpenSUSE 10.2, 10.3 (32 Bit); OpenSUSE 11.0 (32 and 64 Bit)
• Debian 3.0 (Woody), 3.1 (Sarge) and 4.0 (Etch)
• Ubuntu 4.10, 5.04, 6.10, 8.04, 9.04, 9.10, 10.04
• FreeBSD 5.0
Users also reported successful installation and use of the ELDK on the following host systems:
• Suse Linux 7.2, 7.3
• Mandrake 8.2
• Slackware 8.1beta2
• Gentoo Linux 2006.1
Note: It may be necessary, and is usually recommended, to install the latest available software updates on
your host system. For example, on Fedora systems, you can use yum or apt-get to keep your systems
current.
3.3. Supported Host Systems
10
3.4. Supported Target Architectures
The ELDK for ARM systems supports processors complying with the ARM architecture version 2 to 6. This
includes ARM7, ARM9, XScale, AT91RM9200, i.MX31, S3C6400 and other ARM based systems.
The version of 4.2 and higher of ELDK has two ARM targets in distribution - one with the soft-float math
support, and another one with the Vector Floating Point math support. Both targets comply with ARM
Embedded Application Binary Interface (EABI).
The ELDK ARM target architectures are:
• arm-linux = soft-float math
• armVFP-linux = Vector Floating Point (VFP) math
There is also an ELDK for PowerPC and MIPS systems.
3.5. Installation
3.5.1. Product Packaging
Stable versions of the ELDK are distributed in the form of an ISO image, which can be either burned onto a
DVD or mounted directly, using the loopback Linux device driver (Linux host only).
Development versions of the ELDK are available as directory trees so it is easy to update individual packages;
instructions for download of these trees and creation of ISO images from it is described in section 3.5.2.
Downloading the ELDK.
The ELDK contains an installation utility and a number of RPM packages, which are installed onto the hard
disk of the cross development host by the installation procedure. The RPM packages can be logically divided
into two parts:
• Embedded Linux Development Tools (ELDT)
• Target components
The first part contains the cross development tools that are executed on the host system. Most notably, these
are the GNU cross compiler, binutils, and gdb. For a full list of the provided ELDT packages, refer to section
3.9.1. List of ELDT Packages below.
The target components are pre-built tools and libraries which are executed on the target system. The ELDK
includes necessary target components to provide a minimal working NFS-based environment for the target
system. For a list of the target packages included in the ELDK, refer to section 3.9.2. List of Target Packages
below.
The ELDK contains several independent sets of the target packages, one for each supported target architecture
CPU family. Each set has been built using compiler code generation and optimization options specific to the
respective target CPU family.
3.5.2. Downloading the ELDK
3.5.2. Downloading the ELDK
11
You can either download the ready-to-burn ISO-images from one of the mirror sites (see 3.1. ELDK
Availability), or you can download the individual files of the ELDK from the development directory tree and
either use these directly for installation or create an ISO image that can be burned on DVD-ROM.
Change to a directory with sufficient free disk space; for the ARM version of the ELDK you need about 510
MiB, or twice as much (1.1 GiB) if you also want to create an ISO image in this directory.
To download the ISO image from the arm-linux-x86/iso directory of one of the mirror sites you can use
standard tools like wget or ncftpget, for example:
bash$ wget ftp://ftp.sunet.se/pub/Linux/distributions/eldk/4.2/arm-linux-x86/iso/arm-2008-11-24.i
If you want to download the whole ELDK directory tree instead you can - for example - use the ncftp FTP
client:
bash$
...
ncftp
ncftp
ncftp
...
ncftp
ncftp ftp.sunet.se
/ > cd /pub/Linux/distributions/eldk/4.2
/pub/Linux/distributions/eldk/4.2 > bin
/pub/Linux/distributions/eldk/4.2 > get -R arm-linux-x86/distribution
/pub/Linux/distributions/eldk/4.2 > bye
If you don't find the ncftp tool on your system you can download the NcFTP client from
http://www.ncftp.com/download/
There are a few executable files (binaries and scripts) in the ELDK tree. Make sure they have the execute
permissions set in your local copy:
bash$ for file in \
>
tools/bin/rpm \
>
tools/usr/lib/rpm/rpmd \
>
install \
>
ELDK_MAKEDEV \
>
ELDK_FIXOWNER
> do
> chmod +x arm-linux-x86/distribution/$file
> done
Now create an ISO image from the directory tree:
bash$ mkisofs \
> -A "ELDK-4.2 -- Target: ARM -- Host: x86 Linux" \
> -publisher "(C) `date "+%Y"` DENX Software Engineering,
www.denx.de" \
> -p "`id -nu`@`hostname` -- `date`" \
> -V arm-linux-x86 \
> -l -J -R -o eldk-arm-linux-x86.iso arm-linux-x86/distribution
This will create an ISO image eldk-arm-linux-x86.iso in your local directory that can be burned on DVD or
mounted using the loopback device and used for installation as described above. Of course you can use the
local copy of the directory tree directly for the installation, too.
Please refer to section 3.10.2. Setting Up ELDK Build Environment for instructions on obtaining the build
environment needed to re-build the ELDK from scratch.
3.5.3. Initial Installation
3.5.3. Initial Installation
12
The initial installation is performed using the install utility located in the root of the ELDK ISO image
directory tree. The install utility has the following syntax:
$ ./install [-d <dir>] [<cpu_family1>] [<cpu_family2>] ...
-d <dir>
Specifies the root directory of the ELDK being installed. If omitted, the ELDK goes into
the current directory.
<cpu_family> Specifies the target CPU family the user desires to install. If one or more
<cpu_family> parameters are specified, only the target components specific to the
respective CPU families are installed onto the host. If omitted, the target components for
all supported target architecture CPU families are installed.
Note: Make sure that the "exec" option to the mount command is in effect when mounting the ELDK ISO
image. Otherwise the install program cannot be executed. On some distributions, it may be necessary to
modify the /etc/fstab file, adding the "exec" mount option to the cdrom entry - it may also be the case that
other existing mount options, such as "user" prevent a particular configuration from mounting the ELDK
DVD with appropriate "exec" permission. In such cases, consult your distribution documentation or mount the
DVD explicitly using a command such as "sudo mount -o exec /dev/cdrom /mnt/cdrom" (sudo allows regular
users to run certain privileged commands but may not be configured - run the previous command as root
without "sudo" in the case that "sudo" has not been setup for use on your particular GNU/Linux system).
You can install the ELDK to any empty directory you wish, the only requirement being that you have to have
write and execute permissions on the directory. The installation process does not require superuser privileges.
Depending on the parameters the install utility is invoked with, it installs one or more sets of target
components. The ELDT packages are installed in any case.
Refer to section 3.6. Working with ELDK for a sample usage of the ELDK.
Note: If you intend to use the installation as a root filesystem exported over NFS, then you now have to
finish the configuration of the ELDK following the instructions in 3.7. Mounting Target Components via
NFS.
Note: Installation of the Glibc- and uClibc-based ELDK versions into one directory is not yet supported.
Note: Installation of the 32-bit and 64-bit ELDK versions into one directory is not yet supported.
3.5.4. Installation and Removal of Individual
Packages
The ELDK has an RPM-based structure. This means that on the ISO image, individual components of the
ELDK are in the form of RPM packages, and after installation, the ELDK maintains its own database which
contains information about installed packages. The RPM database is kept local to the specific ELDK
installation, which allows you to have multiple independent ELDK installations on your host system. (That is,
you can install several instances of ELDK under different directories and work with them independently).
Also, this provides for easy installation and management of individual ELDK packages.
To list the installed ELDK RPM packages, use the following command:
bash$ ${CROSS_COMPILE}rpm -qa
To remove an ELDK package, use the following command:
bash$ ${CROSS_COMPILE}rpm -e <package_name>
3.5.4. Installation and Removal of Individual Packages
13
To install a package, use the following command:
bash$ ${CROSS_COMPILE}rpm -i <package_file_name>
To update a package, use the following command:
bash$ ${CROSS_COMPILE}rpm -U <package_file_name>
For the above commands to work correctly, it is crucial that the correct rpm binary gets invoked. In case of
multiple ELDK installations and RedHat-based host system, there may well be several rpm tools installed on
the host system.
You must make sure, either by using an explicit path or by having set an appropriate PATH environment
variable, that when you invoke rpm to install/remove components of a ELDK installation, it is the ELDK's
rpm utility that gets actually invoked. The rpm utility is located in the bin subdirectory relative to the ELDK
root installation directory.
To avoid confusion with the host OS (RedHat) rpm utility, the ELDK creates symlinks to its rpm binary with
the names such that it could be invoked using the ${CROSS_COMPILE}rpm notation, for all supported
$CROSS_COMPILE values.
The standard (host OS) rpm utility allows various macros and configuration parameters to specified in
user-specific ~/.rpmrc and ~/.rpmmacros files. The ELDK rpm tool also has this capability, but the names of
the user-specific configuration files are ~/.eldk_rpmrc and ~/.eldk_rpmmacros, respectively.
3.5.5. Removal of the Entire Installation
To remove the entire ELDK installation, use the following command while in the ELDK root directory:
bash$ rm -rf <dir>
where <dir> specifies the root directory of the ELDK to be removed.
3.6. Working with ELDK
After the initial installation is complete, all you have to do to start working with the ELDK is to set and export
the CROSS_COMPILE environment variable. Optionally, you may wish to add the bin and usr/bin
directories of your ELDK installation to the value of your PATH environment variable. For instance, a sample
ELDK installation and usage scenario looks as follows:
• Create a new directory where the ELDK is to be installed, say:
bash$ mkdir /opt/eldk
• Mount a CD or an ISO image with the distribution:
bash$ mount /dev/cdrom /mnt/cdrom
• Run the installation utility included on the distribution to install into that specified directory:
bash$ /mnt/cdrom/install -d /opt/eldk
• After the installation utility completes, export the CROSS_COMPILE variable:
bash$ export CROSS_COMPILE=arm-linux-gnueabi-
3.6. Working with ELDK
14
•
The trailing '-' character in the CROSS_COMPILE variable value is optional and has no effect on
the cross tools behavior. However, it is required when building Linux kernel and U-Boot images.
• Add the directories /opt/eldk/usr/bin and /opt/eldk/bin to PATH:
bash$ PATH=$PATH:/opt/eldk/usr/bin:/opt/eldk/bin
• Compile a file:
bash$ ${CROSS_COMPILE}gcc -o hello_world hello_world.c
You can also call the cross tools using the generic prefix arm-linux- for example:
bash$ arm-linux-gcc -o hello_world hello_world.c
• or, equivalently:
bash /opt/eldk/usr/arm-linux/bin/gcc -o hello_world hello_world.c
The value of the CROSS_COMPILE variable must correspond to the target CPU family you want the cross
tools to work for. Refer to the table below for the supported CROSS_COMPILE variable values:
3.6.A Table of possible values for $CROSS_COMPILE
CROSS_COMPILE Value Predefined Compiler Flag
FPU present or not
arm-linux-mcpu=arm9 -msoft-float
No
armVFP-linux-mfpu=vfp -mfloat-abi=softfp Yes (VFP)
3.6.1. Switching Between Multiple Installations
No special actions are required from the user to switch between multiple ELDK installations on the same host
system. Which ELDK installation is used is determined entirely by the filesystem location of the binary that is
being invoked. This approach can be illustrated using the following example.
Assume the directory /work/denx_tools/usr/bin, where the arm-linux-gcc compiler binary has been
installed, is a part of the PATH environment variable. The user types the command as follows:
$ arm-linux-gcc -c myfile.c
To load the correct include files, find the correct libraries, spec files, etc., the compiler needs to know the
ELDK root directory. The compiler determines this information by analyzing the shell command it was
invoked with ( arm-linux-gcc - without specifying the explicit path in this example) and, if needed, the
value of the PATH environment variable. Thus, the compiler knows that it has been executed from the
/work/denx_tools/usr/bin directory.
Then, it knows that the compiler is installed in the usr/bin subdirectory of the root installation directory, so the
ELDK, the compiler is a part of, has been installed in the subdirectories of the /work/denx_tools directory.
This means that the target include files are in /work/denx_tools/<target_cpu_variant>/usr/include, and so on.
3.7. Mounting Target Components via NFS
The target components of the ELDK can be mounted via NFS as the root file system for your target machine.
For instance, for an AT91-based target, and assuming the ELDK has been installed into the /opt/eldk
directory, you can use the following directory as the NFS-based root file system:
3.7. Mounting Target Components via NFS
15
/opt/eldk/arm
Before the NFS-mounted root file system can work, you must create necessary device nodes in the
<ELDK_root>/<target_cpu_variant>/dev directory. This process requires superuser privileges and thus
cannot be done by the installation procedure (which typically runs as non-root). To facilitate creation of the
device nodes, the ELDK provides a script named ELDK_MAKEDEV, which is located in the root of the ELDK
distribution ISO image. The script acccepts the following optional arguments:
-d <dir>
Specifies the root directory of the ELDK being installed. If omitted, then the current
directory is assumed.
-a <cpu_family> Specifies the target CPU family directory. If omitted, all installed target architecture
directories will be populated with the device nodes.
-h
Prints usage.
# /mnt/cdrom/ELDK_MAKEDEV -d /opt/eldk
NOTE: Compared to older versions of the ELDK, options and behaviour of this command have been changed
significantly. Please read the documentation.
Some of the target utilities included in the ELDK, such as mount and su, have the SUID bit set. This
means that when run, they will have privileges of the file owner of these utilities. That is, normally, they will
have the privileges of the user who installed the ELDK on the host system. However, for these utilities to
work properly, they must have superuser privileges. This means that if the ELDK was not installed by the
superuser, the file owner of the target ELDK utilities that have the SUID bit set must be changed to root
before a target component may be mounted as the root file system. The ELDK distribution image contains an
ELDK_FIXOWNER script, which you can use to change file owners of all the appropriate files of the ELDK
installation to root. The script accepts the same arguments as the ELDK_MAKEDEV script above. Please note
that you must have superuser privileges to run this script. For instance, if you have installed the ELDK in the
/opt/eldk directory, you can use the following commands:
# cd /opt/eldk
# /mnt/cdrom/ELDK_FIXOWNER
Please note, that in the case that the installation directory, where the new ELDK distribution is being installed,
is already populated with other ELDK distributions, the execution of the ELDK_FIXOWNER script without
arguments will make the script work with all installed ELDK target architecture directories. This could take
some time. To save the time, please use the -a argument to specify the appropriate target architecture. For
instance:
# cd /opt/eldk
# /mnt/cdrom/ELDK_FIXOWNER -a arm
3.8. Rebuilding ELDK Components
3.8.1. ELDK Source Distribution
The ELDK is distributed with the full sources of all the components, so you may rebuild any ELDK package.
The sources are provided in the form of SRPM packages, distributed as a separate ISO image.
To rebuild a target or ELDT package, you must first install the appropriate source RPM package from the ISO
image into the ELDK environment. This can be done using the following command:
$ ${CROSS_COMPILE}rpm -i /mnt/cdrom/SRPMS/<source_rpm_file_name>.src.rpm
3.8. Rebuilding ELDK Components
16
After an ELDK source RPM is installed using the above command, its spec file and sources can be found in
the subdirectories of the <ELDK_root>/usr/src/denx subdirectory.
The sections that follow provide detailed instructions on rebuilding ELDT and target components of the
ELDK.
3.8.2. Rebuilding Target Packages
All the target packages can be rebuilt from the provided source RPM packages. At first you have to install the
Source RPM itself:
bash$ ${CROSS_COMPILE}rpm -iv <package_name>.src.rpm
Then you can rebuild the binary target RPM using the following command from the ELDK environment:
bash$ ${CROSS_COMPILE}rpmbuild -ba <package_name>.spec
In order for the rebuilding process to work correctly, the following conditions must be true:
• The $CROSS_COMPILE environment variable must be set as appropriate for the target CPU family.
• The <ELDK_root>/usr/arm-linux/bin directory must be in PATH before the /usr/bin directory. This is
to make sure that the command gcc results in the fact that the ELDK cross compiler is invoked,
rather than the host gcc.
The newly built package can then be installed just as easily:
bash$ ${CROSS_COMPILE}rpm -i <package_name>.rpm
3.8.3. Rebuilding ELDT Packages
All the ELDT packages allow for rebuilding from the provided source RPM packages using the following
command from the ELDK environment:
$ unset CROSS_COMPILE
$ <ELDK_root>/usr/bin/rpmbuild -ba <package_name.spec>
In order for the rebuilding process to work correctly, make sure all of the following is true:
• The $CROSS_COMPILE environment variable must NOT be set.
• Do NOT use the $CROSS_COMPILE command prefix.
• The <ELDK_root>/usr/arm-linux/bin directory must NOT be in PATH. This is to make sure that the
command gcc causes invokation of the host gcc, rather than the ELDK cross compiler.
Note that the newly built package should be installed with the "global" rpm, not with the arch specific one:
bash$ <ELDK_root>/bin/rpm -i <package_name>.rpm
3.8.1. ELDK Source Distribution
17
3.9. ELDK Packages
3.9.1. List of ELDT Packages
Package Name
Package
Version
autoconf
2.61-8
automake
1.10-5
bison
2.3-3
crosstool-devel
0.43-3
dtc
20070802-1
elocaledef
1-1
ftdump
20070802-1
gdb
6.7-2
genext2fs
1.4.1-1
info
4.8-15
ldd
0.1-1
libtool
1.5.22-11
make
3.81-6
mkcramfs
1.1-1
mkimage
1.3.1-1
mtd-utils
1.0.1-2
rpm
4.4.2-46_2
rpm-build
4.4.2-46_2
sed
4.1.4-1
texinfo
4.8-15
Note: The crosstool 0.43 ELDT package provides the following packages: gcc 4.2.2, gcc-c++
4.2.2, gcc-java 4.2.2, cpp 4.2.2 and binutils 2.17.90. For more information about the
crosstool package please refer to http://kegel.com/crosstool.
3.9.2. List of Target Packages
Package Name
Package Version
acl
2.2.39-3.1
appweb
2.2.2-5
attr
2.4.32-2
autoconf
2.61-8
3.9. ELDK Packages
18
bash
3.2-9
bc
1.06-26
bind
9.4.1-8.P1
binutils
2.17.90-1
binutils-devel
2.17.90-1
boa
0.94.14-0.5.rc21
busybox
1.7.1-2
byacc
1.9.20050813-1
bzip2
1.0.4-10
bzip2-devel
1.0.4-10
bzip2-libs
1.0.4-10
ccid
1.2.1-10
chkconfig
1.3.34-1
coreutils
6.9-3
cpio
2.6-27
cpp
4.2.2-2
cracklib
2.8.9-11
cracklib-dicts
2.8.9-11
crosstool-targetcomponents
0.43-3
curl
7.16.2-1
cyrus-sasl
2.1.22-6
cyrus-sasl-devel
2.1.22-6
cyrus-sasl-lib
2.1.22-6
db4
4.5.20-5_2
db4-devel
4.5.20-5_2
db4-utils
4.5.20-5_2
device-mapper
1.02.17-7
device-mapper-devel
1.02.17-7
device-mapper-libs
1.02.17-7
dhclient
3.0.5-38
dhcp
3.0.5-38
diffutils
2.8.1-16
directfb
1.0.0-1
dosfstools
2.11-8
3.9.2. List of Target Packages
19
dropbear
0.50-1
dtc
20070802-1
duma
2.5.8-2
e2fsprogs
1.39-11
e2fsprogs-devel
1.39-11
e2fsprogs-libs
1.39-11
ethtool
5-1
expat
1.95.8-9
expat-devel
1.95.8-9
file
4.21-1
file-libs
4.21-1
findutils
4.2.29-2
flex
2.5.33-9
freetype
2.3.4-3
freetype-devel
2.3.4-3
ftdump
20070802-1
ftp
0.17-40
gawk
3.1.5-15
gcc
4.2.2-2
gcc-c++
4.2.2-2
gcc-java
4.2.2-2
gdb
6.7-1
glib
1.2.10-26
glib2
2.12.13-1
glib2-devel
2.12.13-1
glib-devel
1.2.10-26
gmp
4.1.4-12.3
grep
2.5.1-57
groff
1.18.1.4-2
gzip
1.3.11-2
hdparm
6.9-3
httpd
2.2.4-4.1
httpd-devel
2.2.4-4.1
httpd-manual
2.2.4-4.1
3.9.2. List of Target Packages
20
initscripts
8.54.1-1
iproute
2.6.20-2
iptables
1.3.8-2
iputils
20070202-3
iscsitarget
0.4.15-1
kbd
1.12-22
kernel-headers
2.6.24-1
kernel-source
2.6.24-1
krb5-devel
1.6.1-2.1
krb5-libs
1.6.1-2.1
less
394-9
libattr
2.4.32-2
libattr-devel
2.4.32-2
libcap
1.10-29
libcap-devel
1.10-29
libpng
1.2.16-1
libpng-devel
1.2.16-1
libsysfs
2.1.0-1
libsysfs-devel
2.1.0-1
libtermcap
2.0.8-46.1
libtermcap-devel
2.0.8-46.1
libtirpc
0.1.7-7_2
libtirpc-devel
0.1.7-7_2
libtool
1.5.22-11
libtool-ltdl
1.5.22-11
libtool-ltdl-devel
1.5.22-11
libusb
0.1.12-7
libusb-devel
0.1.12-7
libuser
0.56.2-1
libuser-devel
0.56.2-1
libxml2
2.6.29-1
logrotate
3.7.5-3.1
lrzsz
0.12.20-22.1
lsof
4.78-5
3.9.2. List of Target Packages
21
ltp
20080131-eldk2
lvm2
2.02.24-1
m4
1.4.8-2
mailcap
2.1.23-1
make
3.81-6
MAKEDEV
3.23-1.2
man
1.6e-3
mdadm
2.6.2-4
microwindows
0.91-2
microwindows-fonts
0.91-1
mingetty
1.07-5.2.2
mktemp
1.5-25
module-init-tools
3.3-0.pre11.1.0
mtd-utils
1.0.1-2
ncompress
4.2.4-49
ncurses
5.6-17
ncurses-devel
5.6-17
net-snmp
5.4-14
net-snmp-devel
5.4-14
net-snmp-libs
5.4-14
net-snmp-utils
5.4-14
net-tools
1.60-82
newt
0.52.6-30
newt-devel
0.52.6-30
nfs-utils
1.1.0-1
ntp
4.2.4p2-1
open-iscsi
2.0-865.15
openldap
2.3.34-3
openldap-devel
2.3.34-3
openssl
0.9.8b-12_2
openssl-devel
0.9.8b-12_2
oprofile
0.9.2-8_2
pam
0.99.7.1-5.1
pam-devel
0.99.7.1-5.1
3.9.2. List of Target Packages
22
passwd
0.74-3
patch
2.5.4-29.2.2
pciutils
2.2.4-3_2
pciutils-devel
2.2.4-3_2
pcmciautils
014-9_2
pcre
7.0-2
pcsc-lite
1.3.3-1.0
pcsc-lite-devel
1.3.3-1.0
pcsc-lite-libs
1.3.3-1.0
perl
5.8.8-18_2
perl-libs
5.8.8-18_2
popt
1.12-1
portmap
4.0-65_2
postgresql
8.2.4-1_2
postgresql-devel
8.2.4-1_2
postgresql-libs
8.2.4-1_2
ppp
2.4.4-7
procps
3.2.7-14
psmisc
22.3-2
python
2.5.1-1
rdate
1.4-6
readline
5.2-4
readline-devel
5.2-4
routed
0.17-12_1
rpcbind
0.1.4-6
rpm
4.4.2-46_2
rpm-build
4.4.2-46_2
rpm-devel
4.4.2-46_2
rpm-libs
4.4.2-46_2
rsh
0.17-40
rsh-server
0.17-40
screen
4.0.3-50
sed
4.1.5-7
SELF
1.0-13
3.9.2. List of Target Packages
23
setup
2.6.4-1_2
shadow-utils
4.0.18.1-15
slang
2.0.7-17
slang-devel
2.0.7-17
smartmontools
5.38-2
strace
4.5.15-1
sysfsutils
2.1.0-1
sysklogd
1.4.2-9
sysvinit
2.86-17
tar
1.15.1-26
tcp_wrappers
7.6-48
tcp_wrappers-devel
7.6-48
tcp_wrappers-libs
7.6-48
telnet
0.17-38
telnet-server
0.17-38
termcap
5.5-1.20060701.1
tftp
0.42-4
tftp-server
0.42-4
thttpd
2.25b-13
time
1.7-29
u-boot
1.3.1-1
udev
106-4.1
unixODBC
2.2.12-2
unzip
5.52-4
util-linux
2.13-0.52_2
vim-common
7.1.12-1
vim-minimal
7.1.12-1
vixie-cron
4.1-82
vsftpd
2.0.5-16_2
which
2.16-8
wireless-tools
28-4
wpa_supplicant
0.5.7-3
wu-ftpd
2.6.2-1
xdd
65.013007-1
3.9.2. List of Target Packages
24
xenomai
2.4.2-1
xinetd
2.3.14-12
zip
2.31-3
zlib
1.2.3-10
zlib-devel
1.2.3-10
Note 1: Not all packages will be installed automatically; for example the boa and thttpd web servers
are mutually exclusive - you will have to remove one package before you can (manually) install the other one.
Note 2: The crosstool 0.43 target package provides the following packages: glibc 2.6,
glibc-common 2.6, glibc-devel 2.6, libstdc++ 4.2.2, libgcj 4.2.2, libgcj-devel
4.2.2 and libstdc++-devel 4.2.2. For more information about the crosstool package please
refer to http://kegel.com/crosstool
Note 3: The Xenomai and gcc-java packages are unavailable in ARM ELDK version.
3.10. Rebuilding the ELDK from Scratch
In this section, you will find instructions on how to build the ELDK from scratch, using the pristine package
sources available on the Internet, and patches, spec files, and build scripts provided on the ELDK source
CD-ROM.
3.10.1. ELDK Build Process Overview
The ELDK uses the Fedora 7 Linux distribution as source code reference. Any modifications to Fedora's
sources the ELDK has introduced are in the form of patches applied by the RPM tool while building the
packages. Also, the ELDK uses modified spec files for its RPM packages. So, the sources of almost every
ELDK package consist of the following parts:
• Fedora pristine sources or
• ELDK source tarball,
• ELDK patches,
• ELDK spec file.
The Fedora pristine sources may be obtained from the Internet, see
http://download.fedora.redhat.com/pub/fedora/linux/core.
The ELDK patches and spec files are available on the ELDK source CD-ROM and from the DENX GIT
repositories. Also, for convenience, the pristine Fedora sources are available here, too.
Please use the following commands to check out a copy of one of the modules:
git-clone git://www.denx.de/git/eldk/module
The following ELDK modules are available:
Module Name
Contents
tarballs
Source tarballs
build
Build tools, patches, and spec files
3.10. Rebuilding the ELDK from Scratch
25
SRPMS
Fedora 7 sources
Then you may switch to a specific release of the ELDK using the "git-checkout" command; for example, to
get the files for ELDK release 4.1, please do the following from the module directory:
git-checkout ELDK_4_2
It must be noted that some of the packages which are included in the ELDK are not included in Fedora.
Examples of such packages are appWeb, microwindows, and wu-ftpd. For these packages tarballs are
provided in the DENX GIT repository.
To facilitate building of the ELDK, a build infrastructure has been developed. The infrastructure is composed
of the following components:
• ELDK_BUILD script
• build.sh script
• cpkgs.lst file
• tpkgs.lst file
• SRPMS.lst file
• tarballs.lst file
The ELDK_BUILD script is the main script of the ELDK build procedure. It is the tool that you would
normally use to build the ELDK from scratch. In the simplest case, the script may be invoked without
arguments, and it will perform all necessary steps to build the ELDK in a fully automated way. You may pass
the following optional arguments to the ELDK_BUILD script:
-a <arch>
target architecture: "arm", "ppc" or "ppc64", defaults to "ppc".
-n <build_name>
an identification string for the build. Defaults to the value based on the build
architecture and current date, and has the following format: <arch>-YYYY-MM-DD
-v <version>
ELDK version string
-u
build the uClibc-based ELDK version (on the platforms and versions where this is
available).
-p <builddir>
Optional build directory. By default, build will place the work files and results in the
current directory.
Warning: The ELDK build scripts rely on standard behaviour of the RPM tool. Make sure you don't use
non-standard settings in your personal ~/.rpmmacros file that might cause conflicts.
build.sh is a supplementary script that is called by ELDK_BUILD to accomplish certain steps of the build.
Refer to section 3.10.3. build.sh Usage below for more details.
The cpkgs.lst and tpkgs.lst files are read by build.sh and must contain lines describing sub-steps of the eldt
and trg build procedure steps. Essentially, the files contain the list of the ELDT and target packages to be
included in the ELDK. The SRPMS.lst file contains the list of the Fedora source RPM packages used during
the ELDK build. The tarballs.lst file contains the list of source tarballs of the packages that are included in the
ELDK but are not present in Fedora 7.
For the ELDK_BUILD script to work correctly, it must be invoked from a certain build environment created
on the host system. The build environment can be either checked out from the DENX GIT repository (see
section 3.10.2. Setting Up ELDK Build Environment below for details) or copied from the ELDK build
environment CD-ROM.
To be more specific, the following diagram outlines the build environment needed for correct operation of the
ELDK_BUILD script:
3.10.1. ELDK Build Process Overview
26
<some_directory>/
build/cross_rpms/<package_name>/SPECS/...
SOURCES/...
target_rpms/<package_name>/SPECS/...
SOURCES/...
install/install.c
Makefile
misc/ELDK_MAKEDEV
ELDK_FIXOWNER
README.html
cpkgs.lst
tpkgs.lst
build.sh
ELDK_BUILD
SRPMS.lst
tarballs.lst
tarballs/....
SRPMS/....
SRPMS-updates/....
In subdirectories of the cross_rpms and target_rpms directories, the sources and RPM spec files of,
respectively, the ELDT and target packages are stored. The install subdirectory contains the sources of the
installation utility which will be built and placed in the root of the ISO image. tarballs directory contains the
source tarballs of the packages that are included in the ELDK but are not present in Fedora 7.
The SRPMS and SRPMS-updates directories may contain the source RPM packages of Fedora 7. The
ELDK_BUILD script looks for a package in the SRPMS directory and then, if the package is not found, in the
SRPMS-updates directory. If some (or all) of the Fedora SRPMs needed for the build are missing in the
directories, the ELDK_BUILD script will download the source RPMs automatically from the Internet.
The ELDK build environment CD-ROM provides a ready-to-use ELDK build environment. Please refer to
section 3.10.2. Setting Up ELDK Build Environment below for detailed instructions on setting up the build
environment.
The ELDK_BUILD script examines the contents of the ELDK_PREFIX environment variable to determine
the root directory of the ELDK build environment. If the variable is not set when the script is invoked, it is
assumed that the root directory of the ELDK build environment is /opt/eldk. To build the ELDK in the
example directory layout given above, you must set and export the ELDK_PREFIX variable
<some_directory> prior to invoking ELDK_BUILD.
After all the build steps are complete, the following subdirectories are created in the ELDK build
environment:
build/<build_name>/work/
build/<build_name>/logs/
build/<build_name>/results/b_cdrom/
results/s_cdrom/
results/d_cdrom/
-
full ELDK environment
build procedure log files
binary cdrom tree, ready for mkisofs
source cdrom tree, ready for mkisofs
debuginfo cdrom tree, ready for mkisofs
On Linux hosts, the binary and source ISO images are created automatically by the ELDK_BUILD script and
placed in the results directory. On Solaris hosts, creating the ISO images is a manual step. Use the contents of
the b_cdrom and s_cdrom directories for the contents of the ISO images.
3.10.1. ELDK Build Process Overview
27
3.10.2. Setting Up ELDK Build Environment
For your convenience, the ELDK build environment CD-ROM provides full ELDK build environment. All
you need to do is copy the contents of the CD-ROM to an empty directory on your host system. Assuming the
ELDK build environment CD-ROM is mounted at /mnt/cdrom, and the empty directory where you want to
create the build environment is named /opt/eldk, use the following commands to create the build environment:
bash$ cd /opt/eldk
bash$ cp -r /mnt/cdrom/* .
These commands will create the directory structure as described in section 3.10.1. ELDK Build Process
Overview above. All necessary scripts and ELDK specific source files will be placed in the build
subdirectory, and the required tarballs can be found in the tarballs subdirectory. In the SRPMS subdirectory,
you will find all the Fedora 7 SRPMS needed to build the ELDK.
Alternatively, you can obtain the ELDK build environment from the DENX GIT repository. Two modules are
provided for check out: build and tarballs. The first one contains the files for the build subdirectory in the
build environment, and the second one contains source tarballs of the packages that are included in the ELDK
but are not present in Fedora 7. To create the ELDK build environment from the DENX GIT repository, use
the following commands (the example below assumes that the root directory of the build environment is
/opt/eldk):
bash$
bash$
bash$
bash$
cd /opt/eldk
git-clone git://www.denx.de/git/eldk/build
git-clone git://www.denx.de/git/eldk/tarballs
git-clone git://www.denx.de/git/eldk/SRPMS
Note: To allow to install the ELDK on as many as possible Linux distributions (including old systems), we
use a Red Hat 7.3 host system for building. Also, Fedora Core 5 is known to work as a build environment.
Other, especially more recent Linux distributions, will most likely have problems. We therefor provide a Red
Hat 7.3 based root file system image than can run in some virtualization environment (like qemu etc.). Here is
an application note with detailed instructions:
http://www.denx.de/wiki/DULG/AN2009_02_EldkReleaseBuildEnvironment
3.10.3. build.sh Usage
If you wish to perform only a part of the ELDK build procedure, for instance to re-build or update a certain
package, it may sometimes be convenient to invoke the build.sh script manually, without the aid of the
ELDK_BUILD script. Please note, however, that this approach is in general discouraged.
The whole build procedure is logically divided into six steps, and the build.sh must be told which of the
build steps to perform. The build steps are defined as follows:
• rpm - build RPM
• eldt - build ELDT packages
• seldt - save ELDT SRPM packages to create a source ISO image later on
• trg - build target packages
• biso - prepare the file tree to create the binary ISO image
• siso - prepare the file tree to create the source ISO image
• diso - prepare the file tree to create the debuginfo ISO image
Further, the eldt and trg build steps are devided into sub-steps, as defined in the cpkgs.lst and tpkgs.lst
3.10.2. Setting Up ELDK Build Environment
28
files (see below for details). You may specify which sub-steps of the build step are to be performed.
The formal syntax for the usage of build.sh is as follows:
bash$ ./build.sh [-a <arch>] [-n <name>] [-p <prefix>] [-r <result>] \
[-w <work>] <step_name> [<sub_step_number>]
-a <arch>
target architecture: "ppc", "ppc64", "arm" or "mips", defaults to "ppc".
-n <build_name>
an identification string for the build. It is used as a name for some directories
created during the build. You may use for example the current date as the build
name.
-p <prefix>
is the name of the directory that contains the build environment. Refer to build
overview above for description of the build environment.
-r <result>
is the name of the directory where the resulting RPMs and SRPMs created on this
step will be placed.
-w <work>
is the name of the directory where the build is performed.
<stepname>
is the name of the build step that is to be performed. Refer to the list of the build
procedure steps above.
<sub_step_number> is an optional parameter which identifies sub-steps of the step which are to be
performed. This is useful when you want to re-build only some specific packages.
The numbers are defined in the cpkgs.lst and tpkgs.lst files discussed below. You
can specify a range of numbers here. For instance, "2 5" means do steps from 2 to
5, while simply "2" means do all steps starting at 2.
Please note that you must never use build.sh to build the ELDK from scratch. For build.sh to work
correctly, the script must be invoked from the build environment after a successful build using the
ELDK_BUILD script. A possible scenario of build.sh usage is such that you have a build environment
with results of a build performed using the ELDK_BUILD script and want to re-build certain ELDT and target
packages, for instance, because you have updated sources of a package or added a new package to the build.
When building the target packages (during the trg buildstep), build.sh examines the contents of the
TARGET_CPU_FAMILY_LIST environment variable, which may contain a list indicating which target CPU
variants the packages must be built for. Possible CPU variants are arm. For example, the command below
rebuilds the target RPM listed in the tpckgs.lst file under the number of 47 (see section 3.10.4. Format of the
cpkgs.lst and tpkgs.lst Files for description of the tpckgs.lst and cpkgs.lst files), for the arm CPU:
bash$ TARGET_CPU_FAMILY_LIST="arm" \
> /opt/eldk/build.sh -a arm \
>
-n 2007-01-21 \
>
-p /opt/eldk/build/arm-2007-01-21 \
>
-r /opt/eldk/build/arm-2007-01-21/results \
>
-w /opt/eldk/build/arm-2007-01-21/work \
>
trg 47 47
Note: If you are going to invoke build.sh to re-build a package that has already been built in the build
environment by the ELDK_BUILD script, then you must first manually uninstall the package from ELDK
installation created by the build procedure under the work directory of the build environment.
Note: It is recommended that you use the build.sh script only at the final stage of adding/updating a
package to the ELDK. For debugging purposes, it is much more convenient and efficient to build both ELDT
and target packages using a working ELDK installation, as described in the sections 3.8.2. Rebuilding Target
Packages and 3.8.3. Rebuilding ELDT Packages above.
3.10.3. build.sh Usage
29
3.10.4. Format of the cpkgs.lst and tpkgs.lst Files
Each line of these files has the following format:
<sub_step_number> <package_name> <spec_file_name> \
<binary_package_name> <package_version>
The ELDK source CD-ROM contains the cpkgs.lst and tpkgs.lst files used to build this version of the ELDK
distribution. Use them as reference if you want to include any additional packages into the ELDK, or remove
unneeded packages.
To add a package to the ELDK you must add a line to either the cpkgs.lst file, if you are adding a ELDT
package, or to the tpkgs.lst file, if it is a target package. Keep in mind that the relative positions of packages in
the cpkgs.lst and tpkgs.lst files (the sub-step numbers) are very important. The build procedure builds the
packages sequentially as defined in the *.lst files and installs the packages in the "work" environment as they
are built. This implies that if a package depends on other packages, those packages must be specified earlier
(with smaller sub-step numbers) in the *.lst files.
Note: For cpkgs.lst, the package_version may be replaced by the special keyword "RHAUX". Such packages
are used as auxiliary when building ELDK 4.2 on non-Fedora hosts. These packages will be built and used
during the build process, but will not be put into the ELDK 4.2 distribution ISO images.
• 4. System Setup
♦ 4.1. Serial Console Access
♦ 4.2. Configuring the "cu" command
♦ 4.3. Configuring the "kermit" command
♦ 4.4. Using the "minicom" program
♦ 4.5. Permission Denied Problems
♦ 4.6. Configuration of a TFTP Server
♦ 4.7. Configuration of a BOOTP / DHCP Server
♦ 4.8. Configuring a NFS Server
4. System Setup
Some tools are needed to install and configure U-Boot and Linux on the target system. Also, especially during
development, you will want to be able to interact with the target system. This section describes how to
configure your host system for this purpose.
4.1. Serial Console Access
To use U-Boot and Linux as a development system and to make full use of all their capabilities you will need
access to a serial console port on your target system. Later, U-Boot and Linux can be configured to allow for
automatic execution without any user interaction.
There are several ways to access the serial console port on your target system, such as using a terminal server,
but the most common way is to attach it to a serial port on your host. Additionally, you will need a terminal
emulation program on your host system, such as cu or kermit.
4. System Setup
30
4.2. Configuring the "cu" command
The cu command is part of the UUCP package and can be used to act as a dial-in terminal. It can also do
simple file transfers, which can be used in U-Boot for image download.
On RedHat systems you can check if the UUCP package is installed as follows:
$ rpm -q uucp
If necessary, install the UUCP package from your distribution media.
To configure cu for use with U-Boot and Linux please make sure that the following entries are present in the
UUCP configuration files; depending on your target configuration the serial port and/or the console baudrate
may be different from the values used in this example: (/dev/ttyS0, 115200 bps, 8N1):
• /etc/uucp/sys:
#
# /dev/ttyS0 at 115200 bps:
#
system
S0@115200
port
serial0_115200
time
any
• /etc/uucp/port:
#
# /dev/ttyS0 at 115200 bps:
#
port
serial0_115200
type
direct
device
/dev/ttyS0
speed
115200
hardflow
false
You can then connect to the serial line using the command
$ cu S0@115200
Connected.
To disconnect, type the escape character '~' followed by '.' at the beginning of a line.
See also: cu(1), info uucp.
4.3. Configuring the "kermit" command
The name kermit stands for a whole family of communications software for serial and network connections.
The fact that it is available for most computers and operating systems makes it especially well suited for our
purposes.
kermit executes the commands in its initialization file, .kermrc, in your home directory before it executes
any other commands, so this can be easily used to customize its behaviour using appropriate initialization
commands. The following settings are recommended for use with U-Boot and Linux:
4.2. Configuring the "cu" command
31
• ~/.kermrc:
set line /dev/ttyS0
set speed 115200
set carrier-watch off
set handshake none
set flow-control none
robust
set file type bin
set file name lit
set rec pack 1000
set send pack 1000
set window 5
This example assumes that you use the first serial port of your host system (/dev/ttyS0) at a baudrate of
115200 to connect to the target's serial console port.
You can then connect to the serial line:
$ kermit -c
Connecting to /dev/ttyS0, speed 115200.
The escape character is Ctrl-\ (ASCII 28, FS)
Type the escape character followed by C to get back,
or followed by ? to see other options.
----------------------------------------------------
Due to licensing conditions you will often find two kermit packages in your GNU/Linux distribution. In
this case you will want to install the ckermit package. The gkermit package is only a command line tool
implementing the kermit transfer protocol.
If you cannot find kermit on the distribution media for your Linux host system, you can download it
from the kermit project home page: http://www.columbia.edu/kermit/
4.4. Using the "minicom" program
minicom is another popular serial communication program. Unfortunately, many users have reported
problems using it with U-Boot and Linux, especially when trying to use it for serial image download. It's use
is therefore discouraged.
4.5. Permission Denied Problems
The terminal emulation program must have write access to the serial port and to any locking files that are used
to prevent concurrent access from other applications. Depending on the used Linux distribution you may have
to make sure that:
• the serial device belongs to the same group as the cu command, and that the permissions of cu have
the setgid bit set
• the kermit belongs to the same group as cu and has the setgid bit set
• the /var/lock directory belongs to the same group as the cu command, and that the write permissions
for the group are set
4.3. Configuring the "kermit" command
32
4.6. Configuration of a TFTP Server
The fastest way to use U-Boot to load a Linux kernel or an application image is file transfer over Ethernet. For
this purpose, U-Boot implements the TFTP protocol (see the tftpboot command in U-Boot).
To enable TFTP support on your host system you must make sure that the TFTP daemon program
/usr/sbin/in.tftpd is installed. On RedHat systems you can verify this by running:
$ rpm -q tftp-server
If necessary, install the TFTP daemon program from your distribution media.
Most Linux distributions disable the TFTP service by default. To enable it for example on RedHat systems,
edit the file /etc/xinetd.d/tftp and remove the line
disable = yes
or change it into a comment line by putting a hash character in front of it:
# default: off
# description: The tftp server serves files using the trivial file transfer
#
protocol. The tftp protocol is often used to boot diskless
#
workstations, download configuration files to network-aware printers,
#
and to start the installation process for some operating systems.
service tftp
{
socket_type
= dgram
protocol
= udp
wait
= yes
user
= root
server
= /usr/sbin/in.tftpd
server_args
= -s /tftpboot
#
disable
= yes
per_source
= 11
cps
= 100 2
}
Also, make sure that the /tftpboot directory exists and is world-readable (permissions at least "dr-xr-xr-x").
4.7. Configuration of a BOOTP / DHCP Server
BOOTP resp. DHCP can be used to automatically pass configuration information to the target. The only
thing the target must "know" about itself is its own Ethernet hardware (MAC) address. The following
command can be used to check if DHCP support is available on your host system:
$ rpm -q dhcp
If necessary, install the DHCP package from your distribution media.
Then you have to create the DHCP configuration file /etc/dhcpd.conf that matches your network setup. The
following example gives you an idea what to do:
subnet 192.168.0.0 netmask 255.255.0.0 {
option routers
192.168.1.1;
option subnet-mask
255.255.0.0;
option domain-name
"local.net";
4.6. Configuration of a TFTP Server
33
option domain-name-servers ns.local.net;
host trgt {
hardware ethernet
fixed-address
option root-path
option host-name
next-server
filename
00:30:BF:01:02:D0;
192.168.20.38;
"/opt/eldk-5.2/armv5te/rootfs";
"m28";
192.168.1.1;
"/tftpboot/duts/m28/uImage";
}
}
With this configuration, the DHCP server will reply to a request from the target with the ethernet address
00:30:BF:01:02:D0 with the following information:
• The target is located in the subnet 192.168.0.0 which uses the netmask 255.255.0.0.
• The target has the hostname m28 and the IP address 192.168.20.38.
• The host with the IP address 192.168.1.1 will provide the boot image for the target and provide
NFS server function in cases when the target mounts it's root filesystem over NFS.
The host listed with the next-server option can be different from the host that is running the
DHCP server.
• The host provides the file /tftpboot/duts/m28/uImage as boot image for the target.
• The target can mount the directory /opt/eldk-5.2/armv5te/rootfs on the NFS server as root filesystem.
4.8. Configuring a NFS Server
For a development environment it is very convenient when the host and the target can share the same files
over the network. The easiest way for such a setup is when the host provides NFS server functionality and
exports a directory that can be mounted from the target as the root filesystem.
Assuming NFS server functionality is already provided by your host, the only configuration that needs to be
added is an entry for your target root directory to your /etc/exports file, for instance like this:
/opt/eldk-5.2/armv5te/rootfs
192.168.0.0/255.255.0.0(rw,no_root_squash,sync)
This line exports the /opt/eldk-5.2/armv5te/rootfs directory with read and write permissions to all hosts on the
192.168.0.0 subnet.
After modifying the /etc/exports file you must make sure the NFS system is notified about the change, for
instance by issuing the command:
# /sbin/service nfs restart
• 5. Das U-Boot
♦ 5.1. Current Versions
♦ 5.2. Unpacking the Source Code
♦ 5.3. Configuration
♦ 5.4. Installation
◊ 5.4.1. Before You Begin
⋅ 5.4.1.1. Installation Requirements
⋅ 5.4.1.2. Board Identification Data
4.7. Configuration of a BOOTP / DHCP Server
34
◊ 5.4.2. Installation Using a BDM/JTAG Debugger
◊ 5.4.3. Installation using U-Boot
♦ 5.5. Tool Installation
♦ 5.6. Initialization
♦ 5.7. Initial Steps
♦ 5.8. The First Power-On
♦ 5.9. U-Boot Command Line Interface
◊ 5.9.1. Information Commands
⋅ 5.9.1.1. bdinfo - print Board Info structure
⋅ 5.9.1.2. coninfo - print console devices and informations
⋅ 5.9.1.3. flinfo - print FLASH memory information
⋅ 5.9.1.4. iminfo - print header information for application image
⋅ 5.9.1.5. help - print online help
◊ 5.9.2. Memory Commands
⋅ 5.9.2.1. base - print or set address offset
⋅ 5.9.2.2. crc32 - checksum calculation
⋅ 5.9.2.3. cmp - memory compare
⋅ 5.9.2.4. cp - memory copy
⋅ 5.9.2.5. md - memory display
⋅ 5.9.2.6. mm - memory modify (auto-incrementing)
⋅ 5.9.2.7. mtest - simple RAM test
⋅ 5.9.2.8. mw - memory write (fill)
⋅ 5.9.2.9. nm - memory modify (constant address)
⋅ 5.9.2.10. loop - infinite loop on address range
◊ 5.9.3. Flash Memory Commands
⋅ 5.9.3.1. cp - memory copy
⋅ 5.9.3.2. flinfo - print FLASH memory information
⋅ 5.9.3.3. erase - erase FLASH memory
⋅ 5.9.3.4. protect - enable or disable FLASH write protection
⋅ 5.9.3.5. mtdparts - define a Linux compatible MTD partition scheme
⋅ 5.9.3.6. UBI Usage in U-Boot
◊ 5.9.4. Execution Control Commands
⋅ 5.9.4.1. source - run script from memory
⋅ 5.9.4.2. bootm - boot application image from memory
⋅ 5.9.4.3. go - start application at address 'addr'
◊ 5.9.5. Download Commands
⋅ 5.9.5.1. bootp - boot image via network using BOOTP/TFTP protocol
⋅ 5.9.5.2. dhcp - invoke DHCP client to obtain IP/boot params
⋅ 5.9.5.3. loadb - load binary file over serial line (kermit mode)
⋅ 5.9.5.4. loads - load S-Record file over serial line
⋅ 5.9.5.5. tftpboot- boot image via network using TFTP protocol
◊ 5.9.6. Environment Variables Commands
⋅ 5.9.6.1. printenv- print environment variables
⋅ 5.9.6.2. saveenv - save environment variables to persistent storage
⋅ 5.9.6.3. setenv - set environment variables
⋅ 5.9.6.4. run - run commands in an environment variable
⋅ 5.9.6.5. bootd - boot default, i.e., run 'bootcmd'
◊ 5.9.7. Flattened Device Tree support
⋅ 5.9.7.1. fdt addr - select FDT to work on
⋅ 5.9.7.2. fdt list - print one level
⋅ 5.9.7.3. fdt print - recursive print
⋅ 5.9.7.4. fdt mknode - create new nodes
⋅ 5.9.7.5. fdt set - set node properties
⋅ 5.9.7.6. fdt rm - remove nodes or properties
4.8. Configuring a NFS Server
35
⋅ 5.9.7.7. fdt move - move FDT blob to new address
⋅ 5.9.7.8. fdt chosen - fixup dynamic info
◊ 5.9.8. Special Commands
⋅ 5.9.8.1. i2c - I2C sub-system
◊ 5.9.9. Storage devices
⋅ 5.9.9.1. MMC devices
⋅ 5.9.9.2. NAND devices
• 5.9.9.2.1. nand bad - show bad block information
• 5.9.9.2.2. nand erase - erase region
• 5.9.9.2.3. nand write - write to NAND device
• 5.9.9.2.4. nand read - read from NAND device
◊ 5.9.10. Miscellaneous Commands
⋅ 5.9.10.1. date - get/set/reset date & time
⋅ 5.9.10.2. echo - echo args to console
⋅ 5.9.10.3. reset - Perform RESET of the CPU
⋅ 5.9.10.4. sleep - delay execution for some time
⋅ 5.9.10.5. version - print monitor version
⋅ 5.9.10.6. ? - alias for 'help'
♦ 5.10. U-Boot Environment Variables
♦ 5.11. U-Boot Scripting Capabilities
♦ 5.12. U-Boot Standalone Applications
◊ 5.12.1. "Hello World" Demo
◊ 5.12.2. Timer Demo
♦ 5.13. U-Boot Image Formats
♦ 5.14. U-Boot Advanced Features
◊ 5.14.1. Boot Count Limit
5. Das U-Boot
5.1. Current Versions
Das U-Boot (or just "U-Boot" for short) is Open Source Firmware for Embedded Power Architecture®,
ARM, MIPS, x86 and other processors. The U-Boot project is hosted by DENX, where you can also find the
project home page: http://www.denx.de/wiki/U-Boot/
The current version of the U-Boot source code can be retrieved from the DENX "git" repository.
You can browse the "git" repositories at http://git.denx.de/
The trees can be accessed through the git, HTTP, and rsync protocols. For example you can use one of the
following commands to create a local clone of one of the source trees:
git clone git://git.denx.de/u-boot.git u-boot/
git clone http://git.denx.de/u-boot.git u-boot/
git clone rsync://git.denx.de/u-boot.git u-boot/
For details please see here.
Official releases of U-Boot are also available through FTP. Compressed tar archives can downloaded from
the directory ftp://ftp.denx.de/pub/u-boot/.
5.1. Current Versions
36
5.2. Unpacking the Source Code
If you use GIT to get a copy of the U-Boot sources, here an example how you get the sources with git:
Note: Included topic DULGData_m28.UBootGetSource does not exist yet
If you used GIT to get a copy of the U-Boot sources, then you can skip this next step since you already have
an unpacked directory tree. If you downloaded a compressed tarball from the DENX FTP server, you can
unpack it as follows:
$
$
$
$
$
$
cd /opt/eldk/usr/src
wget ftp://ftp.denx.de/pub/u-boot/2012.07.tar.bz2
rm -f u-boot
bunzip2 < 2012.07.tar.bz2 | tar xf ln -s 2012.07 u-boot
cd u-boot
5.3. Configuration
After changing to the directory with the U-Boot source code you should make sure that there are no build
results from any previous configurations left:
$ make distclean
The following (model) command configures U-Boot for the m28 board:
$ make m28_config
[marex@pollux]$
And finally we can compile the tools and U-Boot itself:
$ make all
By default the build is performed locally and the objects are saved in the source directory. One of the two
methods can be used to change this behaviour and build U-Boot to some external directory:
1. Add O= to the make command line invocations:
make O=/tmp/build distclean
make O=/tmp/build m28_config
make O=/tmp/build all
Note that if the 'O=output/dir' option is used then it must be used for all invocations of make.
2. Set environment variable BUILD_DIR to point to the desired location:
export BUILD_DIR=/tmp/build
make distclean
make m28_config
make all
Note that the command line "O=" setting overrides the BUILD_DIR environment variable.
5.3. Configuration
37
5.4. Installation
5.4.1. Before You Begin
5.4.1.1. Installation Requirements
The following section assumes that flash memory is used as the storage device for the firmware on your
board. If this is not the case, the following instructions will not work - you will probably have to replace the
storage device (probably ROM or EPROM) on such systems to install or update U-Boot.
5.4.1.2. Board Identification Data
All m28 boards use a serial number for identification purposes. Also, all boards have at least one ethernet
(MAC) address assigned. You may lose your warranty on the board if this data gets lost. Before installing
U-Boot or otherwise changing the software configuration of a board (like erasing some flash memory) you
should make sure that you have all necessary information about such data.
5.4.2. Installation Using a BDM/JTAG Debugger
A fast and simple way to write new data to flash memory is via the use of a debugger or flash programmer
with a BDM or JTAG interface. In cases where there is no running firmware at all (for instance on new
hardware), this is usually the only way to install any software at all.
We use (and highly recommend) the BDI2000/BDI3000 by Abatron .
Other BDM / JTAG debuggers may work too, but how to use them is beyond the scope of this document.
Please see the documentation for the tool you want to use.
Before you can use the BDI2000 you have to configure it. A configuration file that can be used with m28
boards is included in section 13.2. BDI2000 Configuration file
To install a new U-Boot image on your m28 board using a BDI2000, proceed as follows:
Note: Included topic DULGData_m28.InstallUBootUsingBDI2000 does not exist yet
5.4.3. Installation using U-Boot
If U-Boot is already installed and running on your board, you can use these instructions to download another
U-Boot image to replace the current one.
Warning: Before you can install the new image, you have to erase the current one. If anything goes wrong
your board will be dead. It is strongly recommended that:
• you have a backup of the old, working U-Boot image
• you know how to install an image on a virgin system
Proceed as follows:
=> printenv load update
load=echo $update_sd_firmware ; run update_sd_firmware
5.4.3. Installation using U-Boot
38
update=echo done
=> setenv u-boot /tftpboot/duts/m28/u-boot.bin
=> run load update
if mmc rescan ; then if tftp ${update_sd_firmware_filename} ; then setexpr fw_sz ${filesize} / 0x
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename 'duts/m28/u-boot.mx28.sd'.
Load address: 0x42000000
Loading: ###############################
done
Bytes transferred = 446080 (6ce80 hex)
MMC write: dev # 0, block # 2048, count 872 ... 872 blocks write: OK
done
=> reset
resetting ...
U-Boot 2012.07-00471-ge8925d7-dirty (Oct 01 2012 - 18:20:02)
CPU:
Freescale i.MX28 rev1.2 at 454 MHz
BOOT: SSP SD/MMC #0, 3V3
I2C:
ready
DRAM: 256 MiB
NAND: 256 MiB
MMC:
MXS MMC: 0
In:
serial
Out:
serial
Err:
serial
Net:
FEC0 [PRIME], FEC1
Hit any key to stop autoboot: 0
=> version
U-Boot 2012.07-00471-ge8925d7-dirty (Oct 01 2012 - 18:20:02)
arm-linux-gnueabi-gcc (Debian 4.7.2-2) 4.7.2
GNU ld (GNU Binutils for Debian) 2.22
=>
5.5. Tool Installation
U-Boot uses a special image format when loading the Linux kernel or ramdisk or other images. This image
contains (among other things) information about the time of creation, operating system, compression type,
image type, image name and CRC32 checksums.
The tool mkimage is used to create such images or to display the information they contain. When using the
ELDK, the mkimage command is already included with the other ELDK tools.
If you don't use the ELDK then you should install mkimage in some directory that is in your command
search PATH, for instance:
$ cp tools/mkimage /usr/local/bin/
5.6. Initialization
To initialize the U-Boot firmware running on your m28 board, you have to connect a terminal to the board's
serial console port.
5.6. Initialization
39
The default configuration of the console port on the m28 board uses a baudrate of 115200/8N1 (115200 bps, 8
Bit per character, no parity, 1 stop bit, no handshake).
If you are running Linux on your host system we recommend either kermit or cu as terminal emulation
programs. Do not use minicom, since this has caused problems for many users, especially for software
download over the serial port.
For the configuration of your terminal program see section 4.1. Serial Console Access
Make sure that both hardware and software flow control are disabled.
5.7. Initial Steps
In the default configuration, U-Boot operates in an interactive mode which provides a simple command
line-oriented user interface using a serial console on port ttyAMA0.
In the simplest case, this means that U-Boot shows a prompt (default: =>) when it is ready to receive user
input. You then type a command, and press enter. U-Boot will try to run the required action(s), and then
prompt for another command.
To see a list of the available U-Boot commands, you can type help (or simply ?). This will print a list of all
commands that are available in your current configuration. [Please note that U-Boot provides a lot of
configuration options; not all options are available for all processors and boards, and some options might be
simply not selected for your configuration.]
=>
=> hel
With the command help <command> you can get additional information about most commands:
=> help tftpboot
tftpboot - boot image via network using TFTP protocol
Usage:
tftpboot [loadAddress] [[hostIPaddr:]bootfilename]
=> help setenv printenv
setenv - set environment variables
Usage:
setenv name value ...
- set environment variable 'name' to 'value ...'
setenv name
- delete environment variable 'name'
printenv - print environment variables
Usage:
printenv
- print values of all environment variables
printenv name ...
- print value of environment variable 'name'
=>
Most commands can be abbreviated as long as the string remains unambiguous:
=> help printe tftp
printenv - print environment variables
Usage:
printenv
5.7. Initial Steps
40
- print values of all environment variables
printenv name ...
- print value of environment variable 'name'
tftpboot - boot image via network using TFTP protocol
Usage:
tftpboot [loadAddress] [[hostIPaddr:]bootfilename]
=>
5.8. The First Power-On
Note: If you bought your m28 board with U-Boot already installed, you can skip this section since the
manufacturer probably has already performed these steps.
Connect the port labeled ttyAMA0 on your m28 board to the designated serial port of your host, start the
terminal program, and connect the power supply of your m28 board. You should see messages like this:
=>
=> reset
resetting ...
U-Boot 2012.07-00471-ge8925d7-dirty (Oct 01 2012 - 18:20:02)
CPU:
Freescale i.MX28 rev1.2 at 454 MHz
BOOT: SSP SD/MMC #0, 3V3
I2C:
ready
DRAM: 256 MiB
NAND: 256 MiB
MMC:
MXS MMC: 0
In:
serial
Out:
serial
Err:
serial
Net:
FEC0 [PRIME], FEC1
Hit any key to stop autoboot: 0
=>
You can interrupt the "Count-Down" by pressing any key. If you don't you will probably see some (harmless)
error messages because the system has not been initialized yet.
In some cases you may see a message
*** Warning - bad CRC, using default environment
This is harmless and will go away as soon as you have initialized and saved the environment variables.
At first you have to enter the serial number and the ethernet address of your board. Pay special attention here
since these parameters are write protected and cannot be changed once saved (usually this is done by the
manufacturer of the board). To enter the data you have to use the U-Boot command setenv, followed by the
variable name and the data, all separated by white space (blank and/or TAB characters). Use the variable
name serial# for the board ID and/or serial number, and ethaddr for the ethernet address, for instance:
=> setenv serial# DUTS
=> setenv ethaddr !!!!!!FILL_THIS!!!!!!
Can't overwrite "ethaddr"
=>
Use the printenv command to verify that you have entered the correct values:
5.8. The First Power-On
41
=> printenv serial# ethaddr
serial#=DUTS
ethaddr=C0:E5:4E:02:00:00
=>
Please double check that the printed values are correct! You will not be able to correct any errors later! If
there is something wrong, reset the board and restart from the beginning; otherwise you can store the
parameters permanently using the saveenv command:
=> saveenv
Saving Environment to NAND...
Erasing NAND...
Erasing at 0x300000 -- 25% complete.Erasing at 0x320000 -Writing to NAND... done
=>
50% complete.Erasing at 0x340000 --
5.9. U-Boot Command Line Interface
The following section describes the most important commands available in U-Boot. Please note that U-Boot is
highly configurable, so not all of these commands may be available in the configuration of U-Boot installed
on your hardware, or additional commands may exist. You can use the help command to print a list of all
available commands for your configuration.
For most commands, you do not need to type in the full command name; instead it is sufficient to type a few
characters. For instance, help can be abbreviated as h.
The behaviour of some commands depends on the configuration of U-Boot and on the definition of some
variables in your U-Boot environment.
Almost all U-Boot commands expect numbers to be entered in hexadecimal input format. (Exception: for
historical reasons, the sleep command takes it's argument in decimal input format.)
Be careful not to use edit keys besides 'Backspace', as hidden characters in things like environment
variables can be very difficult to find.
5.9.1. Information Commands
5.9.1.1. bdinfo - print Board Info structure
=> help bdinfo
bdinfo - print Board Info structure
Usage:
bdinfo
=>
The bdinfo command (short: bdi) prints the information that U-Boot passes about the board such as
memory addresses and sizes, clock frequencies, MAC address, etc. This information is mainly needed to be
passed to the Linux kernel.
=> bdi
arch_number
boot_params
DRAM bank
-> start
=
=
=
=
0x00000E1D
0x40000100
0x00000000
0x40000000
5.9.1. Information Commands
42
-> size
ethaddr
ip_addr
baudrate
TLB addr
relocaddr
reloc off
irq_sp
sp start
FB base
=>
=
=
=
=
=
=
=
=
=
=
0x10000000
C0:E5:4E:02:00:00
192.168.20.33
115200 bps
0x4FFF0000
0x4FF48000
0x0FF47F00
0x4FB43F68
0x4FB43F58
0x00000000
5.9.1.2. coninfo - print console devices and informations
=> help conin
coninfo - print console devices and information
Usage:
coninfo
=>
The coninfo command (short: conin) displays information about the available console I/O devices.
=> conin
List of available devices:
serial
80000003 SIO stdin stdout stderr
=>
The output contains the device name, flags, and the current usage. For example, the output
serial
80000003 SIO stdin stdout stderr
means that the serial device is a system device (flag 'S') which provides input (flag 'I') and output
(flag 'O') functionality and is currently assigned to the 3 standard I/O streams stdin, stdout and
stderr.
5.9.1.3. flinfo - print FLASH memory information
Note: Included topic DULGData_m28.UBootFlinfoHelp does not exist yet
The command flinfo (short: fli) can be used to get information about the available flash memory (see
Flash Memory Commands below).
Note: Included topic DULGData_m28.UBootFlinfo does not exist yet
5.9.1.4. iminfo - print header information for application
image
=> help iminfo
iminfo - print header information for application image
Usage:
iminfo addr [addr ...]
- print header information for application image starting at
address 'addr' in memory; this includes verification of the
image contents (magic number, header and payload checksums)
=>
5.9.1.1. bdinfo - print Board Info structure
43
iminfo (short: imi) is used to print the header information for images like Linux kernels or ramdisks. It
prints (among other information) the image name, type and size and verifies that the CRC32 checksums stored
within the image are OK.
=> tftp ${ram_ws} ${bootfile}
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename '/tftpboot/duts/m28/uImage'.
Load address: 0x42000000
Loading: #################################################################
#################################################################
####################
done
Bytes transferred = 2191008 (216ea0 hex)
=> imi ${ram_ws}
## Checking Image at 42000000 ...
Legacy image found
Image Name:
Linux-3.6.0-next-20121001-00014Created:
2012-10-02 13:23:40 UTC
Image Type:
ARM Linux Kernel Image (uncompressed)
Data Size:
2190944 Bytes = 2.1 MiB
Load Address: 40008000
Entry Point: 40008000
Verifying Checksum ... OK
=>
Like with many other commands, the exact operation of this command can be controlled by the settings of
some U-Boot environment variables (here: the verify variable). See below for details.
5.9.1.5. help - print online help
=> help help
help - print command description/usage
Usage:
help
- print brief description of all commands
help command ...
- print detailed usage of 'command'
=>
The help command (short: h or ?) prints online help. Without any arguments, it prints a list of all U-Boot
commands that are available in your configuration of U-Boot. You can get detailed information for a specific
command by typing its name as argument to the help command:
Note: Included topic DULGData_m28.UBootProtectHelp does not exist yet
5.9.2. Memory Commands
5.9.2.1. base - print or set address offset
=> help base
base - print or set address offset
Usage:
base
- print address offset for memory commands
base off
- set address offset for memory commands to 'off'
5.9.2. Memory Commands
44
=>
You can use the base command (short: ba) to print or set a "base address" that is used as address offset for
all memory commands; the default value of the base address is 0, so all addresses you enter are used
unmodified. However, when you repeatedly have to access a certain memory region (like the internal memory
of some embedded Power Architecture® processors) it can be very convenient to set the base address to the
start of this area and then use only the offsets:
=> base
Base Address: 0x00000000
=> md 0 0xc
00000000: ea00000e ea00000e
00000010: ea00000e ea00000e
00000020: 4ff48000 4ff48004
=> base 0x42000000
Base Address: 0x42000000
=> md 0 0xc
42000000: 00000001 00000001
42000010: 00000000 00000000
42000020: 00000367 00000000
=>
ea00000e ea00000e
ea00000e ea00000e
4ff48008 4ff4800c
................
................
...O...O...O...O
00000001 00000001
00000001 00000801
00000000 00000000
................
................
g...............
5.9.2.2. crc32 - checksum calculation
The crc32 command (short: crc) can be used to caculate a CRC32 checksum over a range of memory:
=> crc 0x42000004 0x3FC
CRC32 for 42000004 ... 420003ff ==> 1ec64665
=>
When used with 3 arguments, the command stores the calculated checksum at the given address:
=> crc 0x42000004 0x3FC 0x42000000
CRC32 for 42000004 ... 420003ff ==> 1ec64665
=> md 0x42000000 4
42000000: 1ec64665 00000001 00000001 00000001
=>
eF..............
As you can see, the CRC32 checksum was not only printed, but also stored at address 0x100000.
5.9.2.3. cmp - memory compare
=> help cmp
cmp - memory compare
Usage:
cmp [.b, .w, .l] addr1 addr2 count
=>
With the cmp command you can test of the contents of two memory areas is identical or not. The command
will either test the whole area as specified by the 3rd (length) argument, or stop at the first difference.
=> cmp 0x42000000 0x43000000 0x400
Total of 1024 word(s) were the same
=> md 0x42000000 0xc
42000000: 56190527 8daa7c80 dcea6a50
42000010: 00800040 00800040 9de1110f
42000020: 756e694c 2e332d78 2d302e36
=> md 0x43000000 0xc
43000000: 56190527 8daa7c80 dcea6a50
5.9.2.1. base - print or set address offset
606e2100
00020205
7478656e
'..V.|..Pj...!n`
@...@...........
Linux-3.6.0-next
606e2100
'..V.|..Pj...!n`
45
43000010: 00800040 00800040 9de1110f 00020205
43000020: 756e694c 2e332d78 2d302e36 7478656e
=>
@...@...........
Linux-3.6.0-next
Like most memory commands the cmp can access the memory in different sizes: as 32 bit (long word), 16 bit
(word) or 8 bit (byte) data. If invoked just as cmp the default size (32 bit or long words) is used; the same can
be selected explicitely by typing cmp.l instead. If you want to access memory as 16 bit or word data, you
can use the variant cmp.w instead; and to access memory as 8 bit or byte data please use cmp.b.
Please note that the count argument specifies the number of data items to process, i. e. the number of long
words or words or bytes to compare.
=> cmp.l
Total of
=> cmp.w
Total of
=> cmp.b
Total of
=>
0x42000000 0x43000000
1024 word(s) were the
0x42000000 0x43000000
2048 halfword(s) were
0x42000000 0x43000000
4096 byte(s) were the
0x400
same
0x800
the same
0x1000
same
5.9.2.4. cp - memory copy
=> help cp
cp - memory copy
Usage:
cp [.b, .w, .l] source target count
=> help cp
cp - memory copy
Usage:
cp [.b, .w, .l] source target count
=>
The cp is used to copy memory areas.
=> cp 0x42000000 0x43000000 0x10000
=>
The cp understands the type extensions .l, .w and .b :
=> cp.l 0x43000000 0x42000000 0x10000
=> cp.w 0x43000000 0x42000000 0x20000
=> cp.b 0x43000000 0x42000000 0x40000
=>
5.9.2.5. md - memory display
=> help md
md - memory display
Usage:
md [.b, .w, .l] address [# of objects]
=>
The md can be used to display memory contents both as hexadecimal and ASCII data.
=> md 0x42000000
42000000: 56190527 8daa7c80 dcea6a50 606e2100
42000010: 00800040 00800040 9de1110f 00020205
5.9.2.3. cmp - memory compare
'..V.|..Pj...!n`
@...@...........
46
42000020:
=>
42000030:
42000040:
42000050:
=>
756e694c 2e332d78 2d302e36 7478656e
Linux-3.6.0-next
3130322d 30303132 30302d31 2d343130
e1a00000 e1a00000 e1a00000 e1a00000
e1a00000 e1a00000 e1a00000 e1a00000
-20121001-00014................
................
This command, too, can be used with the type extensions .l, .w and .b :
=>
=> md.w 0x42000000
42000000: 0527 5619 7c80 8daa 6a50 dcea 2100 606e
42000010: 0040 0080 0040 0080
@...@...
=> d.b 0x4200000
'..V.|..Pj...!n`
The last displayed memory address and the value of the count argument are remembered, so when you enter
md again without arguments it will automatically continue at the next address, and use the same count again.
=>
=> md.b 0x42000000 0x20
42000000: 27 05 19 56 80 7c aa 8d 50 6a ea dc 00 21 6e 60
42000010: 40 00 80 00 40 00 80 00 0f 11 e1 9d 05 02 02 00
=> d.w 0x42000000
Unknown command 'd.w' - try 'help'
=> md 0x4200000
'..V.|..Pj...!n`
@...@...........
5.9.2.6. mm - memory modify (auto-incrementing)
=>
=> help
The mm is a method to interactively modify memory contents. It will display the address and current contents
and then prompt for user input. If you enter a legal hexadecimal number, this new value will be written to the
address. Then the next address will be prompted. If you don't enter any value and just press ENTER, then the
contents of this address will remain unchanged. The command stops as soon as you enter any data that is not a
hex number (like .):
=>
=>
=> mm 0x42000000
42000000: 56190527 ? 0
42000004: 8daa7c80 ? 0xaabbccdd
42000008: dcea6a50 ? 0x01234567
4200000c: 606e2100 ? .
=> md 0x42000000 0x10
42000000: 00000000 aabbccdd 01234567
42000010: 00800040 00800040 9de1110f
42000020: 756e694c 2e332d78 2d302e36
42000030: 3130322d 30303132 30302d31
=>
606e2100
00020205
7478656e
2d343130
........gE#..!n`
@...@...........
Linux-3.6.0-next
-20121001-00014-
Again this command can be used with the type extensions .l, .w and .b :
=>
=> mm.w 0x42000000
42000000: 0000 ? 0x0101
42000002: 0000 ? 0x0202
42000004: ccdd ? 0x4321
42000006: aabb ? 0x8765
42000008: 4567 ? .
=> md 0x42000000 0x10
42000000: 02020101 87654321 01234567 606e2100
5.9.2.5. md - memory display
....!Ce.gE#..!n`
47
42000010: 00800040 00800040 9de1110f 00020205
42000020: 756e694c 2e332d78 2d302e36 7478656e
42000030: 3130322d 30303132 30302d31 2d343130
=>
=>
=> mm.b 0x42000000
42000000: 01 ? 0x48
42000001: 01 ? 0x65
42000002: 02 ? 0x6c
42000003: 02 ? 0x6c
42000004: 21 ? 0x6f
42000005: 43 ? 0x20
42000006: 65 ? 0x20
42000007: 87 ? 0x20
42000008: 67 ? .
=> md 0x42000000 0x10
42000000: 6c6c6548 2020206f
42000010: 00800040 00800040
42000020: 756e694c 2e332d78
42000030: 3130322d 30303132
=>
01234567
9de1110f
2d302e36
30302d31
606e2100
00020205
7478656e
2d343130
@...@...........
Linux-3.6.0-next
-20121001-00014-
Hello
gE#..!n`
@...@...........
Linux-3.6.0-next
-20121001-00014-
5.9.2.7. mtest - simple RAM test
=> help mtest
mtest - simple RAM read/write test
Usage:
mtest [start [end [pattern [iterations]]]]
=>
The mtest provides a simple memory test.
=>
=> mtest 0x42000000 0x42100000
Pattern 00000000 Writing... Reading...Pattern FFFFFFFF
=>
Writing...
Reading...Pattern 00000001
This tests writes to memory, thus modifying the memory contents. It will fail when applied to ROM or
flash memory.
This command may crash the system when the tested memory range includes areas that are needed for the
operation of the U-Boot firnware (like exception vector code, or U-Boot's internal program code, stack or
heap memory areas).
5.9.2.8. mw - memory write (fill)
=> help mw
mw - memory write (fill)
Usage:
mw [.b, .w, .l] address value [count]
=>
The mw is a way to initialize (fill) memory with some value. When called without a count argument, the value
will be written only to the specified address. When used with a count, then a whole memory areas will be
initialized with this value:
=> md 0x42000000 0x10
42000000: ffffffee ffffffed ffffffec ffffffeb
5.9.2.6. mm - memory modify (auto-incrementing)
................
48
42000010: ffffffea ffffffe9
42000020: ffffffe6 ffffffe5
42000030: ffffffe2 ffffffe1
=> mw 0x42000000 0xaabbccdd
=> md 0x42000000 0x10
42000000: aabbccdd ffffffed
42000010: ffffffea ffffffe9
42000020: ffffffe6 ffffffe5
42000030: ffffffe2 ffffffe1
=> mw 0x42000000 0 6
=> md 0x42000000 0x10
42000000: 00000000 00000000
42000010: 00000000 00000000
42000020: ffffffe6 ffffffe5
42000030: ffffffe2 ffffffe1
=>
ffffffe8 ffffffe7
ffffffe4 ffffffe3
ffffffe0 ffffffdf
................
................
................
ffffffec
ffffffe8
ffffffe4
ffffffe0
ffffffeb
ffffffe7
ffffffe3
ffffffdf
................
................
................
................
00000000
ffffffe8
ffffffe4
ffffffe0
00000000
ffffffe7
ffffffe3
ffffffdf
................
................
................
................
This is another command that accepts the type extensions .l, .w and .b :
=> mw.w 0x42000004 0x1155 6
=> md 0x42000000 0x10
42000000: 00000000 11551155 11551155
42000010: 00000000 00000000 ffffffe8
42000020: ffffffe6 ffffffe5 ffffffe4
42000030: ffffffe2 ffffffe1 ffffffe0
=> mw.b 0x42000007 0xff 7
=> md 0x42000000 0x10
42000000: 00000000 ff551155 ffffffff
42000010: 00000000 00000000 ffffffe8
42000020: ffffffe6 ffffffe5 ffffffe4
42000030: ffffffe2 ffffffe1 ffffffe0
=>
11551155
ffffffe7
ffffffe3
ffffffdf
....U.U.U.U.U.U.
................
................
................
1155ffff
ffffffe7
ffffffe3
ffffffdf
....U.U.......U.
................
................
................
5.9.2.9. nm - memory modify (constant address)
=> help nm
nm - memory modify (constant address)
Usage:
nm [.b, .w, .l] address
=>
The nm command (non-incrementing memory modify) can be used to interactively write different data several
times to the same address. This can be useful for instance to access and modify device registers:
=>
=> nm.b 0x42000000
42000000: 00 ? 0x48
42000000: 48 ? 0x65
42000000: 65 ? 0x6c
42000000: 6c ? 0x6c
42000000: 6c ? 0x6f
42000000: 6f ? .
=> md 0x42000000 8
42000000: 0000006f ff551155 ffffffff 1155ffff
42000010: 00000000 00000000 ffffffe8 ffffffe7
=>
o...U.U.......U.
................
The nm command too accepts the type extensions .l, .w and .b.
5.9.2.8. mw - memory write (fill)
49
5.9.2.10. loop - infinite loop on address range
=> help loop
loop - infinite loop on address range
Usage:
loop [.b, .w, .l] address number_of_objects
=>
The loop command reads in a tight loop from a range of memory. This is intended as a special form of a
memory test, since this command tries to read the memory as fast as possible.
This command will never terminate. There is no way to stop it but to reset the board!
=> loop 100000 8
5.9.3. Flash Memory Commands
5.9.3.1. cp - memory copy
=> help cp
cp - memory copy
Usage:
cp [.b, .w, .l] source target count
=> help cp
cp - memory copy
Usage:
cp [.b, .w, .l] source target count
=>
The cp command "knows" about flash memory areas and will automatically invoke the necessary flash
programming algorithm when the target area is in flash memory.
Note: Included topic DULGData_m28.UBootCpFlash does not exist yet
Writing to flash memory may fail when the target area has not been erased (see erase below), or if it is
write-protected (see protect below).
Note: Included topic DULGData_m28.UBootCpFlashErrors does not exist yet
Remember that the count argument specifies the number of items to copy. If you have a "length" instead (=
byte count) you should use cp.b or you will have to calculate the correct number of items.
5.9.3.2. flinfo - print FLASH memory information
The command flinfo (short: fli) can be used to get information about the available flash memory. The
number of flash banks is printed with information about the size and organization into flash "sectors" or erase
units. For all sectors the start addresses are printed; write-protected sectors are marked as read-only (RO).
Some configurations of U-Boot also mark empty sectors with an (E).
Note: Included topic DULGData_m28.UBootFlinfo does not exist yet
5.9.3. Flash Memory Commands
50
5.9.3.3. erase - erase FLASH memory
Note: Included topic DULGData_m28.UBootEraseHelp does not exist yet
The erase command (short: era) is used to erase the contents of one or more sectors of the flash memory. It
is one of the more complex commands; the help output shows this.
Probably the most frequent usage of this command is to pass the start and end addresses of the area to be
erased:
Note: Included topic DULGData_m28.UBootEraseStartEnd does not exist yet
Note that both the start and end addresses for this command must point exactly at the start resp. end
addresses of flash sectors. Otherwise the command will not be executed.
Another way to select certain areas of the flash memory for the erase command uses the notation of flash
banks and sectors:
Technically speaking, a bank is an area of memory implemented by one or more memory chips that are
connected to the same chip select signal of the CPU, and a flash sector or erase unit is the smallest area that
can be erased in one operation.
For practical purposes it is sufficient to remember that with flash memory a bank is something that eventually
may be erased as a whole in a single operation. This may be more efficient (faster) than erasing the same area
sector by sector.
[It depends on the actual type of flash chips used on the board if such a fast bank erase algorithm exists, and
on the implementation of the flash device driver if is actually used.]
In U-Boot, flash banks are numbered starting with 1, while flash sectors start with 0.
To erase the same flash area as specified using start and end addresses in the example above you could also
type:
Note: Included topic DULGData_m28.UBootEraseSectors does not exist yet
To erase a whole bank of flash memory you can use a command like this one:
Note: Included topic DULGData_m28.UBootEraseBank does not exist yet
Note that a warning message is printed because some write protected sectors exist in this flash bank which
were not erased.
With the command:
Note: Included topic DULGData_m28.UBootEraseAll does not exist yet
the whole flash memory (except for the write-protected sectors) can be erased.
5.9.3.4. protect - enable or disable FLASH write protection
Note: Included topic DULGData_m28.UBootProtectHelp does not exist yet
5.9.3.3. erase - erase FLASH memory
51
The protect command is another complex one. It is used to set certain parts of the flash memory to
read-only mode or to make them writable again. Flash memory that is "protected" (= read-only) cannot be
written (with the cp command) or erased (with the erase command). Protected areas are marked as (RO)
(for "read-only") in the output of the flinfo command:
Note: Included topic DULGData_m28.UBootProtect does not exist yet
The actual level of protection depends on the flash chips used on your hardware, and on the
implementation of the flash device driver for this board. In most cases U-Boot provides just a simple
software-protection, i. e. it prevents you from erasing or overwriting important stuff by accident (like the
U-Boot code itself or U-Boot's environment variables), but it cannot prevent you from circumventing these
restrictions - a nasty user who is loading and running his own flash driver code cannot and will not be stopped
by this mechanism. Also, in most cases this protection is only effective while running U-Boot, i. e. any
operating system will not know about "protected" flash areas and will happily erase these if requested to do
so.
5.9.3.5. mtdparts - define a Linux compatible MTD partition
scheme
U-Boot implements two different approaches to define a MTD partition scheme that can be shared easily with
the linux kernel.
The first one is to define a single, static partition in your board config file, for example:
#undef CONFIG_JFFS2_CMDLINE
#define CONFIG_JFFS2_DEV
#define CONFIG_JFFS2_PART_SIZE
#define CONFIG_JFFS2_PART_SIZE
#define CONFIG_JFFS2_PART_OFFSET
"nor0"
0xFFFFFFFF
0x00100000
0x00000000
/* use whole device */
/* use 1MB */
The second method uses the Linux kernel's mtdparts command line option and dynamic partitioning:
#define CONFIG_CMD_MTDPARTS
#define MTDIDS_DEFAULT
"nor1=zuma-1,nor2=zuma-2"
#define MTDPARTS_DEFAULT
"mtdparts=zuma-1:-(jffs2),zuma-2:-(user)"
Command line of course produces bigger images, and may be inappropriate for some targets, so by default it's
off.
The mtdparts command offers an easy to use and powerful interface to define the contents of the
environment variable of the same name that can be passed as boot argument to the Linux kernel:
=> help mtdparts
mtdparts - define flash/nand partitions
Usage:
mtdparts
- list partition table
mtdparts delall
- delete all partitions
mtdparts del part-id
- delete partition (e.g. part-id = nand0,1)
mtdparts add <mtd-dev> <size>[@<offset>] [<name>] [ro]
- add partition
mtdparts default
- reset partition table to defaults
-----
5.9.3.4. protect - enable or disable FLASH write protection
52
this command uses three environment variables:
'partition' - keeps current partition identifier
partition
<part-id>
:= <part-id>
:= <dev-id>,part_num
'mtdids' - linux kernel mtd device id <-> u-boot device id mapping
mtdids=<idmap>[,<idmap>,...]
<idmap>
<dev-id>
<dev-num>
<mtd-id>
:=
:=
:=
:=
<dev-id>=<mtd-id>
'nand'|'nor'|'onenand'<dev-num>
mtd device number, 0...
unique device tag used by linux kernel to find mtd device (mtd->name)
'mtdparts' - partition list
mtdparts=mtdparts=<mtd-def>[;<mtd-def>...]
<mtd-def>
<mtd-id>
<part-def>
<size>
<offset>
<name>
<ro-flag>
=>
:=
:=
:=
:=
:=
:=
:=
<mtd-id>:<part-def>[,<part-def>...]
unique device tag used by linux kernel to find mtd device (mtd->name)
<size>[@<offset>][<name>][<ro-flag>]
standard linux memsize OR '-' to denote all remaining space
partition start offset within the device
'(' NAME ')'
when set to 'ro' makes partition read-only (not used, passed to kernel)
For example, on the m28 target system the mtdparts command display this information:
=> mtdparts
device nand0 <gpmi-nand>, # parts = 5
#: name
size
0: bootloader
0x00300000
1: environment
0x00080000
2: redundant-environment0x00080000
3: kernel
0x00400000
4: filesystem
0x0f800000
offset
0x00000000
0x00300000
0x00380000
0x00400000
0x00800000
mask_flags
1
0
0
0
0
active partition: nand0,0 - (bootloader) 0x00300000 @ 0x00000000
defaults:
mtdids : nand0=gpmi-nand
mtdparts: mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ke
=>
The partition table printed here obviously differs from the default value for the mtdparts variable printed in
the last line. To verify this, we can check the current content of this variable:
=> print mtdparts
mtdparts=mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ker
=>
and we can see that it exactly matches the partition table printed above.
Then we delete the last 2 partitions ...
=> print mtdparts
mtdparts=mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ker
=> mtdparts del kernel
=> mtdparts del filesystem
5.9.3.5. mtdparts - define a Linux compatible MTD partitionscheme
53
=> mtdparts
device nand0 <gpmi-nand>, # parts = 3
#: name
size
0: bootloader
0x00300000
1: environment
0x00080000
2: redundant-environment0x00080000
offset
0x00000000
0x00300000
0x00380000
mask_flags
1
0
0
active partition: nand0,0 - (bootloader) 0x00300000 @ 0x00000000
defaults:
mtdids : nand0=gpmi-nand
mtdparts: mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ke
=>
... and combine the free space into a singe big partition:
=> print mtdparts
mtdparts=mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ker
=> mtdparts add nand0 - filesystem
=> mtdparts
device nand0 <gpmi-nand>, # parts = 5
#: name
size
0: bootloader
0x00300000
1: environment
0x00080000
2: redundant-environment0x00080000
3: kernel
0x00400000
4: filesystem
0x0f800000
offset
0x00000000
0x00300000
0x00380000
0x00400000
0x00800000
mask_flags
1
0
0
0
0
active partition: nand0,0 - (bootloader) 0x00300000 @ 0x00000000
defaults:
mtdids : nand0=gpmi-nand
mtdparts: mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ke
=>
Now let's switch back to the default settings:
=> mtdparts default
=> mtdparts
device nand0 <gpmi-nand>, # parts = 5
#: name
size
0: bootloader
0x00300000
1: environment
0x00080000
2: redundant-environment0x00080000
3: kernel
0x00400000
4: filesystem
0x0f800000
offset
0x00000000
0x00300000
0x00380000
0x00400000
0x00800000
mask_flags
1
0
0
0
0
active partition: nand0,0 - (bootloader) 0x00300000 @ 0x00000000
defaults:
mtdids : nand0=gpmi-nand
mtdparts: mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ke
=>
5.9.3.6. UBI Usage in U-Boot
As in Linux, UBI access in U-Boot refers to MTD partitions, either through their partition number (like
"nand0,7") or partition name (like "userfs"). So let's first check the partitions on the device:
=> mtdparts
5.9.3.6. UBI Usage in U-Boot
54
device nand0 <gpmi-nand>, # parts = 5
#: name
size
0: bootloader
0x00300000
1: environment
0x00080000
2: redundant-environment0x00080000
3: kernel
0x00400000
4: filesystem
0x0f800000
offset
0x00000000
0x00300000
0x00380000
0x00400000
0x00800000
mask_flags
1
0
0
0
0
active partition: nand0,0 - (bootloader) 0x00300000 @ 0x00000000
defaults:
mtdids : nand0=gpmi-nand
mtdparts: mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ke
=>
U-Boot provides the following command line interface to UBI:
=> help ubi
ubi - ubi commands
Usage:
ubi part [part] [offset]
- Show or set current partition (with optional VID header offset)
ubi info [l[ayout]] - Display volume and ubi layout information
ubi create[vol] volume [size] [type] - create volume name with size
ubi write[vol] address volume size - Write volume from address with size
ubi read[vol] address volume [size] - Read volume to address with size
ubi remove[vol] volume - Remove volume
[Legends]
volume: character name
size: specified in bytes
type: s[tatic] or d[ynamic] (default=dynamic)
=>
To make a UBI device available to U-Boot it needs to be attached. This is done using the "ubi part" command.
If an UBI device exists on the specified MTD partition it will be attached, otherwise a new UBI device will be
created.
* WARNING * "ubi part" will, without any warning, overwrite any existing data and create a new UBI
device if you run it on a partition that does not contain an UBI device yet.
Let's attach the "userfs" partition to UBI:
=> ubi part filesystem 2048
Creating 1 MTD partitions on "nand0":
0x000000800000-0x000010000000 : "mtd=4"
UBI: attaching mtd1 to ubi0
UBI: physical eraseblock size:
131072 bytes (128 KiB)
UBI: logical eraseblock size:
126976 bytes
UBI: smallest flash I/O unit:
2048
UBI: VID header offset:
2048 (aligned 2048)
UBI: data offset:
4096
UBI: empty MTD device detected
UBI: create volume table (copy #1)
UBI: create volume table (copy #2)
UBI: attached mtd1 to ubi0
UBI: MTD device name:
"mtd=4"
UBI: MTD device size:
248 MiB
UBI: number of good PEBs:
1984
UBI: number of bad PEBs:
0
UBI: max. allowed volumes:
128
UBI: wear-leveling threshold:
4096
UBI: number of internal volumes: 1
UBI: number of user volumes:
0
5.9.3.6. UBI Usage in U-Boot
55
UBI:
UBI:
UBI:
UBI:
=>
available PEBs:
1961
total number of reserved PEBs: 23
number of PEBs reserved for bad PEB handling: 19
max/mean erase counter: 1/0
Now that the UBI device is attached, this device can be accessed using the following commands:
ubi
ubi
ubi
ubi
ubi
info
createvol
removevol
read
write
Display volume and ubi layout information
Create UBI volume on UBI device
Remove UBI volume from UBI device
Read data from UBI volume to memory
Write data from memory to UBI volume
For example display volume and ubi layout information with ubi info:
=> ubi info l
UBI: volume information dump:
UBI: vol_id
2147479551
UBI: reserved_pebs
2
UBI: alignment
1
UBI: data_pad
0
UBI: vol_type
3
UBI: name_len
13
UBI: usable_leb_size 126976
UBI: used_ebs
2
UBI: used_bytes
253952
UBI: last_eb_bytes
2
UBI: corrupted
0
UBI: upd_marker
0
UBI: name
layout volume
=>
There is another set of commands to access UBIFS file systems:
ubifsmount - mount UBIFS volume
ubifsls
- list files in a directory
ubifsload - load file from an UBIFS filesystem
First, we have to mount the UBIFS file system:
=> ubifsmount filesystem
UBIFS: mounted UBI device 0, volume 0, name "filesystem"
UBIFS: mounted read-only
UBIFS: file system size:
247603200 bytes (241800 KiB, 236 MiB, 1950 LEBs)
UBIFS: journal size:
9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)
UBIFS: media format:
w4/r0 (latest is w4/r0)
UBIFS: default compressor: LZO
UBIFS: reserved for root: 0 bytes (0 KiB)
=>
after successfully mounted we can access it:
=> ubifsls
30 Tue Oct 02 14:57:09 2012 date_of_creation
30 Tue Oct 02 14:57:11 2012 date_of_modification
16 Tue Oct 02 14:57:08 2012 README
=> ubifsload 0x42000000 date_of_creation
Loading file 'date_of_creation' to addr 0x42000000 with size 30 (0x0000001e)...
Done
=> md 0x42000000
42000000: 20657554 2074634f 31203220 37353a36
Tue Oct 2 16:57
42000010: 2039303a 54534543 31303220 00000a32
:09 CEST 2012...
5.9.3.6. UBI Usage in U-Boot
56
42000020: 00000800 0001f000 0000000e 000007c0
................
42000030: 00800000 00000000 00000005 00000002
................
42000040: 00000001 00000001 00000008 00000100
................
42000050: 00000004 00000001 00000000 00000000
................
42000060: 00000000 00000000 3b9aca00 71b3e5e9
...........;...q
42000070: fa46cc48 aabe65a2 32ec78f1 00000000
H.F..e...x.2....
42000080: 00000000 00000000 00000000 00000000
................
42000090: 00000000 00000000 00000000 00000000
................
420000a0: 00000000 00000000 00000000 00000000
................
420000b0: 00000000 00000000 00000000 00000000
................
420000c0: 00000000 00000000 00000000 00000000
................
420000d0: 00000000 00000000 00000000 00000000
................
420000e0: 00000000 00000000 00000000 00000000
................
420000f0: 00000000 00000000 00000000 00000000
................
=> ubifsload 0x42000000 README
Loading file 'README' to addr 0x42000000 with size 16 (0x00000010)...
Done
=> md 0x42000000
42000000: 7473754a 206e6120 6d617865 0a656c70
Just an example.
42000010: 2039303a 54534543 31303220 00000a32
:09 CEST 2012...
42000020: 00000800 0001f000 0000000e 000007c0
................
42000030: 00800000 00000000 00000005 00000002
................
42000040: 00000001 00000001 00000008 00000100
................
42000050: 00000004 00000001 00000000 00000000
................
42000060: 00000000 00000000 3b9aca00 71b3e5e9
...........;...q
42000070: fa46cc48 aabe65a2 32ec78f1 00000000
H.F..e...x.2....
42000080: 00000000 00000000 00000000 00000000
................
42000090: 00000000 00000000 00000000 00000000
................
420000a0: 00000000 00000000 00000000 00000000
................
420000b0: 00000000 00000000 00000000 00000000
................
420000c0: 00000000 00000000 00000000 00000000
................
420000d0: 00000000 00000000 00000000 00000000
................
420000e0: 00000000 00000000 00000000 00000000
................
420000f0: 00000000 00000000 00000000 00000000
................
=>
* NOTE * In U-Boot, there is no clean way to detach an UBI device; all you can do is to attach a different
device - assuming there is another one; alternatively, you can give a non-existent partition name: this will give
an error, but it will detach the previously attached UBI device:
=> ubi part foobar
incorrect device type in foobar
Partition foobar not found!
=>
Update of an UBI Volume using U-Boot:
=> ubi part filesystem 2048
Unmounting UBIFS volume filesystem!
UBI: mtd1 is detached from ubi0
Creating 1 MTD partitions on "nand0":
0x000000800000-0x000010000000 : "mtd=4"
UBI: attaching mtd1 to ubi0
UBI: physical eraseblock size:
131072 bytes (128 KiB)
UBI: logical eraseblock size:
126976 bytes
UBI: smallest flash I/O unit:
2048
UBI: VID header offset:
2048 (aligned 2048)
UBI: data offset:
4096
UBI: attached mtd1 to ubi0
UBI: MTD device name:
"mtd=4"
UBI: MTD device size:
248 MiB
UBI: number of good PEBs:
1984
UBI: number of bad PEBs:
0
UBI: max. allowed volumes:
128
UBI: wear-leveling threshold:
4096
5.9.3.6. UBI Usage in U-Boot
57
UBI: number of internal volumes: 1
UBI: number of user volumes:
1
UBI: available PEBs:
0
UBI: total number of reserved PEBs: 1984
UBI: number of PEBs reserved for bad PEB handling: 19
UBI: max/mean erase counter: 4/1
=> ubifsmount filesystem
UBIFS: mounted UBI device 0, volume 0, name "filesystem"
UBIFS: mounted read-only
UBIFS: file system size:
247603200 bytes (241800 KiB, 236 MiB, 1950 LEBs)
UBIFS: journal size:
9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)
UBIFS: media format:
w4/r0 (latest is w4/r0)
UBIFS: default compressor: LZO
UBIFS: reserved for root: 0 bytes (0 KiB)
=> ubifsls
30 Tue Oct 02 14:57:09 2012 date_of_creation
30 Tue Oct 02 14:57:11 2012 date_of_modification
16 Tue Oct 02 14:57:08 2012 README
=> tftp 0x42000000 duts/m28/image-filesystem-update.ubifs
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename 'duts/m28/image-filesystem-update.ubifs'.
Load address: 0x42000000
Loading: #################################################################
#########################################################
done
Bytes transferred = 1777664 (1b2000 hex)
=> ubi write 0x42000000 filesystem ${filesize}
1777664 bytes written to volume filesystem
=> ubifsmount filesystem
UBIFS: mounted UBI device 0, volume 0, name "filesystem"
UBIFS: mounted read-only
UBIFS: file system size:
247603200 bytes (241800 KiB, 236 MiB, 1950 LEBs)
UBIFS: journal size:
9023488 bytes (8812 KiB, 8 MiB, 72 LEBs)
UBIFS: media format:
w4/r0 (latest is w4/r0)
UBIFS: default compressor: LZO
UBIFS: reserved for root: 0 bytes (0 KiB)
=> ubifsls
30 Tue Oct 02 14:57:17 2012 date_of_modification.update
30 Tue Oct 02 14:57:15 2012 date_of_creation.update
15 Tue Oct 02 14:57:13 2012 README.update
=>
Useful definitions:
update_data=ubi part data;tftp 40000000 m28/image-data.ubifs;ubi write 40000000 data ${filesize}
update_user=ubi part user;tftp 40000000 m28/image-user.ubifs;ubi write 40000000 user ${filesize}
5.9.4. Execution Control Commands
5.9.4.1. source - run script from memory
=> help source
source - run script from memory
Usage:
source [addr]
- run script starting at addr
- A valid image header must be present
=>
5.9.4. Execution Control Commands
58
With the source command you can run "shell" scripts under U-Boot: You create a U-Boot script image by
simply writing the commands you want to run into a text file; then you will have to use the mkimage tool to
convert this text file into a U-Boot image (using the image type script).
This image can be loaded like any other image file, and with source you can run the commands in such an
image. For instance, the following text file:
[marex@pollux]$ echo
echo Network Configuration:
echo ---------------------echo Target:
printenv ipaddr hostname
echo
echo Server:
printenv serverip rootpath
echo
can be converted into a U-Boot script image using the mkimage command like this:
[marex@pollux]$
Now you can load and execute this script image in U-Boot:
=> tftp 0x42000000 /tftpboot/duts/m28/example.scr
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename '/tftpboot/duts/m28/example.scr'.
Load address: 0x42000000
Loading: #
done
Bytes transferred = 221 (dd hex)
=> imi
## Checking Image at 42000000 ...
Legacy image found
Image Name:
U-Boot example script
Created:
2012-09-05 10:24:29 UTC
Image Type:
PowerPC Linux Script (uncompressed)
Data Size:
157 Bytes = 157 Bytes
Load Address: 00000000
Entry Point: 00000000
Contents:
Image 0: 149 Bytes = 149 Bytes
Verifying Checksum ... OK
=> source 0x42000000
## Executing script at 42000000
Network Configuration:
---------------------Target:
ipaddr=192.168.20.33
hostname=m28
Server:
serverip=192.168.1.1
rootpath=/opt/eldk-5.2.1/armv5te/rootfs-qte-sdk
=>
5.9.4.1. source - run script from memory
59
5.9.4.2. bootm - boot application image from memory
=> help bootm
bootm - boot application image from memory
Usage:
bootm [addr [arg ...]]
- boot application image stored in memory
passing arguments 'arg ...'; when booting a Linux kernel,
'arg' can be the address of an initrd image
When booting a Linux kernel which requires a flat device-tree
a third argument is required which is the address of the
device-tree blob. To boot that kernel without an initrd image,
use a '-' for the second argument. If you do not pass a third
a bd_info struct will be passed instead
Sub-commands to do part of the bootm sequence. The sub-commands must be
issued in the order below (it's ok to not issue all sub-commands):
start [addr [arg ...]]
loados - load OS image
fdt
- relocate flat device tree
cmdline - OS specific command line processing/setup
bdt
- OS specific bd_t processing
prep
- OS specific prep before relocation or go
go
- start OS
=>
The bootm command is used to start operating system images. From the image header it gets information
about the type of the operating system, the file compression method used (if any), the load and entry point
addresses, etc. The command will then load the image to the required memory address, uncompressing it on
the fly if necessary. Depending on the OS it will pass the required boot arguments and start the OS at it's entry
point.
The first argument to bootm is the memory address (in RAM, ROM or flash memory) where the image is
stored, followed by optional arguments that depend on the OS.
For Linux, exactly one optional argument can be passed. If it is present, it is interpreted as the start address
of a initrd ramdisk image (in RAM, ROM or flash memory). In this case the bootm command consists of
three steps: first the Linux kernel image is uncompressed and copied into RAM, then the ramdisk image is
loaded to RAM, and finally controll is passed to the Linux kernel, passing information about the location and
size of the ramdisk image.
To boot a Linux kernel image without a initrd ramdisk image, the following command can be used:
=> bootm ${kernel_addr}
If a ramdisk image shall be used, you can type:
=> bootm ${kernel_addr} ${ramdisk_addr}
Both examples of course imply that the variables used are set to correct addresses for a kernel and a initrd
ramdisk image.
When booting images that have been loaded to RAM (for instance using TFTP download) you have to be
careful that the locations where the (compressed) images were stored do not overlap with the memory needed
to load the uncompressed kernel. For instance, if you load a ramdisk image at a location in low memory, it
may be overwritten when the Linux kernel gets loaded. This will cause undefined system crashes.
5.9.4.2. bootm - boot application image from memory
60
5.9.4.3. go - start application at address 'addr'
=> help go
go - start application at address 'addr'
Usage:
go addr [arg ...]
- start application at address 'addr'
passing 'arg' as arguments
=>
U-Boot has support for so-called standalone applications. These are programs that do not require the complex
environment of an operating system to run. Instead they can be loaded and executed by U-Boot directly,
utilizing U-Boot's service functions like console I/O or malloc() and free().
This can be used to dynamically load and run special extensions to U-Boot like special hardware test routines
or bootstrap code to load an OS image from some filesystem.
The go command is used to start such standalone applications. The optional arguments are passed to the
application without modification. For more informatoin see 5.12. U-Boot Standalone Applications.
5.9.5. Download Commands
5.9.5.1. bootp - boot image via network using BOOTP/TFTP
protocol
=> help bootp
bootp - boot image via network using BOOTP/TFTP protocol
Usage:
bootp [loadAddress] [[hostIPaddr:]bootfilename]
=>
5.9.5.2. dhcp - invoke DHCP client to obtain IP/boot params
=> help dhcp
dhcp - boot image via network using DHCP/TFTP protocol
Usage:
dhcp [loadAddress] [[hostIPaddr:]bootfilename]
=>
5.9.5.3. loadb - load binary file over serial line (kermit mode)
=> help loadb
loadb - load binary file over serial line (kermit mode)
Usage:
loadb [ off ] [ baud ]
- load binary file over serial line with offset 'off' and baudrate 'baud'
=>
With kermit you can download binary data via the serial line. Here we show how to download uImage, the
Linux kernel image. Please make sure, that you have set up kermit as described in section 4.3. Configuring
the "kermit" command and then type:
5.9.5. Download Commands
61
=> loadb 100000
## Ready for binary (kermit) download ...
Ctrl-\c
(Back at denx.denx.de)
---------------------------------------------------C-Kermit 7.0.197, 8 Feb 2000, for Linux
Copyright (C) 1985, 2000,
Trustees of Columbia University in the City of New York.
Type ? or HELP for help.
Kermit> send /bin /tftpboot/pImage
...
Kermit> connect
Connecting to /dev/ttyS0, speed 115200.
The escape character is Ctrl-\ (ASCII 28, FS)
Type the escape character followed by C to get back,
or followed by ? to see other options.
---------------------------------------------------= 550260 Bytes
## Start Addr
= 0x00100000
=> iminfo 100000
## Checking Image at 00100000 ...
Image Name:
Linux-2.4.4
Created:
2002-07-02 22:10:11 UTC
Image Type:
PowerPC Linux Kernel Image (gzip compressed)
Data Size:
550196 Bytes = 537 kB = 0 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
5.9.5.4. loads - load S-Record file over serial line
=> help loads
loads - load S-Record file over serial line
Usage:
loads [ off ]
- load S-Record file over serial line with offset 'off'
=>
5.9.5.5. tftpboot- boot image via network using TFTP
protocol
=> help tftp
tftpboot - boot image via network using TFTP protocol
Usage:
tftpboot [loadAddress] [[hostIPaddr:]bootfilename]
=>
5.9.6. Environment Variables Commands
5.9.6.1. printenv- print environment variables
=> help printenv
printenv - print environment variables
Usage:
printenv
5.9.6. Environment Variables Commands
62
- print values of all environment variables
printenv name ...
- print value of environment variable 'name'
=>
The printenv command prints one, several or all variables of the U-Boot environment. When arguments
are given, these are interpreted as the names of environment variables which will be printed with their values:
=> printenv ipaddr hostname netmask
ipaddr=192.168.20.33
hostname=m28
netmask=255.255.0.0
=>
Without arguments, printenv prints all a list with all variables in the environment and their values, plus
some statistics about the current usage and the total size of the memory available for the environment.
=> printenv
addcons=setenv bootargs ${bootargs} console=${consdev},${baudrate}
addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostname}:${
addmisc=setenv bootargs ${bootargs} ${miscargs}
addmtd=setenv bootargs ${bootargs} ${mtdparts}
addvideo=setenv bootargs ${bootargs} video=imx28-fb
base_offset=44040000
baudrate=115200
bootcmd=run net_nfs
bootdelay=1
bootdev=/dev/mmcblk0p2
bootfile=duts/m28/uImage
cmp_addr_r=0x44000000
cons_opts=console=tty0 console=ttyS0,${baudrate}
consdev=ttyAMA0
eth1addr=C0:E5:4E:02:00:01
ethact=FEC0
ethaddr=C0:E5:4E:02:00:00
ethprime=FEC0
fdt_addr_r=0x41000000
fdt_mmcload=mmc rescan ; fatload mmc 0:2 ${fdt_addr_r} ${fdtfile}
fdt_netload=tftp ${fdt_addr_r} ${fdtfile}
fdtfile=duts/m28/imx28-m28evk.dtb
fileaddr=43000000
filesize=216EA0
gatewayip=192.168.1.254
hostname=m28
ipaddr=192.168.20.33
kernel_addr_r=0x42000000
kernel_mmcload=mmc rescan ; fatload mmc 0:2 ${kernel_addr_r} uImage
kernel_nandload=nand read ${kernel_addr_r} 0 ${kernel_size}
kernel_netload=tftp ${kernel_addr_r} ${bootfile}
kernel_size=280000
load=echo $update_sd_firmware ; run update_sd_firmware
loadaddr=0x42000000
miscargs=fec_mac=${ethaddr} earlyprintk user_debug=29
mmc_mmc=run fdt_mmcload kernel_mmcload mmcargs addip addcons addmtd addmisc;bootm ${kernel_addr_r
mmcargs=setenv bootargs root=${rootdev} rw rootwait
mtddevname=bootloader
mtddevnum=0
mtdids=nand0=gpmi-nand
mtdparts=mtdparts=gpmi-nand:3m(bootloader)ro,512k(environment),512k(redundant-environment),4m(ker
nand_erasesize=20000
nand_mmc=run kernel_nandload mmcargs addip addcons addmtd addmisc;bootm ${kernel_addr_r} - ${fdt_
nand_nfs=run kernel_nandload nfsargs addip addcons addmtd addmisc;bootm ${kernel_addr_r} - ${fdt_
nand_oobsize=40
nand_writesize=800
net_mmc=run fdt_netload kernel_netload mmcargs addip addcons addmtd addmisc;bootm ${kernel_addr_r
5.9.6.1. printenv- print environment variables
63
net_nfs=run fdt_netload kernel_netload nfsargs addip addcons addmtd addmisc;bootm ${kernel_addr_r
net_nfs_nodt=run kernel_netload nfsargs addip addcons addmtd addmisc;bootm ${kernel_addr_r}
netdev=eth0
netmask=255.255.0.0
nfsargs=setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath},v3,tcp
partition=nand0,0
rootdev=/dev/mmcblk0p3
rootpath=/opt/eldk-5.2.1/armv5te/rootfs-qte-sdk
serverip=192.168.1.1
stderr=serial
stdin=serial
stdout=serial
update=echo done
update_nand_count=0x4
update_nand_firmware=if tftp ${update_nand_firmware_filename} ; then run update_nand_get_fcb_size
update_nand_firmware_filename=u-boot.sb
update_nand_firmware_maxsz=0x100000
update_nand_full=if tftp ${update_nand_full_filename} ; then run update_nand_get_fcb_size ; nand
update_nand_full_filename=u-boot.nand
update_nand_get_fcb_size=nand device 0 ; nand info ; setexpr fcb_sz ${update_nand_stride} * ${upd
update_nand_stride=0x40
update_sd_firmware=if mmc rescan ; then if tftp ${update_sd_firmware_filename} ; then setexpr fw_
update_sd_firmware_filename=duts/m28/u-boot.mx28.sd
ver=U-Boot 2012.07-00471-ge8925d7-dirty (Oct 01 2012 - 18:20:02)
videomode=video=ctfb:x:800,y:480,depth:18,mode:0,pclk:30066,le:0,ri:256,up:0,lo:45,hs:1,vs:1,sync
Environment size: 4044/16379 bytes
=>
5.9.6.2. saveenv - save environment variables to persistent
storage
=> help saveenv
saveenv - save environment variables to persistent storage
Usage:
saveenv
=>
All changes you make to the U-Boot environment are made in RAM only. They are lost as soon as you reboot
the system. If you want to make your changes permanent you have to use the saveenv command to write a
copy of the environment settings to persistent storage, from where they are automatically loaded during
startup:
=> saveenv
Saving Environment to NAND...
Erasing NAND...
Erasing at 0x300000 -- 25% complete.Erasing at 0x320000 -Writing to NAND... done
=>
50% complete.Erasing at 0x340000 --
5.9.6.3. setenv - set environment variables
=> help setenv
setenv - set environment variables
Usage:
setenv name value ...
- set environment variable 'name' to 'value ...'
setenv name
- delete environment variable 'name'
=>
5.9.6.2. saveenv - save environment variables to persistent storage
64
To modify the U-Boot environment you have to use the setenv command. When called with exactly one
argument, it will delete any variable of that name from U-Boot's environment, if such a variable exists. Any
storage occupied for such a variable will be automatically reclaimed:
=> setenv foo This is an example value.
=> printenv foo
foo=This is an example value.
=> setenv foo
=> printenv foo
## Error: "foo" not defined
=>
When called with more arguments, the first one will again be the name of the variable, and all following
arguments will (concatenated by single space characters) form the value that gets stored for this variable. New
variables will be automatically created, existing ones overwritten.
=> printenv bar
## Error: "bar" not defined
=> setenv bar This is a new example.
=> printenv bar
bar=This is a new example.
=>
Remember standard shell quoting rules when the value of a variable shall contain characters that have a
special meaning to the command line parser (like the $ character that is used for variable substitution or the
semicolon which separates commands). Use the backslash (\) character to escape such special characters, or
enclose the whole phrase in apstrophes ('). Use "${name}" for variable expansion (see 14.2.17. How the
Command Line Parsing Works for details).
=> setenv cons_opts 'console=tty0 console=ttyS0,${baudrate}'
=> printenv cons_opts
cons_opts=console=tty0 console=ttyS0,${baudrate}
=>
There is no restriction on the characters that can be used in a variable name except the restrictions imposed
by the command line parser (like using backslash for quoting, space and tab characters to separate arguments,
or semicolon and newline to separate commands). Even strange input like "=-/|()+=" is a perfectly legal
variable name in U-Boot.
A common mistake is to write
setenv name=value
instead of
setenv name value
There will be no error message, which lets you believe everything went OK, but it didn't: instead of setting the
variable name to the value value you tried to delete a variable with the name name=value - this is probably
not what you intended! Always remember that name and value have to be separated by space and/or tab
characters!
5.9.6.4. run - run commands in an environment variable
=> help run
run - run commands in an environment variable
Usage:
5.9.6.3. setenv - set environment variables
65
run var [...]
- run the commands in the environment variable(s) 'var'
=>
You can use U-Boot environment variables to store commands and even sequences of commands. To execute
such a command, you use the run command:
=> setenv test echo This is a test\;printenv ipaddr\;echo Done.
=> printenv test
test=echo This is a test;printenv ipaddr;echo Done.
=> run test
This is a test
ipaddr=192.168.20.33
Done.
=>
You can call run with several variables as arguments, in which case these commands will be executed in
sequence:
=> setenv test2 echo This is another Test\;printenv hostname\;echo Done.
=> printenv test test2
test=echo This is a test;printenv ipaddr;echo Done.
test2=echo This is another Test;printenv hostname;echo Done.
=> run test test2
This is a test
ipaddr=192.168.20.33
Done.
This is another Test
hostname=m28
Done.
=>
If a U-Boot variable contains several commands (separated by semicolon), and one of these commands
fails when you "run" this variable, the remaining commands will be executed anyway.
If you execute several variables with one call to run, any failing command will cause "run" to terminate, i.
e. the remaining variables are not executed.
5.9.6.5. bootd - boot default, i.e., run 'bootcmd'
=> help bootd
bootd - boot default, i.e., run 'bootcmd'
Usage:
bootd
=>
The bootd (short: boot) executes the default boot command, i. e. what happens when you don't interrupt
the initial countdown. This is a synonym for the run bootcmd command.
5.9.7. Flattened Device Tree support
U-Boot is capable of quite comprehensive handling of the flattened device tree blob, implemented by the fdt
family of commands:
=> help fdt
fdt - flattened device tree utility commands
Usage:
5.9.7. Flattened Device Tree support
66
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
fdt
addr
<addr> [<length>]
move
<fdt> <newaddr> <length>
resize
print <path> [<prop>]
list
<path> [<prop>]
set
<path> <prop> [<val>]
mknode <path> <node>
rm
<path> [<prop>]
header
bootcpu <id>
memory <addr> <size>
rsvmem print
rsvmem add <addr> <size>
rsvmem delete <index>
chosen [<start> <end>]
-
Set the fdt location to <addr>
Copy the fdt to <addr> and make it active
Resize fdt to size + padding to 4k addr
Recursive print starting at <path>
Print one level starting at <path>
Set <property> [to <val>]
Create a new node after <path>
Delete the node or <property>
Display header info
Set boot cpuid
Add/Update memory node
Show current mem reserves
Add a mem reserve
Delete a mem reserves
Add/update the /chosen branch in the tree
<start>/<end> - initrd start/end addr
NOTE: Dereference aliases by omiting the leading '/', e.g. fdt print ethernet0.
=>
5.9.7.1. fdt addr - select FDT to work on
First, the blob that is to be operated on should be stored in memory, and U-Boot has to be informed about its
location by the fdt addr command. Once this command has been issued, all subsequent fdt handling
commands will use the blob stored at the given address. This address can be changed later on by issuing fdt
addr or fdt move command. Here's how to load the blob into memory and tell U-Boot its location:
=> print fdt_addr_r
fdt_addr_r=0x41000000
=> print fdt_file
fdt_file=/tftpboot/duts/m28/imx28-m28evk.dtb
=> tftp ${fdt_addr_r} ${fdt_file}
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename '/tftpboot/duts/m28/imx28-m28evk.dtb'.
Load address: 0x41000000
Loading: ##
done
Bytes transferred = 16547 (40a3 hex)
=> fdt addr ${fdt_addr_r}
=>
5.9.7.2. fdt list - print one level
Having selected the device tree stored in the blob just loaded, we can inspect its contents. As an FDT usually
is quite extensive, it is easier to get information about the structure by looking at selected levels rather than
full hierarchies. fdt list allows us to do exactly this. Let's have a look at the hierarchy one level below the
cpus node:
=> fdt list /cpus
cpus {
cpu@0 {
};
};
=>
5.9.7.3. fdt print - recursive print
To print a complete subtree we use fdt print. In comparison to the previous example it is obvious that the
whole subtree is printed:
5.9.7.1. fdt addr - select FDT to work on
67
=> fdt print /cpus
cpus {
cpu@0 {
compatible = "arm,arm926ejs";
};
};
=>
5.9.7.4. fdt mknode - create new nodes
fdt mknode can be used to attach a new node to the tree. We will use the fdt list command to verify
that the new node has been created and that it is empty:
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
regulators {
};
sound {
};
};
=> fdt mknode / testnode
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
testnode {
};
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
regulators {
};
sound {
};
};
=> fdt list /testnode
5.9.7.3. fdt print - recursive print
68
testnode {
};
=>
5.9.7.5. fdt set - set node properties
Now, let's create a property at the newly created node; again we'll use fdt list for verification:
=> fdt set /testnode testprop testvalue
=> fdt list /testnode
testnode {
testprop = "testvalue";
};
=>
5.9.7.6. fdt rm - remove nodes or properties
The fdt rm command is used to remove nodes and properties. Let's delete the test property created in the
previous paragraph and verify the results:
=> fdt rm /testnode testprop
=> fdt list /testnode
testnode {
};
=> fdt rm /testnode
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
regulators {
};
sound {
};
};
=>
5.9.7.7. fdt move - move FDT blob to new address
To move the blob from one memory location to another we will use the fdt move command. Besides
moving the blob, it makes the new address the "active" one - similar to fdt addr:
=> fdt move ${fdt_addr_r} 0x42000000
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
5.9.7.4. fdt mknode - create new nodes
69
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
regulators {
};
sound {
};
};
=> fdt mknod / foobar
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
foobar {
};
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
regulators {
};
sound {
};
};
=> fdt addr ${fdt_addr_r}
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
5.9.7.7. fdt move - move FDT blob to new address
70
regulators {
};
sound {
};
};
=>
5.9.7.8. fdt chosen - fixup dynamic info
One of the modifications made by U-Boot to the blob before passing it to the kernel is the addition of the
/chosen node. Linux 2.6 Documentation/powerpc/booting-without-of.txt says that this node is used to store
"some variable environment information, like the arguments, or the default input/output devices." To force
U-Boot to add the /chosen node to the current blob, fdt chosen command can be used. Let's now verify
its operation:
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
regulators {
};
sound {
};
};
=> fdt chosen
=> fdt list /
/ {
#address-cells = <0x1>;
#size-cells = <0x1>;
interrupt-parent = <0x1>;
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
chosen {
};
aliases {
};
memory {
};
cpus {
};
apb@80000000 {
};
ahb@80080000 {
};
regulators {
};
sound {
};
};
5.9.7.8. fdt chosen - fixup dynamic info
71
=> fdt list /chosen
chosen {
};
=>
Note: fdt boardsetup performs board-specific blob updates, most commonly setting clock frequencies,
etc. Discovering its operation is left as an excercise for the reader.
5.9.8. Special Commands
5.9.8.1. i2c - I2C sub-system
=> help i2c
i2c - I2C sub-system
Usage:
i2c crc32 chip address[.0, .1, .2] count - compute CRC32 checksum
i2c loop chip address[.0, .1, .2] [# of objects] - looping read of device
i2c md chip address[.0, .1, .2] [# of objects] - read from I2C device
i2c mm chip address[.0, .1, .2] - write to I2C device (auto-incrementing)
i2c mw chip address[.0, .1, .2] value [count] - write to I2C device (fill)
i2c nm chip address[.0, .1, .2] - write to I2C device (constant address)
i2c probe - show devices on the I2C bus
i2c read chip address[.0, .1, .2] length memaddress - read to memory
i2c reset - re-init the I2C Controller
i2c speed [speed] - show or set I2C bus speed
=>
5.9.9. Storage devices
This chapter introduces commands to work with storage devices, i.e. ATA, CF, SATA, SCSI, USB, NAND,
etc. connected to the board.
5.9.9.1. MMC devices
=> help mmc
mmc - MMC sub system
Usage:
mmc read addr blk# cnt
mmc write addr blk# cnt
mmc erase blk# cnt
mmc rescan
mmc part - lists available partition on current mmc device
mmc dev [dev] [part] - show or set current mmc device [partition]
mmc list - lists available devices
=>
The mmc dev command displays the current device
=> mmc dev
mmc0 is current device
=>
The mmc list command displays the available mmc devices
=> mmc list
5.9.9.1. MMC devices
72
MXS MMC: 0
=>
With the mmc rescan command you can rescan the actual mmc device.
=> mmc rescan
=>
The mmcinfo command displays the information about the actual mmc device
=> mmcinfo
Device: MXS MMC
Manufacturer ID: 1b
OEM: 534d
Name: 00000
Tran Speed: 50000000
Rd Block Len: 512
SD version 2.0
High Capacity: No
Capacity: 1.9 GiB
Bus Width: 4-bit
=>
The mmc part command displays the available partitions on the actual mmc device.
=> mmc part
Partition Map for MMC device 0
Partition
1
2
3
=>
Start Sector
2048
4096
65536
--
Partition Type: DOS
Num Sectors
2048
61440
3620864
Type
53
6
83
You can read data from the mmc with the mmc read command:
=> mmc read 0x42000000 247 10
MMC read: dev # 0,
=> md 0x42000000
42000000: 00000000
42000010: 00000000
42000020: 00000000
42000030: 00000000
42000040: 00000000
42000050: 00000000
42000060: 00000000
42000070: 00000000
42000080: 00000000
42000090: 00000000
420000a0: 00000000
420000b0: 00000000
420000c0: 00000000
420000d0: 00000000
420000e0: 00000000
420000f0: 00000000
=>
block # 583, count 16 ... 16 blocks read: OK
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
You can erase/write data from the mmc with the mmc erase / mmc write commands:
=> mmc read 0x43000000 247 10
MMC read: dev # 0, block # 583, count 16 ... 16 blocks read: OK
5.9.9.1. MMC devices
73
=> md 0x43000000
43000000: 00000000 00000000
43000010: 00000000 00000000
43000020: 00000000 00000000
43000030: 00000000 00000000
43000040: 00000000 00000000
43000050: 00000000 00000000
43000060: 00000000 00000000
43000070: 00000000 00000000
43000080: 00000000 00000000
43000090: 00000000 00000000
430000a0: 00000000 00000000
430000b0: 00000000 00000000
430000c0: 00000000 00000000
430000d0: 00000000 00000000
430000e0: 00000000 00000000
430000f0: 00000000 00000000
=> mw 0x42000000 0xdeadface
=> md 0x42000000
42000000: deadface deadface
42000010: deadface deadface
42000020: deadface deadface
42000030: deadface deadface
42000040: deadface deadface
42000050: deadface deadface
42000060: deadface deadface
42000070: deadface deadface
42000080: deadface deadface
42000090: deadface deadface
420000a0: deadface deadface
420000b0: deadface deadface
420000c0: deadface deadface
420000d0: deadface deadface
420000e0: deadface deadface
420000f0: deadface deadface
=> mmc erase 247 10
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
1000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
deadface
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
MMC erase: dev # 0, block # 583, count 16 ... 16 blocks erase: OK
=> mmc write 0x42000000 247 10
MMC write: dev # 0, block # 583, count 16 ... 16 blocks write: OK
=> mw 0x42000000 0x0 1000
=> mmc read 0x42000000 247 10
MMC read: dev # 0, block # 583, count 16 ... 16 blocks read: OK
=> md 0x42000000
42000000: deadface deadface deadface deadface
................
42000010: deadface deadface deadface deadface
................
42000020: deadface deadface deadface deadface
................
42000030: deadface deadface deadface deadface
................
42000040: deadface deadface deadface deadface
................
42000050: deadface deadface deadface deadface
................
42000060: deadface deadface deadface deadface
................
42000070: deadface deadface deadface deadface
................
42000080: deadface deadface deadface deadface
................
42000090: deadface deadface deadface deadface
................
420000a0: deadface deadface deadface deadface
................
420000b0: deadface deadface deadface deadface
................
420000c0: deadface deadface deadface deadface
................
420000d0: deadface deadface deadface deadface
................
420000e0: deadface deadface deadface deadface
................
420000f0: deadface deadface deadface deadface
................
=> mmc erase 247 10
MMC erase: dev # 0, block # 583, count 16 ... 16 blocks erase: OK
=> mmc write 0x43000000 247 10
5.9.9.1. MMC devices
74
MMC write: dev # 0, block # 583, count 16 ... 16 blocks write: OK
=> mmc read 0x42000000 247 10
MMC read: dev # 0,
=> md 0x42000000
42000000: 00000000
42000010: 00000000
42000020: 00000000
42000030: 00000000
42000040: 00000000
42000050: 00000000
42000060: 00000000
42000070: 00000000
42000080: 00000000
42000090: 00000000
420000a0: 00000000
420000b0: 00000000
420000c0: 00000000
420000d0: 00000000
420000e0: 00000000
420000f0: 00000000
=>
block # 583, count 16 ... 16 blocks read: OK
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
................
if you have a dos partition on the device, you can list the content with:
=> fatls mmc 0:2 /
2340744
uimage
5410
env.txt
1152054
img1.bmp
1152054
img.bmp
233738
slide-1.bmp
1152054
slide-2.bmp
1152054
slide-3.bmp
1152054
slide-4.bmp
1152054
slide-5.bmp
1152054
slide-6.bmp
1152054
slide-7.bmp
1152054
slide-8.bmp
3754
env.txt.old
29
date_of_creation
29
date_of_modification
1024
random.hex
16 file(s), 0 dir(s)
=>
and load a file in RAM with:
=> fatload mmc 0:2 0x42000000 date_of_creation
reading date_of_creation
29 bytes read
=> md 0x42000000
42000000: 20657554
42000010: 2035353a
42000020: 00000000
42000030: 00000000
42000040: 00000000
42000050: 00000000
42000060: 00000000
42000070: 00000000
42000080: 00000000
42000090: 00000000
420000a0: 00000000
420000b0: 00000000
2074634f
20435455
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
5.9.9.1. MMC devices
31203220
32313032
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
34343a35
0000000a
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
Tue Oct 2 15:44
:55 UTC 2012....
................
................
................
................
................
................
................
................
................
................
75
420000c0:
420000d0:
420000e0:
420000f0:
=>
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
00000000
................
................
................
................
5.9.9.2. NAND devices
U-Boot allows us to directly work with NAND devices attached directly or through a NAND controller. The
commands are grouped under the nand subsystem:
=> help nand
nand - NAND sub-system
Usage:
nand info - show available NAND devices
nand device [dev] - show or set current device
nand read - addr off|partition size
nand write - addr off|partition size
read/write 'size' bytes starting at offset 'off'
to/from memory address 'addr', skipping bad blocks.
nand read.raw - addr off|partition [count]
nand write.raw - addr off|partition [count]
Use read.raw/write.raw to avoid ECC and access the flash as-is.
nand erase[.spread] [clean] off size - erase 'size' bytes from offset 'off'
With '.spread', erase enough for given file size, otherwise,
'size' includes skipped bad blocks.
nand erase.part [clean] partition - erase entire mtd partition'
nand erase.chip [clean] - erase entire chip'
nand bad - show bad blocks
nand dump[.oob] off - dump page
nand scrub [-y] off size | scrub.part partition | scrub.chip
really clean NAND erasing bad blocks (UNSAFE)
nand markbad off [...] - mark bad block(s) at offset (UNSAFE)
nand biterr off - make a bit error at offset (UNSAFE)
=>
5.9.9.2.1. nand bad - show bad block information
As NAND devices can develop bad blocks over their lifetime and usually even are delivered with bad blocks
already, the NAND commands need to be aware of this fact. Getting information of the current bad block list
is easy:
=> nand bad
Device 0 bad blocks:
=>
5.9.9.2.2. nand erase - erase region
Ensuring that the NAND device functions properly, we will use the basic commands to construct a testpattern
in memory, write that to the device, of course erasing it first, and read the data back. A final comparison will
show if all data was transferred correctly.
We begin be erasing 64k at the start of the NAND device:
=> nand erase 0x00400000 0x10000
5.9.9.2. NAND devices
76
NAND erase: device 0 offset 0x400000, size 0x10000
Erasing at 0x400000 -- 100% complete.
OK
=>
5.9.9.2.3. nand write - write to NAND device
Let's create a testpattern in memory and write that to the previously erased NAND area:
=> mw 0x42000000 0x55aa55aa 0x4000
=> nand write 0x42000000 0x00400000 0x10000
NAND write: device 0 offset 0x400000, size 0x10000
65536 bytes written: OK
=>
5.9.9.2.4. nand read - read from NAND device
As everything worked ok, we ensure everything was fine by transferring the data to a different location in
RAM and check this against the original written content:
=> nand read 0x43000000 0x00400000 0x10000
NAND read: device 0 offset 0x400000, size 0x10000
65536 bytes read: OK
=> md 0x43000000
43000000: 55aa55aa 55aa55aa 55aa55aa 55aa55aa
.U.U.U.U.U.U.U.U
43000010: 55aa55aa 55aa55aa 55aa55aa 55aa55aa
.U.U.U.U.U.U.U.U
=> cmp 0x42000000 0x43000000 0x4000
Total of 16384 word(s) were the same
=>
5.9.10. Miscellaneous Commands
5.9.10.1. date - get/set/reset date & time
=> help date
date - get/set/reset date & time
Usage:
date [MMDDhhmm[[CC]YY][.ss]]
date reset
- without arguments: print date & time
- with numeric argument: set the system date & time
- with 'reset' argument: reset the RTC
=>
The date command is used to display the current time in a standard format, or to set the system date. On
some systems it can also be used to reset (initialize) the system clock:
=> date reset
Reset RTC...
Date: 1970-01-01 (Thursday)
=> date 100216462012
Date: 2012-10-02 (Tuesday)
=> date
Date: 2012-10-02 (Tuesday)
=>
Time:
0:00:00
Time: 16:46:00
Time: 16:46:00
5.9.10. Miscellaneous Commands
77
5.9.10.2. echo - echo args to console
=> help echo
echo - echo args to console
Usage:
echo [args..]
- echo args to console; \c suppresses newline
=>
The echo command echoes the arguments to the console:
=> echo The quick brown fox jumped over the lazy dog.
The quick brown fox jumped over the lazy dog.
=>
5.9.10.3. reset - Perform RESET of the CPU
=> help reset
reset - Perform RESET of the CPU
Usage:
reset
=>
The reset command reboots the system.
=>
=> reset
resetting ...
U-Boot 2012.07-00471-ge8925d7-dirty (Oct 01 2012 - 18:20:02)
CPU:
Freescale i.MX28 rev1.2 at 454 MHz
BOOT: SSP SD/MMC #0, 3V3
I2C:
ready
DRAM: 256 MiB
NAND: 256 MiB
MMC:
MXS MMC: 0
In:
serial
Out:
serial
Err:
serial
Net:
FEC0 [PRIME], FEC1
Hit any key to stop autoboot: 0
=>
5.9.10.4. sleep - delay execution for some time
=> help sleep
sleep - delay execution for some time
Usage:
sleep N
- delay execution for N seconds (N is _decimal_ !!!)
=>
The sleep command pauses execution for the number of seconds given as the argument:
=> sleep 5
=>
5.9.10.2. echo - echo args to console
78
5.9.10.5. version - print monitor version
=> help version
version - print monitor, compiler and linker version
Usage:
version
=>
You can print the version and build date of the U-Boot image running on your system using the version
command (short: vers):
=> version
U-Boot 2012.07-00471-ge8925d7-dirty (Oct 01 2012 - 18:20:02)
arm-linux-gnueabi-gcc (Debian 4.7.2-2) 4.7.2
GNU ld (GNU Binutils for Debian) 2.22
=>
5.9.10.6. ? - alias for 'help'
You can use ? as a short form for the help command (see description above).
5.10. U-Boot Environment Variables
The U-Boot environment is a block of memory that is kept on persistent storage and copied to RAM when
U-Boot starts. It is used to store environment variables which can be used to configure the system. The
environment is protected by a CRC32 checksum.
This section lists the most important environment variables, some of which have a special meaning to U-Boot.
You can use these variables to configure the behaviour of U-Boot to your liking.
• autoload: if set to "no" (or any string beginning with 'n'), the rarpb, bootp or dhcp commands
will perform only a configuration lookup from the BOOTP / DHCP server, but not try to load any
image using TFTP.
• autostart: if set to "yes", an image loaded using the rarpb, bootp, dhcp, tftp, disk, or
docb commands will be automatically started (by internally calling the bootm command).
• baudrate: a decimal number that selects the console baudrate (in bps). Only a predefined list of
baudrate settings is available.
When you change the baudrate (using the "setenv baudrate ..." command), U-Boot will switch the
baudrate of the console terminal and wait for a newline which must be entered with the new speed
setting. This is to make sure you can actually type at the new speed. If this fails, you have to reset the
board (which will operate at the old speed since you were not able to saveenv the new settings.)
If no "baudrate" variable is defined, the default baudrate of 115200 is used.
• bootargs: The contents of this variable are passed to the Linux kernel as boot arguments (aka
"command line").
• bootcmd: This variable defines a command string that is automatically executed when the initial
countdown is not interrupted.
This command is only executed when the variable bootdelay is also defined!
5.10. U-Boot Environment Variables
79
• bootdelay: After reset, U-Boot will wait this number of seconds before it executes the contents of
the bootcmd variable. During this time a countdown is printed, which can be interrupted by pressing
any key.
Set this variable to 0 boot without delay. Be careful: depending on the contents of your bootcmd
variable, this can prevent you from entering interactive commands again forever!
Set this variable to -1 to disable autoboot.
• bootfile: name of the default image to load with TFTP
• cpuclk: (Only with MPC859 / MPC866 / MPC885 processors) On some processors, the CPU clock
frequency can be adjusted by the user (for example to optimize performance versus power
dissipation). On such systems the cpuclk variable can be set to the desired CPU clock value, in
MHz. If the cpuclk variable exists and its value is within the compile-time defined limits
(CFG_866_CPUCLK_MIN and CFG_866_CPUCLK_MAX = minimum resp. maximum allowed CPU
clock), then the specified value is used. Otherwise, the default CPU clock value is set.
• ethaddr: Ethernet MAC address for first/only ethernet interface (= eth0 in Linux).
This variable can be set only once (usually during manufacturing of the board). U-Boot refuses to
delete or overwrite this variable once it has been set.
• eth1addr: Ethernet MAC address for second ethernet interface (= eth1 in Linux).
• eth2addr: Ethernet MAC address for third ethernet interface (= eth2 in Linux).
...
• initrd_high: used to restrict positioning of initrd ramdisk images:
If this variable is not set, initrd images will be copied to the highest possible address in RAM; this is
usually what you want since it allows for maximum initrd size. If for some reason you want to make
sure that the initrd image is loaded below the CFG_BOOTMAPSZ limit, you can set this environment
variable to a value of "no" or "off" or "0". Alternatively, you can set it to a maximum upper address to
use (U-Boot will still check that it does not overwrite the U-Boot stack and data).
For instance, when you have a system with 16 MB RAM, and want to reserve 4 MB from use by
Linux, you can do this by adding "mem=12M" to the value of the "bootargs" variable. However, now
you must make sure that the initrd image is placed in the first 12 MB as well - this can be done with
=> setenv initrd_high 00c00000
Setting initrd_high to the highest possible address in your system (0xFFFFFFFF) prevents U-Boot from
copying the image to RAM at all. This allows for faster boot times, but requires a Linux kernel with zero-copy
ramdisk support.
• ipaddr: IP address; needed for tftp command
• loadaddr: Default load address for commands like tftp or loads.
• loads_echo: If set to 1, all characters received during a serial download (using the loads
command) are echoed back. This might be needed by some terminal emulations (like cu), but may as
well just take time on others.
• mtdparts: This variable (usually defined using the mtdparts command) allows to share a common
MTD partition scheme between U-Boot and the Linux kernel.
• pram: If the "Protected RAM" feature is enabled in your board's configuration, this variable can be
defined to enable the reservation of such "protected RAM", i. e. RAM which is not overwritten by
5.10. U-Boot Environment Variables
80
U-Boot. Define this variable to hold the number of kB you want to reserve for pRAM. Note that the
board info structure will still show the full amount of RAM. If pRAM is reserved, a new environment
variable "mem" will automatically be defined to hold the amount of remaining RAM in a form that
can be passed as boot argument to Linux, for instance like that:
=> setenv bootargs ${bootargs} mem=\${mem}
=> saveenv
This way you can tell Linux not to use this memory, either, which results in a memory region that will not be
affected by reboots.
• serverip: TFTP server IP address; needed for tftp command.
• serial#: contains hardware identification information such as type string and/or serial number.
This variable can be set only once (usually during manufacturing of the board). U-Boot refuses to
delete or overwrite this variable once it hass been set.
• silent: If the configuration option CONFIG_SILENT_CONSOLE has been enabled for your board,
setting this variable to any value will suppress all console messages. Please see
doc/README.silent for details.
• verify: If set to n or no disables the checksum calculation over the complete image in the bootm
command to trade speed for safety in the boot process. Note that the header checksum is still verified.
The following environment variables may be used and automatically updated by the network boot commands
(bootp, dhcp, or tftp), depending the information provided by your boot server:
• bootfile: see above
• dnsip: IP address of your Domain Name Server
• gatewayip: IP address of the Gateway (Router) to use
• hostname: Target hostname
• ipaddr: see above
• netmask: Subnet Mask
• rootpath: Pathname of the root filesystem on the NFS server
• serverip: see above
• filesize: Size (as hex number in bytes) of the file downloaded using the last bootp, dhcp, or
tftp command.
5.11. U-Boot Scripting Capabilities
U-Boot allows to store commands or command sequences in a plain text file. Using the mkimage tool you
can then convert this file into a script image which can be executed using U-Boot's autoscr command.
For example, assume that you will have to run the following sequence of commands on many boards, so you
store them in a text file, say "setenv-commands":
bash$ cat setenv-commands
setenv loadaddr 00200000
echo ===== U-Boot settings =====
setenv u-boot /tftpboot/TQM860L/u-boot.bin
setenv u-boot_addr 40000000
setenv load_u-boot 'tftp ${loadaddr} ${u-boot}'
setenv install_u-boot 'protect off ${u-boot_addr} +${filesize};era ${u-boot_addr} +${filesize};cp
setenv update_u-boot run load_u-boot install_u-boot
5.11. U-Boot Scripting Capabilities
81
echo ===== Linux Kernel settings =====
setenv bootfile /tftpboot/TQM860L/uImage
setenv kernel_addr 40040000
setenv load_kernel 'tftp ${loadaddr} ${bootfile};'
setenv install_kernel 'era ${kernel_addr} +${filesize};cp.b ${loadaddr} ${kernel_addr} ${filesize
setenv update_kernel run load_kernel install_kernel
echo ===== Ramdisk settings =====
setenv ramdisk /tftpboot/TQM860L/uRamdisk
setenv ramdisk_addr 40100000
setenv load_ramdisk 'tftp ${loadaddr} ${ramdisk};'
setenv install_ramdisk 'era ${ramdisk_addr} +${filesize};cp.b ${loadaddr} ${ramdisk_addr} ${files
setenv update_ramdisk run load_ramdisk install_ramdisk
echo ===== Save new definitions =====
saveenv
bash$
To convert the text file into a script image for U-Boot, you have to use the mkimage tool as follows:
bash$ mkimage
Image Name:
Created:
Image Type:
Data Size:
Load Address:
Entry Point:
Contents:
Image 0:
bash$
-T script -C none -n 'Demo Script File' -d setenv-commands setenv.img
Demo Script File
Mon Jun 6 13:33:14 2005
PowerPC Linux Script (uncompressed)
1147 Bytes = 1.12 kB = 0.00 MB
0x00000000
0x00000000
1139 Bytes =
1 kB = 0 MB
On the target, you can download this image as usual (for example, using the "tftp" command). Use the
"autoscr" command to execute it:
=> tftp 100000 /tftpboot/TQM860L/setenv.img
Using FEC ETHERNET device
TFTP from server 192.168.3.1; our IP address is 192.168.3.80
Filename '/tftpboot/TQM860L/setenv.img'.
Load address: 0x100000
Loading: #
done
Bytes transferred = 1211 (4bb hex)
=> imi 100000
## Checking Image at 00100000 ...
Image Name:
Demo Script File
Created:
2005-06-06 11:33:14 UTC
Image Type:
PowerPC Linux Script (uncompressed)
Data Size:
1147 Bytes = 1.1 kB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
=> autoscr 100000
## Executing script at 00100000
===== U-Boot settings =====
===== Linux Kernel settings =====
===== Ramdisk settings =====
===== Save new definitions =====
Saving Environment to Flash...
Un-Protected 1 sectors
Un-Protected 1 sectors
Erasing Flash...
. done
Erased 1 sectors
Writing to Flash... done
Protected 1 sectors
Protected 1 sectors
5.11. U-Boot Scripting Capabilities
82
=>
Hint: maximum flexibility can be achieved if you are using the Hush shell as command interpreter in
U-Boot; see section 14.2.17. How the Command Line Parsing Works
5.12. U-Boot Standalone Applications
U-Boot supports "standalone" applications, which are loaded dynamically; these applications can have access
to the U-Boot console I/O functions, memory allocation and interrupt services.
A couple of simple examples are included with the U-Boot source code:
5.12.1. "Hello World" Demo
examples/hello_world.c contains a small "Hello World" Demo application; it is automatically compiled when
you build U-Boot. It's configured to run at address 0x00040004, so you can play with it like that:
=> loads
## Ready for S-Record download ...
~>examples/hello_world.srec
1 2 3 4 5 6 7 8 9 10 11 ...
[file transfer complete]
[connected]
## Start Addr = 0x00040004
=> go 40004 Hello World! This is a test.
## Starting application at 0x00040004 ...
Hello World
argc = 7
argv[0] = "40004"
argv[1] = "Hello"
argv[2] = "World!"
argv[3] = "This"
argv[4] = "is"
argv[5] = "a"
argv[6] = "test."
argv[7] = ""
Hit any key to exit ...
## Application terminated, rc = 0x0
Alternatively, you can of course use TFTP to download the image over the network. In this case the binary
image (hello_world.bin) is used.
Note that the entry point of the program is at offset 0x0004 from the start of file, i. e. the download address
and the entry point address differ by four bytes.
=> tftp 40000 /tftpboot/hello_world.bin
...
=> go 40004 This is another test.
## Starting application at 0x00040004 ...
Hello World
argc = 5
argv[0] = "40004"
argv[1] = "This"
argv[2] = "is"
argv[3] = "another"
argv[4] = "test."
argv[5] = ""
Hit any key to exit ...
5.12. U-Boot Standalone Applications
83
## Application terminated, rc = 0x0
5.12.2. Timer Demo
This example is only available on MPC8xx CPUs.
5.13. U-Boot Image Formats
U-Boot operates on "image" files which can be basically anything, preceeded by a special header; see the
definitions in include/image.h for details; basically, the header defines the following image properties:
• Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD, 4.4BSD, Linux, SVR4, Esix,
Solaris, Irix, SCO, Dell, NCR, LynxOS, pSOS, QNX, RTEMS, U-Boot, ARTOS, Unity OS, Integrity;
Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, ARTOS, Unity OS, Integrity).
• Target CPU Architecture (Provisions for Alpha, ARM, AVR32, BlackFin, IA64, M68K, Microblaze,
MIPS, MIPS64, NIOS, NIOS2, Power Architecture®, IBM S390, SuperH, Sparc, Sparc 64 Bit, Intel
x86; Currently supported: ARM, AVR32, BlackFin, M68K, Microblaze, MIPS, MIPS64, NIOS,
NIOS2, Power Architecture®, SuperH, Sparc, Sparc 64 Bit, Intel x86).
• Compression Type (Provisions for uncompressed, gzip, bzip2, lzo; Currently supported:
uncompressed, gzip, bzip2, lzo).
• Load Address
• Entry Point
• Image Name
• Image Timestamp
The header is marked by a special Magic Number, and both the header and the data portions of the image are
secured against corruption by CRC32 checksums.
5.14. U-Boot Advanced Features
5.14.1. Boot Count Limit
The Open Source Development Labs Carrier Grade Linux Requirements Definition version 2.0
(http://www.osdl.org/docs/carrier_grade_linux_requirements_definition___version_20_final_public_draft.pdf)
contains the following requirement definition (ID PLT.4.0, p. 44):
CGL shall provide support for detecting a repeating reboot cycle due to recurring failures and will go to an
offline state if this occurs.
This feature is available in U-Boot if you enable the CONFIG_BOOTCOUNT_LIMIT configuration option.
The implementation uses the following environment variables:
bootcount:
5.14.1. Boot Count Limit
84
This variable will be automatically created if it does not exist, and it will be updated at each reset of
the processor. After a power-on reset, it will be initialized with 1, and each reboot will increment the
value by 1.
bootlimit:
If this variable exists, its contents are taken as the maximum number of reboot cycles allowed.
altbootcmd:
If, after a reboot, the new value of bootcount exceeds the value of bootlimit, then instead of
the standard boot action (executing the contents of bootcmd) an alternate boot action will be
performed, and the contents of altbootcmd will be executed.
If the variable bootlimit is not defined in the environment, the Boot Count Limit feature is disabled. If it is
enabled, but altbootcmd is not defined, then U-Boot will drop into interactive mode and remain there.
It is the responsibility of some application code (typically a Linux application) to reset the variable
bootcount, thus allowing for more boot cycles.
At the moment, the Boot Count Limit feature is available only for MPC8xx, MPC82xx and MPC5200
Power Architecture® processors.
• ubootBootcountAccess.c: C-source: bootcount access through /proc file system
• 6. Embedded Linux Configuration
♦ 6.1. Download and Unpack the Linux Kernel Sources
♦ 6.2. Kernel Configuration and Compilation
♦ 6.3. Installation
6. Embedded Linux Configuration
6.1. Download and Unpack the Linux Kernel Sources
You can download the Linux Kernel Sources from our anonymous git server at http://git.denx.de/. To
checkout the module for the first time, proceed as follows:
bash$ cd /opt/eldk/usr/src
bash$ git clone git://git.denx.de/linux-denx.git linux-denx
bash$ cd linux-denx
bash$ git checkout -b duts remotes/origin/m28
Branch duts set up to track remote branch m28 from origin.
Switched to a new branch 'duts'
bash$
6.2. Kernel Configuration and Compilation
The m28 board is fully supported by DENX Software Engineering. This means that you will always be able to
build a working default configuration with just minimal interaction.
Please be aware that you will need the "arm" cross development tools for the following steps. Make sure that
the directory which contains the binaries of your ELDK are in your PATH.
To be sure that no intermediate results of previous builds are left in your Linux kernel source tree you can
clean it up as follows:
bash$ make mrproper
6. Embedded Linux Configuration
85
The following command selects a standard configuration for the m28 board that has been extensively tested. It
is recommended to use this as a starting point for other, customized configurations:
bash$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- m28_defconfig
[marex@pollux]$
Note: The name of this default configuration file is arch/arm/configs/XXX . By (recursively) listing
the contents of the arch/arm/configs/ directory you can easily find out which other default
configurations are available.
If you don't want to change the default configuration you can now continue to use it to build a kernel image:
bash$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- uImage
Otherwise you can modify the kernel configuration as follows:
bash$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-
config
or
bash$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi-
menuconfig
Note: Because of problems (especially with some older Linux kernel versions) the use of "make xconfig"
is not recommended.
bash$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- uImage
The make target uImage uses the tool mkimage (from the U-Boot package) to create a Linux kernel image in
arch/arm/boot/uImage which is immediately usable for download and booting with U-Boot.
In case you need a DTB to boot your linux kernel, you need the following step:
bash$ make m28.dtb
In case you configured modules you will also need to compile the modules:
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- modules
add install the modules (make sure to pass the correct root path for module installation):
bash$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- INSTALL_MOD_PATH=/opt/eldk-5.2/armv5te/rootf
6.3. Installation
For now it is sufficient to copy the Linux kernel image into the directory used by your TFTP server:
bash$ cp arch/arm/boot/uImage /tftpboot/uImage
• 7. Booting Embedded Linux
♦ 7.1. Introduction
♦ 7.2. Flattened Device Tree Blob
♦ 7.3. Passing Kernel Arguments
♦ 7.4. Boot Arguments Unleashed
♦ 7.5. Networked Operation with Root Filesystem over NFS
6.2. Kernel Configuration and Compilation
86
◊ 7.5.1. Bootlog of tftp'd Linux kernel with Root Filesystem over NFS
♦ 7.6. Boot from NAND Flash Memory
♦ 7.7. Standalone Operation with Ramdisk Image
7. Booting Embedded Linux
7.1. Introduction
In principle, if you have a Linux kernel image and the flattened device tree blob somewhere in system
memory (RAM, ROM, flash...), then all you need to boot the system is the bootm command. Assume a
Linux kernel image has been stored at address 0x42000000 and the flattened device tree blob has been stored
at address 0x41000000 - then you can boot this image with the following command:
=> bootm 42000000 - 41000000
7.2. Flattened Device Tree Blob
Linux kernel expects certain information on the hardware that it runs on. For kernels compiled with fdt
support, this information has the form of a device tree, which is based on the Open Firmware specification.
Bootloaders like U-Boot that do not implement the Open Firmware API, are expected to pass to the kernel a
binary form of the flattened device tree, commonly referred to as FDT blob or simply the blob.
Device trees are defined in human-readable text files, which are part of the Linux 2.6 source tree. Device tree
source for the m28 board is found in arch/arm/boot/dts/m28.dts file. Before the device tree can be
passed to the kernel, it has to be compiled to the binary form by the dtc compiler. The dtc compiler is
included with the Linux kernel since 2.6.25. Since 2.6.26 there is also a simple makefile rule to generate the
blob:
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- m28.dtb
After the blob has been compiled, it has to be transferred from where it was built
("arch/arm/boot/m28.dtb") to target's memory, for example over the TFTP protocol using U-Boot's
tftp command. Then, the blob is passed to the kernel by the bootm command, and its address in memory is
one of the arguments to bootm - refer to the description of this command in UBootCmdGroupExec for more
details.
Note that U-Boot makes some automatic modifications to the blob before passing it to the kernel - mainly
adding and modifying information that is learnt at run-time. See the board-specific function ft_board_setup()
and related routines.
U-Boot also has provisions to alter a flattened device tree in arbitrary ways from the command line, refer to
the description of the fdt commands found in UBootCmdFDT.
Notes:
• Flattened Device Tree custodian's page at http://www.denx.de/wiki/U-Boot/UBootFdtInfo contains
useful information, and a number of references.
• At the time of this writing (September 2007) blob handling is still a very fresh feature and undergoing
frequent changes. Reader is encouraged to watch the u-boot-users and linuxppc-dev mailing
lists for important news (required version of the dtc compiler, blob compilation options, flattened
7.2. Flattened Device Tree Blob
87
device tree source file structure, etc.).
7.3. Passing Kernel Arguments
In nearly all cases, you will want to pass additional information to the Linux kernel; for instance, information
about the root device or network configuration.
In U-Boot, this is supported using the bootargs environment variable. Its contents are automatically passed
to the Linux kernel as boot arguments (or "command line" arguments). This allows the use of the same Linux
kernel image in a wide range of configurations. For instance, by just changing the contents of the bootargs
variable you can use the very same Linux kernel image to boot with an initrd ramdisk image, with a root
filesystem over NFS, with a CompactFlash disk or from a flash filesystem.
As one example, to boot the Linux kernel image at address 0x42000000 using the initrd ramdisk image at
address 0x44100000 as root filesystem, and with the flattened device tree blob at address 0x41000000, you
can use the following commands:
=> setenv bootargs root=/dev/ram rw
=> bootm 0x42000000 0x44100000 0x41000000
To boot the same kernel image with a root filesystem over NFS, the following command sequence can be
used. This example assumes that your NFS server has the IP address "192.168.1.1" and exports the directory
"/opt/eldk-5.2/armv5te/rootfs" as root filesystem for the target. The target has been assigned the IP address
"192.168.20.38" and the hostname "m28". A netmask of "255.255.0.0" is used:
=> setenv bootargs root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk-5.2/armv5te/rootfs ip=192.168.2
=> bootm 0x42000000 - 0x41000000
Please see also the files Documentation/initrd.txt and Documentation/nfsroot.txt in your
Linux kernel source directory for more information about which options can be passed to the Linux kernel.
Note: Once your system is up and running, if you have a simple shell login, you can normally examine the
boot arguments that were used by the kernel for the most recent boot with the command:
$ cat /proc/cmdline
7.4. Boot Arguments Unleashed
Passing command line arguments to the Linux kernel allows for very flexible and efficient configuration
which is especially important in Embedded Systems. It is somewhat strange that these features are nearly
undocumented everywhere else. One reason for that is certainly the very limited capabilities of other boot
loaders.
It is especially U-Boot's capability to easily define, store, and use environment variables that makes it such a
powerful tool in this area. In the examples above we have already seen how we can use for instance the root
and ip boot arguments to pass information about the root filesystem or network configuration. The ip
argument is not only useful in configurations with root filesystem over NFS; if the Linux kernel has the
CONFIG_IP_PNP configuration enabled (IP kernel level autoconfiguration), this can be used to enable
automatic configuration of IP addresses of devices and of the routing table during kernel boot, based on either
information supplied on the kernel command line or by BOOTP or RARP protocols.
7.4. Boot Arguments Unleashed
88
The advantage of this mechanism is that you don't have to spend precious system memory (RAM and flash)
for network configuration tools like ifconfig or route - especially in Embedded Systems where you
seldom have to change the network configuration while the system is running.
We can use U-Boot environment variables to store all necessary configuration parameters:
=>
=>
=>
=>
=>
=>
setenv ipaddr 192.168.20.38
setenv serverip 192.168.1.1
setenv netmask 255.255.0.0
setenv hostname m28
setenv rootpath /opt/eldk-5.2/armv5te/rootfs
saveenv
Then you can use these variables to build the boot arguments to be passed to the Linux kernel:
=> setenv nfsargs 'root=/dev/nfs rw nfsroot=${serverip}:${rootpath}'
Note how apostrophes are used to delay the substitution of the referenced environment variables. This way,
the current values of these variables get inserted when assigning values to the "bootargs" variable itself
later, i. e. when it gets assembled from the given parts before passing it to the kernel. This allows us to simply
redefine any of the variables (say, the value of "ipaddr" if it has to be changed), and the changes will
automatically propagate to the Linux kernel.
Note: You cannot use this method directly to define for example the "bootargs" environment variable,
as the implicit usage of this variable by the "bootm" command will not trigger variable expansion - this
happens only when using the "setenv" command.
In the next step, this can be used for a flexible method to define the "bootargs" environment variable by
using a function-like approach to build the boot arguments step by step:
=>
=>
=>
=>
=>
setenv
setenv
setenv
setenv
setenv
ramargs setenv bootargs root=/dev/ram rw
nfsargs 'setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath}'
addip 'setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${h
ram_root 'run ramargs addip;bootm ${kernel_addr} ${ramdisk_addr} ${fdt_addr} '
nfs_root 'run nfsargs addip;bootm ${kernel_addr} - ${fdt_addr} '
In this setup we define two variables, ram_root and nfs_root, to boot with root filesystem from a
ramdisk image or over NFS, respecively. The variables can be executed using U-Boot's run command. These
variables make use of the run command itself:
• First, either run ramargs or run nfsargs is used to initialize the bootargs environment
variable as needed to boot with ramdisk image or with root over NFS.
• Then, in both cases, run addip is used to append the ip parameter to use the Linux kernel IP
autoconfiguration mechanism for configuration of the network settings.
• Finally, the bootm command is used with three resp. two address arguments to boot the Linux kernel
image with resp. without a ramdisk image. (We assume here that the variables kernel_addr ,
ramdisk_addr and fdt_addr have already been set.)
This method can be easily extended to add more customization options when needed.
If you have used U-Boot's network commands before (and/or read the documentation), you will probably have
recognized that the names of the U-Boot environment variables we used in the examples above are exactly the
same as those used with the U-Boot commands to boot over a network using DHCP or BOOTP. That means
that, instead of manually setting network configuration parameters like IP address, etc., these variables will be
set automatically to the values retrieved with the network boot protocols. This is explained in detail in the
7.4. Boot Arguments Unleashed
89
sections about the respective U-Boot commands.
7.5. Networked Operation with Root Filesystem
over NFS
This section will show how to boot the target into Linux with no more than U-Boot residing on it. For this we
will use the tftp command of U-Boot to transfer a Linux kernel and boot it with the NFS rootfilesystem
provided by the ELDK.
For this to work, we rely on some U-Boot environment variables to be set up correctly, i.e. the network
parameters, the names of files to transfer via tftp and last but not least some scripts easing the assembly of the
Linux command line. The whole process is packaged up into one script shown before we actually execute it.
Note that the Linux kernel will also output the command line used, so you can easily check if everything
worked like expected. The command line in this example passes at least the following information to the:
• root=/dev/nfs rw: the root filesystem will be mounted using NFS, and it will be writable.
• nfsroot=192.168.1.1:/opt/eldk-5.2/armv5te/rootfs: the NFS server has the IP
address 192.168.1.1, and exports the directory /opt/eldk-5.2/armv5te/rootfs for our system to use as
root filesystem.
• ip=192.168.20.38:192.168.1.1:192.168.1.1:255.255.0.0:m28::off: the target
has the IP address 192.168.20.38; the NFS server is 192.168.1.1; there is a gateway at IP
address 192.168.1.1; the netmask is 255.255.0.0 and our hostname is m28. The first ethernet
interface (eth0) willbe used, and the Linux kernel will immediately use this network configuration
and not try to re-negotiate it (IP autoconfiguration is off).
See Documentation/nfsroot.txt in you Linux kernel source directory for more information about these
parameters and other options.
7.5.1. Bootlog of tftp'd Linux kernel with Root Filesystem
over NFS
=> setenv bootfile /tftpboot/duts/m28/uImage
=> setenv rootpath /opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/
=> printenv net_nfs
net_nfs=run fdt_netload kernel_netload nfsargs addip addcons addmtd addmisc;bootm ${kernel_addr_r
=> run net_nfs
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename 'duts/m28/imx28-m28evk.dtb'.
Load address: 0x41000000
Loading: ##
done
Bytes transferred = 16547 (40a3 hex)
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename '/tftpboot/duts/m28/uImage'.
Load address: 0x42000000
Loading: #################################################################
#################################################################
####################
done
Bytes transferred = 2191008 (216ea0 hex)
## Booting kernel from Legacy Image at 42000000 ...
7.5. Networked Operation with Root Filesystem over NFS
90
Image Name:
Linux-3.6.0-next-20121001-00014Created:
2012-10-02 13:23:40 UTC
Image Type:
ARM Linux Kernel Image (uncompressed)
Data Size:
2190944 Bytes = 2.1 MiB
Load Address: 40008000
Entry Point: 40008000
Verifying Checksum ... OK
## Flattened Device Tree blob at 41000000
Booting using the fdt blob at 0x41000000
Loading Kernel Image ... OK
OK
Loading Device Tree to 4fb3c000, end 4fb430a2 ... OK
Starting kernel ...
Uncompressing Linux... done, booting the kernel.
[
0.000000] Booting Linux on physical CPU 0
[
0.000000] Initializing cgroup subsys cpu
[
0.000000] Linux version 3.6.0-next-20121001-00014-g61a70ae (root@mashiro) (gcc version 4.7.2
[
0.000000] CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00053177
[
0.000000] CPU: VIVT data cache, VIVT instruction cache
[
0.000000] Machine: Freescale i.MX28 (Device Tree), model: DENX M28EVK
[
0.000000] bootconsole [earlycon0] enabled
[
0.000000] Memory policy: ECC disabled, Data cache writeback
[
0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 65024
[
0.000000] Kernel command line: root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk-5.2.1/armv5te/
[
0.000000] PID hash table entries: 1024 (order: 0, 4096 bytes)
[
0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
[
0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
[
0.000000] Memory: 256MB = 256MB total
[
0.000000] Memory: 254044k/254044k available, 8100k reserved, 0K highmem
[
0.000000] Virtual kernel memory layout:
[
0.000000]
vector : 0xffff0000 - 0xffff1000
(
4 kB)
[
0.000000]
fixmap : 0xfff00000 - 0xfffe0000
( 896 kB)
[
0.000000]
vmalloc : 0x90800000 - 0xff000000
(1768 MB)
[
0.000000]
lowmem : 0x80000000 - 0x90000000
( 256 MB)
[
0.000000]
.text : 0x80008000 - 0x8050df88
(5144 kB)
[
0.000000]
.init : 0x8050e000 - 0x80538b64
( 171 kB)
[
0.000000]
.data : 0x8053a000 - 0x80565e40
( 176 kB)
[
0.000000]
.bss : 0x80565e64 - 0x8059b8f4
( 215 kB)
[
0.000000] SLUB: Genslabs=13, HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[
0.000000] NR_IRQS:16 nr_irqs:16 16
[
0.000000] of_irq_init: children remain, but no parents
[
0.000000] sched_clock: 32 bits at 100 Hz, resolution 10000000ns, wraps every 4294967286ms
[
0.000000] Console: colour dummy device 80x30
[
0.010000] Calibrating delay loop... 226.09 BogoMIPS (lpj=1130496)
[
0.090000] pid_max: default: 32768 minimum: 301
[
0.090000] Mount-cache hash table entries: 512
[
0.100000] CPU: Testing write buffer coherency: ok
[
0.110000] Setting up static identity map for 0x40404d20 - 0x40404d5c
[
0.120000] devtmpfs: initialized
[
0.120000] pinctrl core: initialized pinctrl subsystem
[
0.130000] regulator-dummy: no parameters
[
0.130000] NET: Registered protocol family 16
[
0.140000] DMA: preallocated 256 KiB pool for atomic coherent allocations
[
0.170000] Serial: AMBA PL011 UART driver
[
0.170000] 80074000.serial: ttyAMA0 at MMIO 0x80074000 (irq = 218) is a PL011 rev2
[
0.180000] console [ttyAMA0] enabled, bootconsole disabled
[
0.180000] console [ttyAMA0] enabled, bootconsole disabled
[
0.200000] bio: create slab <bio-0> at 0
[
0.200000] mxs-dma 80004000.dma-apbh: initialized
[
0.210000] mxs-dma 80024000.dma-apbx: initialized
[
0.210000] 3P3V: 3300 mV
[
0.220000] vddio-sd0: 3300 mV
[
0.220000] usb0_vbus: 5000 mV
[
0.220000] usb1_vbus: 5000 mV
[
0.230000] SCSI subsystem initialized
7.5.1. Bootlog of tftp'd Linux kernel with Root Filesystemover NFS
91
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
[
0.230000]
0.240000]
0.240000]
0.250000]
0.250000]
0.260000]
0.260000]
0.270000]
0.290000]
0.300000]
0.300000]
0.310000]
0.320000]
0.320000]
0.330000]
0.330000]
0.340000]
0.340000]
0.350000]
0.350000]
0.360000]
0.400000]
0.400000]
0.410000]
0.410000]
0.420000]
0.420000]
0.440000]
0.460000]
0.630000]
0.640000]
0.650000]
0.670000]
0.680000]
0.680000]
0.690000]
0.700000]
0.700000]
0.710000]
1.050000]
1.050000]
1.060000]
1.070000]
1.080000]
1.080000]
1.090000]
1.100000]
1.130000]
1.140000]
1.140000]
1.150000]
1.160000]
1.170000]
1.180000]
1.190000]
1.190000]
1.200000]
1.200000]
1.210000]
1.260000]
1.260000]
1.270000]
1.270000]
1.280000]
1.280000]
1.340000]
1.340000]
usbcore: registered new interface driver usbfs
usbcore: registered new interface driver hub
usbcore: registered new device driver usb
pps_core: LinuxPPS API ver. 1 registered
pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@lin
PTP clock support registered
Advanced Linux Sound Architecture Driver Initialized.
Switching to clocksource mxs_timer
NET: Registered protocol family 2
TCP established hash table entries: 8192 (order: 4, 65536 bytes)
TCP bind hash table entries: 8192 (order: 3, 32768 bytes)
TCP: Hash tables configured (established 8192 bind 8192)
TCP: reno registered
UDP hash table entries: 256 (order: 0, 4096 bytes)
UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
NetWinder Floating Point Emulator V0.97 (double precision)
NFS: Registering the id_resolver key type
Key type id_resolver registered
Key type id_legacy registered
msgmni has been set to 496
Block layer SCSI generic (bsg) driver version 0.4 loaded (major 250)
io scheduler noop registered (default)
Console: switching to colour frame buffer device 100x30
mxsfb 80030000.lcdif: initialized
uart-pl011 80074000.serial: no DMA platform data
8006a000.serial: ttyAPP0 at MMIO 0x8006a000 (irq = 215) is a 8006a000.serial
mxs-auart 8006a000.serial: Found APPUART 3.1.0
brd: module loaded
loop: module loaded
at24 0-0051: 16384 byte 24c128 EEPROM, writable, 32 bytes/write
ONFI param page 0 valid
ONFI flash detected
NAND device: Manufacturer ID: 0x2c, Chip ID: 0xda (Micron MT29F2G08ABAEAWP), page
Scanning device for bad blocks
5 cmdlinepart partitions found on MTD device gpmi-nand
Creating 5 MTD partitions on "gpmi-nand":
0x000000000000-0x000000300000 : "bootloader"
0x000000300000-0x000000380000 : "environment"
0x000000380000-0x000000400000 : "redundant-environment"
0x000000400000-0x000000800000 : "kernel"
0x000000800000-0x000010000000 : "filesystem"
gpmi-nand 8000c000.gpmi-nand: driver registered.
m25p80 spi32766.0: m25p80 (1024 Kbytes)
libphy: Fixed MDIO Bus: probed
CAN device driver interface
flexcan 80032000.can: device registered (reg_base=f5032000, irq=190)
flexcan 80034000.can: device registered (reg_base=f5034000, irq=191)
libphy: fec_enet_mii_bus: probed
Initializing USB Mass Storage driver...
usbcore: registered new interface driver usb-storage
USB Mass Storage support registered.
ci_hdrc ci_hdrc.0: doesn't support gadget
ci_hdrc ci_hdrc.0: ChipIdea HDRC EHCI
ci_hdrc ci_hdrc.0: new USB bus registered, assigned bus number 1
ci_hdrc ci_hdrc.0: USB 2.0 started, EHCI 1.00
hub 1-0:1.0: USB hub found
hub 1-0:1.0: 1 port detected
ci_hdrc ci_hdrc.1: doesn't support gadget
ci_hdrc ci_hdrc.1: ChipIdea HDRC EHCI
ci_hdrc ci_hdrc.1: new USB bus registered, assigned bus number 2
ci_hdrc ci_hdrc.1: USB 2.0 started, EHCI 1.00
hub 2-0:1.0: USB hub found
7.5.1. Bootlog of tftp'd Linux kernel with Root Filesystemover NFS
92
[
1.350000] hub 2-0:1.0: 1 port detected
[
1.350000] mousedev: PS/2 mouse device common for all mice
[
1.360000] stmp3xxx-rtc 80056000.rtc: rtc core: registered 80056000.rtc as rtc0
[
1.370000] i2c /dev entries driver
[
1.410000] mxs-mmc 80010000.ssp: initialized
[
1.410000] usbcore: registered new interface driver usbhid
[
1.420000] usbhid: USB HID core driver
[
1.440000] sgtl5000 0-000a: Failed to get supply 'VDDD': -517
[
1.450000] 0-000a: 1200 mV normal
[
1.450000] sgtl5000 0-000a: Using internal LDO instead of VDDD
[
1.460000] sgtl5000 0-000a: sgtl5000 revision 0x11
[
1.470000] mxs-sgtl5000 sound.10: sgtl5000 <-> 80042000.saif mapping ok
[
1.480000] mxs-sgtl5000 sound.10: sgtl5000 <-> 80046000.saif mapping ok
[
1.490000] TCP: cubic registered
[
1.490000] Initializing XFRM netlink socket
[
1.500000] NET: Registered protocol family 17
[
1.500000] NET: Registered protocol family 15
[
1.510000] can: controller area network core (rev 20120528 abi 9)
[
1.510000] NET: Registered protocol family 29
[
1.520000] can: raw protocol (rev 20120528)
[
1.520000] can: broadcast manager protocol (rev 20120528 t)
[
1.530000] Key type dns_resolver registered
[
1.540000] stmp3xxx-rtc 80056000.rtc: setting system clock to 2012-10-02 16:55:53 UTC (134919
[
1.550000] eth0: Freescale FEC PHY driver [Micrel KSZ8021] (mii_bus:phy_addr=800f0000.etherne
[
1.660000] mmc0: new high speed SD card at address 0002
[
1.670000] mmcblk0: mmc0:0002 00000 1.90 GiB
[
1.680000] mmcblk0: p1 p2 p3
[
3.550000] libphy: 800f0000.etherne:00 - Link is Up - 100/Full
[
3.580000] IP-Config: Complete:
[
3.580000]
device=eth0, addr=192.168.20.33, mask=255.255.0.0, gw=192.168.1.254
[
3.590000]
host=m28, domain=, nis-domain=(none)
[
3.590000]
bootserver=192.168.1.1, rootserver=192.168.1.1, rootpath=
[
3.600000] ALSA device list:
[
3.600000]
#0: mxs_sgtl5000
[
3.620000] VFS: Mounted root (nfs filesystem) on device 0:12.
[
3.630000] Freeing init memory: 168K
INIT: version 2.88 booting
Starting udev
[
20.630000] EXT4-fs (mmcblk0): VFS: Can't find ext4 filesystem
[
20.640000] EXT3-fs (mmcblk0): error: can't find ext3 filesystem on dev mmcblk0.
[
20.650000] EXT2-fs (mmcblk0): error: can't find an ext2 filesystem on dev mmcblk0.
[
20.660000] FAT-fs (mmcblk0): bogus number of reserved sectors
[
20.660000] FAT-fs (mmcblk0): Can't find a valid FAT filesystem
[
20.680000] FAT-fs (mmcblk0): bogus number of reserved sectors
[
20.690000] FAT-fs (mmcblk0): Can't find a valid FAT filesystem
[
22.250000] EXT4-fs (mmcblk0p1): VFS: Can't find ext4 filesystem
[
22.260000] EXT3-fs (mmcblk0p1): error: can't find ext3 filesystem on dev mmcblk0p1.
[
22.270000] EXT2-fs (mmcblk0p1): error: can't find an ext2 filesystem on dev mmcblk0p1.
[
22.290000] FAT-fs (mmcblk0p1): bogus number of reserved sectors
[
22.290000] FAT-fs (mmcblk0p1): Can't find a valid FAT filesystem
[
22.330000] FAT-fs (mmcblk0p1): bogus number of reserved sectors
[
22.330000] FAT-fs (mmcblk0p1): Can't find a valid FAT filesystem
[
22.800000] EXT4-fs (mmcblk0p3): warning: maximal mount count reached, running e2fsck is recom
[
22.860000] EXT4-fs (mmcblk0p3): mounted filesystem with ordered data mode. Opts: (null)
Starting Bootlog daemon: bootlogd.
Configuring network interfaces... ifup skipped for nfsroot interface eth0
run-parts: /etc/network/if-pre-up.d/nfsroot exited with code 1
done.
Starting portmap daemon...
Unknown HZ value! (91) Assume 100.
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.all.rp_filter = 1
Starting atd: OK
INIT: Entering runlevel: 5
Starting system message bus: dbus.
Starting OpenBSD Secure Shell server: sshd
done.
7.5.1. Bootlog of tftp'd Linux kernel with Root Filesystemover NFS
93
Starting Distributed Compiler Daemon: distcc.
creating NFS state directory: done
starting 8 nfsd kernel threads: rpc.nfsd: Unable to access /proc/fs/nfsd errno 2 (No such file or
Please try, as root, 'mount -t nfsd nfsd /proc/fs/nfsd' and then restart rpc.nfsd to correct the
done
starting mountd: done
starting statd: done
Starting system log daemon...0
Starting kernel log daemon...0
Starting internet superserver: xinetd.
Starting Lighttpd Web Server: lighttpd.
Unknown HZ value! (90) Assume 100.
cups: started scheduler.
Starting crond: OK
Starting tcf-agent: OK
Stopping Bootlog daemon: bootlogd.
getty: ioctl() TIOCSPGR
ELDK 5.2.1 generic-armv5te console
generic-armv5te login: root
root@generic-armv5te:~#
7.6. Boot from NAND Flash Memory
The previous section described how to load the Linux kernel image over ethernet using TFTP. This is
especially well suited for your development and test environment, when the kernel image is still undergoing
frequent changes, for instance because you are modifying kernel code or configuration.
Later in your development cycle you will work on application code or device drivers, which can be loaded
dynamically as modules. If the Linux kernel remains the same then you can save the time needed for the
TFTP download and put the kernel image into the NAND flash memory of your m28 board.
After having deleted the target flash area, you can download the Linux image and write it to flash. Below is a
transcript of the complete operation with a final iminfo command to check the newly placed Linux kernel
image in the flash memory.
=> setenv kernel_addr_r 0x42000000
=> setenv nand_off 0x400000
=> nand erase 0x400000 0x3f8000
NAND erase: device 0 offset 0x400000, size 0x3f8000
Erasing at 0x400000 -3% complete.Erasing at 0x420000 -6% complete.Erasing at 0x440000 -OK
=> tftp 0x42000000 /tftpboot/duts/m28/uImage
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename '/tftpboot/duts/m28/uImage'.
Load address: 0x42000000
Loading: #################################################################
#################################################################
####################
done
Bytes transferred = 2191008 (216ea0 hex)
=> iminfo 0x42000000
## Checking Image at 42000000 ...
Legacy image found
Image Name:
Linux-3.6.0-next-20121001-00014Created:
2012-10-02 13:23:40 UTC
Image Type:
ARM Linux Kernel Image (uncompressed)
Data Size:
2190944 Bytes = 2.1 MiB
7.6. Boot from NAND Flash Memory
94
Load Address: 40008000
Entry Point: 40008000
Verifying Checksum ... OK
=> nand write ${kernel_addr_r} ${nand_off} ${filesize}
NAND write: device 0 offset 0x400000, size 0x216ea0
2191008 bytes written: OK
=> setenv nand_off
=> saveenv
Saving Environment to NAND...
Erasing redundant NAND...
Erasing at 0x380000 -- 25% complete.Erasing at 0x3a0000 -Writing to redundant NAND... done
=>
50% complete.Erasing at 0x3c0000 --
Note how the filesize variable (which gets set by the TFTP transfer) is used to automatically adjust for
the actual image size.
Since kernel requires the flattened device tree blob to be passed at boot time, you have to also write the blob
to the flash memory. Below is a transcript of this operation.
=>
=>
=>
=>
=>
setenv fdt_addr_r 0x41000000
setenv nand_off 0x007e0000
setenv nand_len 0x20000
setenv cmp_addr_r 0x44000000
nand erase ${nand_off} ${nand_len}
NAND erase: device 0 offset 0x7e0000, size 0x20000
Erasing at 0x7e0000 -- 100% complete.
OK
=> tftp 0x41000000 /tftpboot/duts/m28/imx28-m28evk.dtb
Using FEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.20.33
Filename '/tftpboot/duts/m28/imx28-m28evk.dtb'.
Load address: 0x41000000
Loading: ##
done
Bytes transferred = 16547 (40a3 hex)
=> nand write ${fdt_addr_r} ${nand_off} ${filesize}
NAND write: device 0 offset 0x7e0000, size 0x40a3
16547 bytes written: OK
=> setenv nand_off
=> setenv nand_len
=> saveenv
Saving Environment to NAND...
Erasing NAND...
Erasing at 0x300000 -- 25% complete.Erasing at 0x320000 -Writing to NAND... done
=>
50% complete.Erasing at 0x340000 --
Now we can boot directly from flash. All we need to do is passing the in-flash address of the image
(42000000) and the in-flash address of the flattened device tree (41000000) with the bootm command; we
also make the definition of the bootargs variable permanent now:
=> setenv bootcmd bootm 42000000 - 41000000
=> setenv bootargs root=/dev/nfs rw nfsroot=${serverip}:${rootpath} ip=${ipaddr}:${serverip}:${ga
Use printenv to verify that everything is OK before you save the environment settings:
=> printenv
bootdelay=5
baudrate=115200
stdin=serial
7.6. Boot from NAND Flash Memory
95
stdout=serial
stderr=serial
bootcmd=bootm 42000000 - 41000000
bootargs=root=/dev/nfs rw nfsroot=192.168.1.1:/opt/eldk-5.2/armv5te/rootfs
ip=192.168.20.38:192.168.1.1:192.168.1.1:255.255.0.0:m28::off
....
=> saveenv
To test booting from flash you can now reset the board (either by power-cycling it, or using the U-Boot
command reset), or you can manually call the boot command which will run the commands in the
bootcmd variable:
Note: Included topic DULGData_m28.LinuxBootSelfNand does not exist yet
-- HeikoSchocher - 04 Nov 2011
7.7. Standalone Operation with Ramdisk Image
When your application development is completed, you usually will want to run your Embedded System
standalone, i. e. independent from external resources like NFS filesystems. Instead of mounting the root
filesystem from a remote server you can use a compressed ramdisk image, which is stored in flash memory
and loaded into RAM when the system boots.
Load the ramdisk image into RAM and write it to flash as follows:
Note: Included topic DULGData_m28.UBootInstallNandRamdisk does not exist yet
To tell the Linux kernel to use the ramdisk image as root filesystem you have to modify the command line
arguments passed to the kernel, and to pass two arguments to the bootm command, the first is the memory
address of the Linux kernel image, the second that of the ramdisk image:
Note: Included topic DULGData_m28.LinuxBootSelfNand does not exist yet
8. Building and Using Modules
This section still needs to be written (this is a wiki, so please feel free to contribute!).
In the meantime, please refer to file Documentation/kbuild/modules.txt in the Linux source tree.
• 9. Advanced Topics
♦ 9.1. Flash Filesystems
◊ 9.1.1. Memory Technology Devices
◊ 9.1.2. Journalling Flash File System
◊ 9.1.3. Second Version of JFFS
◊ 9.1.4. Compressed ROM Filesystem
◊ 9.1.5. UBI and UBIFS file systems
⋅ 9.1.5.1. Create Device Files
⋅ 9.1.5.2. Using UBI on NAND Flash:
⋅ 9.1.5.3. Creating UBIFS File System Images
• 9.1.5.3.1. Determining the Parameters of the used Flash Types:
• 9.1.5.3.2. Create some Test File System Hierarchy
• 9.1.5.3.3. Installing UBIFS images into existing UBI Volume:
• 9.1.5.3.4. Installing UBI images (if no UBI Volumes exist):
8. Building and Using Modules
96
♦ 9.2. The TMPFS Virtual Memory Filesystem
◊ 9.2.1. Mount Parameters
◊ 9.2.2. Kernel Support for tmpfs
◊ 9.2.3. Usage of tmpfs in Embedded Systems
♦ 9.3. Using MultiMediaCards in Linux"
♦ 9.4. Splash Screen Support in Linux
♦ 9.5. Root File System: Design and Building
◊ 9.5.1. Root File System on a Ramdisk
◊ 9.5.2. Root File System on a JFFS2 File System
◊ 9.5.3. Root File System on a cramfs File System
◊ 9.5.4. Root File System on a Read-Only ext2 File System
◊ 9.5.5. Root File System on a Flash Card
◊ 9.5.6. Root File System in a Read-Only File in a FAT File System
♦ 9.6. Root File System Selection
♦ 9.7. Overlay File Systems
♦ 9.8. The Persistent RAM File system (PRAMFS)
◊ 9.8.1. Mount Parameters
◊ 9.8.2. Example
9. Advanced Topics
This section lists some advanced topics of interest to users of U-Boot and Linux.
9.1. Flash Filesystems
9.1.1. Memory Technology Devices
All currently available flash filesystems are based on the Memory Technology Devices MTD layer, so you
must enable (at least) the following configuration options to get flash filesystem support in your system:
CONFIG_MTD=y
CONFIG_MTD_PARTITIONS=y
CONFIG_MTD_CHAR=y
CONFIG_MTD_BLOCK=y
CONFIG_MTD_CFI=y
CONFIG_MTD_GEN_PROBE=y
CONFIG_MTD_CFI_AMDSTD=y
CONFIG_MTD_ROM=y
CONFIG_MTD_m28=y
Note: this configuration uses CFI conformant AMD flash chips; you may need to adjust these settings on
other boards.
The partition layout of the flash devices is contained in the flat device tree for the system (see 13.1. Flat
Device Tree).
Informational messages of the MTD subsystem can be found in the Linux bootlog, i.e. see section 7.5.1.
Bootlog of tftp'd Linux kernel with Root Filesystem over NFS.
One can discover this information in a running system using the proc filesystem:
root@generic-armv5te:~#
root@generic-armv5te:~# cat /proc/mt
9.1.1. Memory Technology Devices
97
Now we can run some basic tests to verify that the flash driver routines and the partitioning works as
expected:
root@generic-armv5te:~#
root@generic-armv5te:~# hexdump -C /dev/mtd4 | head
In the hex-dumps of the MTD devices you can identify some strings that verify that we indeed see an U-Boot
environment, a Linux kernel, a ramdisk image and an empty partition to play wih.
The last output shows the partition to be empty. We can try write some data into it:
0
root@generic-armv5te:~#
root@generic-armv5te:~# date > /tmp/tempfile
root@generic-armv5te:~# dd if=/dev/zero of=/tmp/tempfile bs=1 count=4096 seek=50 Aroot@generic-ar
d4096+0 records in
4096+0 records out
4096 bytes (4.1 kB) copied, 0.0759063 s, 54.0 kB/s
root@generic-armv5te:~# dd if=/tmp/tempfile of=/dev/mtd4 bs=4096 count=1
1+0 records in
1+0 records out
4096 bytes (4.1 kB) copied, 0.0023125 s, 1.8 MB/s
root@generic-armv5te:~# head -1 /dev/mtd4
Tue Oct 2 16:57:16 UTC 2012
root@generic-armv5te:~# dd if=/tmp/tempfile of=/dev/mtd4 bs=4096 count=
As you can see it worked the first time. When we tried to write the (new date) again, we got an error. The
reason is that the date has changed (probably at least the seconds) and flash memory cannot be simply
overwritten - it has to be erased first.
You can use the eraseall Linux commands to erase a whole MTD partition:
p
root@generic-armv5te:~#
root@generic-armv5te:~# flash_erase -q /dev/mtd4 0 0
date > /tmp/tempfile
root@generic-armv5te:~# date > /tmp/tempfile
root@generic-armv5te:~# dd if=/dev/zero of=/tmp/tempfile bs=1 count=4096 seek=50 Aroot@generic-ar
d 4096+0 records in
4096+0 records out
4096 bytes (4.1 kB) copied, 0.0732188 s, 55.9 kB/s
root@generic-armv5te:~# dd if=/tmp/tempfile of=/dev/mtd4 bs=4096 count=1
1+0 records in
1+0 records out
4096 bytes (4.1 kB) copied, 0.00228125 s, 1.8 MB/s
root@generic-armv5te:~# head -1 /dev/mtd
We have now sufficient proof that the MTD layer is working as expected, so we can try creating a flash
filesystem.
9.1.2. Journalling Flash File System
At the moment it seems that the Journalling Flash File System JFFS is the best choice for filesystems in flash
memory of embedded devices. You must enable the following configuration options to get JFFS support in
your system:
CONFIG_JFFS_FS=y
CONFIG_JFFS_FS_VERBOSE=0
9.1.2. Journalling Flash File System
98
If the flash device is erased, we can simply mount it, and the creation of the JFFS filesystem is performed
automagically.
Note: For simple accesses like direct read or write operations or erasing you use the character device
interface (/dev/mtd*) of the MTD layer, while for filesystem operations like mounting we must use the block
device interface (/dev/mtdblock*).
# eraseall /dev/mtd2
Erased 4096 Kibyte @ 0 -- 100% complete.
# mount -t jffs /dev/mtdblock2 /mnt
# mount
/dev/root on / type nfs (rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.0.0.2)
proc on /proc type proc (rw)
devpts on /dev/pts type devpts (rw)
/dev/mtdblock2 on /mnt type jffs (rw)
# df
Filesystem
1k-blocks
Used Available Use% Mounted on
/dev/root
2087212
1232060
855152 60% /
/dev/mtdblock2
3584
0
3584
0% /mnt
Now you can access the files in the JFFS filesystem in the /mnt directory.
9.1.3. Second Version of JFFS
Probably even more interesting for embedded systems is the second version of JFFS, JFFS2, since it not only
fixes a few design issues with JFFS, but also adds transparent compression, so that you can save a lot of
precious flash memory.
The mkfs.jffs2 tool is used to create a JFFS2 filesystem image; it populates the image with files from a
given directory. For instance, to create a JFFS2 image for a flash partition of 3 MB total size and to populate it
with the files from the /tmp/flashtools directory you would use:
# mkfs.jffs2 --pad=3145728 --eraseblock=262144 \
--root=/tmp/flashtools/ --output image.jffs2
# eraseall /dev/mtd4
Erased 3072 Kibyte @ 0 -- 100% complete.
\# dd if=image.jffs2 of=/dev/mtd4 bs=256k
12+0 records in
12+0 records out
# mount -t jffs2 /dev/mtdblock4 /mnt
# df /mnt
Filesystem
1k-blocks
Used Available Use% Mounted on
/dev/mtdblock4
3072
2488
584 81% /mnt
Note: Especially when you are running time-critical applications on your system you should carefully
study if the behaviour of the flash filesystem might have any negative impact on your application. After all, a
flash device is not a normal harddisk. This is especially important when your flash filesystem gets full; JFFS2
acts a bit weird then:
• You will note that an increasing amount of CPU time is spent by the filesystem's garbage collection
kernel thread.
• Access times to the files on the flash filesystem may increase drastically.
• Attempts to truncate a file (to free space) or to rename it may fail:
...
# cp /bin/bash file
cp: writing `file': No space left on device
9.1.3. Second Version of JFFS
99
# >file
bash: file: No space left on device
# mv file foo
mv: cannot create regular file `foo': No space left on device
You will have to use rm to actually delete a file in this situation.
This is especially critical when you are using the flash filesystem to store log files: when your application
detects some abnormal condition and produces lots of log messages (which usually are especially important in
this situation) the filesystem may fill up and cause extreme long delays - if your system crashes, the most
important messages may never be logged at all.
9.1.4. Compressed ROM Filesystem
In some cases it is sufficent to have read-only access to some files, and if the files are big enough it becomes
desirable to use some method of compression. The Compressed ROM Filesystem CramFs might be a
solution here.
Please note that CramFs has - beside the fact that it is a read-only filesystem - some severe limitations (like
missing support for timestamps, hard links, and 16/32 bit uid/gids), but there are many situations in Embedded
Systems where it's still useful.
To create a CramFs filesystem a special tool mkcramfs is used to create a file which contains the CramFs
image. Note that the CramFs filesystem can be written and read only by kernels with PAGE_CACHE_SIZE
== 4096, and some versions of the mkcramfs program may have other restrictions like that the filesystem
must be written and read with architectures of the same endianness. Especially the endianness requirement
makes it impossible to build the CramFs image on x86 PC host when you want to use it on a Power
Architecture® target. The endianness problem has been fixed in the version of mkcramfs that comes with
the ELDK.
In some cases you can use a target system running with root filesystem mounted over NFS to create the
CramFs image on the native system and store it to flash for further use.
Note: The normal version of the mkcramfs program tries to initialize some entries in the filesystem's
superblock with random numbers by reading /dev/random; this may hang permanently on your target because
there is not enough input (like mouse movement) to the entropy pool. You may want to use a modified
version of mkcramfs which does not depend on /dev/random.
To create a CramFs image, you put all files you want in the filesystem into one directory, and then use the
mkcramfs= program as follows:
$ mkdir /tmp/test
$ cp ... /tmp/test
$ du -sk /tmp/test
64
/tmp/test
$ mkcramfs /tmp/test test.cramfs.img
Super block: 76 bytes
erase
eraseall
mkfs.jffs
lock
unlock
Directory data: 176 bytes
-54.96% (-4784 bytes)
erase
-55.46% (-5010 bytes)
eraseall
-51.94% (-8863 bytes)
mkfs.jffs
-58.76% (-4383 bytes)
lock
-59.68% (-4215 bytes)
unlock
9.1.4. Compressed ROM Filesystem
100
Everything: 24 kilobytes
$ ls -l test.cramfs.img
-rw-r--r-1 wd
users
24576 Nov 10 23:44 test.cramfs.img
As you can see, the CramFs image test.cramfs.img takes just 24 kB, while the input directory contained 64 kB
of data. Savings of some 60% like in this case are typical CramFs.
Now we write the CramFs image to a partition in flash and test it:
# cp test.cramfs.img /dev/mtd3
# mount -t cramfs /dev/mtdblock3 /mnt
# mount
/dev/root on / type nfs (rw,v2,rsize=4096,wsize=4096,hard,udp,nolock,addr=10.0.0.2)
proc on /proc type proc (rw)
devpts on /dev/pts type devpts (rw)
/dev/mtdblock3 on /mnt type cramfs (rw)
# ls -l /mnt
total 54
-rwxr-xr-x
1 wd
users
8704 Jan 9 16:32 erase
-rwxr-xr-x
1 wd
users
9034 Jan 1 01:00 eraseall
-rwxr-xr-x
1 wd
users
7459 Jan 1 01:00 lock
-rwxr-xr-x
1 wd
users
17063 Jan 1 01:00 mkfs.jffs
-rwxr-xr-x
1 wd
users
7063 Jan 1 01:00 unlock
Note that all the timestamps in the CramFs filesyste are bogus, and so is for instance the output of the df
command for such filesystems:
# df /mnt
Filesystem
/dev/mtdblock3
1k-blocks
0
Used Available Use% Mounted on
0
0
- /mnt
9.1.5. UBI and UBIFS file systems
UBIFS is a flash filesystem, which work on top of the Linux MTD layer. UBI itself is a software layer which
basically is a volume management and wear-leveling layer. It provides so called UBI volumes which is a
higher level abstraction than a MTD device.
For more documentation about UBI/UBIFS see:
• linux source:Documentation/filesystems/ubifs.txt
• http://www.linux-mtd.infradead.org/doc/ubi.html
This document illustrates the usage of UBI/UBIFS for the m28 board.
9.1.5.1. Create Device Files
First we have to create some device files, which are necessary for using UBI/UBIFS:
ot
root@generic-armv5te:~#
root@generic-armv5te:~# mknod /dev/ubi_ctrl c 10 63
mknod: `/dev/ubi_ctrl': File exists
root@generic-armv5te:~# mknod /dev/ubi0 c 253 0
root@generic-armv5te:~# for i in $(seq 0 9); do mknod /dev/ubi0_$i c 253 $((i +
knodroot@generic-armv5te:~# mknod /dev/ubi1 c 252 0
root@generic-armv5te:~# for i in $(seq 0 9); do mknod /dev/ubi1_$i c 252 $((i +
ls -lroot@generic-armv5te:~# ls -l /dev/ubi
9.1.5. UBI and UBIFS file systems
1)); done
1)); done
101
9.1.5.2. Using UBI on NAND Flash:
Erase the flash partition:
root@generic-armv5te:~# flash_erase -q /dev/mtd4 0 0
root@generic-armv5te:~#
and attach it to UBI:
root@generic-armv5te:~# ubiattach /dev/ubi_ctrl -m 4 -O 2048
[ 115.210000] UBI: attaching mtd4 to ubi0
[ 116.580000] UBI: scanning is finished
[ 116.590000] UBI: empty MTD device detected
[ 116.630000] UBI: attached mtd4 (name "filesystem", size 248 MiB) to ubi0
[ 116.630000] UBI: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
[ 116.650000] UBI: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
[ 116.650000] UBI: VID header offset: 2048 (aligned 2048), data offset: 4096
[ 116.660000] UBI: good PEBs: 1984, bad PEBs: 0, corrupted PEBs: 0
[ 116.670000] UBI: user volume: 0, internal volumes: 1, max. volumes count: 128
[ 116.680000] UBI: max/mean erase counter: 0/0, WL threshold: 4096, image sequence number: 19519
[ 116.690000] UBI: available PEBs: 1976, total reserved PEBs: 8, PEBs reserved for bad PEB handl
[ 116.700000] UBI: background thread "ubi_bgt0d" started, PID 719
UBI device number 0, total 1984 LEBs (251920384 bytes, 240.2 MiB), available 1976 LEBs (250904576
root@generic-armv5te:~#
As this is done, we check if things are done correct:
root@generic-armv5te:~# ubinfo
UBI version:
Count of UBI devices:
UBI control device major/minor:
Present UBI devices:
root@generic-armv5te:~#
1
1
10:59
ubi0
Create a Volume on the UBI Device:
root@generic-armv5te:~# ubimkvol /dev/ubi0 -N filesystem -m
Set volume size to 250904576
Volume ID 0, size 1976 LEBs (250904576 bytes, 239.3 MiB), LEB size 126976 bytes (124.0 KiB), dyna
root@generic-armv5te:~#
As we intend to create just a single volume, we use maximum size ("-m" option).
Mount and use it:
root@generic-armv5te:~# mkdir /mnt/filesystem
root@generic-armv5te:~# mount -t ubifs /dev/ubi0_0 /mnt/filesystem
[ 126.720000] UBIFS: default file-system created
[ 126.720000] UBIFS: background thread "ubifs_bgt0_0" started, PID 726
[ 126.860000] UBIFS: mounted UBI device 0, volume 0, name "filesystem"(null)
[ 126.870000] UBIFS: LEB size: 126976 bytes (124 KiB), min./max. I/O unit sizes: 2048 bytes/2048
[ 126.880000] UBIFS: FS size: 249253888 bytes (237 MiB, 1963 LEBs), journal size 12443648 bytes
[ 126.890000] UBIFS: reserved for root: 4952683 bytes (4836 KiB)
[ 126.900000] UBIFS: media format: w4/r0 (latest is w4/r0), UUID F5A040E7-EFDA-4732-A803-99C0066
root@generic-armv5te:~#
Check with "-a" option:
root@generic-armv5te:~# ubinfo -a
UBI version:
1
Count of UBI devices:
1
UBI control device major/minor: 10:59
9.1.5.2. Using UBI on NAND Flash:
102
Present UBI devices:
ubi0
ubi0
Volumes count:
Logical eraseblock size:
Total amount of logical eraseblocks:
Amount of available logical eraseblocks:
Maximum count of volumes
Count of bad physical eraseblocks:
Count of reserved physical eraseblocks:
Current maximum erase counter value:
Minimum input/output unit size:
Character device major/minor:
Present volumes:
1
126976 bytes, 124.0 KiB
1984 (251920384 bytes, 240.2 MiB)
0 (0 bytes)
128
0
4
2
2048 bytes
247:0
0
Volume ID:
0 (on ubi0)
Type:
dynamic
Alignment:
1
Size:
1976 LEBs (250904576 bytes, 239.3 MiB)
State:
OK
Name:
filesystem
Character device major/minor: 247:1
root@generic-armv5te:~#
List which partitions we have mounted, and how many space we have available:
root@generic-armv5te:~# df -h
Filesystem
rootfs
192.168.1.1:/opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/
none
/dev/mmcblk0p2
/dev/mmcblk0p3
tmpfs
tmpfs
/dev/ubi0_0
root@generic-armv5te:~#
Size
315G
315G
125M
30M
1.7G
125M
125M
220M
Used Avail Use% Mounted on
148G 152G 50% /
148G 152G 50% /
140K 124M
1% /dev
13M
18M 42% /media/mmcblk0p2
1.2G 493M 71% /media/mmcblk0p3
152K 124M
1% /var/volatile
0 125M
0% /media/ram
24K 215M
1% /mnt/filesystem
9.1.5.3. Creating UBIFS File System Images
9.1.5.3.1. Determining the Parameters of the used Flash Types:
The "mkfs.ubifs" requires a few parameters that describe the specific features of the underlying flash chips.
The easiest way to determine these parameters is to run the "mtdinfo" utility on a running Linux
system./dev/mtd7 is NAND flash:
root@generic-armv5te:~# cat /proc/mtd
dev:
size
erasesize name
mtd0: 00300000 00020000 "bootloader"
mtd1: 00080000 00020000 "environment"
mtd2: 00080000 00020000 "redundant-environment"
mtd3: 00400000 00020000 "kernel"
mtd4: 0f800000 00020000 "filesystem"
mtd5: 00100000 00010000 "spi32766.0"
root@generic-armv5te:~#
root@generic-armv5te:~# mtdinfo
mtd4
Name:
Type:
Eraseblock size:
Amount of eraseblocks:
Minimum input/output unit size:
-u /dev/mtd4
filesystem
nand
131072 bytes, 128.0 KiB
1984 (260046848 bytes, 248.0 MiB)
2048 bytes
9.1.5.3. Creating UBIFS File System Images
103
Sub-page size:
OOB size:
Character device major/minor:
Bad blocks are allowed:
Device is writable:
Default UBI VID header offset:
Default UBI data offset:
Default UBI LEB size:
Maximum UBI volumes count:
2048 bytes
64 bytes
90:8
true
true
2048
4096
126976 bytes, 124.0 KiB
128
root@generic-armv5te:~# ubinfo /dev/ubi0
ubi0
Volumes count:
Logical eraseblock size:
Total amount of logical eraseblocks:
Amount of available logical eraseblocks:
Maximum count of volumes
Count of bad physical eraseblocks:
Count of reserved physical eraseblocks:
Current maximum erase counter value:
Minimum input/output unit size:
Character device major/minor:
Present volumes:
root@generic-armv5te:~#
1
126976 bytes, 124.0 KiB
1984 (251920384 bytes, 240.2 MiB)
0 (0 bytes)
128
0
4
2
2048 bytes
247:0
0
The interesting parameters are:
- min-io-size:
- max-leb-cnt:
corresponds to "Minimum input/output unit size"
corresponds to "Amount of eraseblocks"
One more needed parameter from the "ubinfo -a" command:
- leb-size:
corresponds to "Logical eraseblock size"
9.1.5.3.2. Create some Test File System Hierarchy
[marex@pollux]$ cd /tmp/duts-${pid}
[marex@pollux]$ mkdir fs
[marex@pollux]$ chmod 777 fs
[marex@pollux]$ echo Just an example >fs/README
[marex@pollux]$ date >fs/date_of_creation
[marex@pollux]$ ls -l fs
total 8
-rw-rw-r-- 1 marex marex 16 Oct 2 17:01 README
-rw-rw-r-- 1 marex marex 30 Oct 2 17:01 date_of_creation
[marex@pollux]$
Create UBIFS Images for ""userfs"" (NAND)
[marex@pollux]$ mkfs.ubifs --root=fs --min-io-size=2048 --leb-size=126976 --max-leb-cnt=1984 -o i
WARNING: setting root UBIFS inode UID=GID=0 (root) and permissions to u+rwx,go+rx; use --squash-r
[marex@pollux]$ ls -lh image-filesystem.ubifs
-rw-rw-r-- 1 marex marex 1.7M Oct 2 17:01 image-filesystem.ubifs
[marex@pollux]$ cp image-filesystem.ubifs /opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk//home/duts/
[marex@pollux]$
9.1.5.3.3. Installing UBIFS images into existing UBI Volume:
root@generic-armv5te:~# ubiattach /dev/ubi_ctrl -m 4 -O 2048
[ 158.760000] UBI: attaching mtd4 to ubi0
[ 161.500000] UBI: scanning is finished
[ 161.530000] UBI: attached mtd4 (name "filesystem", size 248 MiB) to ubi0
[ 161.530000] UBI: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
9.1.5.3.1. Determining the Parameters of the used Flash Types:
104
[ 161.550000] UBI: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
[ 161.550000] UBI: VID header offset: 2048 (aligned 2048), data offset: 4096
[ 161.560000] UBI: good PEBs: 1984, bad PEBs: 0, corrupted PEBs: 0
[ 161.580000] UBI: user volume: 1, internal volumes: 1, max. volumes count: 128
[ 161.580000] UBI: max/mean erase counter: 2/1, WL threshold: 4096, image sequence number: 19519
[ 161.600000] UBI: available PEBs: 0, total reserved PEBs: 1984, PEBs reserved for bad PEB handl
[ 161.600000] UBI: background thread "ubi_bgt0d" started, PID 735
UBI device number 0, total 1984 LEBs (251920384 bytes, 240.2 MiB), available 0 LEBs (0 bytes), LE
root@generic-armv5te:~# ubiupdatevol /dev/ubi0_0 /home/duts/image-filesystem.ubi fs
root@generic-armv5te:~# mount -t ubifs /dev/ubi0_0 /mnt/filesystem
[ 167.500000] UBIFS: background thread "ubifs_bgt0_0" started, PID 738
[ 167.640000] UBIFS: mounted UBI device 0, volume 0, name "filesystem"(null)
[ 167.640000] UBIFS: LEB size: 126976 bytes (124 KiB), min./max. I/O unit sizes: 2048 bytes/2048
[ 167.650000] UBIFS: FS size: 249507840 bytes (237 MiB, 1965 LEBs), journal size 9023488 bytes (
[ 167.670000] UBIFS: reserved for root: 0 bytes (0 KiB)
[ 167.670000] UBIFS: media format: w4/r0 (latest is w4/r0), UUID F31EAD94-B13A-4F8F-9927-E150346
root@generic-armv5te:~# ls -l /mnt/filesystem
total 8
-rw-rw-r-- 1 555 555 16 Oct 2 15:01 README
-rw-rw-r-- 1 555 555 30 Oct 2 15:01 date_of_creation
root@generic-armv5te:~# hexdump -C /mnt/filesystem/date_of_creation
00000000 54 75 65 20 4f 63 74 20 20 32 20 31 37 3a 30 31 |Tue Oct 2 17:01|
00000010 3a 32 38 20 43 45 53 54 20 32 30 31 32 0a
|:28 CEST 2012.|
0000001e
root@generic-armv5te:~#
9.1.5.3.4. Installing UBI images (if no UBI Volumes exist):
If the UBI device is not already formatted to contain suitable volumes, we have to generate UBI images. An
UBI image may contain one or more UBI volumes, which in turn may be used to store an UBIFS file system.
This is done using the "ubinize" tool, which unfortunately is a bit weird to use: an input configuration ini-file
defines all the UBI volumes - their characteristics and the contents, but it does not define the characteristics of
the flash flash device - these have to be specified as command-line options.
Also, we should keep in mind that we should no longer use "flash_eraseall" to erase the MTD device, as this
has no knowledge about the UBI erase counters. Instead, we should use "ubiformat" to erase the flash and
install a new UBI image.
Unmount and detach previously used UBI devices:
root@generic-armv5te:~# umount /mnt/filesystem
[ 154.740000] UBIFS: un-mount UBI device 0, volume 0
[ 154.750000] UBIFS: background thread "ubifs_bgt0_0" stops
root@generic-armv5te:~# ubidetach /dev/ubi_ctrl -m 4
[ 156.310000] UBI: detaching mtd4 from ubi0
[ 156.320000] UBI: mtd4 is detached from ubi0
root@generic-armv5te:~#
Create UBI ini-file and create UBI images:
Note: for the volume sizes we use the byte count previously determined by running "ubinfo -a" above.
[marex@pollux]$ cat ubi-filesystem.cfg
[ubifs]
mode=ubi
image=image-filesystem.ubifs
vol_id=0
vol_size=251920384
vol_type=dynamic
vol_name=filesystem
[marex@pollux]$ ubinize --min-io-size=2048 --peb-size=128KiB -s 2048 -o image-filesystem.ubi ubi[marex@pollux]$ cp image-filesystem.ubi /opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk//home/duts/
9.1.5.3.3. Installing UBIFS images into existing UBI Volume:
105
[marex@pollux]$
Note that for the NAND device we must pass the "-s 2048" option to ubinize; if we don't, an attempt to attach
the created UBI device will result in error messages like these:
root@generic-armv5te:~# ubiattach /dev/ubi_ctrl -m 4
[ 196.320000] UBI: attaching mtd4 to ubi0
[ 199.060000] UBI: scanning is finished
[ 199.090000] UBI: attached mtd4 (name "filesystem", size 248 MiB) to ubi0
[ 199.090000] UBI: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
[ 199.110000] UBI: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
[ 199.110000] UBI: VID header offset: 2048 (aligned 2048), data offset: 4096
[ 199.130000] UBI: good PEBs: 1984, bad PEBs: 0, corrupted PEBs: 0
[ 199.130000] UBI: user volume: 1, internal volumes: 1, max. volumes count: 128
[ 199.150000] UBI: max/mean erase counter: 2/1, WL threshold: 4096, image sequence number: 19519
[ 199.150000] UBI: available PEBs: 0, total reserved PEBs: 1984, PEBs reserved for bad PEB handl
[ 199.170000] UBI: background thread "ubi_bgt0d" started, PID 745
UBI device number 0, total 1984 LEBs (251920384 bytes, 240.2 MiB), available 0 LEBs (0 bytes), LE
root@generic-armv5te:~#
For background information please see
http://www.linux-mtd.infradead.org/faq/ubi.html#L_vid_offset_mismatch
Erase MTD partitions and install UBI images:
root@generic-armv5te:/home/duts# ubiformat -q -s 2048 -f /home/duts/image-filesy stem.ubi /dev/mt
root@generic-armv5te:/home/duts#
Verify that it worked:
root@generic-armv5te:/home/duts# ubiattach /dev/ubi_ctrl -m 4 -O 2048
[ 213.240000] UBI: attaching mtd4 to ubi0
[ 215.970000] UBI: scanning is finished
[ 216.000000] UBI error: init_volumes: not enough PEBs, required 1986, available 1984
[ 216.010000] UBI error: ubi_wl_init: no enough physical eraseblocks (-2, need 1)
[ 216.030000] UBI error: ubi_attach_mtd_dev: failed to attach mtd4, error -12
ubiattach: error!: cannot attach mtd4
error 12 (Cannot allocate memory)
root@generic-armv5te:/home/duts# mount -t ubifs /dev/ubi0_0 /mnt/filesystem
[ 218.290000] UBIFS error (pid 749): ubifs_mount: cannot open "/dev/ubi0_0", error -22
mount: wrong fs type, bad option, bad superblock on /dev/ubi0_0,
missing codepage or helper program, or other error
(for several filesystems (e.g. nfs, cifs) you might
need a /sbin/mount.<type> helper program)
In some cases useful info is found in syslog - try
dmesg | tail or so
root@generic-armv5te:/home/duts# ls -al /mnt/filesystem
total 8
drwxr-xr-x 2 root root 4096 Oct 2 15:01 .
drwxr-xr-x 4 root root 4096 Oct 2 15:01 ..
root@generic-armv5te:/home/duts# hexdump -C /mnt/filesystem/date_of_creation
hexdump: /mnt/filesystem/date_of_creation: No such file or directory
hexdump: /mnt/filesystem/date_of_creation: Bad file descriptor
root@generic-armv5te:/home/duts#
9.2. The TMPFS Virtual Memory Filesystem
The tmpfs filesystem, formerly known as shmfs, is a filesystem keeping all files in virtual memory.
9.2. The TMPFS Virtual Memory Filesystem
106
Everything in tmpfs is temporary in the sense that no files will be created on any device. If you unmount a
tmpfs instance, everything stored therein is lost.
tmpfs puts everything into the kernel internal caches and grows and shrinks to accommodate the files it
contains and is able to swap unneeded pages out to swap space. It has maximum size limits which can be
adjusted on the fly via 'mount -o remount ...'
If you compare it to ramfs (which was the template to create tmpfs) you gain swapping and limit checking.
Another similar thing is the RAM disk (/dev/ram*), which simulates a fixed size hard disk in physical RAM,
where you have to create an ordinary filesystem on top. Ramdisks cannot swap and you do not have the
possibility to resize them.
9.2.1. Mount Parameters
tmpfs has a couple of mount options:
• size: The limit of allocated bytes for this tmpfs instance. The default is half of your physical RAM
without swap. If you oversize your tmpfs instances the machine will deadlock since the OOM handler
will not be able to free that memory.
• nr_blocks: The same as size, but in blocks of PAGECACHE_SIZE.
• nr_inodes: The maximum number of inodes for this instance. The default is half of the number of
your physical RAM pages.
These parameters accept a suffix k, m or g for kilo, mega and giga and can be changed on remount.
To specify the initial root directory you can use the following mount options:
• mode: The permissions as an octal number
• uid: The user id
• gid: The group id
These options do not have any effect on remount. You can change these parameters with chmod(1),
chown(1) and chgrp(1) on a mounted filesystem.
So the following mount command will give you a tmpfs instance on /mytmpfs which can allocate 12MB of
RAM/SWAP and it is only accessible by root.
mount -t tmpfs -o size=12M,mode=700 tmpfs /mytmpfs
9.2.2. Kernel Support for tmpfs
In order to use a tmpfs filesystem, the CONFIG_TMPFS option has to be enabled for your kernel
configuration. It can be found in the Filesystems configuration group. You can simply check if a running
kernel supports tmpfs by searching the contents of /proc/fileysystems:
bash# grep tmpfs /proc/filesystems
nodev
tmpfs
bash#
9.2.3. Usage of tmpfs in Embedded Systems
In embedded systems tmpfs is very well suited to provide read and write space (e.g. /tmp and /var) for a
read-only root file system such as CramFs described in section 9.1.4. Compressed ROM Filesystem. One way
to achieve this is to use symbolic links. The following code could be part of the startup file /etc/rc.sh of the
9.2.1. Mount Parameters
107
read-only ramdisk:
#!/bin/sh
...
# Won't work on read-only root: mkdir /tmpfs
mount -t tmpfs tmpfs /tmpfs
mkdir /tmpfs/tmp /tmpfs/var
# Won't work on read-only root: ln -sf /tmpfs/tmp /tmpfs/var /
...
The commented out sections will of course fail on a read-only root filesystem, so you have to create the
/tmpfs mount-point and the symbolic links in your root filesystem beforehand in order to successfully use
this setup.
9.3. Using MultiMediaCards in Linux"
The MultiMediaCard (MMC) is a flash memory card standard.
Booting Linux with a MMC card connected to the m28 you should find in the bootlog something like that:
mmc0: new high speed SD card at address 0002
mmcblk0: mmc0:0002 00000 1.90 GiB
mmcblk0: p1
If the mmc card is detected, you should see at least the following device files:
/dev/mmcblk0
If there are partitions on it, you see the following device files:
/dev/mmcblk0pX
X =[1..n] with n=number of partitions
mount the partition:
root@generic-armv5te:~# cd /tmp/duts
root@generic-armv5te:/tmp/duts# ls -al mmc
total 0
drwxr-xr-x 2 root root 40 Oct 2 16:59 .
drwxr-xr-x 3 root root 60 Oct 2 16:59 ..
root@generic-armv5te:/tmp/duts# mount
rootfs on / type rootfs (rw)
192.168.1.1:/opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/ on / type nfs (rw,relatime,vers=3,rsize=4096,
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,relatime)
none on /dev type tmpfs (rw,relatime,mode=755)
/dev/mmcblk0p2 on /media/mmcblk0p2 type vfat (rw,sync,relatime,fmask=0022,dmask=0022,codepage=cp4
/dev/mmcblk0p3 on /media/mmcblk0p3 type ext4 (rw,sync,relatime,data=ordered)
devpts on /dev/pts type devpts (rw,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /var/volatile type tmpfs (rw,relatime)
tmpfs on /media/ram type tmpfs (rw,relatime)
root@generic-armv5te:/tmp/duts# df
Filesystem
1K-blocks
Used Available Use% Mounted on
rootfs
330279532 155153328 158348988 50% /
192.168.1.1:/opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/ 330279532 155153328 158348988 50% /
none
127104
140
126964
1% /dev
/dev/mmcblk0p2
30642
12666
17976 42% /media/mmc
/dev/mmcblk0p3
1781936
1187500
503916 71% /media/mmc
tmpfs
127104
168
126936
1% /var/volat
tmpfs
127104
0
127104
0% /media/ram
9.3. Using MultiMediaCards in Linux"
108
root@generic-armv5te:/tmp/duts# mount -t vfat /dev/mmcblk0p2 /tmp/duts/mmc
root@generic-armv5te:/tmp/duts# mount
rootfs on / type rootfs (rw)
192.168.1.1:/opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/ on / type nfs (rw,relatime,vers=3,rsize=4096,
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,relatime)
none on /dev type tmpfs (rw,relatime,mode=755)
/dev/mmcblk0p2 on /media/mmcblk0p2 type vfat (rw,sync,relatime,fmask=0022,dmask=0022,codepage=cp4
/dev/mmcblk0p3 on /media/mmcblk0p3 type ext4 (rw,sync,relatime,data=ordered)
devpts on /dev/pts type devpts (rw,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /var/volatile type tmpfs (rw,relatime)
tmpfs on /media/ram type tmpfs (rw,relatime)
/dev/mmcblk0p2 on /var/volatile/tmp/duts/mmc type vfat (rw,sync,relatime,fmask=0022,dmask=0022,co
root@generic-armv5te:/tmp/duts# df
Filesystem
1K-blocks
Used Available Use% Mounted on
rootfs
330279532 155153328 158348988 50% /
192.168.1.1:/opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/ 330279532 155153328 158348988 50% /
none
127104
140
126964
1% /dev
/dev/mmcblk0p2
30642
12666
17976 42% /media/mmc
/dev/mmcblk0p3
1781936
1187500
503916 71% /media/mmc
tmpfs
127104
168
126936
1% /var/volat
tmpfs
127104
0
127104
0% /media/ram
/dev/mmcblk0p2
30642
12666
17976 42% /var/volat
root@generic-armv5te:/tmp/duts# ls -al mmc
total 12682
drwxr-xr-x 2 root root
16384 Jan 1 1970 .
drwxr-xr-x 3 root root
60 Oct 2 16:59 ..
-rwxr-xr-x 1 root root
29 Oct 2 15:44 date_of_creation
-rwxr-xr-x 1 root root
29 Sep 5 04:12 date_of_modification
-rwxr-xr-x 1 root root
5410 May 22 11:32 env.txt
-rwxr-xr-x 1 root root
3754 Apr 17 10:13 env.txt.OLD
-rwxr-xr-x 1 root root 1152054 Feb 7 2012 img.bmp
-rwxr-xr-x 1 root root 1152054 Feb 7 2012 img1.bmp
-rwxr-xr-x 1 root root
1024 Oct 2 15:44 random.hex
-rwxr-xr-x 1 root root 233738 Feb 8 2012 slide-1.bmp
-rwxr-xr-x 1 root root 1152054 Feb 8 2012 slide-2.bmp
-rwxr-xr-x 1 root root 1152054 Feb 8 2012 slide-3.bmp
-rwxr-xr-x 1 root root 1152054 Feb 8 2012 slide-4.bmp
-rwxr-xr-x 1 root root 1152054 Feb 8 2012 slide-5.bmp
-rwxr-xr-x 1 root root 1152054 Feb 8 2012 slide-6.bmp
-rwxr-xr-x 1 root root 1152054 Feb 8 2012 slide-7.bmp
-rwxr-xr-x 1 root root 1152054 Feb 8 2012 slide-8.bmp
-rwxr-xr-x 1 root root 2340744 Apr 18 07:07 uImage
root@generic-armv5te:/tmp/duts#
write some files to the MMC:
root@generic-armv5te:/tmp/duts# date > /tmp/duts/mmc/date_of_creation
root@generic-armv5te:/tmp/duts# dd if=/dev/urandom of=/tmp/duts/random.hex bs=10 24 count=1
1+0 records in
1+0 records out
1024 bytes (1.0 kB) copied, 0.00196875 s, 520 kB/s
root@generic-armv5te:/tmp/duts# cp random.hex mmc/
root@generic-armv5te:/tmp/duts# cmp random.hex mmc/random.hex
root@generic-armv5te:/tmp/duts# ls -al mmc/
total 12682
drwxr-xr-x 2 root root
16384 Jan 1 1970 .
drwxr-xr-x 3 root root
80 Oct 2 16:59 ..
-rwxr-xr-x 1 root root
29 Oct 2 16:59 date_of_creation
-rwxr-xr-x 1 root root
29 Sep 5 04:12 date_of_modification
-rwxr-xr-x 1 root root
5410 May 22 11:32 env.txt
-rwxr-xr-x 1 root root
3754 Apr 17 10:13 env.txt.OLD
-rwxr-xr-x 1 root root 1152054 Feb 7 2012 img.bmp
-rwxr-xr-x 1 root root 1152054 Feb 7 2012 img1.bmp
-rwxr-xr-x 1 root root
1024 Oct 2 16:59 random.hex
-rwxr-xr-x 1 root root 233738 Feb 8 2012 slide-1.bmp
9.3. Using MultiMediaCards in Linux"
109
-rwxr-xr-x 1 root root 1152054 Feb 8 2012
-rwxr-xr-x 1 root root 1152054 Feb 8 2012
-rwxr-xr-x 1 root root 1152054 Feb 8 2012
-rwxr-xr-x 1 root root 1152054 Feb 8 2012
-rwxr-xr-x 1 root root 1152054 Feb 8 2012
-rwxr-xr-x 1 root root 1152054 Feb 8 2012
-rwxr-xr-x 1 root root 1152054 Feb 8 2012
-rwxr-xr-x 1 root root 2340744 Apr 18 07:07
root@generic-armv5te:/tmp/duts#
slide-2.bmp
slide-3.bmp
slide-4.bmp
slide-5.bmp
slide-6.bmp
slide-7.bmp
slide-8.bmp
uImage
unmount the partition with:
root@generic-armv5te:/tmp/duts# umount /tmp/duts/mmc
root@generic-armv5te:/tmp/duts# mount
rootfs on / type rootfs (rw)
192.168.1.1:/opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/ on / type nfs (rw,relatime,vers=3,rsize=4096,
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,relatime)
none on /dev type tmpfs (rw,relatime,mode=755)
/dev/mmcblk0p2 on /media/mmcblk0p2 type vfat (rw,sync,relatime,fmask=0022,dmask=0022,codepage=cp4
/dev/mmcblk0p3 on /media/mmcblk0p3 type ext4 (rw,sync,relatime,data=ordered)
devpts on /dev/pts type devpts (rw,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /var/volatile type tmpfs (rw,relatime)
tmpfs on /media/ram type tmpfs (rw,relatime)
root@generic-armv5te:/tmp/duts# df
Filesystem
1K-blocks
Used Available Use% Mounted on
rootfs
330279532 155153328 158348988 50% /
192.168.1.1:/opt/eldk-5.2.1/armv5te/rootfs-lsb-sdk/ 330279532 155153328 158348988 50% /
none
127104
140
126964
1% /dev
/dev/mmcblk0p2
30642
12666
17976 42% /media/mmc
/dev/mmcblk0p3
1781936
1187500
503916 71% /media/mmc
tmpfs
127104
172
126932
1% /var/volat
tmpfs
127104
0
127104
0% /media/ram
root@generic-armv5te:/tmp/duts#
9.4. Splash Screen Support in Linux
To complement the U-Boot Splash Screen feature the new configuration option
"CONFIG_FB_PRE_INIT_FB" was added to the Linux kernel. This allows the Linux kernel to skip certain
parts of the framebuffer initialization and to reuse the framebuffer contents that was set up by the U-Boot
firmware. This allows to have an image displayed nearly immediately after power-on, so the delay needed to
boot the Linux kernel is masked to the user.
The current implementation has some limitations:
• We did not succeed in reusing the previously allocated framebuffer contents directly. Instead, Linux
will allocate a new framebuffer, copy the contents, and then switch the display. This adds a minimal
delay to the boot time, but is otherwise invisible to the user.
• Linux manages its own colormap, and we considered it too much effort to keep the same settings as
used by U-Boot. Instead we use the "trick" that U-Boot will fill the color map table backwards (top
down). This works pretty well for images which use no more than 200...225 colors. If the images uses
more colors, a bad color mapping may result.
We strongly recommend to convert all images that will be loaded as Linux splash screens to use no
more than 225 colors. The "ppmquant" tool can be used for this purpose (see Bitmap Support in
U-Boot for details).
• Usually there will be a Linux device driver that is used to adjust the brightness and contrast of the
display. When this driver starts, a visible change of brightness will happen if the default settings as
used by U-Boot differ.
9.4. Splash Screen Support in Linux
110
We recommend to store settings of brightness and contrast in U-Boot environment variables that
can be shared between U-Boot and Linux. This way it is possible (assuming adequate driver support)
to adjust the display settings correctly already in U-Boot and thus to avoid any flicker of the display
when Linux takes over control.
9.5. Root File System: Design and Building
It is not an easy task to design the root file system for an embedded system. There are three major problems to
be solved:
1. what to put in it
2. which file system type to use
3. where to store and how to boot it
For now we will assume that the contents of the root file system is aready known; for example, it is given to
us as a directory tree or a tarball which contains all the required files.
We will also assume that our system is a typical resource-limited embedded system so we will especially look
for solutions where the root file system can be stored on on-board flash memory or other flash memory based
devices like CompactFlash or SD cards, MMC or USB memory sticks.
A widespread approach to build a root file system is to use some Linux distribution (like the ELDK) and to
remove things not needed. This approach may be pretty common, but it is almost always terribly wrong. You
also don't build a family home by taking a skyscraper and removing parts. Like a house, a root file system
should be built bottom up, starting from scratch and adding things you know you need. Never add anything
where you don't exactly know what it's needed for.
But our focus here is on the second item: the options we have for chosing a file system type and the
consequences this has.
In all cases we will base our experiments on the same content of the root filesystem; we use the images of the
SELF (Simple Embedded Linux Framework) that come with the ELDK. In a first step we will transform the
SELF images into a tarball to meet the requirements mentioned above:
In a ELDK installation, the SELF images can be found in the /opt/eldk/<architecture>/images/
directory. There is already a compressed ramdisk image in this directory, which we will use
(ramdisk_image.gz):
1. Uncompress ramdisk image:
bash$ gzip -d -c -v /opt/eldk/ppc_8xx/images/ramdisk_image.gz >/tmp/ramdisk_image
/opt/eldk/ppc_8xx/images/ramdisk_image.gz:
61.4%
Note: The following steps require root permissions!
2. Mount ramdisk image:
bash# mount -o loop /tmp/ramdisk_image /mnt/tmp
3. Create tarball; to avoid the need for root permissions in the following steps we don't include the
device files in our tarball:
bash# cd /mnt/tmp
bash# tar -zc --exclude='dev/*' -f /tmp/rootfs.tar.gz *
9.5. Root File System: Design and Building
111
4. Instead, we create a separate tarball which contains only the device entries so we can use them when
necessary (with cramfs):
bash# tar -zcf /tmp/devices.tar.gz dev/
bash# cd /tmp
5. Unmount ramdisk image:
bash# umount /mnt/tmp
We will use the /tmp/rootfs.tar.gz tarball as master file in all following experiments.
9.5.1. Root File System on a Ramdisk
Ram disks are used very often to hold the root file system of embedded systems. They have several
advantages:
• well-known
• well-supported by the Linux kernel
• simple to build
• simple to use - you can even combine the ramdisk with the Linux kernel into a single image file
• RAM based, thus pretty fast
• writable file system
• original state of file system after each reboot = easy recovery from accidental or malicious data
corruption etc.
On the other hand, there are several disadvantages, too:
• big memory footprint: you always have to load the complete filesystem into RAM, even if only small
parts of are actually used
• slow boot time: you have to load (and uncompress) the whole image before the first application
process can start
• only the whole image can be replaced (not individual files)
• additional storage needed for writable persistent data
Actually there are only very few situations where a ramdisk image is the optimal solution. But because they
are so easy to build and use we will discuss them here anyway.
In almost all cases you will use an ext2 file system in your ramdisk image. The following steps are needed to
create it:
1. Create a directory tree with the content of the target root filesystem. We do this by unpacking our
master tarball:
$ mkdir rootfs
$ cd rootfs
$ tar zxf /tmp/rootfs.tar.gz
2. We use the genext2fs tool to create the ramdisk image as this allows to use a simple text file to
describe which devices shall be created in the generated file system image. That means that no root
permissions are required at all. We use the following device table rootfs_devices.tab:
#<name>
<type> <mode> <uid> <gid> <major> <minor> <start>
/dev
d 755 0
0
/dev/console
c 640 0
0
5
1
/dev/fb0
c 640 0
0
29
0
/dev/full
c 640 0
0
1
7
/dev/hda
b 640 0
0
3
0
-
9.5.1. Root File System on a Ramdisk
<inc>
-
<count>
-
112
/dev/hda
/dev/kmem
/dev/mem
/dev/mtd
/dev/mtdblock
/dev/mtdr
/dev/nftla
/dev/nftla
/dev/nftlb
/dev/nftlb
/dev/null
/dev/ptyp
/dev/ptypa
/dev/ptypb
/dev/ptypc
/dev/ptypd
/dev/ptype
/dev/ptypf
/dev/ram
/dev/ram
/dev/rtc
/dev/tty
/dev/tty
/dev/ttyS
/dev/ttyp
/dev/ttypa
/dev/ttypb
/dev/ttypc
/dev/ttypd
/dev/ttype
/dev/ttypf
/dev/zero
b
c
c
c
b
c
b
b
b
b
c
c
c
c
c
c
c
c
b
b
c
c
c
c
c
c
c
c
c
c
c
c
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
640
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
1
1
90
31
90
93
93
93
93
1
2
2
2
2
2
2
2
1
1
10
4
5
4
3
3
3
3
3
3
3
1
1
2
1
0
0
1
0
1
16
17
3
0
10
11
12
13
14
15
0
1
135
0
0
64
0
10
11
12
13
14
15
5
1
0
0
0
1
1
0
0
0
0
0
-
1
2
1
2
1
1
1
1
1
1
1
-
16
16
16
16
8
8
10
2
4
8
10
-
A description of the format of this table is part of the manual page for the genext2fs tool,
genext2fs(8).
3. We can now create an ext2 file system image using the genext2fs tool:
$
$
$
$
$
$
ROOTFS_DIR=rootfs
ROOTFS_SIZE=3700
ROOTFS_FREE=100
ROOTFS_INODES=380
ROOTFS_DEVICES=rootfs_devices.tab
ROOTFS_IMAGE=ramdisk.img
#
#
#
#
#
#
directory with root file system content
size of file system image
free space wanted
number of inodes
device description file
generated file system image
$ genext2fs -U \
-d ${ROOTFS_DIR} \
-D ${ROOTFS_DEVICES} \
-b ${ROOTFS_SIZE} \
-r ${ROOTFS_FREE} \
-i ${ROOTFS_INODES} \
${ROOTFS_IMAGE}
4. Compress the file system image:
$ gzip -v9 ramdisk.img
rootfs.img:
55.6% -- replaced with ramdisk.img.gz
5. Create an U-Boot image file from it:
$ mkimage -T ramdisk -C gzip -n 'Test Ramdisk Image' \
> -d ramdisk.img.gz uRamdisk
Image Name:
Test Ramdisk Image
Created:
Sun Jun 12 16:58:06 2005
Image Type:
PowerPC Linux RAMDisk Image (gzip compressed)
Data Size:
1618547 Bytes = 1580.61 kB = 1.54 MB
Load Address: 0x00000000
Entry Point: 0x00000000
9.5.1. Root File System on a Ramdisk
113
We now have a root file system image uRamdisk that can be used with U-Boot.
9.5.2. Root File System on a JFFS2 File System
JFFS2 (Journalling Flash File System version 2) was specifically designed for use on flash memory devices in
embedded systems. It is a log-structured file system which means that it is robust against loss of power,
crashes or other unorderly shutdowns of the system ("robust" means that data that is just being written when
the system goes down may be lost, but the file system itself does not get corrupted and the system can be
rebootet without need for any kind of file system check).
Some of the advantages of using JFFS2 as root file system in embedded systems are:
• file system uses compression, thus making efficient use of flash memory
• log-structured file system, thus robust against unorderly shutdown
• flash sector wear-leveling
• writable flash file system
Disadvantages are:
• long mount times (especially older versions)
• slow when reading: files to be read get uncompressed on the fly which eats CPU cycles and takes time
• slow when writing: files to be written get compressed, which eats CPU cycles and takes time, but it
may even take much longer until data gets actually stored in flash if the file system becomes full and
blocks must be erased first or - even worse - if garbage collection becomes necessary
• The garbage collector thread may run at any time, consuming CPU cycles and blocking accesses to
the file system.
Despite the aforementioned disadvantages, systems using a JFFS2 based root file system are easy to build,
make efficient use of the available resources and can run pretty reliably.
To create a JFFS2 based root file system please proceed as follows:
1. Create a directory tree with the content of the target root filesystem. We do this by unpacking our
master tarball:
$ mkdir rootfs
$ cd rootfs
$ tar zxf /tmp/rootfs.tar.gz
2. We can now create a JFFS2 file system image using the mkfs.jffs2 tool:
$
$
$
$
$
ROOTFS_DIR=rootfs
ROOTFS_EBSIZE=0x20000
ROOTFS_ENDIAN=b
ROOTFS_DEVICES=rootfs_devices.tab
ROOTFS_IMAGE=jffs2.img
#
#
#
#
#
directory with root file system content
erase block size of flash memory
target system is big endian
device description file
generated file system image
$ mkfs.jffs2 -U \
-d ${ROOTFS_DIR} \
-D ${ROOTFS_DEVICES} \
-${ROOTFS_ENDIAN} \
-e ${ROOTFS_EBSIZE} \
-o ${ROOTFS_IMAGE}
mkfs.jffs2: skipping device_table entry '/dev': no parent directory!
Note: When you intend to write the JFFS2 file system image to a NAND flash device, you should also
add the "-n" (or "--no-cleanmarkers") option, as cleanmarkers are not needed then.
9.5.2. Root File System on a JFFS2 File System
114
When booting the Linux kernel prints the following messages showing the default partition map which is used
for the flash memory on the TQM8xxL boards:
TQM flash bank 0: Using static image partition definition
Creating 7 MTD partitions on "TQM8xxL0":
0x00000000-0x00040000 : "u-boot"
0x00040000-0x00100000 : "kernel"
0x00100000-0x00200000 : "user"
0x00200000-0x00400000 : "initrd"
0x00400000-0x00600000 : "cramfs"
0x00600000-0x00800000 : "jffs"
0x00400000-0x00800000 : "big_fs"
We use U-Boot to load and store the JFFS2 image into the last partition and set up the Linux boot arguments
to use this as root device:
1. Erase flash:
=> era 40400000 407FFFFF
................. done
Erased 35 sectors
2. Download JFFS2 image:
=> tftp 100000 /tftpboot/TQM860L/jffs2.img
Using FEC ETHERNET device
TFTP from server 192.168.3.1; our IP address is 192.168.3.80
Filename '/tftpboot/TQM860L/jffs2.img'.
Load address: 0x100000
Loading: #################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
########
done
Bytes transferred = 2033888 (1f08e0 hex)
3. Copy image to flash:
=> cp.b 100000 40400000 ${filesize}
Copy to Flash... done
4. set up boot arguments to use flash partition 6 as root device:
=> setenv mtd_args setenv bootargs root=/dev/mtdblock6 rw rootfstype=jffs2
=> printenv addip
addip=setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}:${hostna
=> setenv flash_mtd 'run mtd_args addip;bootm ${kernel_addr}'
=> run flash_mtd
Using FEC ETHERNET device
TFTP from server 192.168.3.1; our IP address is 192.168.3.80
Filename '/tftpboot/TQM860L/uImage'.
Load address: 0x200000
Loading: #################################################################
#################################################################
###########
done
Bytes transferred = 719233 (af981 hex)
## Booting image at 40040000 ...
Image Name:
Linux-2.4.25
Created:
2005-06-12 16:32:24 UTC
Image Type:
PowerPC Linux Kernel Image (gzip compressed)
Data Size:
782219 Bytes = 763.9 kB
Load Address: 00000000
9.5.2. Root File System on a JFFS2 File System
115
Entry Point: 00000000
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Linux version 2.4.25 (wd@xpert) (gcc version 3.3.3 (DENX ELDK 3.1.1 3.3.3-9)) #1 Sun Jun 12
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/mtdblock6 rw rootfstype=jffs2 ip=192.168.3.80:192.168.3.1::2
Decrementer Frequency = 187500000/60
Calibrating delay loop... 49.86 BogoMIPS
...
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
VFS: Mounted root (jffs2 filesystem).
Freeing unused kernel memory: 56k init
BusyBox v0.60.5 (2005.03.07-06:54+0000) Built-in shell (msh)
Enter 'help' for a list of built-in commands.
# ### Application running ...
# mount
rootfs on / type rootfs (rw)
/dev/mtdblock6 on / type jffs2 (rw)
/proc on /proc type proc (rw)
# df /
Filesystem
1k-blocks
Used Available Use% Mounted on
rootfs
4096
2372
1724 58% /
9.5.3. Root File System on a cramfs File System
cramfs is a compressed, read-only file system.
Advantages are:
• file system uses compression, thus making efficient use of flash memory
• Allows for quick boot times as only used files get loaded and uncompressed
Disadvantages are:
• only the whole image can be replaced (not individual files)
• additional storage needed for writable persistent data
• mkcramfs tool does not support device table, so we need root permissions to create the required
device files
To create a cramfs based root file system please proceed as follows:
1. Create a directory tree with the content of the target root filesystem. We do this by unpacking our
master tarball:
$ mkdir rootfs
$ cd rootfs
$ tar -zxf /tmp/rootfs.tar.gz
2. Create the required device files. We do this here by unpacking a special tarball which holds only the
device file entries.
Note: this requires root permissions!
# cd rootfs
# tar -zxf /tmp/devices.tar.gz
9.5.3. Root File System on a cramfs File System
116
Many tools require some storage place in a filesystem, so we must provide at least one (small)
writable filesystem. For all data which may be lost when the system goes down, a "tmpfs"
filesystem is the optimal choice. To create such a writable tmpfs filesystem we add the following lines
to the /etc/rc.sh script:
# mount TMPFS because root-fs is readonly
/bin/mount -t tmpfs -o size=2M tmpfs /tmpfs
Some tools require write permissions on some device nodes (for example, to change ownership and
permissions), or dynamically (re-) create such files (for example, /dev/log which is usually a Unix
Domain socket). The files are placed in a writable filesystem; in the root filesystem symbolic links are
used to point to their new locations:
dev/ptyp0
→ /tmpfs/dev/ptyp0
dev/ptyp1
→ /tmpfs/dev/ptyp1
dev/ptyp2
→ /tmpfs/dev/ptyp2
dev/ptyp3
→ /tmpfs/dev/ptyp3
dev/ptyp4
→ /tmpfs/dev/ptyp4
dev/ptyp5
→ /tmpfs/dev/ptyp5
dev/ptyp6
→ /tmpfs/dev/ptyp6
dev/ptyp7
→ /tmpfs/dev/ptyp7
dev/ptyp8
→ /tmpfs/dev/ptyp8
dev/ptyp9
→ /tmpfs/dev/ptyp9
dev/ptypa
→ /tmpfs/dev/ptypa
dev/ptypb
→ /tmpfs/dev/ptypb
dev/ptypc
→ /tmpfs/dev/ptypc
dev/ptypd
→ /tmpfs/dev/ptypd
dev/ptype
→ /tmpfs/dev/ptype
dev/ptypf
→ /tmpfs/dev/ptypf
tmp
→ /tmpfs/tmp
dev/log
→ /var/log/log
In case you use dhclient also:
etc/dhclient.conf → /tmpfs/var/lib/dhclient.conf
dev/ttyp0
dev/ttyp1
dev/ttyp2
dev/ttyp3
dev/ttyp4
dev/ttyp5
dev/ttyp6
dev/ttyp7
dev/ttyp8
dev/ttyp9
dev/ttypa
dev/ttypb
dev/ttypc
dev/ttypd
dev/ttype
dev/ttypf
var
→
→
→
→
→
→
→
→
→
→
→
→
→
→
→
→
→
/tmpfs/dev/ttyp0
/tmpfs/dev/ttyp1
/tmpfs/dev/ttyp2
/tmpfs/dev/ttyp3
/tmpfs/dev/ttyp4
/tmpfs/dev/ttyp5
/tmpfs/dev/ttyp6
/tmpfs/dev/ttyp7
/tmpfs/dev/ttyp8
/tmpfs/dev/ttyp9
/tmpfs/dev/ttypa
/tmpfs/dev/ttypb
/tmpfs/dev/ttypc
/tmpfs/dev/ttypd
/tmpfs/dev/ttype
/tmpfs/dev/ttypf
/tmpfs/var
etc/resolv.conf → /tmpfs/var/lib/resolv.conf
To place the corresponding directories and device files in the tmpfs file system, the following code
is added to the /etc/rc.sh script:
mkdir -p /tmpfs/tmp /tmpfs/dev \
/tmpfs/var/lib/dhcp /tmpfs/var/lock /tmpfs/var/run
while read name minor
do
mknod /tmpfs/dev/ptyp$name c 2 $minor
mknod /tmpfs/dev/ttyp$name c 3 $minor
done <<__EOD__
0 0
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
9.5.3. Root File System on a cramfs File System
117
3. a 10
b 11
c 12
d 13
e 14
f 15
__EOD__
chmod 0666 /tmpfs/dev/*
4. We can now create a cramfs file system image using the mkcramfs tool:
$ ROOTFS_DIR=rootfs
$ ROOTFS_ENDIAN="-r"
$ ROOTFS_IMAGE=cramfs.img
# directory with root file system content
# target system has reversed (big) endianess
# generated file system image
PATH=/opt/eldk/usr/bin:$PATH
mkcramfs ${ROOTFS_ENDIAN} ${DEVICES} ${ROOTFS_DIR} ${ROOTFS_IMAGE}
Swapping filesystem endian-ness
bin
dev
etc
...
-48.78% (-86348 bytes) in.ftpd
-46.02% (-16280 bytes) in.telnetd
-45.31% (-74444 bytes) xinetd
Everything: 1864 kilobytes
Super block: 76 bytes
CRC: c166be6d
warning: gids truncated to 8 bits. (This may be a security concern.)
5. We can use the same setup as before for the JFFS2 filesystem, just changing the bootargument to
"rootfstype=cramfs"
9.5.4. Root File System on a Read-Only ext2 File
System
When storing the root file system in on-board flash memory it seems only natural to look for special flash
filesystems like JFFS2, or for other file system types that are designed for such environments like cramfs. It
seems to be a bad idea to use a standard ext2 file system because it contains neither any type of wear
leveling which is needed for writable file systems in flash memory, nor is it robust against unorderly
shutdowns.
The situation changes if we use an ext2 file system which we mount read-only. Such a configuration can be
very useful in some situations.
Advantages:
• very fast
• low RAM memory footprint
Disadvantages:
• high flash memory footprint because no compression
To create an ext2 image that can be used as a read-only root file system the following steps are necessary:
1. Create a directory tree with the content of the target root filesystem. We do this by unpacking our
master tarball:
9.5.4. Root File System on a Read-Only ext2 File System
118
$ mkdir rootfs
$ cd rootfs
$ tar -zxf /tmp/rootfs.tar.gz
2. Like with the cramfs root file system, we use "tmpfs" for cases where a writable file system is
needed and add the following lines to the /etc/rc.sh script:
# mount TMPFS because root-fs is readonly
/bin/mount -t tmpfs -o size=2M tmpfs /tmpfs
We also create the same symbolic links for device files that must be placed in a writable filesystem:
dev/ptyp0
→ /tmpfs/dev/ptyp0
dev/ptyp1
→ /tmpfs/dev/ptyp1
dev/ptyp2
→ /tmpfs/dev/ptyp2
dev/ptyp3
→ /tmpfs/dev/ptyp3
dev/ptyp4
→ /tmpfs/dev/ptyp4
dev/ptyp5
→ /tmpfs/dev/ptyp5
dev/ptyp6
→ /tmpfs/dev/ptyp6
dev/ptyp7
→ /tmpfs/dev/ptyp7
dev/ptyp8
→ /tmpfs/dev/ptyp8
dev/ptyp9
→ /tmpfs/dev/ptyp9
dev/ptypa
→ /tmpfs/dev/ptypa
dev/ptypb
→ /tmpfs/dev/ptypb
dev/ptypc
→ /tmpfs/dev/ptypc
dev/ptypd
→ /tmpfs/dev/ptypd
dev/ptype
→ /tmpfs/dev/ptype
dev/ptypf
→ /tmpfs/dev/ptypf
tmp
→ /tmpfs/tmp
dev/log
→ /var/log/log
In case you use dhclient also:
etc/dhclient.conf → /tmpfs/var/lib/dhclient.conf
dev/ttyp0
dev/ttyp1
dev/ttyp2
dev/ttyp3
dev/ttyp4
dev/ttyp5
dev/ttyp6
dev/ttyp7
dev/ttyp8
dev/ttyp9
dev/ttypa
dev/ttypb
dev/ttypc
dev/ttypd
dev/ttype
dev/ttypf
var
→
→
→
→
→
→
→
→
→
→
→
→
→
→
→
→
→
/tmpfs/dev/ttyp0
/tmpfs/dev/ttyp1
/tmpfs/dev/ttyp2
/tmpfs/dev/ttyp3
/tmpfs/dev/ttyp4
/tmpfs/dev/ttyp5
/tmpfs/dev/ttyp6
/tmpfs/dev/ttyp7
/tmpfs/dev/ttyp8
/tmpfs/dev/ttyp9
/tmpfs/dev/ttypa
/tmpfs/dev/ttypb
/tmpfs/dev/ttypc
/tmpfs/dev/ttypd
/tmpfs/dev/ttype
/tmpfs/dev/ttypf
/tmpfs/var
etc/resolv.conf → /tmpfs/var/lib/resolv.conf
To place the corresponding directories and device files in the tmpfs file system, the following code
is added to the /etc/rc.sh script:
mkdir -p /tmpfs/tmp /tmpfs/dev \
/tmpfs/var/lib/dhcp /tmpfs/var/lock /tmpfs/var/run
while read name minor
do
mknod /tmpfs/dev/ptyp$name c 2 $minor
mknod /tmpfs/dev/ttyp$name c 3 $minor
done <<__EOD__
0 0
1 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
a 10
b 11
c 12
9.5.4. Root File System on a Read-Only ext2 File System
119
d 13
e 14
f 15
__EOD__
chmod 0666 /tmpfs/dev/*
3. Like we did for the ramdisk, we now create an ext2 file system image using the genext2fs tool:
$
$
$
$
$
$
ROOTFS_DIR=rootfs
ROOTFS_SIZE=3700
ROOTFS_FREE=100
ROOTFS_INODES=380
ROOTFS_DEVICES=rootfs_devices.tab
ROOTFS_IMAGE=ext2.img
#
#
#
#
#
#
directory with root file system content
size of file system image
free space wanted
number of inodes
device description file
generated file system image
$ genext2fs -U \
-d ${ROOTFS_DIR} \
-D ${ROOTFS_DEVICES} \
-b ${ROOTFS_SIZE} \
-r ${ROOTFS_FREE} \
-i ${ROOTFS_INODES} \
${ROOTFS_IMAGE}
4. We can again use the same setup as before for the JFFS2 filesystem, just changing the boot argument
to "rootfstype=ext2" (or simply omit it completely as this is the default anyway), and we must
change the "rw" argument into "ro" to mount our root file system really read-only:
...
Linux version 2.4.25 (wd@xpert) (gcc version 3.3.3 (DENX ELDK 3.1.1 3.3.3-9)) #1 Sun Jun 12
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/mtdblock6 ro rootfstype=ext2 ip=192.168.3.80:192.168.3.1::25
Decrementer Frequency = 187500000/60
Calibrating delay loop... 49.86 BogoMIPS
...
9.5.5. Root File System on a Flash Card
Using an ext2 file system on a flash memory card (like CompactFlash, SD, MMC or a USB memory stick)
is standard technology. To avoid unnecessary flash wear it is a good idea to mount the root file system
read-only, or at least using the "noatime" mount option.
For our test we can use the "ext2.img" file from the previous step without changes:
1. In this test we use a standard CompactFlash card which comes with a single partition on it. We use
U-Boot to copy the ext2 file system image into this partition:
=> tftp 100000 /tftpboot/TQM860L/ext2.img
Using FEC ETHERNET device
TFTP from server 192.168.3.1; our IP address is 192.168.3.80
Filename '/tftpboot/TQM860L/ext2.img'.
Load address: 0x100000
Loading: #################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
#################################################################
9.5.5. Root File System on a Flash Card
120
#################################################################
#################################################################
#################################################################
#################################################################
##########################
done
Bytes transferred = 3788800 (39d000 hex)
=> ide part
Partition Map for IDE device 0
Partition
Start Sector
1
32
=> ide write 100000 20 1ce8
--
Partition Type: DOS
Num Sectors
500704
Type
6
IDE write: device 0 block # 32, count 7400 ... 7400 blocks written: OK
Note that the "ide write" command takes parameters as hex numbers, and the write count is in
terms of disk blocks of 512 bytes each. So we have to use 0x20 for the starts sector of the first
partition, and 3788800 / 512 = 7400 = 0x1CE8 for the block count.
2. We now prepare the Linux boot arguments to take this partition as read-only root device:
=> setenv cf_args setenv bootargs root=/dev/hda1 ro
=> setenv flash_cf 'run cf_args addip;bootm ${kernel_addr}'
=> setenv bootcmd run flash_cf
3. ...and boot the system:
...
Linux version 2.4.25 (wd@xpert) (gcc version 3.3.3 (DENX ELDK 3.1.1 3.3.3-9)) #1 Sun Jun 12
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: root=/dev/hda1 ro ip=192.168.3.80:192.168.3.1::255.255.255.0:tqm860l:e
Decrementer Frequency = 187500000/60
Calibrating delay loop... 49.86 BogoMIPS
...
9.5.6. Root File System in a Read-Only File in a
FAT File System
This is a more complicated example that shows that - depending on project requirements - many other
alternatives for chosing a root file system for your embedded system exist.
The scenario is as follows: on your embedded device you use a cheap and popular storage medium like
CompactFlash, MMC or SD cards or USB memory sticks to store both the Linux kernel and your root file
system. You want to distribute software updates over the internet: your customers can download the file from
your web site, or you sent the images by email. Your customers may use any flash card or memory stick they
happen to find, so you have no information about brand or size of the storage device.
Unfortunately most of your customers use Windows systems. And they don't want to be bothered with long
instructions how to create special partitions on the storage device or how to write binary images or things like
that. A simple "copy file" operation is nearly exhausting their capabilities.
What to do? Well, if copying a file is all your customers can do we should not ask for more. Storage devices
like CompactFlash cards etc. typically come with a single partition on it, which holds a FAT or VFAT file
system. This cannot be used as a Linux root file system directly, so we have to use some trickery.
9.5.6. Root File System in a Read-Only File in a FAT File System
121
Here is one possible solution: Your software distribution consistes of two files: The first file is the Linux
kernel with a minimal ramdisk image attached (using the multi-file image format for U-Boot); U-Boot can
load and boot such files from a FAT or VFAT file system. The second file is your root file system. For
convenience and speed we use again an image of an ext2 file system. When Linux boots, it will initially use
the attached ramdisk as root file system. The programs in this ramdisk will mount the FAT or VFAT file
system - read-only. Then we can use a loop device (see losetup(8)) to associate the root file system image with
a block device which can be used as a mount point. And finally we use pivot_root(8) to change the root file
system to our image on the CF card.
This sounds not so complicated, and actually it is quite simple once you understand what needs to be done.
Here is a more detailed description:
1. The root file system image is easy: as mantioned before, we will use an ext2 file system image, and
to avoid wearing the flash storage device we will use it in read-only mode - we did a read-only ext2
root file system image before, and here we can just re-use the existing image file.
2. The initial ramdisk image that performs the pivot_root step must be created from scratch, but we
already know how to create ramdisk images, so we just have to figure out what to put in it.
The most important tool here is nash, a script interpreter that was specifically designed for such
purposes (see nash(8)). We don't need any additional tools, and if we use static linking, then the
nash binary plus a small script to control it is all we need for our initial ramdisk.
To be precise, we need a couple of (empty) directories (bin, dev, etc, lib, loopfs, mnt, proc,
and sysroot), the bin/nash binary, the linuxrc script and a symbolic link sbin pointing to
bin:
drwxr-xr-x
-rwxr-xr-x
drwxr-xr-x
drwxr-xr-x
drwxr-xr-x
-rwxr-xr-x
drwxr-xr-x
drwxr-xr-x
drwxr-xr-x
lrwxrwxrwx
drwxr-xr-x
2
1
2
2
2
1
2
2
2
1
2
wd
wd
wd
wd
wd
wd
wd
wd
wd
wd
wd
users
users
users
users
users
users
users
users
users
users
users
4096
469512
4096
4096
4096
511
4096
4096
4096
3
4096
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Apr
Jun
Apr
13
11
12
12
12
13
12
12
12
12
12
01:11
22:47
00:04
00:04
00:04
01:28
00:04
00:09
00:04
18:54
00:04
bin
bin/nash
dev
etc
lib
linuxrc
loopfs
mnt
proc
sbin -> bin
sysroot
3. We also need only a minimal device table for creating the initial ramdisk:
#<name>
<type> <mode> <uid> <gid> <major> <minor> <start>
/dev
d 755 0
0
/dev/console
c 640 0
0
5
1
/dev/hda
b 640 0
0
3
0
/dev/hda
b 640 0
0
3
1
1
/dev/loop
b 640 0
0
7
0
0
/dev/null
c 640 0
0
1
3
/dev/ram
b 640 0
0
1
0
0
/dev/ram
b 640 0
0
1
1
/dev/tty
c 640 0
0
4
0
0
/dev/tty
c 640 0
0
5
0
/dev/ttyS
c 640 0
0
4
64
0
/dev/zero
c 640 0
0
1
5
-
<inc>
1
1
1
1
1
-
<count>
8
4
2
4
4
-
4. To create the initial ramdisk we perform the usual steps:
$
$
$
$
$
$
INITRD_DIR=initrd
INITRD_SIZE=490
INITRD_FREE=0
INITRD_INODES=54
INITRD_DEVICES=initrd_devices.tab
INITRD_IMAGE=initrd.img
9.5.6. Root File System in a Read-Only File in a FAT File System
122
$ genext2fs -U \
-d ${INITRD_DIR} \
-D ${INITRD_DEVICES} \
-b ${INITRD_SIZE} \
-r ${INITRD_FREE} \
-i ${INITRD_INODES} \
${INITRD_IMAGE}
$ gzip -v9 ${INITRD_IMAGE}
The result is a really small (233 kB) compressed ramdisk image.
5. Assuming you already have your Linux kernel image, you can now use mkimage to build an U-Boot
multi-file image that combines the Linux kernel and the initial ramdisk:
$ LINUX_KERNEL=linuxppc_2_4_devel/arch/ppc/boot/images/vmlinux.gz
$ mkimage -A ppc -O Linux -T multi -C gzip \
> -n 'Linux with Pivot Root Helper' \
> -d ${LINUX_KERNEL}:${INITRD_IMAGE}.gz linux.img
Image Name:
Linux with Pivot Root Helper
Created:
Mon Jun 13 01:48:11 2005
Image Type:
PowerPC Linux Multi-File Image (gzip compressed)
Data Size:
1020665 Bytes = 996.74 kB = 0.97 MB
Load Address: 0x00000000
Entry Point: 0x00000000
Contents:
Image 0:
782219 Bytes = 763 kB = 0 MB
Image 1:
238433 Bytes = 232 kB = 0 MB
The newly created file linux.img is the second image we have to copy to the CF card.
We are done.
But wait - one essential part was not mentioned yet: the linuxrc script in our initial ramdisk image which
contains all the magic. This script is quite simple:
#!/bin/nash
echo Mounting /proc filesystem
mount -t proc /proc /proc
echo Creating block devices
mkdevices /dev
echo Creating root device
mkrootdev /dev/root
echo 0x0100 > /proc/sys/kernel/real-root-dev
echo Mounting flash card
mount -o noatime -t vfat /dev/hda1 /mnt
echo losetup for filesystem image
losetup /dev/loop0 /mnt/rootfs.img
echo Mounting root filesystem image
mount -o defaults --ro -t ext2 /dev/loop0 /sysroot
echo Running pivot_root
pivot_root /sysroot /sysroot/initrd
umount /initrd/proc
Let's go though it step by step:
9.5.6. Root File System in a Read-Only File in a FAT File System
123
• The first line says that it's a script file for the /bin/nash interpreter.
Note: even if this file looks like a shell script it is NOT interpreted by a shell, but by the nash
interpreter. For a complete list of available nash commands and their syntax please refer to the
manual page, nash(8).
• The first action is to mount the /proc pseudo file system which is needed to find out some required
information.
• Then we create block device entries for all partitions listed in /proc/partitions (mkdevices
command).
• In the next step a block device for our new root file system is created (mkrootdev command).
• Then we mount the CF card. We assume that there is only a single partition on it (/dev/hda1)
which is of type VFAT (which also will work with FAT file systems). These assumptions work fine
with basicly all memory devices used under Windows.
• We further assume that the file name of the root file system image on the CF card is
"rootfs.img" - this file now gets mounted using a loop device (losetup and mount
commands).
• Our file system image, is now mounted on the /sysroot directory. In the last step we use
pivot_root to make this the new root file system.
• As a final cleanup we unmount the /proc file system which is not needed any more.
There is one tiny flaw in this method: since we mount the CF card on a directory in the ramdisk to be able to
access to root file system image. This means that we cannot unmount the CF card, which in turn prevents us
from freeing the space for the inital ramdisk. The consequence is that you permanently lose approx. 450 kB of
RAM for the ramdisk. [We could of course re-use this ramdisk space for temporary data, but such
optimization is beyond the scope of this document.]
And how does this work on our target?
1. First we copy the two images to the CF card; we do this on the target under Linux:
bash-2.05b# fdisk -l /dev/hda
Disk /dev/hda: 256 MB, 256376832 bytes
16 heads, 32 sectors/track, 978 cylinders
Units = cylinders of 512 * 512 = 262144 bytes
Device Boot
Start
End
Blocks
Id
/dev/hda1
*
1
978
250352
6
bash-2.05b# mkfs.vfat /dev/hda1
mkfs.vfat 2.8 (28 Feb 2001)
bash-2.05b# mount -t vfat /dev/hda1 /mnt
bash-2.05b# cp -v linux.img rootfs.img /mnt/
`linux.img' -> `/mnt/linux.img'
`rootfs.img' -> `/mnt/rootfs.img'
bash-2.05b# ls -l /mnt
total 4700
-rwxr--r-1 root
root
1020729 Jun 14
-rwxr--r-1 root
root
3788800 Jun 14
bash-2.05b# umount /mnt
System
FAT16
05:36 linux.img
05:36 rootfs.img
2. We now prepare U-Boot to load the "uMulti" file (combined Linux kernel and initial ramdisk)
from the CF card and boot it:
=> setenv fat_args setenv bootargs rw
=> setenv fat_boot 'run fat_args addip;fatload ide 0:1 200000 linux.img;bootm'
=> setenv bootcmd run fat_boot
3. And finally we try it out:
U-Boot 1.1.3 (Jun 13 2005 - 02:24:00)
CPU:
XPC86xxxZPnnD4 at 50 MHz: 4 kB I-Cache 4 kB D-Cache FEC present
9.5.6. Root File System in a Read-Only File in a FAT File System
124
Board: TQM860LDB0A3-T50.202
DRAM: 16 MB
FLASH: 8 MB
In:
serial
Out:
serial
Err:
serial
Net:
SCC ETHERNET, FEC ETHERNET [PRIME]
PCMCIA: 3.3V card found: Transcend
256M
Fixed Disk Card
IDE interface
[silicon] [unique] [single] [sleep] [standby] [idle] [low power]
Bus 0: OK
Device 0: Model: Transcend
256M Firm: 1.1 Ser#: SSSC256M04Z27A25906T
Type: Removable Hard Disk
Capacity: 244.5 MB = 0.2 GB (500736 x 512)
Type "run flash_nfs" to mount root filesystem over NFS
Hit any key to stop autoboot:
reading linux.img
0
1025657 bytes read
## Booting image at 00200000 ...
Image Name:
Linux with Pivot Root Helper
Created:
2005-06-13
0:32:41 UTC
Image Type:
PowerPC Linux Multi-File Image (gzip compressed)
Data Size:
1025593 Bytes = 1001.6 kB
Load Address: 00000000
Entry Point: 00000000
Contents:
Image 0:
787146 Bytes = 768.7 kB
Image 1:
238433 Bytes = 232.8 kB
Verifying Checksum ... OK
Uncompressing Multi-File Image ... OK
Loading Ramdisk to 00f3d000, end 00f77361 ... OK
Linux version 2.4.25 (wd@xpert) (gcc version 3.3.3 (DENX ELDK 3.1.1 3.3.3-9)) #1 Mon Jun 13
On node 0 totalpages: 4096
zone(0): 4096 pages.
zone(1): 0 pages.
zone(2): 0 pages.
Kernel command line: rw ip=192.168.3.80:192.168.3.1::255.255.255.0:tqm860l:eth1:off panic=1
Decrementer Frequency = 187500000/60
Calibrating delay loop... 49.86 BogoMIPS
...
NET4: Unix domain sockets 1.0/SMP for Linux NET4.0.
RAMDISK: Compressed image found at block 0
Freeing initrd memory: 232k freed
VFS: Mounted root (ext2 filesystem).
Red Hat nash version 4.1.18 starting
Mounting /proc filesystem
Creating block devices
Creating root device
Mounting flash card
hda: hda1
hda: hda1
losetup for filesystem image
Mounting root filesystem image
Running pivot_root
Freeing unused kernel memory: 60k init
BusyBox v0.60.5 (2005.03.07-06:54+0000) Built-in shell (msh)
Enter 'help' for a list of built-in commands.
# ### Application running ...
9.5.6. Root File System in a Read-Only File in a FAT File System
125
9.6. Root File System Selection
Now we know several options for file systems we can use, and know how to create the corresponding images.
But how can we decide which one to chose?
For practical purposes in embedded systems the following criteria are often essential:
• boot time (i. e. time needed from power on until application code is running)
• flash memory footprint
• RAM memory footprint
• effects on software updates
The following data was measured for the different configurations. All measurements were performed on the
same TQM860L board (MPC860 CPU at 50 MHz, 16 MB RAM, 8 MB flash, 256 MB CompactFlash card):
File System Type
Boot Time
Free Mem
Updates
while running
ramdisk
16.3 sec
6.58 MB
whole image
yes
JFFS2
21.4 sec
10.3 MB
per file
only non-active files
cramfs
10.8 sec
10.3 MB
whole image
no
ext2 (ro)
9.1 sec
10.8 MB
whole image
no
ext2 on CF (ro)
9.3 sec
10.9 MB
whole image
no
File on FAT fs
11.4 sec
7.8 MB
whole image
yes
As you can see, the ramdisk solution is the worst of all in terms of RAM memory footprint; also it takes a
pretty long time to boot. However, it is one of the few solutions that allow an in-situ update while the system
is running.
JFFS2 is easy to use as it's a writable file system but it takes a long time to boot.
A read-only ext2 file system shines when boot time and RAM memory footprint are important; you pay for
this with an increased flash memory footprint.
External flash memory devices like CompactFlash cards or USB memory sticks can be cheap and efficient
solutions especially when lots of data need to be stored or when easy update procedures are required. -
9.7. Overlay File Systems
Introduction
Overlay File Systems provide an interesting approach to several frequent problems in Embedded Systems. For
example, mini_fo is a virtual kernel file system that can make read-only file systems writable. This is done
by redirecting modifying operations to a writeable location called "storage directory", and leaving the original
data in the "base directory" untouched. When reading, the file system merges the modifed and original data so
that only the newest versions will appear. This occurs transparently to the user, who can access the data like
on any other read-write file system.
9.7. Overlay File Systems
126
What it is good for?
In embedded systems the main use of mini_fo is to overlay the root file system. This means it is mounted
on top of the regular root file system, thereby allowing applications or users to transparently make
modifications to it but redirecting these to a different location.
Some examples of why this is usefull are explained in the following sections.
Making a read-only root filesystem writeable
Root file systems stored in flash are often read only, such as cramfs or read only ext2. While this offers major
advantages in terms of speed and flash memory footprint, it nevertheless is often desireable to be able to
modify the root file system, for example to
• apply (small) software updates without having to burn a whole new root file system image to flash
• make modifications during developement when frequent changes to the root file system occur.
This can be achieved by mounting mini_fo on top of the root file system and using a (probably small)
writeable partition as the storage file system. This could be either a JFFS2 flash file system, or during
development even an external hard disk. This has the following advantages:
• read-only file systems (fast, small memory footprint) can be used like persistent writable file systems
(in contrast to a ramdisk)
• slow flash journalling file systems with large flash memory footprint can be avoided.
Non persistant changes
Ramdisks are often used when the root file system needs to be modified non-persistantly. This works well, but
downsides are the large RAM memory footprint and the time costly operation of copying the ramdisk into
RAM during startup. These can be avoided by overlaying the root file system as in the previous example but
with the difference that the tmpfs file system is used as storage. Thus only modified files are stored in RAM,
and can even be swapped out if neccessary. This saves boot time and RAM!
Resetable changes
Mini_fo can be easily used to implement a "reset to factory defaults" function by overlaying the default root
file system. When configuration changes are made, these are automatically directed to the storage file system
and take precedence over the original files. Now, to restore the system to factory defaults, all that needs to be
done is delete the contents of the storage directory. This will remove all changes made to the root file system
and return it to the original state.
Note: Deleting the contents of the storage directory should only be done when the overlay file system is
unmounted.
Examples
Generally, there are two different ways of overlaying the root file system, which both make sense in different
scenarios.
Starting a single application in a chrooted overlayed environment
What it is good for?
127
This is easy. Let's assume "/" is the read-only root file system and /dev/mtdblock5 contains a small JFFS2
flash partition that shall be used to store modifications made by application "/usr/bin/autoPilot":
#
#
#
#
#
mount -t jffs2 /dev/mtdblock5 /tmp/sto
insmod mini_fo.o
mount -t mini_fo -o base=/,sto=/tmp/sto/ / /mnt/mini_fo/
cd /mnt/mini_fo/
chroot . /usr/bin/autoPilot
The mini_fo file system is mounted with "/" as base directory, "/tmp/sto/" as storage directory to the mount
point "/mnt/mini_fo". After that, chroot(1) is used to start the application with the new file system root
"/mnt/mini_fo". All modifications made by the application will be stored to the JFFS2 file system in /tmp/sto.
Starting the whole system system in chrooted overlayed environment
This is more interesting, and a bit trickier, as mounting needs to be done during system startup after the root
file system has been mounted, but before init is started. The best way to do this is to have a script that mounts
the mini_fo file system on top of root and then starts init in the chrooted overlayed environment. For example
assume the following script "overlay_init", stored in /sbin/:
#!/bin/bash
#
# mount mini_fo overlay file system and execute init
#
# make sure these exist in the read-only file system
STORAGE=/tmp/sto
MOUNT_POINT=/mnt/mini_fo/
# mount tmpfs as storage file system with a maximum size of 32MB
mount -t tmpfs -o rw,size=32M none $STORAGE
/sbin/modprobe mini_fo
mount -t mini_fo -o base=/,sto=$STORAGE / $MOUNT_POINT
exec /usr/sbin/chroot $MOUNT_POINT /sbin/init
echo "exec chroot failed, bad!"
exec /bin/sh
exit 1
Now its easy to choose between a mini_fo overlayed and the regular non overlayed system just by setting
the "init" kernel parameter in the boot loader to "init=/sbin/overlay_init".
Tips
• pivot_root(1) can be used with chroot if there is need to access the original non overlayed root
file system from the chrooted overlayed environment.
Performance overhead
The mini_fo file system is inserted as an additional layer between the VFS and the native file system, and
thus creates some overhead that varies strongly depending of the operation performed.
1. modifying a regular file for the first time
This results in a copy of the original file beeing created in the storage directory, that is then modified.
Overhead depends on the size of the modified file.
Starting a single application in a chrooted overlayed environment
128
2. Reading from files, creating new files, modifying already modified files
These operations are passed directly through to the lower native layer, and only impose an overhead
of 1-2%.
Further information
This section discusses how the mini_fo overlay file system can be used in embedded systems. More general
information is available at the mini_fo project page: http://www.denx.de/wiki/Know/MiniFOHome.
9.8. The Persistent RAM File system (PRAMFS)
The pramfs file system supports persistent memory devices such as SRAM. Instead of having a block
emulation layer over such a memory area and using a normal file system on top of that, pramfs seeks to
induce minimal overhead in this situation. Most important in this respect is that the normal block layer
caching of the Linux kernel is circumvented in pramfs.
9.8.1. Mount Parameters
The most important parameters for normal usage are
• physaddr: The physical address of the static memory.
• init: When given, it will initialize the file system to that size.
9.8.2. Example
We will show a sample usage of pramfs in this section using normal DRAM on a board with at least 256MB
of memory. For pramfs we reserve the upper 32MB by appending mem=224M to the kernel command line.
First off we generate some testdata on a persistent file system (/tmp) to demonstrate that pramfs survives a
reboot (of course with power always applied to keep the DRAM refreshed):
bash-3.00# dd if=/dev/urandom bs=1M count=8 of=/tmp/testdata
8+0 records in
8+0 records out
bash-3.00#
Next we mount the 32MB that we reserved and initialize it to be 32MB in size and copy the testfile. A final
compare shows that the copy was indeed successful so we can reboot:
bash-3.00#
bash-3.00#
bash-3.00#
bash-3.00#
mount -t pramfs -o physaddr=0xe000000,init=0x2000000 none /mnt
cp /tmp/testdata /mnt
cmp /tmp/testdata /mnt/testdata
reboot
Having rebooted (using mem=224M on the kernel command line again of course) we mount the file system
but this time without the init parameter because it is preinitialized. We then check the contents again:
bash-3.00# mount -t pramfs -o physaddr=0xe000000 none /mnt
bash-3.00# ls /mnt
testdata
bash-3.00# cmp /tmp/testdata /mnt/testdata
bash-3.00#
9.8. The Persistent RAM File system (PRAMFS)
129
• 10. Debugging
♦ 10.1. Debugging of U-Boot
◊ 10.1.1. Debugging of U-Boot Before Relocation
◊ 10.1.2. Debugging of U-Boot After Relocation
♦ 10.2. Linux Kernel Debugging
◊ 10.2.1. Linux Kernel and Statically Linked Device Drivers
◊ 10.2.2. Dynamically Loaded Device Drivers (Modules)
◊ 10.2.3. GDB Macros to Simplify Module Loading
♦ 10.3. GDB Startup File and Utility Scripts
♦ 10.4. Tips and Tricks
♦ 10.5. Application Debugging
◊ 10.5.1. Local Debugging
◊ 10.5.2. Remote Debugging
♦ 10.6. Debugging with Graphical User Interfaces
10. Debugging
The purpose of this document is not to provide an introduction into programming and debugging in general.
We assume that you know how to use the GNU debugger gdb and probably it's graphical frontends like ddd.
We also assume that you have access to adequate tools for your work, i. e. a BDI2000 BDM/JTAG debugger.
The following discussion assumes that the host name of your BDI2000 is bdi.
Please note that there are several limitations in earlier versions of GDB. The version of GDB as distributed
with the ELDK contains several bug fixes and extensions. If you find that your GDB behaves differently, have
a look at the GDB sources and patches that come with the ELDK source.
10.1. Debugging of U-Boot
When U-Boot starts it is running from ROM space. Running from flash would make it nearly impossible to
read from flash while executing code from flash not to speak of updating the U-Boot image in flash itself. To
be able to do just that, U-Boot relocates itself to RAM. We therefore have two phases with different program
addresses. The following sections show how to debug U-Boot in both phases.
10.1.1. Debugging of U-Boot Before Relocation
Before relocation, the addresses in the ELF file can be used without any problems, so debugging U-Boot in
this phase with the BDI2000 is quite easy:
bash[0]$ ${CROSS_COMPILE}gdb u-boot
GNU gdb 5.1.1
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "--host=i386-redhat-linux --target=ppc-linux"...
(gdb) target remote bdi:2001
Remote debugging using bdi:2001
0xfffffffc in ?? ()
(gdb) b cpu_init_f
Breakpoint 1 at 0xfffd3310: file cpu_init.c, line 136.
(gdb) c
Continuing.
Breakpoint 1, cpu_init_f () at cpu_init.c:136
10.1. Debugging of U-Boot
130
136
(gdb) s
137
(gdb)
138
(gdb)
asm volatile("
bl
0f"
::: "lr");
asm volatile("0:
mflr
asm volatile("
4, 0, 14"
addi
3"
::: "r3");
::: "r4");
cpu_init_f is the first C function called from the code in start.C.
10.1.2. Debugging of U-Boot After Relocation
For debugging U-Boot after relocation we need to know the address to which U-Boot relocates itself to. When
no exotic features like PRAM are used, this address usually is <MAXMEM> - CONFIG_SYS_MONITOR_LEN.
In our example with 16MB RAM and CONFIG_SYS_MONITOR_LEN = 192KB this yields the address
0x1000000 - 0x30000 = 0xFD0000.
In other cases, check the source code, and apply some common sense. For example, on Power Architecture®
we use "r2" to hold a pointer to the "global data" structure ("struct global_data"); this structure
contains a field
unsigned long
relocaddr;
/* Start address of U-Boot in RAM */
which is the start addresses of U-Boot after relocation to RAM. You can easily print this value in gdb like
that:
(gdb) print/x ((gd_t *)$r2)->relocaddr
With this knowledge, we can instruct gdb to forget the old symbol table and reload the symbols with our
calculated offset:
(gdb) symbol-file
Discard symbol table from `/home/dzu/denx/cvs-trees/u-boot/u-boot'? (y or n) y
No symbol file now.
(gdb) add-symbol-file u-boot 0xfd0000
add symbol table from file "u-boot" at
.text_addr = 0xfd0000
(y or n) y
Reading symbols from u-boot...done.
(gdb) b board_init_r
Breakpoint 2 at 0xfd99ac: file board.c, line 533.
(gdb) c
Continuing.
Breakpoint 2, board_init_r (id=0xfbb1f0, dest_addr=16495088) at board.c:533
533
{
(gdb)
board_init_r is the first C routine running in the newly relocated C friendly RAM environment.
The simple example above relocates the symbols of only one section, .text. Other sections of the
executable image (like .data, .bss, etc.) are not relocated and this prevents gdb from accessing static and
global variables by name. See more sophisticated examples in section 10.3. GDB Startup File and Utility
Scripts.
10.2. Linux Kernel Debugging
10.2. Linux Kernel Debugging
131
10.2.1. Linux Kernel and Statically Linked Device Drivers
10.2.2. Dynamically Loaded Device Drivers (Modules)
First start GDB in the root directory of your Linux kernel, using the vmlinux kernel image as file to debug:
bash$ cd <linux-root>
bash$ ${CROSS_COMPILE}gdb vmlinux
GNU gdb 5.1.1
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "--host=i386-redhat-linux --target=ppc-linux".
(gdb)
Now attach to the target and start execution with the commands:
(gdb) target remote bdi:2001
Remote debugging using bdi:2001
0x00000100 in ?? ()
(gdb) c
Continuing.
Now the target should boot Linux as usual. Next you need to load your kernel module on the target:
bash# insmod -m ex_sw.o
Sections:
Size
.this
00000060
.text
000002f4
.rodata
00000134
.data
00000000
.sdata
0000000c
.kstrtab
00000085
.bss
00000000
.sbss
00000008
...
Address
cf030000
cf030060
cf030354
cf030488
cf030488
cf030494
cf030519
cf03051c
Align
2**2
2**2
2**2
2**0
2**2
2**0
2**0
2**2
The option -m prints out the addresses of the various code and data segments ( .text, .data, .sdata, .bss, .sbss )
after relocation. GDB needs these addresses to know where all the symbols are located. We now interrupt
GDB to load the symbol table of the module as follows:
(gdb) ^C
Program received signal SIGSTOP, Stopped (signal).
...
(gdb) add-symbol-file <path-to-module-dir>/ex_sw.o 0xcf030060\
-s .rodata 0xcf030354\
-s .data
0xcf030488\
-s .sdata 0xcf030488\
-s .bss
0xcf030519\
-s .sbss
0xcf03051c
add symbol table from file "<path-to-module-dir>/ex_sw.o" at
.text_addr = 0xcf030060
.rodata_addr = 0xcf030354
.data_addr = 0xcf030488
.sdata_addr = 0xcf030488
.bss_addr = 0xcf030519
.sbss_addr = 0xcf03051c
(y or n) y
Reading symbols from <path-to-module-dir>/ex_sw.o...done.
10.2.1. Linux Kernel and Statically Linked Device Drivers
132
Now you can list the source code of the module, set break points or inspect variables as usual:
(gdb) l fun
61
static RT_TASK *thread;
62
63
static int cpu_used[NR_RT_CPUS];
64
65
static void fun(int t)
66
{
67
unsigned int loops = LOOPS;
68
while(loops--) {
69
cpu_used[hard_cpu_id()]++;
70
rt_leds_set_mask(1,t);
(gdb)
(gdb) b ex_sw.c:69
Breakpoint 1 at 0xcf03007c: file ex_sw.c, line 69.
(gdb) c
Continuing.
Breakpoint 1, fun (t=1) at ex_sw.c:69
69
cpu_used[hard_cpu_id()]++;
(gdb) p ntasks
$1 = 16
(gdb) p stack_size
$2 = 3000
The next section demonstrates a way to automate the symbol table loading procedure.
10.2.3. GDB Macros to Simplify Module Loading
The following GDB macros and scripts help you to load kernel modules into GDB in a half-automatic way. It
assumes, that the module on the target has been installed with the command:
bash# insmod -m my_module.o > my_module.o.map
In your $HOME directory you need the scripts add-symbol-file.sh and the GDB startup file .gdbinit, which are
listed in 10.3. GDB Startup File and Utility Scripts below.
Now you can include the symbol definition into GDB with:
bash$ ${CROSS_COMPILE}gdb vmlinux
GNU gdb 5.1.1
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "--host=i386-redhat-linux --target=ppc-linux".
0x00000100 in ?? ()
c
Continuing.
^C
Program received signal SIGSTOP, Stopped (signal).
0xcf02a91c in ?? ()
(gdb) add-module rtai4/examples/sw/ex_sw.o
add symbol table from file "/HHL/8xx/target/home/wolf/rtai4/examples/sw/ex_sw.o" at
.text_addr = 0xcf030060
.rodata_addr = 0xcf030340
.data_addr = 0xcf030464
.sdata_addr = 0xcf030464
.bss_addr = 0xcf0304f5
.sbss_addr = 0xcf0304f8
(gdb) b ex_sw.c:69
Breakpoint 1 at 0xcf03007c: file ex_sw.c, line 69.
10.2.2. Dynamically Loaded Device Drivers (Modules)
133
(gdb) c
Continuing.
Breakpoint 1, fun (t=0x1) at ex_sw.c:69
69
cpu_used[hard_cpu_id()]++;
(gdb) p/d loops
$2 = 999986939
(gdb) p t
$3 = 0x1
(gdb) d b
Delete all breakpoints? (y or n) y
(gdb) c
Continuing.
10.3. GDB Startup File and Utility Scripts
In addition to the add-module macro, the followin example GDB startup file contains a few other useful
settings and macros, which you may want to adjust to your local environment:
set output-radix 16
target remote bdi:2001
define reset
detach
target remote bdi:2001
end
define add-module
shell ~/add-symbol-file.sh $arg0
source ~/add-symbol-file.gdb
end
document add-module
Usage: add-module <module>
Do add-symbol-file for module <module> automatically.
Note: A map file with the extension ".map" must have
been created with "insmod -m <module> > <module>.map"
in advance.
end
The following shell script ~/add-symbol-file.sh is used to run the GDB add-symbol-file command
automatically:
#!/bin/sh
#
# Constructs the GDB "add-symbol-file" command string
# from the map file of the specified kernel module.
add_sect() {
ADDR=`awk '/^'$1' / {print $3}' $MAPFILE`
if [ "$ADDR" != "" ]; then
echo "-s $1 0x`awk '/^'$1' / {print $3}' $MAPFILE`"
fi
}
[ $# == 1 ] && [ -r "$1" ] || { echo "Usage: $0 <module>" >&2 ; exit 1 ; }
MAPFILE=$1.map
ARGS="0x`awk '/^.text / {print $3}' $MAPFILE`\
`add_sect .rodata`\
10.3. GDB Startup File and Utility Scripts
134
`add_sect
`add_sect
`add_sect
`add_sect
.data`\
.sdata`\
.bss`\
.sbss`\
"
echo "add-symbol-file $1 $ARGS" > ~/add-symbol-file.gdb
10.4. Tips and Tricks
• To prevent GDB from jumping around in the code when trying to single step, i. e. when it seems as if
the code is not executing line by line, you can recompile your code with the following additional
compiler options:
-fno-schedule-insns -fno-schedule-insns2
• On some systems (like the MPC8xx or MPC8260) you can only define one hardware breakpoint.
Therefore you must delete an existing breakpoint before you can define a new one:
(gdb) d b
Delete all breakpoints? (y or n) y
(gdb) b ex_preempt.c:63
Breakpoint 2 at 0xcf030080: file ex_preempt.c, line 63.
10.5. Application Debugging
10.5.1. Local Debugging
In case there is a native GDB available for your target you can use it for application debugging as usual:
bash$ gcc -Wall -g -o hello hello.c
bash$ gdb hello
...
(gdb) l
1
#include <stdio.h>
2
3
int main(int argc, char* argv[])
4
{
5
printf ("Hello world\n");
6
return 0;
7
}
(gdb) break 5
Breakpoint 1 at 0x8048466: file hello.c, line 5.
(gdb) run
Starting program: /opt/eldk/ppc_8xx/tmp/hello
Breakpoint 1, main (argc=0x1, argv=0xbffff9f4) at hello.c:5
5
printf ("Hello world\n");
(gdb) c
Continuing.
Hello world
Program exited normally.
10.5. Application Debugging
135
10.5.2. Remote Debugging
gdbserver allows you to connect your program with a remote GDB using the "target remote" command.
On the target machine, you need to have a copy of the program you want to debug. gdbserver does not
need your program's symbol table, so you can strip the program if necessary to save space. GDB on the host
system does all the symbol handling. Here is an example:
bash$ ${CROSS_COMPILE}gcc -Wall -g -o hello hello.c
bash$ cp -p hello <directory-shared-with-target>/hello-stripped
bash$ ${CROSS_COMPILE}strip <directory-shared-with-target>/hello-stripped
To use the server, you must tell it how to communicate with GDB, the name of your program, and the
arguments for your program. To start a debugging session via network type on the target:
bash$ cd <directory-shared-with-host>
bash$ gdbserver 192.168.1.1:12345 hello-stripped
Process hello-stripped created; pid = 353
And then on the host:
bash$ ${CROSS_COMPILE}gdb hello
...
(gdb) set solib-absolute-prefix /opt/eldk/$CROSS_COMPILE
(gdb) dir /opt/eldk/$CROSS_COMPILE
Source directories searched:
/opt/eldk/$CROSS_COMPILE:$cdir:$cwd
(gdb) target remote 192.168.1.99:12345
Remote debugging using 192.168.1.99:12345
0x30012748 in ?? ()
...
(gdb) l
1
#include <stdio.h>
2
3
int main(int argc, char* argv[])
4
{
5
printf ("Hello world\n");
6
return 0;
7
}
(gdb) break 5
Breakpoint 1 at 0x10000498: file hello.c, line 5.
(gdb) continue
Continuing.
Breakpoint 1, main (argc=1, argv=0x7ffffbe4) at hello.c:5
5
printf ("Hello world\n");
(gdb) p argc
$1 = 1
(gdb) continue
Continuing.
Program exited normally.
If the target program you want to debug is linked against shared libraries, you must tell GDB where the
proper target libraries are located. This is done using the set solib-absolute-prefix GDB
command. If this command is omitted, then, apparently, GDB loads the host versions of the libraries and gets
crazy because of that.
10.6. Debugging with Graphical User Interfaces
10.6. Debugging with Graphical User Interfaces
136
It is convenient to use DDD, a Graphical User Interface to GDB, for debugging as it allows to define and
execute frequently used commands via buttons. You can start DDD with the command:
bash$ ddd --debugger ${CROSS_COMPILE}gdb &
If DDD is not already installed on your Linux system, have a look at your distribution media.
11. Simple Embedded Linux Framework
12. Books, Mailing Lists, Links, etc.
This section provides references on where to find more information
Contents:
• 12. Books, Mailing Lists, Links, etc.
♦ 12.1. Application Notes
♦ 12.2. Further Reading
◊ 12.2.1. License Issues
◊ 12.2.2. Linux kernel
◊ 12.2.3. General Linux / Unix programming
◊ 12.2.4. Network Programming
◊ 12.2.5. C++ programming
◊ 12.2.6. Java programming
◊ 12.2.7. Internationalization And Character Sets
◊ 12.2.8. ARM Architecture Programming
◊ 12.2.9. Power Architecture® Programming
◊ 12.2.10. Embedded Topics
♦ 12.3. Mailing Lists
♦ 12.4. Links
♦ 12.5. Tools
12.1. Application Notes
A collection of Application Notes relevant for embedded computing can be found on the DENX web server.
12.2. Further Reading
12.2.1. License Issues
Articles
• http://www.gnu.org/licenses/gpl-2.0.html: GNU General Public License, version 2
• http://www.gnu.org/copyleft/gpl.html: GNU General Public License
• http://www.softwarefreedom.org/resources/2008/compliance-guide.html: A Practical Guide to GPL
Compliance
• http://article.gmane.org/gmane.comp.video.dri.devel/52751 Alan Cox about combining GPL device
drivers with closed source user space libraries
12.2. Further Reading
137
12.2.2. Linux kernel
Books
• Karim Yaghmour, Jon Masters, Gilad Ben-Yossef, Philippe Gerum: "Building Embedded Linux
Systems 2nd edition",
Paperback: 462 pages, O'Reilly & Associates; (August 2008); ISBN 10: 0-596-52968-6; ISBN 13:
9780596529680 ISBN 059600222X - IMHO the best book about Embedded Linux so far. An
absolute must have.
• Greg Kroah-Hartman: "Linux Kernel in a Nutshell",
198 pages, O'Reilly ("In Nutshell" series), (December 2006), ISBN 10: 0-596-10079-5; ISBN 13:
9780596100797
- Tarball of PDF files (3 MB):
http://www.kernel.org/pub/linux/kernel/people/gregkh/lkn/lkn_pdf.tar.bz2
- Tarball of DocBook files (1 MB):
http://www.kernel.org/pub/linux/kernel/people/gregkh/lkn/lkn_xml.tar.bz2
• Craig Hollabaugh: "Embedded Linux: Hardware, Software, and Interfacing",
Paperback: 432 pages; Addison Wesley Professional; (March 7, 2002); ISBN 0672322269
• Christopher Hallinan: "Embedded Linux Primer: A Practical Real-World Approach",
576 pages, Prentice Hall, September 2006, ISBN-10: 0-13-167984-8; ISBN-13: 978-0-13-167984-9
• Jonathan Corbet, Alessandro Rubini, Greg Kroah-Hartman: "Linux Device Drivers", 3rd Edition
;
Paperback: 636 pages; O'Reilly & Associates; 3rd edition (February 2005); ISBN: 0-596-00590-31 The reference book for writing Linux device drivers. An absolute must have. => Read online
• Jürgen Quade, Eva-Katharina Kunst: "Linux-Treiber entwickeln"; Broschur: 436 pages;
dpunkt.verlag, Juni 2004; ISBN 3898642380
- focused on kernel 2.6, unfortunately German only
- => Read online
• Sreekrishnan Venkateswaran: "Essential Linux Device Drivers",
744 pages, Prentice Hall, March 2008, ISBN-10: 0-13-239655-6; ISBN-13: 978-0-13-239655-4
- => Read online
Articles
• The Linux Kernel - describing most aspects of the Linux Kernel. Probably, the first reference for
beginners. Lots of illustrations explaining data structures use and relationships. In short: a must have.
• Linux Kernel Module Programming Guide - Very nice 92 pages GPL book on the topic of modules
programming. Lots of examples.
• LWN: Porting device drivers to the 2.6 kernel - Series of articles (37) in Linux Weekly News:
http://lwn.net/Articles/driver-porting/
• MIPS Linux Porting Guide: http://linux.junsun.net/porting-howto/porting-howto.html
• Andries Brouwers remarks to the linux kernel: http://www.win.tue.nl/~aeb/linux/lk/lk.html
12.2.3. General Linux / Unix programming
Books
• W. Richard Stevens: "Advanced Programming in the UNIX Environment", Addision Wesley, ISBN
0-201-56317-7
• Eric S. Raymond: "The Art of Unix Programming", Addision Wesley, ISBN 0131429019 => Read
online. If you don't want to read the whole book then at least look at the Basics of the Unix
philosophy condensing lots of experience into a few rules. This is essential reading.
12.2.2. Linux kernel
138
• David R. Butenhof: "Programming with POSIX Threads", Addision Wesley, ISBN 0-201-63392-2.
• Bradford Nichols, Dick Buttlar and Jacqueline Proulx Farrell: "Pthreads Programming", O'Reilly
& Associates
• "Git Community Book"
See http://book.git-scm.com/ or download the PDF version.
Articles
• The GNU C Library: http://www.linuxselfhelp.com/gnu/glibc/html_chapter/libc_toc.html
General Linux Programming: http://www.linuxselfhelp.com/cats/programming.html
• Multi-Threaded Programming With POSIX Threads:
http://users.actcom.co.il/~choo/lupg/tutorials/multi-thread/multi-thread.html
• Brad Hards: The Linux USB Input Subsystem, Part I
http://www.linuxjournal.com/article/6396
• Brad Hards: Using the Input Subsystem, Part II
http://www.linuxjournal.com/article/6429
• Ulrich Drepper: Position Independent Binaries: "Text Relocations"
http://people.redhat.com/drepper/textrelocs.html
• Ulrich Drepper: "How to Write Shared Libraries"
http://people.redhat.com/drepper/dsohowto.pdf
• Ulrich Drepper: "What Every Programmer Should Know About Memory"
http://people.redhat.com/drepper/cpumemory.pdf
• David Goldberg: "What Every Computer Scientist Should Know About Floating-Point Arithmetic"
http://www.physics.ohio-state.edu/~dws/grouplinks/floating_point_math.pdf
• More Ulrich Drepper stuff: http://people.redhat.com/drepper/
• How to optimize DSOs by identifying unused non-exported functions and data.
http://blog.flameeyes.eu/articles/2008/01/17/today-how-to-identify-unused-exported-functions-and-variables
• A quite complete history of the UNIX family can be found here: http://www.levenez.com/unix/
• Unix Manual, first edition, 3 November 1971: http://cm.bell-labs.com/cm/cs/who/dmr/1stEdman.html
• John Graham-Cumming: Debugging Makefiles
http://newsletter.embedded.com/cgi-bin4/DM/y/e4Kd0G1ErD0FrY0E3FS0EZ
• Binutils / ld documentation: Linker Scripts
• git ready - learn one git command at a time: http://gitready.com/
Standards:
• POSIX.1-2008, IEEE Std 1003.1 -2008, The Open Group Technical Standard Base Specifications,
Issue 7: http://pubs.opengroup.org/onlinepubs/9699919799/mindex.html
• Linux Standard Base: http://refspecs.freestandards.org/lsb.shtml
• Single UNIX Specification, Version 3 (needs registration even for online viewing)
• Single UNIX Specification, Version 2
• PCI Bus Bindings - Standard for Boot Firmware:
http://playground.sun.com/1275/bindings/pci/pci2_1.pdf
• International standardization working group for the programming language C:
http://www.open-std.org/jtc1/sc22/WG14/
12.2.4. Network Programming
Books
• W. Richard Stevens: "TCP/IP Illustrated, Volume 1 - The Protocols", Addision Wesley, ISBN
0-201-63346-9
Books
139
• Gary R. Wright, W. Richard Stevens: "TCP/IP Illustrated, Volume 2 - The Implementation",
Addision Wesley, ISBN 0-201-63354-X
• W. Richard Stevens: "TCP/IP Illustrated, Volume 3 - TCP for Transactions", Addision Wesley,
ISBN 0-201-63495-3
• W. Richard Stevens: "UNIX Network Programming, Volume 1 - Networking APIs: Sockets and
XTI", 2nd ed., Prentice Hall, ISBN-0-13-490012-X
• W. Richard Stevens: "UNIX Network Programming, Volume 2 - Interprocess Communication", 2nd
ed., Prentice Hall, ISBN-0-13-081081-9
Articles
• Linux Networking topics (like NAPI, GSO, VLAN, IPsec etc.):
http://linux-net.osdl.org/index.php/Main_Page
12.2.5. C++ programming
Books
• Scott Meyers: "Effective C++: 55 Specific Ways to Improve Your Programs and Designs (3rd
Edition)", Addison-Wesley, May 20, 2005, ISBN: 0321334876
12.2.6. Java programming
Books
• Joshua Bloch: "Effective Java -- Programming Language Guide", 2001, Addison Wesley, ISBN
0-201-31005-8, 250 pages
12.2.7. Internationalization And Character Sets
Articles
• Wikipedia article on UTF-8: http://en.wikipedia.org/wiki/UTF-8
• "The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About
Unicode and Character Sets (No Excuses!)" by Joel Spolsky:
http://www.joelonsoftware.com/articles/Unicode.html
• "UTF-8 and Unicode FAQ for Unix/Linux" by Markus Kuhn
http://www.cl.cam.ac.uk/~mgk25/unicode.html
• Understanding Encodings: http://foswiki.org/Development/UnderstandingEncodings
Detailed primer on character sets and encodings, especially in the context of web design
12.2.8. ARM Architecture Programming
Articles
• ARM atomic operations: http://www.jonmasters.org/blog/2012/11/13/arm-atomic-operations/
Books
140
12.2.9. Power Architecture® Programming
Books
• Programming Environments Manual for 32-Bit Implementations of the PowerPC architecture:
http://www.freescale.com/files/product/doc/MPCFPE32B.pdf
• IBM PDF file (600+ page book) on PowerPC assembly language:
http://www-3.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF778525699600719DF2
• Power.org™ Standard for Embedded Power Architecture™ Platform Requirements (ePAPR):
https://www.power.org/documentation/epapr-version-1-1/ (registration needed)
Articles
• Introduction to Assembly on the PowerPC:
http://www-106.ibm.com/developerworks/library/l-ppc/?t=gr,lnxw09=PowPC
• IBM PDF compiler writers guide on PPC asm tuning etc.:
http://www-3.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF7785256996007558C6
• A developer's guide to the POWER architecture:
http://www-128.ibm.com/developerworks/linux/library/l-powarch/index.html
• PowerPC EABI Calling Sequence:
ftp://sourceware.redhat.com/pub/binutils/ppc-docs/ppc-eabi-calling-sequence
• PowerPC Embedded Application Binary Interface (32-Bit Implementation):
ftp://sourceware.redhat.com/pub/binutils/ppc-docs/ppc-eabi-1995-01.pdf
• Developing PowerPC Embedded Application Binary Interface (EABI) Compliant Programs
http://www-306.ibm.com/chips/techlib/techlib.nsf/techdocs/852569B20050FF77852569970071B0D6
• System V Application Binary Interface - PowerPC Processor Supplement:
http://refspecs.freestandards.org/elf/elfspec_ppc.pdf
• Device Tree Wiki: http://devicetree.org/Main_Page
• Device Tree Usage: http://devicetree.org/Device_Tree_Usage
• Linux for PowerPC Embedded Systems HOWTO (very old):
http://penguinppc.org/embedded/howto/PowerPC-Embedded-HOWTO.html
• Linux for PowerPC Embedded Systems HOWTO (old):
http://www.denx.de/twiki/bin/view/PPCEmbedded
• Understanding MPC5200 Bestcomm Firmware: Posting on linuxppc-embedded@ozlabs.org mailing
list (see also the mailing list archive entry), source code disasm.c for a disassember, and "SmartDMA
Hand-Assembly Guides" document.
12.2.10. Embedded Topics
Articles
• Things you always wanted to know about NAND flash but never dared to ask: Micron Application
Note
• The ultimate goal of Embedded C++ is to provide embedded systems programmers with a subset of
C++ that is easy for the average C programmer to understand and use.
• Our contribution to the Darwin year 2009: Hardware designs that will not replicate: Topic in DENX
Wiki
12.2.9. Power Architecture® Programming
141
12.3. Mailing Lists
These are some mailing lists of interest. If you are new to mailing lists then please take the time to read at
least RFC 1855.
• linux-arm-kernel - Communications among developers and users of Linux on arm boards
• linuxppc-embedded - Communications among developers and users of Linux on embedded Power
Architecture® boards
This mailing list has been merged into the linuxppc-dev mailing list below and thus does not
exist anymore.
• linuxppc-dev - Communications among active developers of Linux on 32 bit Power Architecture®
plattforms. Not intended for user support.
• u-boot - Support for "U-Boot" Universal Bootloader
• ELDK - Support for DENX Embedded Linux Development Kit
12.4. Links
Linux Kernel Resources:
• The Linux Documentation Project : http://www.tldp.org/
• Generic ("official") Linux Kernel sources:
git: http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=tree
FTP: ftp://ftp.kernel.org/pub/linux/kernel/v2.6/
• Full git history of Linux: http://thread.gmane.org/gmane.linux.kernel/690811
• Generic kernel sources for Power Architecture™ systems: http://penguinppc.org/dev/kernel.shtml
• DENX kernel sources: http://git.denx.de/?p=linux-denx.git;a=summary
• Cross-Referencing the Linx Kernel: http://lxr.linux.no/source/?a=ppc
• Starting point for Linux based asm (mostly x86): http://linuxassembly.org/
Realtime, Xenomai, RTAI:
• Xenomai Home Page: http://www.xenomai.org/
• Hackbench, a commonly used system stress tool
• Calibrator, determines cache
• RTAI Home Page: http://www.rtai.org/
• DENX RTAI Patches: ftp://ftp.denx.de/pub/RTAI/ sizes at runtime, rendering it another useful system
stress tool
U-Boot:
• U-Boot Project Page: http://www.denx.de/wiki/U-Boot/WebHome.
Note that the old SourceForge page is not maintained anymore.
• DENX U-Boot and Linux Guide: http://www.denx.de/twiki/bin/view/DULG
Cross Development Tools:
• DENX Embedded Linux Development Kit: http://www.denx.de/twiki/bin/view/DULG/ELDK
12.4. Links
142
Miscalleneous or unsorted material:
• BDI2000 List of supported Flash Memories: This document not only lists the currently supported
flash chips, but also the required settings in the BDI config file.
• BDI2000 configuration files: ftp://78.31.64.234/bdigdb/config/
12.5. Tools
• http://lxr.linux.no/source/ - Cross-Referencing the Linux Kernel - using a versatile hypertext
cross-referencing tool for the Linux Kernel source tree (the Linux Cross-Reference project)
• ftp://ftp.denx.de/pub/tools/backtrace - Decode Stack Backtrace - Perl script to decode the Stack
Backtrace printed by the Linux Kernel when it panics
• ftp://ftp.denx.de/pub/tools/clone_tree - "Clone" a Source Tree - Perl script to create a working copy of
a source tree (for example the Linux Kernel) which contains mainly symbolic links (and
automagically omits "unwanted" files like CVS repository data, etc.)
• 13. Appendix
♦ 13.1. Flat Device Tree
♦ 13.2. BDI2000 Configuration file
13. Appendix
13.1. Flat Device Tree
[marex@pollux]$ /*
* Copyright (C) 2012 Marek Vasut <marex@denx.de>
*
* The code contained herein is licensed under the GNU General Public
* License. You may obtain a copy of the GNU General Public License
* Version 2 or later at the following locations:
*
* http://www.opensource.org/licenses/gpl-license.html
* http://www.gnu.org/copyleft/gpl.html
*/
/dts-v1/;
/include/ "imx28.dtsi"
/ {
model = "DENX M28EVK";
compatible = "denx,m28evk", "fsl,imx28";
memory {
reg = <0x40000000 0x08000000>;
};
apb@80000000 {
apbh@80000000 {
gpmi-nand@8000c000 {
#address-cells = <1>;
#size-cells = <1>;
pinctrl-names = "default";
pinctrl-0 = <&gpmi_pins_a &gpmi_status_cfg>;
status = "okay";
partition@0 {
13. Appendix
143
label = "bootloader";
reg = <0x00000000 0x00300000>;
read-only;
};
partition@1 {
label = "environment";
reg = <0x00300000 0x00080000>;
};
partition@2 {
label = "redundant-environment";
reg = <0x00380000 0x00080000>;
};
partition@3 {
label = "kernel";
reg = <0x00400000 0x00400000>;
};
partition@4 {
label = "filesystem";
reg = <0x00800000 0x0f800000>;
};
};
ssp0: ssp@80010000 {
compatible = "fsl,imx28-mmc";
pinctrl-names = "default";
pinctrl-0 = <&mmc0_8bit_pins_a
&mmc0_cd_cfg
&mmc0_sck_cfg>;
bus-width = <8>;
wp-gpios = <&gpio3 10 0>;
vmmc-supply = <&reg_vddio_sd0>;
status = "okay";
};
ssp2: ssp@80014000 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "fsl,imx28-spi";
pinctrl-names = "default";
pinctrl-0 = <&spi2_pins_a>;
status = "okay";
flash: m25p80@0 {
#address-cells = <1>;
#size-cells = <1>;
compatible = "m25p80";
spi-max-frequency = <40000000>;
m25p,fast-read;
reg = <0>;
};
};
pinctrl@80018000 {
pinctrl-names = "default";
pinctrl-0 = <&hog_pins_a>;
hog_pins_a: hog@0 {
reg = <0>;
fsl,pinmux-ids
0x31c3
0x30a3
0x30b3
0x30c3
13.1. Flat Device Tree
= <
/* MX28_PAD_PWM3__GPIO_3_28 */
/* MX28_PAD_AUART2_CTS__GPIO_3_10 */
/* MX28_PAD_AUART2_RTS__GPIO_3_11 */
/* MX28_PAD_AUART3_RX__GPIO_3_12 */
144
0x30d3 /* MX28_PAD_AUART3_TX__GPIO_3_13 */
>;
fsl,drive-strength = <0>;
fsl,voltage = <1>;
fsl,pull-up = <0>;
};
lcdif_pins_m28: lcdif-m28@0 {
reg = <0>;
fsl,pinmux-ids = <
0x11e0 /* MX28_PAD_LCD_DOTCLK__LCD_DOTCLK */
0x11f0 /* MX28_PAD_LCD_ENABLE__LCD_ENABLE */
>;
fsl,drive-strength = <0>;
fsl,voltage = <1>;
fsl,pull-up = <0>;
};
};
lcdif@80030000 {
pinctrl-names = "default";
pinctrl-0 = <&lcdif_24bit_pins_a
&lcdif_pins_m28>;
status = "okay";
};
can0: can@80032000 {
pinctrl-names = "default";
pinctrl-0 = <&can0_pins_a>;
status = "okay";
};
can1: can@80034000 {
pinctrl-names = "default";
pinctrl-0 = <&can1_pins_a>;
status = "okay";
};
};
apbx@80040000 {
saif0: saif@80042000 {
pinctrl-names = "default";
pinctrl-0 = <&saif0_pins_a>;
status = "okay";
};
saif1: saif@80046000 {
pinctrl-names = "default";
pinctrl-0 = <&saif1_pins_a>;
fsl,saif-master = <&saif0>;
status = "okay";
};
i2c0: i2c@80058000 {
pinctrl-names = "default";
pinctrl-0 = <&i2c0_pins_a>;
clock-frequency = <400000>;
status = "okay";
sgtl5000: codec@0a {
compatible = "fsl,sgtl5000";
reg = <0x0a>;
VDDA-supply = <&reg_3p3v>;
VDDIO-supply = <&reg_3p3v>;
};
13.1. Flat Device Tree
145
eeprom: eeprom@51 {
compatible = "atmel,24c128";
reg = <0x51>;
pagesize = <32>;
};
rtc: rtc@68 {
compatible = "stm,mt41t62";
reg = <0x68>;
};
};
lradc@80050000 {
status = "okay";
};
duart: serial@80074000 {
pinctrl-names = "default";
pinctrl-0 = <&duart_pins_a>;
status = "okay";
};
usbphy0: usbphy@8007c000 {
status = "okay";
};
usbphy1: usbphy@8007e000 {
status = "okay";
};
auart0: serial@8006a000 {
pinctrl-names = "default";
pinctrl-0 = <&auart0_2pins_a>;
status = "okay";
};
};
};
ahb@80080000 {
usb0: usb@80080000 {
vbus-supply = <&reg_usb0_vbus>;
pinctrl-names = "default";
pinctrl-0 = <&usbphy0_pins_a>;
status = "okay";
};
usb1: usb@80090000 {
vbus-supply = <&reg_usb1_vbus>;
pinctrl-names = "default";
pinctrl-0 = <&usbphy1_pins_a>;
status = "okay";
};
mac0: ethernet@800f0000 {
phy-mode = "rmii";
pinctrl-names = "default";
pinctrl-0 = <&mac0_pins_a>;
status = "okay";
};
mac1: ethernet@800f4000 {
phy-mode = "rmii";
pinctrl-names = "default";
pinctrl-0 = <&mac1_pins_a>;
status = "okay";
};
};
13.1. Flat Device Tree
146
regulators {
compatible = "simple-bus";
reg_3p3v: 3p3v {
compatible = "regulator-fixed";
regulator-name = "3P3V";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
regulator-always-on;
};
reg_vddio_sd0: vddio-sd0 {
compatible = "regulator-fixed";
regulator-name = "vddio-sd0";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
gpio = <&gpio3 28 0>;
};
reg_usb0_vbus: usb0_vbus {
compatible = "regulator-fixed";
regulator-name = "usb0_vbus";
regulator-min-microvolt = <5000000>;
regulator-max-microvolt = <5000000>;
gpio = <&gpio3 12 0>;
};
reg_usb1_vbus: usb1_vbus {
compatible = "regulator-fixed";
regulator-name = "usb1_vbus";
regulator-min-microvolt = <5000000>;
regulator-max-microvolt = <5000000>;
gpio = <&gpio3 13 0>;
};
};
sound {
compatible = "denx,m28evk-sgtl5000",
"fsl,mxs-audio-sgtl5000";
model = "m28evk-sgtl5000";
saif-controllers = <&saif0 &saif1>;
audio-codec = <&sgtl5000>;
};
};
13.2. BDI2000 Configuration file
[marex@pollux]$ [INIT]
;WM32
0x800401E0 0x00000002
;DELAY 1000
;WM32 0x80056050 0x1
;WM32 0x80056000 0x10
;DELAY 100
WREG
CPSR
0x000000D3
[TARGET]
CPUTYPE
CLOCK
;CLOCK
WAKEUP
RESET
TRST
ENDIAN
ARM926E
0 8
4
500
HARD 500
PUSHPULL
LITTLE
13.2. BDI2000 Configuration file
; Restart the chip altogether (HW_CLKCTRL_RESET = CHIP)
; Configure CPSR
;JTAG clock (0=Adaptive, 1=8MHz, 2=4MHz, 3=2MHz)
;JTAG clock (0=Adaptive, 1=8MHz, 2=4MHz, 3=2MHz)
;because of slow rising reset line
;because of heavy capacitive load on reset line
;memory model (LITTLE | BIG)
147
BREAKMODE
SCANSUCC
STARTUP
;BDIMODE
[HOST]
IP
PROMPT
HARD
0 0
RESET
;SOFT or HARD, ARM / Thumb break code
; 1 4 when the ETMBUF after the ARM926 core is enabled via TESTMO
; the ARM 926 core is stop after reset
LOADONLY
192.168.1.1
M28>
[FLASH]
; only nand and this is not supported directly from the bdi
[REGS]
FILE
BDI2000/reg926e.def
• 14. FAQ - Frequently Asked Questions
♦ 14.1. ELDK
◊ 14.1.1. ELDK Installation under FreeBSD
◊ 14.1.2. ELDK Installation Hangs
◊ 14.1.3. .gvfs: Permission Denied
◊ 14.1.4. Installation on Local Harddisk
◊ 14.1.5. System Include Files Missing
◊ 14.1.6. patch: command not found
◊ 14.1.7. ELDK Include Files Missing
◊ 14.1.8. Using the ELDK on a 64 bit platform
◊ 14.1.9. How can I check if Floating Point support is working?
◊ 14.1.10. ELDK 2.x Installation Aborts
◊ 14.1.11. Enable SSH Access
♦ 14.2. U-Boot
◊ 14.2.1. Can U-Boot be configured such that it can be started in RAM?
◊ 14.2.2. Relocation cannot be done when using -mrelocatable
◊ 14.2.3. Source object has EABI version 4, but target has EABI version 0
◊ 14.2.4. U-Boot crashes after relocation to RAM
◊ 14.2.5. Warning - bad CRC, using default environment
◊ 14.2.6. Net: No ethernet found
◊ 14.2.7. Wrong debug symbols after relocation
◊ 14.2.8. Decoding U-Boot Crash Dumps
◊ 14.2.9. Porting Problem: cannot move location counter backwards
◊ 14.2.10. U-Boot Doesn't Run after Upgrading my Compiler
◊ 14.2.11. How Can I Reduce The Image Size?
◊ 14.2.12. Erasing Flash Fails
◊ 14.2.13. Ethernet Does Not Work
◊ 14.2.14. Where Can I Get a Valid MAC Address from?
◊ 14.2.15. Why do I get TFTP timeouts?
◊ 14.2.16. Why is my Ethernet operation not reliable?
◊ 14.2.17. How the Command Line Parsing Works
⋅ 14.2.17.1. Old, simple command line parser
⋅ 14.2.17.2. Hush shell
⋅ 14.2.17.3. Hush shell scripts
⋅ 14.2.17.4. General rules
◊ 14.2.18. How can I load and uncompress a compressed image
◊ 14.2.19. How can I create an uImage from a ELF file
◊ 14.2.20. My standalone program does not work
◊ 14.2.21. Linux hangs after uncompressing the kernel
◊ 14.2.22. How can I implement automatic software updates?
13.2. BDI2000 Configuration file
148
♦ 14.3. Linux
◊ 14.3.1. Linux crashes randomly
◊ 14.3.2. Linux crashes when uncompressing the kernel
◊ 14.3.3. Linux Post Mortem Analysis
◊ 14.3.4. Linux kernel register usage
◊ 14.3.5. Linux Kernel Ignores my bootargs
◊ 14.3.6. Cannot configure Root Filesystem over NFS
◊ 14.3.7. Linux Kernel Panics because "init" process dies
◊ 14.3.8. Unable to open an initial console
◊ 14.3.9. System hangs when entering User Space (ARM)
◊ 14.3.10. Mounting a Filesystem over NFS hangs forever
◊ 14.3.11. Ethernet does not work in Linux
◊ 14.3.12. Loopback interface does not work
◊ 14.3.13. Linux kernel messages are not printed on the console
◊ 14.3.14. Linux ignores input when using the framebuffer driver
◊ 14.3.15. How to switch off the screen saver and the blinking cursor?
◊ 14.3.16. BogoMIPS Value too low
◊ 14.3.17. Linux Kernel crashes when using a ramdisk image
◊ 14.3.18. Ramdisk Greater than 4 MB Causes Problems
◊ 14.3.19. Combining a Kernel and a Ramdisk into a Multi-File Image
◊ 14.3.20. Adding Files to Ramdisk is Non Persistent
◊ 14.3.21. Kernel Configuration for PCMCIA
◊ 14.3.22. Configure Linux for PCMCIA Cards using the Card Services package
◊ 14.3.23. Configure Linux for PCMCIA Cards without the Card Services package
⋅ 14.3.23.1. Using a MacOS Partition Table
⋅ 14.3.23.2. Using a MS-DOS Partition Table
◊ 14.3.24. Boot-Time Configuration of MTD Partitions
◊ 14.3.25. Use NTP to synchronize system time against RTC
◊ 14.3.26. Configure Linux for XIP (Execution In Place)
⋅ 14.3.26.1. XIP Kernel
⋅ 14.3.26.2. Cramfs Filesystem
⋅ 14.3.26.3. Hints and Notes
⋅ 14.3.26.4. Space requirements and RAM saving, an example
◊ 14.3.27. Use SCC UART with Hardware Handshake
◊ 14.3.28. How can I access U-Boot environment variables in Linux?
◊ 14.3.29. The =appWeb= server hangs *OR* /dev/random hangs
◊ 14.3.30. Swapping over NFS
◊ 14.3.31. Using NFSv3 for NFS Root Filesystem
◊ 14.3.32. Using and Configuring the SocketCAN Driver
◊ 14.3.33. Telnet / SSH (dropbear) server not working
♦ 14.4. Self
◊ 14.4.1. How to Add Files to a SELF Ramdisk
◊ 14.4.2. How to Increase the Size of the Ramdisk
♦ 14.5. RTAI
◊ 14.5.1. Conflicts with asm clobber list
♦ 14.6. BDI2000
◊ 14.6.1. Where can I find BDI2000 Configuration Files?
◊ 14.6.2. How to Debug Linux Exceptions
◊ 14.6.3. How to single step through "RFI" instruction
◊ 14.6.4. Setting a breakpoint doesn't work
◊ 14.6.5. Remote 'g' packet reply is too long
♦ 14.7. Motorola LITE5200 Board
◊ 14.7.1. LITE5200 Installation Howto
◊ 14.7.2. USB does not work on Lite5200 board
13.2. BDI2000 Configuration file
149
14. FAQ - Frequently Asked Questions
This is a collection of questions which came up repeatedly. Give me more feedback and I will add more stuff
here.
The items are categorized whether they concern U-Boot itself, the Linux kernel or the SELF framework.
14.1. ELDK
14.1.1. ELDK Installation under FreeBSD
Question:
How can I install ELDK on a FreeBSD system?
Answer:
[Thanks to Rafal Jaworowski for these detailed instructions.] This is a short tutorial how to host
ELDK on FreeBSD 5.x and 6.x. The procedure described below was tested on 5.2.1, 5.3 and 6-current
releases; we assume the reader is equipped with the ELDK 3.x CDROM or ISO image for installation,
and is familiar with FreeBSD basic administration tasks like ports/packages installation.
1. Prerequisites:
1. Install linux_base
The first step is to install the Linux compatibility layer from ports
/usr/ports/emulators/linux_base/ or packages
ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages/emulators
Please make sure to install version 7.1_5 (linux_base-7.1_5.tbz) or later;
in particular, version 6.1.5 which can also be found in the ports tree does not work
properly!
The compatibility layer is activated by
# kldload linux
2. Install bash
Since ELDK and Linux build scripts are organised around bash while FreeBSD does
not have it in base, this shell needs to be installed either from ports
/usr/ports/shells/bash2/ or packages collection
ftp://ftp.freebsd.org/pub/FreeBSD/ports/i386/packages/shells/
The installation puts the bash binary in /usr/local/bin. It is a good idea to
create a symlink in /bin so that hash bang from scripts (#!/bin/bash) works
without modifications:
# cd /bin
# ln -s /usr/local/bin/bash
2. Prepare ELDK
This step is only needed for ELDK release 3.1 and older versions.
Copy the install files from the CDROM or ISO image to a writable location. Brand the ELDK
installer as Linux ELF file:
14.1.1. ELDK Installation under FreeBSD
150
# cd <elkd_install_dir>
# brandelf -t Linux ./install
Note: The following workaround might be a good alternative for the tedious copying of
the installation CDROM to a writable location and manual branding: you can set a fallback
branding in FreeBSD - when the loader cannot recognise the ELF brand it will switch to the
last resort defined.
# sysctl -w kern.elf32.fallback_brand=3
kern.elf32.fallback_brand: -1 -> 3
With this setting, the normal ELDK CDROM images should work.
3. Install ELDK normally as described in 3.5.3. Initial Installation
4. Set envrionment variables and PATH as needed for ELDK (in bash); for example:
bash$ export CROSS_COMPILE=ppc_8xxbash$ export PATH=${PATH}:/opt/eldk/bin:/opt/eldk/usr/bin
5. Hints for building U-Boot:
FreeBSD normally uses BSD-style 'make' in base, but in order to compile U-Boot
'gmake' (GNU make) has to be used; this is installed as part of the 'linux_base'
package (see above).
U-Boot should build according to standard ELDK instructions, for example:
bash$ cd /opt/eldk/ppc_8xx/usr/src/u-boot-1.1.2
bash$ gmake TQM823L_config
bash$ gmake all
6. Hints for building Linux:
There are three issues with the Makefile in the Linux kernel source tree:
⋅ GNU make has to be used.
⋅ The 'expr' utility in FreeBSD base behaves differently from the version than is
used in Linux so we need to modify the Makefile to explicitly use the Linux version
(which is part of the Linux compatibility package). This is best achieved with
defining "EXPR = /compat/linux/usr/bin/expr" somewhere at
=Makefile='s beginning and replacing all references to 'expr' with the variable
${EXPR).
⋅ Some build steps (like when running 'scripts/mkdep' can generate very long
arguments lists (especially is the Linux kernel tree is in a directory with long absolute
filenames). A solution is to use xargs to split such long commands into several with
shorter argument lists.
The Linux kernel can then be built following the standard instructions, for example:
bash$
bash$
bash$
bash$
bash$
bash$
cd /opt/eldk/ppc_8xx/usr/src/linux-2.4.25/
gmake mrproper
gmake TQM823L_config
gmake oldconfig
gmake dep
gmake -j6 uImage
ELDK Installation Hangs
Question:
ELDK Installation Hangs
151
I try to install the ELDK on a Linux PC, and the installation hangs. It starts fine, but then it freezes
like this:
...
Preparing...
1:db4-devel-ppc_4xx
Preparing...
1:db4-utils-ppc_4xx
Preparing...
1:glib2-ppc_4xx
Preparing...
1:glib2-devel-ppc_4xx
Preparing...
###########################################
###########################################
###########################################
###########################################
###########################################
###########################################
###########################################
###########################################
###########################################
[100%]
[100%]
[100%]
[100%]
[100%]
[100%]
[100%]
[100%]
[100%]
<hangs here>
Answer:
This is almost certainly a FUTEX problem. To verify this, please wait until the process grinds to a
halt, then use ps to find the pid of the "rpm" process that was started by the "install" program
(use "ps -axf" which gives you a nice hierarchy, look for the "install" process, then for
"rpm") and then attach to it with "strace -p". Most probably you will see the something like
this:
# strace -p 21197
Process 21197 attached - interrupt to quit
futex(0x96fe17c, FUTEX_WAIT_PRIVATE, 1, NULL
i. e. the process is hanging in a futex call.
We have seen this more than once with differing Linux systems, but unfortunately we don't know a
clean and reliable way to fix it yet. We suspect that it is a kernel/libc combination problem because it
usually went away usually after changing the exact used kernel version.
The only workaround we can recommend so far is to update your host system and install more recent
versions of the Linux kernel and/or the glibc C library (assuming such are available for your Linux
distribution; if not, falling back to a previous kernel version may help, too).
Note: This is only needed for the installer, the problem does not happen with the regular use of the
ELDK.
14.1.3. .gvfs: Permission Denied
Question:
When trying to install the ELDK, I get error messages like this for each and every package that gets
installed:
Preparing...
################### 100%
1: rpm...
################### 100%
Error: Failed to stat /home/wd/.gvfs: Permission Denied
This happens even though I run the installer as root.
Answer:
Even though flagged as an error, these messages are harmless warnings that can be safely ignored.
Before the RPM tool starts to install a package, it checks if there is sufficient space for it in the file
system. Unfortunately it is dumb and checks all mounted file systems for space, but the permissions
of the ".gvfs" directory (the mount point for the Gnome Virtual File System) do not permit this.
Note:
Actually the messages are not printed despite the fact that you are running as root, but because you
run as root. You have permissions to check the "$HOME/.gvfs" directory, while root gets an error:
14.1.3. .gvfs: Permission Denied
152
$ df -h /home/wd/.gvfs
Filesystem
Size Used Avail Use% Mounted on
gvfs-fuse-daemon
0
0
0
- /home/wd/.gvfs
$ sudo df -h /home/wd/.gvfs
df: `/home/wd/.gvfs': Permission denied
df: no file systems processed
14.1.4. Installation on Local Harddisk
Question:
I have a local harddisk drive connected to my target board. Can I install the ELDK on it and run it like
a standard Linux distribution?
Answer:
Yes, this is possible. It requires only minor adjustments. The following example assumes you are
using a SCSI disk drive, but the same can be done with standard SATA or PATA drives, too:
1. Boot the target with root file system over NFS.
2. Create the necessary partitions on your disk drive: you need at last a swap partition and a file
system partition.
bash-3.00# fdisk -l
Disk /dev/sda: 36.9 GB, 36951490048 bytes
64 heads, 32 sectors/track, 35239 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Device Boot
/dev/sda1
/dev/sda2
/dev/sda3
/dev/sda4
Start
1
979
12424
23869
End
978
12423
23868
35239
Blocks
1001456
11719680
11719680
11643904
Id
82
83
83
83
System
Linux swap / Solaris
Linux
Linux
Linux
3. Format the partititons:
bash-3.00# mkswap /dev/sda1
bash-3.00# mke2fs -j -m1 /dev/sda2
4. Mount the file system:
bash-3.00# mount /dev/sda2 /mnt
5. Copy the content of the (NFS) root file system into the mounted file system:
bash-3.00# tar --one-file-system -c -f - / | ( cd /mnt ; tar xpf - )
6. Adjust /etc/fstab for the disk file system:
bash-3.00# vi /mnt/etc/fstab
bash-3.00# cat /mnt/etc/fstab
/dev/sda2
/
/dev/sda1
swap
proc
/proc
sysfs
/sys
ext3
swap
proc
sysfs
defaults
defaults
defaults
defaults
1
0
0
0
1
0
0
0
7. Adjust /etc/rc.sysinit for running from local disk; remove the following comments:
bash-3.00# diff -u /mnt/etc/rc.sysinit.ORIG /mnt/etc/rc.sysinit
--- /mnt/etc/rc.sysinit.ORIG
2007-01-21 04:37:00.000000000 +0100
+++ /mnt/etc/rc.sysinit 2007-03-02 10:58:22.000000000 +0100
@@ -460,9 +460,9 @@
# Remount the root filesystem read-write.
update_boot_stage RCmountfs
-#state=`LC_ALL=C awk '/ \/ / && ($3 !~ /rootfs/) { print $4 }' /proc/mounts`
14.1.4. Installation on Local Harddisk
153
-#[ "$state" != "rw" -a "$READONLY" != "yes" ] && \
-# action $"Remounting root filesystem in read-write mode: " mount -n -o remount,rw
+state=`LC_ALL=C awk '/ \/ / && ($3 !~ /rootfs/) { print $4 }' /proc/mounts`
+[ "$state" != "rw" -a "$READONLY" != "yes" ] && \
+ action $"Remounting root filesystem in read-write mode: " mount -n -o remount,rw
# Clean up SELinux labels
if [ -n "$SELINUX" ]; then
8. Unmount disk:
bash-3.00# umount /mnt
9. Reboot, and adjust boot arguments to use disk partition as root file system
=> setenv diskargs setenv bootargs root=/dev/sda2 ro
=> setenv net_disk 'tftp ${loadaddr} ${bootfile};run diskargs addip addcons;bootm'
=> saveenv
10. Boot with these settings
=> run net_disk
14.1.5. System Include Files Missing
Question:
when installing ELDK on Ubuntu 6.06 dapper drake I get the following error messages....
Preparing...
########################################### [100%]
1:kernel-source-ppc_6xx ########################################### [100%]
Configuring kernel...
scripts/basic/fixdep.c:107:23: error: sys/types.h: No such file or directory
scripts/basic/fixdep.c:108:22: error: sys/stat.h: No such file or directory
scripts/basic/fixdep.c:109:22: error: sys/mman.h: No such file or directory
...
Answer:
The Linux installation on your host is missing essential files that are needed to perform software
development and use a C compiler. On Ubuntu, check for example if you miss a "libc6-dev" package.
The specific package name differs from distribution to distribution; on Fedora, you need for example
the "glibc-headers" package.
If you want to work with a Linux kernel you will probably also need other packages.
14.1.6. patch: command not found
Question:
When installing ELDK on Ubuntu I get the following error message:
...prepare-kernel.sh: line 376: patch: command not found
Answer:
The error message contains clear hints for the solution: the "patch" command cannot be found on
your system, so most probably it has not been installed yet. Please try:
$ sudo apt-get install patch
14.1.6. patch: command not found
154
14.1.7. ELDK Include Files Missing
Question:
After configuring and compiling a Linux kernel in the kernel source tree that comes with the ELDK, I
cannot compile user space programs any more - I get error messages because many #include file like
<errno.h> etc. are missing.
This is with ELDK 4.0 or 4.1.
Answer:
This problem is caused by the way how the ELDK is packaged. At the moment, the ELDK kernel
headers are not packed into a separate "kernel-headers" RPM to avoid duplication, because the kernel
source tree is always installed. Instead, the ELDK "kernel-headers" package is just a set of symlinks.
This worked fine in the past, but fails with the new support for ARCH=powerpc systems.
The next version of the ELDK will contain a real kernel-headers RPM, which will fix this problem.
As a workaround on current systems, you can install the real kernel include files into the
"include/asm", "include/linux" and "include/mtd" directories.
To do this, the following commands can be used:
bash$
bash$
bash$
bash$
<eldkroot>/bin/rpm -e kernel-headers-ppc_<target>
cd <eldkroot>/ppc_<target>
rm usr/include/asm
tar -xvzf kernel-headers-powerpc.tar.gz
The tarball mentioned above can be downloaded here. It contains the include files that get installed by
running the "make ARCH=powerpc headers_install" command in the Linux kernel tree.
This problem is fixed in ELDK 4.2 and later releases.
14.1.8. Using the ELDK on a 64 bit platform
As the ELDK is compiled for 32-bit host systems, a compatibility layer is required on 64-bit systems. This
package is usually called ia32-libs. So on a Debian or Ubuntu system a
sudo apt-get install ia32-libs
should be enough to make the ELDK work.
On the U-Boot mailing list, it was reported that for a 64 bit Fedora 11 the following should be enough:
sudo yum -y install glibc.i686 zlib.i686
14.1.9. How can I check if Floating Point support is
working?
Question:
The floating point performance of my P2020 QorIQ processor is really poor. I am not using the
ELDK, but a tool chain from FOOBAR. Can this be a problem? What can I do to verify this?
Answer:
The P20xx QorIQ processors use an e500v2 core which does not include a normal Floating Point Unit
(FPU), but instead a Signal Processing Engine (SPE Version 2). You can run FP calculations on the
14.1.9. How can I check if Floating Point support is working?
155
SPE, but there are no special FP registers available as on a normal FPU, so General Purpose Registers
must be used for passing of FP operands. While this is still much faster than pure soft-float emulation,
it is missing the advantages and the speed of a full-blown, separate standard FPU with a full FP
register set.
Also, your tool chain needs to be aware of this feature, and must contain support for it. Eventually
special compiler options are needed - check your documentation.
With the ELDK, the needed settings are automatically pre-set when you just chose the correct target
architecture packages, cf. 3.4. Supported Target Architectures
To test what your tool chain is doing, you best compile a smal test program and check the generated
code. The following examples were done with ELDK 4.2 for Power Architecture® targets:
1. Test Program:
$ cat fp_test.c
double foo (double x, double y)
{
double z;
z = (x + y) / (x * y);
return z;
}
2. Build for normal FPU support (using the ppc_6xx target architecture):
$ export CROSS_COMPILE=ppc_6xx$ ppc_6xx-gcc -S -O fp_test.c
Check results:
$ cat fp_test.s
.file
"fp_test.c"
.section
".text"
.align 2
.globl foo
.type
foo, @function
foo:
fadd 0,1,2
fmul 1,1,2
fdiv 1,0,1
blr
.size
foo, .-foo
.ident "GCC: (GNU) 4.2.2"
.section
.note.GNU-stack,"",@progbits
The use of floating point machine instructions ("fadd", "fmul", "fdiv") and the fact that no
additional register use is needed is a clear indication that full support for the hardware FPU is
available in this configuration.
3. Build for soft-float emulation (using the ppc_8xx target architecure):
$ export CROSS_COMPILE=ppc_8xx$ ppc_8xx-gcc -S -O fp_test.c
$ cat fp_test.s
.file
"fp_test.c"
.globl __adddf3
.globl __muldf3
.globl __divdf3
.section
".text"
.align 2
14.1.9. How can I check if Floating Point support is working?
156
.globl foo
.type
foo, @function
foo:
stwu 1,-48(1)
mflr 0
stw 24,16(1)
stw 25,20(1)
stw 26,24(1)
stw 27,28(1)
stw 28,32(1)
stw 29,36(1)
stw 0,52(1)
mr 28,3
mr 29,4
mr 26,5
mr 27,6
bl __adddf3
mr 24,3
mr 25,4
mr 3,28
mr 4,29
mr 5,26
mr 6,27
bl __muldf3
mr 5,3
mr 6,4
mr 3,24
mr 4,25
bl __divdf3
lwz 0,52(1)
mtlr 0
lwz 24,16(1)
lwz 25,20(1)
lwz 26,24(1)
lwz 27,28(1)
lwz 28,32(1)
lwz 29,36(1)
addi 1,1,48
blr
.size
foo, .-foo
.ident "GCC: (GNU) 4.2.2"
.section
.note.GNU-stack,"",@progbits
The fact that the compiler is calling helper functions (__adddf3, __muldf3, __divdf3)
combined with heavy use of the General Purpose Registers is a clear indication for
software-emulated FP support - and explains why this is so slow compared to a real FPU.
4. Build for SPE v2 support (as needed for example for a P2020 QorIQ processor, using the
ppc_85xxDP target architecture):
$ export CROSS_COMPILE=ppc_85xxDP$ ppc_85xxDP-gcc -S -O fp_test.c
$ cat fp_test.s
.file
"fp_test.c"
.section
".text"
.align 2
.globl foo
.type
foo, @function
foo:
stwu 1,-48(1)
stw 3,8(1)
stw 4,12(1)
stw 5,16(1)
stw 6,20(1)
evmergelo 0,3,4
14.1.9. How can I check if Floating Point support is working?
157
evmergelo 9,5,6
efdadd 11,0,9
efdmul 0,0,9
efddiv 11,11,0
evstdd 11,24(1)
evmergehi 9,11,11
mr 10,11
stw 9,32(1)
stw 10,36(1)
mr 3,9
mr 4,10
addi 1,1,48
blr
.size
foo, .-foo
.ident "GCC: (GNU) 4.2.2"
.section
.note.GNU-stack,"",@progbits
Here we can see moderate use of General Purpos Registers combined with the use of SPE
machine instructions (evmergelo, efdadd, efdmul, efddiv, evstdd, evmergehi) which proves
that the compiler really generates code that supports the SPE.
14.1.10. ELDK 2.x Installation Aborts
Question:
I tried to install ELDK version 2.x on a SuSE 8.2 / SuSE 9 / RedHat-9 Linux host but failed - it
terminated without installing any packages. Why?
Answer:
Newer Linux distributions use libraries that are incompatible to those used by the ELDK's installation
tools. This problem was fixed in later releases of the ELDK (version 3.0 and later). It is therefore
recommended to use a more recent version of the ELDK. If you really want to install an old version,
the following back-port is available:
Please download the file ftp://ftp.denx.de/pub/tmp/ELDK-update-2.2.0.tar.bz2
Then change into the source tree with the ELDK files and perform the following operations:
bash$ rm RPMS/rpm-4.0.3-1.03b_2.i386.rpm \
RPMS/rpm-build-4.0.3-1.03b_2.i386.rpm \
RPMS/rpm-devel-4.0.3-1.03b_2.i386.rpm \
tools/usr/lib/rpm/rpmpopt-4.0.3
bash$ tar jxf /tmp/ELDK-update-2.2.0.tar.bz2
Then build the ISO image as documented, and try again.
14.1.11. Enable SSH Access
Question:
How can I enable SSH access to the target system when running with the ELDK file system mounted
over NFS?
Answer:
The ELDK includes the dropbear SSH server and client packages (see
http://matt.ucc.asn.au/dropbear/dropbear.html). To enable SSH access, you must first generate the
SSH host keys for RSA and DSS:
14.1.11. Enable SSH Access
158
# dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key
Will output 1024 bit rsa secret key to '/etc/dropbear/dropbear_rsa_host_key'
Generating key, this may take a while...
Public key portion is:
ssh-rsa ...
Fingerprint: md5 ...
# dropbearkey -t dss -f /etc/dropbear/dropbear_dss_host_key
Will output 1024 bit dss secret key to '/etc/dropbear/dropbear_dss_host_key'
Generating key, this may take a while...
Public key portion is:
ssh-dss ...
Fingerprint: md5 ...
Then you can start the dropbear daemon:
# dropbear
Now you should be able to access the target system through SSH.
14.2. U-Boot
14.2.1. Can U-Boot be configured such that it can
be started in RAM?
Question:
I don't want to erase my flash memory because I'm not sure if my new U-Boot image will work. Is it
possible to configure U-Boot such that I can load it into RAM instead of flash, and start it from my
old boot loader?
Answer:
No. (Unless you're using a Blackfin processor, but you probably aren't.)
Question:
But I've been told it is possible??
Answer:
Well, yes. Of course this is possible. This is software, so everything is possible. But it is difficult,
unsupported, and fraught with peril. You are on your own if you choose to do it. And it will not help
you to solve your problem.
Question:
Why?
Answer:
U-Boot expects to see a virgin CPU, i. e. the CPU state must match what you see if the processor
starts executing the first instructions when it comes out of reset. If you want to start U-Boot from
another boot loader, you must disable a lot of code, i. e. all initialization parts that already have been
performed by this other boot loader, like setting up the memory controller, initializing the SDRAM,
initializing the serial port, setting up a stack frame etc. Also you must disable the relocation to RAM
and adjust the link addresses etc.
This requires a lot of experience with U-Boot, and the fact that you had to ask if this can be done
means that you are not in a position to do this.
The code you have to disable contains the most critical parts in U-Boot, i. e. these are the areas where
14.2.1. Can U-Boot be configured such that it can be started in RAM?
159
99% or more of all errors are located when you port U-Boot to a new hardware. In the result, your
RAM image may work, but in the end you will need a full image to program the flash memory with it,
and then you will have to enable all this highly critical and completely untested code.
You see? You cannot use a RAM version of U-Boot to avoid testing a flash version, so you can save
all this effort and just burn your image to flash.
Question:
So how can I test an U-Boot image and recover my system if it doesn't work?
Answer:
Attach a BDI2000 (or any appropriate JTAG ICE) to your board, burn the image to flash, and debug it
in its natural environment, i.e. U-Boot being the boot loader of the system and taking control over the
CPU right as it comes out of reset. If something goes wrong, erase the flash and program a new
image. This is a routine job using a BDI2000.
14.2.2. Relocation cannot be done when using
-mrelocatable
Question:
I use ELDK version 3.0. When I build U-Boot I get error messages like this:
{standard input}: Assembler messages:
{standard input}:4998: Error: Relocation cannot be done when using -mrelocatable
...
Answer:
ELDK 3.0 uses GCC-3.2.2; your U-Boot sources are too old for this compiler. GCC-3.x requires a
few adaptions which were added in later versions of U-Boot. Use for example the source tree (1.0.2)
which is included with the ELDK, or download the latest version from CVS.
14.2.3. Source object has EABI version 4, but
target has EABI version 0
Question:
When trying to build U-Boot with an EABI compliant tool chain, I get such error messages:
arm-ld: ERROR: Source object ... has EABI version 4, but target ... has EABI version 0
What does that mean, and how can I fix that?
Answer:
"EABI version 0" means the "apcs-gnu" ABI, while "EABI version 4" is the "aapcs-linux"
ABI, aka "gnueabi".
All U-Boot ARM sources are built with "-mapcs-gnu" option set in "cpu/arm/config.mk",
while libgcc.a modules are built in "gnueabi" format, which is for example the ARM GCC default
in ELDK Release 4.2.
So the real problem is compatibility between toolchain ABI and U-Boot ARM ABI. In the Linux
kernel there is a special kernel config option for EABI-enabled tool chains (CONFIG_AEABI), which
enables special pieces of code in ARM assembler modules. We could follow this approach, reworking
existing assembler sources and respective config.mk files in U-Boot.
14.2.3. Source object has EABI version 4, but target has EABI version 0
160
Alternatively, the tool chain could provide a separate version of libgcc.a built with old ABI. This
could be done using the multilib approach. The advantage here is that no U-boot changes will be
required.
14.2.4. U-Boot crashes after relocation to RAM
Question:
I have ported U-Boot to a custom board. It starts OK, but crashes or hangs after relocating itself to
RAM. Why?
Answer:
Your SDRAM initialization is bad, and the system crashes when it tries to fetch instructions from
RAM. Note that simple read and write accesses may still work, it's the burst mode that is failing. This
only shows up when caches are enabled because cache is the primary (or only) user of burst
operations in U-Boot. In Linux, burst accesses may also result from DMA. For example, it is typical
that a system may crash under heavy network load if the Ethernet controller uses DMA to memory.
It is NOT sufficient to program the memory controller of your CPU; each SDRAM chip also
requires a specific initialization sequence which you must adhere to to the letter - check with the chip
manufacturer's manual.
It has been observed that some operating systems like pSOS+ or VxWorks do not stress the memory
subsystem as much as Linux or other UNIX systems like LynxOS do, so just because your board
appears to work running another OS does not mean it is 100% OK.
Standard memory tests are not effective in identifying this type of problem because they do not cause
stressful cache burst read/write operations.
With this caveat in mind, reportedly this program has found memory problems before:
http://pyropus.ca/software/memtester/
Argument:
But my board ran fine with bootloader XYZ and/or operating system ABC.
Answer:
Double-check your configuration that you claim runs properly...
1. Are you sure the SDRAM is initialized using the same init sequence and values?
2. Are you sure the memory controlling registers are set the same?
3. Are you sure your other configuration uses caches and/or DMA? If it doesn't, it isn't a valid
comparison.
14.2.5. Warning - bad CRC, using default
environment
Question:
I have ported U-Boot to a custom board. It seems to boot OK, but it prints:
*** Warning - bad CRC, using default environment
14.2.5. Warning - bad CRC, using default environment
161
Why?
Answer:
Most probably everything is OK. The message is printed because the flash sector or ERPROM
containing the environment variables has never been initialized yet. The message will go away as
soon as you save the envrionment variables using the saveenv command.
14.2.6. Net: No ethernet found
Question:
I have ported U-Boot to a custom board. It seems to boot OK, but it prints:
Net:
No ethernet found.
Why?
Answer:
Some network drivers (especially on ppc4xx) respond with such a message when no valid MAC
address has been defined. Please make sure that a valid MAC address has been defined in the
environment (using the "setenv" command). Then store the environment (using the "saveenv"
command). After the next reboot, the Ethernet interface should be available.
14.2.7. Wrong debug symbols after relocation
Question:
I want to debug U-Boot after relocation to RAM, but it doesn't work since all the symbols are at
wrong addresses now.
Answer:
To debug parts of U-Boot that are running from ROM/flash, i. e. before relocation, just use a
command like "powerpc-linux-gdb uboot" as usual.
For parts of U-Boot that run from RAM, i. e. after relocation, use "powerpc-linux-gdb"
without arguments, and use the add-symbol-file command in GDB to load the symbol table at
the relocation address in RAM. The only problem is that you need to know that address, which
depends on RAM size, length reserved for U-Boot, size of "protected RAM" area, etc. If in doubt,
enable DEBUG mode when building U-Boot so it prints the address to the console.
Hint: I use definitions like these in my .gdbinit file:
define rom
symbol-file
file u-boot
end
define ram
symbol-file
add-symbol-file u-boot
end
0x01fe0000
Note: when you want to switch modes during one debug session (i. e. without restarting GDB) you
can "delete" the current symbol information by using the symbol-file command without
arguments, and then either using "symbol-file u-boot" for code before relocation, or
14.2.7. Wrong debug symbols after relocation
162
"add-symbol-file u-boot _offset_" for code after relocation.
14.2.8. Decoding U-Boot Crash Dumps
When you are porting U-Boot to new hardware, or implementing extensions, you might run into situations
where U-Boot crashes and prints a register dump and a stack trace, for example like this:
Bus Fault @ 0x00f8d70c, fixup 0x00000000
Machine check in kernel mode.
Caused by (from msr): regs 00f52cf8 Unknown values in msr
NIP: 00F8D70C XER: 0000005F LR: 00F8D6F4 REGS: 00f52cf8 TRAP: 0200 DAR: F9F68C00
MSR: 00009002 EE: 1 PR: 0 FP: 0 ME: 1 IR/DR: 00
GPR00: 00016ACC 00F52DE8 00000000 F9F68C00 00FA38EC 00000001 F9F68BF8
GPR08: 00000002 00F55470 00000000 00F52D94 44004024 00000000 00FA2F00
GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000
GPR24: 00000000 00FA38EC 00F553C0 00F55480 00000000 00F52F80 00FA41C0
Call backtrace:
00000000 00F8F998 00F8FA88 00F8FAF8 00F90B5C 00F90CF8 00F8385C
00F79E6C 00F773B0
machine check
0000000B
C0F75000
00000000
00000001
To find out what happened, you can try to decode the stack backtrace (the list of addresses printed after the
"Call backtrace:" line. The backtrace tool can be used for this purpose. However, there is a little
problem: the addresses printed for the stack backtrace are after relocation of the U-Boot code to RAM; to use
the backtrace tool you need to know U-Boot's address offset (the difference between the start address of
U-Boot in flash and its relocation address in RAM).
The easiest way to find out the relocation address is to enable debugging for the U-Boot source file
lib_*/board.c - U-Boot will then print some debug messages
...
Now running in RAM - U-Boot at: 00f75000
...
Now you have to calculate the address offset between your link address (The value of the TEXT_BASE
definition in your board/?/config.mk file). In our case this value is 0x40000000, so the address offset
is 0x40000000 - 0x00f75000 = 0x3f08b000
Now we use the backtrace script with the System.map file in the U-Boot source tree and this address
offset:
-> backtrace System.map 0x3f08b000
Reading symbols from System.map
Using Address Offset 0x3f08b000
0x3f08b000 -- unknown address
0x4001a998 -- 0x4001a8d0 + 0x00c8
0x4001aa88 -- 0x4001aa2c + 0x005c
0x4001aaf8 -- 0x4001aad0 + 0x0028
0x4001bb5c -- 0x4001ba68 + 0x00f4
0x4001bcf8 -- 0x4001bcd8 + 0x0020
0x4000e85c -- 0x4000e6f8 + 0x0164
0x40004e6c -- 0x40004b9c + 0x02d0
0x400023b0 -- 0x400023b0 + 0x0000
free_pipe
free_pipe_list
run_list
parse_stream_outer
parse_file_outer
main_loop
board_init_r
trap_init
In this case the last "good" entry on the stack was in free_pipe...
14.2.8. Decoding U-Boot Crash Dumps
163
14.2.9. Porting Problem: cannot move location
counter backwards
Question:
I'm trying to port U-Boot to a new board and the linker throws an error message like this:
board/<your_board>/u-boot.lds:75 cannot move location counter backwards (from 00000000b0008
Answer:
Check your linker script board/your_board/u-boot.lds which controls how the object files
are linked together to build the U-Boot image.
It looks as if your board uses an "embedded" environment, i. e. the flash sector containing the
environment variables is surrounded by code. The u-boot.lds tries to collect as many as possible
code in the first part, making the gap between this first part and the environment sector as small as
possible. Everything that does not fit is then placed in the second part, after the environment sector.
Some your modifications caused the code that was put in this first part to grow, so that the linker finds
that it would have to overwrite space that is already used.
Try commenting out one (or more) line(s) before the line containing the
"common/environment.o" statement. [ "lib_generic/zlib.o" is usually a good
candidate for testing as it's big ]. Once you get U-Boot linked, you can check in the u-boot.map
file how big the gap is, and which object files could be used to fill it up again.
14.2.10. U-Boot Doesn't Run after Upgrading my
Compiler
Question:
I encountered a big problem that U-Boot 1.1.4 compiled by ELDK 4.1 for MPC82xx crashed.
But if I build it using gcc-3.4.6 based cross tools, U-Boot on my board boots correctly.
The same U-Boot code built by ELDK 4.1 (gcc-4.0) failed, nothing occurs on the serial port.
Answer:
This is often a missing volatile attribute on shared variable references, particularly hardware
registers. Newer compiler versions optimize more aggressively, making missing volatile
attributes visible.
If you use -O0 (no optimization) does it fix the problem?
If it does, it most likely is an optimization/volatile issue. The hard part is figuring out where. Device
handling and board-specific code is the place to start.
14.2.11. How Can I Reduce The Image Size?
Question:
I am trying to reduce the size of the u-boot.bin file so that it fits into 256 KB. I disabled all the drivers
that I didn't need but the binary size is still 512KB, it seems to be a hard number coded in somewhere.
14.2.11. How Can I Reduce The Image Size?
164
Where can the image size be altered from?
Answer:
Some processors have a fixed reset vector address at 0xFFFFFFFC, so the U-Boot image has to
include that address, i. e. it covers the full range from the start address to the end of the 32 bit address
space. In such a case, the start address must be changed - check the setting of TEXT_BASE in your
board/<name>/config.mk file.
14.2.12. Erasing Flash Fails
Question:
I tried to erase the flash memory like
erase 40050000 40050100
It fails. What am I doing wrong?
Answer:
Remember that flash memory cannot be erased in arbitrary areas, but only in so called "erase regions"
or "sectors". If you have U-Boot running you can use the flinfo (Flash information, short fli)
command to print information about the flash memory on your board, for instance:
=> fli
Bank # 1: AMD AM29LV160B (16 Mbit, bottom boot sect)
Size: 4 MB in 35 Sectors
Sector Start Addresses:
40000000 (RO) 40008000 (RO) 4000C000 (RO) 40010000 (RO) 40020000 (RO)
40040000
40060000
40080000
400A0000
400C0000
400E0000
40100000
40120000
40140000
40160000
40180000
401A0000
401C0000
401E0000
40200000
40220000
40240000
40260000
40280000
402A0000
402C0000
402E0000
40300000
40320000
40340000
40360000
40380000
403A0000
403C0000
403E0000
In the example above, the area 40050000 ... 40050100 lies right in the middle of a erase unit
(40040000 ... 4005FFFF), so you cannot erase it without erasing the whole sector, i. e. you have to
type
=> erase 40040000 4005FFFF
Also note that there are some sectors marked as read-only ((RO)); you cannot erase or overwrite
these sectors without un-protecting the sectors first (see the U-Boot protect command).
14.2.13. Ethernet Does Not Work
Question:
Ethernet does not work on my board.
Answer:
Maybe you forgot to set a MAC address? Check if the "ethaddr" environment variable is defined,
and if it has a sane value. If there are more than one Ethernet interfaces on your board, you may also
have to check the MAC addresses for these, i. e. check the "eth1addr", "eth2addr", etc.
14.2.13. Ethernet Does Not Work
165
variables, too.
Question:
I have configured a MAC address of 01:02:03:04:05:06, and I can see that an ARP packet is sent by
U-Boot, and that an ARP reply is sent by the server, but U-Boot never receives any packets. What's
wrong?
Answer:
You have chosen a MAC address which, according to the ANSI/IEEE 802-1990 standard, has the
multicast bit set. Under normal conditions a network interface discards such packets, and this is what
U-Boot is doing. This is not a bug, but correct behaviour.
Please use only valid MAC addresses that were assigned to you.
For bring-up testing in the lab you can also use so-called locally administered ethernet addresses.
These are addresses that have the 2nd LSB in the most significant byte of MAC address set. The
gen_eth_addr tool that comes with U-Boot (see "tools/gen_eth_addr" ) can be used to
generate random addresses from this pool.
14.2.14. Where Can I Get a Valid MAC Address
from?
Question:
Where can I get a valid MAC address from?
Answer:
You have to buy a block of 4096 MAC addresses (IAB = Individual Address Block) or a block of
16M MAC addresses (OUI = Organizationally Unique Identifier, also referred to as 'company id')
from IEEE Registration Authority. The current cost of an IAB is $550.00, the cost of an OUI is
$1,650.00. See http://standards.ieee.org/regauth/oui/index.shtml
You can buy Eproms containing MAC addresses from: Maxim or Microchip.
You can set the "locally administered" bit to make your own MAC address (no guarantee of
uniqueness, but pretty good odds if you don't do something dumb). Ref: Wikipedia
Universally administered and locally administered addresses are distinguished by
setting the second least significant bit of the most significant byte of the address. If
the bit is 0, the address is universally administered. If it is 1, the address is locally
administered. The bit is 0 in all OUIs. For example, 02-00-00-00-00-01. The most
significant byte is 02h. The binary is 00000010 and the second least significant bit is
1. Therefore, it is a locally administered address.
In U-Boot, you can use the "gen_eth_addr" tool to generate a random "locally administered"
MAC address. Here are the needed commands:
$ make tools/gen_eth_addr
cc
tools/gen_eth_addr.c
$ tools/gen_eth_addr
ba:d0:4a:9c:4e:ce
-o tools/gen_eth_addr
14.2.14. Where Can I Get a Valid MAC Address from?
166
14.2.15. Why do I get TFTP timeouts?
Question 1:: When trying to download a file from the TFTP server I always get timeouts like these:
...
Loading: #######T ##################################T###################T ####T ##T #
###T #T #########T ########T #############T ##T #############T ########T #############T
#####T ###T ######T #######T #######T #############T ##T ##############T ###########
###########
done
If the target is connected directly to the host PC (i. e. without a switch inbetween) the problem goes away or is
at least less incisive.
What's wrong?
Answer 1:: Most probably you have a full duplex/half duplex problem. Verify that U-Boot is setting the
ethernet interface on your board to the proper duplex mode (full/half). I'm guessing your board is half duplex
but your switch is full (typical of a switch ;-).
The switch sends traffic to your board while your board is transmitting... that is a collision (late collision at
that) to your board but is OK to the switch. This doesn't happen nearly as much with a direct link to your PC
since then you have a dedicated link without much asynchronous traffic.
The software (U-Boot/Linux) needs to poll the PHY chip for duplex mode and then (re)configure the MAC
chip (separate or built into the CPU) to match. If the poll isn't happening or has a bug, you have problems like
described above.
Question 2:: When I use tftp, there are some problems. My terminal always displays "Loading: T T T T T T T
T T T T T T T T T T T T T". The whole information as follows:
U-Boot 1.1.4_XT (Jun 6 2006 - 17:36:18)
U-Boot code: 0C300000 -> 0C31AD70 BSS: -> 0C31EF98
RAM Configuration:
Bank #0: 0c000000 8 MB
Bank #1: 0c800000 8 MB
Flash: 2 MB
*** Warning - bad CRC, using default environment
In:
serial
Out:
serial
Err:
serial
Hit any key to stop autoboot: 0
XT=> help tftp
tftpboot [loadAddress] [bootfilename]
XT=> tftpboot 0x0c700000 image.bin
TFTP from server 192.168.0.23; our IP address is 192.168.0.70
Filename 'image.bin'.
Load address: 0xc700000
Loading: T T T T T T T T T T T T T T T T T T T T
Retry count exceeded; starting again
TFTP from server 192.168.0.23; our IP address is 192.168.0.70
Would someone give me some suggestions?
Answer 2:: (1) Verify your TFTP server is working. On a machine (not the TFTP server nor your
development board) use tftp to read the target file.
$ tftp 192.168.0.23 get image.bin
14.2.15. Why do I get TFTP timeouts?
167
If this doesn't work, fix your TFTP server configuration and make sure it is running.
(2) If your TFTP server is working, run ethereal (or equivalent ethernet sniffing) to see what ethernet packets
are being sent by your development board. It usually works best to run ethereal on your TFTP server (if you
run it on a different machine and you use an ethernet switch, the third machine likely won't see the tftp
packets).
14.2.16. Why is my Ethernet operation not reliable?
Question:
My ethernet connection is not working reliable. On one switch it works fine, but on another one it
doesn't.
or:
Question:
I always see transmit errors or timeouts for the first packet of a download, but then it works well.
or:
Question:
I cannot mount the Linux root file system over NFS; especially not with recent Linux kernel versions
(older kernel versions work better). Specifying "proto=tcp" as mount option greatly improves the
situation.
etc.
Answer:
There are many possible explanations for such problems. After eliminating the obvious sources (like
broken cables etc.) you should check the configuration of your Ethernet PHY. One common cause of
problems is if your PHY is hard configured in duplex mode (for example 100baseTX Full Duplex or
10baseT Full Duplex). If such a setup is combined with a autonegotiating switch, then trouble is
ahead.
Jerry Van Baren explained this as follows:
Ignoring the configuration where both ends are (presumably correctly)
manually configured, you end up with five cases, two of them
misconfigured and WRONG:
1) Autonegotiation
<-> autonegotiation - reliable.
2) 10bT half duplex
<-> autonegotiation - reliable.
3) 100bT half duplex
<-> autonegotiation - reliable.
4) 10bT *FULL* duplex <-> autonegotiation - *UNreliable*.
5) 100bT *FULL* duplex <-> autonegotiation - *UNreliable*.
The problem that I've observed is that the *humans* (the weak links)
that do the manual configuration don't understand that "parallel
detection" *must be* half duplex by definition in the spec (it is hard
to define a reliable algorithm to detect full duplex capability so the
spec writers punted). As a result, the human invariably picks "full
duplex" because everybody knows full duplex is better... and end up as
case (4) or (5). They inadvertently end up with a slower unreliable
link (lots of "collisions" resulting in runt packets) rather than the
faster better link they thought they were picking (d'oh!). The really
bad thing is that the network works fine in testing on an isolated LAN
with no traffic and absolutely craps its pants when it hits the real
world.
That is my reasoning behind my statement that we can generally ignore
14.2.16. Why is my Ethernet operation not reliable?
168
the autonegotiation <-> fixed configuration case because the odds of it
working properly are poor anyway.
Rule:
Always try to set up your PHY for autonegotiation.
If you must use some fixed setting, then set it to half duplex mode.
If you really must use a fixed full-duplex setting, then you absolutley must make sure that the link
partner is configured exactly the same.
See also:
Wikipedia: Autonegotiation and Wikipedia: Duplex mismatch
14.2.17. How the Command Line Parsing Works
There are two different command line parsers available with U-Boot: the old "simple" one, and the much
more powerful "hush" shell:
14.2.17.1. Old, simple command line parser
• supports environment variables (through setenv / saveenv commands)
• several commands on one line, separated by ';'
• variable substitution using "... ${_variablename_} ..." syntax
NOTE: Older versions of U-Boot used "$(...)" for variable substitution. Support for this
syntax is still present in current versions, but will be removed soon. Please use "${...}" instead,
which has the additional benefit that your environment definitions are compatible with the Hush shell,
too.
• special characters ('$', ';') can be escaped by prefixing with '\', for example:
setenv bootcmd bootm \${address}
• You can also escape text by enclosing in single apostrophes, for example:
setenv addip 'setenv bootargs ${bootargs} ip=${ipaddr}:${serverip}:${gatewayip}:${n
14.2.17.2. Hush shell
• similar to Bourne shell, with control structures like if...then...else...fi,
for...do...done, while...do...done, until...do...done, ...
• supports environment ("global") variables (through setenv / saveenv commands) and local shell
variables (through standard shell syntax name=value ); only environment variables can be used
with the run command, especially as the variable to run (i. e. the first argument).
• In the current implementation, the local variables space and global environment variables space are
separated. Local variables are those you define by simply typing like name=value. To access a
local variable later on, you have to write '$name' or '${name}'; to execute the contents of a
variable directly you can type '$name' at the command prompt. Note that local variables can only
be used for simple commands, not for compound commands etc.
• Global environment variables are those you can set and print using setenv and printenv. To run
a command stored in such a variable, you need to use the run command, and you must not use the '$'
sign to access them.
• To store commands and special characters in a variable, use single quotation marks surrounding the
whole text of the variable, instead of the backslashes before semicolons and special symbols.
• Be careful when using the hash ('#') character - like with a "real" Bourne shell it is the comment
character, so you have to escape it when you use it in the value of a variable.
Examples:
14.2.17. How the Command Line Parsing Works
169
setenv bootcmd bootm \$address
setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostnam
14.2.17.3. Hush shell scripts
Here are a few examples for the use of the advanced capabilities of the hush shell in U-Boot environment
variables or scripts:
Example:
=> setenv check 'if imi $addr; then echo Image OK; else echo Image corrupted!!; fi'
=> print check
check=if imi $addr; then echo Image OK; else echo Image corrupted!!; fi
=> addr=0 ; run check
## Checking Image at 00000000 ...
Bad Magic Number
Image corrupted!!
=> addr=40000 ;run check
## Checking Image at 00040000 ...
Image Name:
ARM Linux-2.4.18
Created:
2003-06-02 14:10:54 UTC
Image Type:
ARM Linux Kernel Image (gzip compressed)
Data Size:
801609 Bytes = 782.8 kB
Load Address: 0c008000
Entry Point: 0c008000
Verifying Checksum ... OK
Image OK
Instead of "echo Image OK" there could be a command (sequence) to boot or otherwise deal with
the correct image; instead of the "echo Image corrupted!!" there could be a command
(sequence) to (load and) boot an alternative image, etc.
Example:
=> addr1=0
=> addr2=10
=> bootm $addr1 || bootm $addr2 || tftpboot $loadaddr $loadfile && bootm
## Booting image at 00000000 ...
Bad Magic Number
## Booting image at 00000010 ...
Bad Magic Number
TFTP from server 192.168.3.1; our IP address is 192.168.3.68
Filename '/tftpboot/TRAB/uImage'.
Load address: 0xc400000
Loading: #################################################################
#################################################################
###########################
done
Bytes transferred = 801673 (c3b89 hex)
## Booting image at 0c400000 ...
Image Name:
ARM Linux-2.4.18
This will check if the image at (flash?) address "addr1" is ok and boot it; if the image is not ok, the
alternative image at address "addr2" will be checked and booted if it is found to be OK. If both
images are missing or corrupted, a new image will be loaded over TFTP and booted.
14.2.17.2. Hush shell
170
14.2.17.4. General rules
1. If a command line (or an environment variable executed by a run command) contains several
commands separated by semicolons, and one of these commands fails, the remaining commands will
still be executed.
2. If you execute several variables with one call to run (i. e. calling run with a list of variables as
arguments), any failing command will cause run to terminate, i. e. the remaining variables are not
executed.
14.2.18. How can I load and uncompress a
compressed image
Question:
Can I use U-Boot to load and uncompress a compressed image from flash into RAM? And can I
choose whether I want to automatically run it at that time, or wait until later?
Answer:
Yes to both questions. First, you should generate your image as type "standalone" (using "mkimage
... -T standalone ..."). When you use the bootm command for such an image, U-Boot
will automatically uncompress the code while it is storing it at that image's load address in RAM
(given by the -a option to the mkimage command).
As to the second question, by default, unless you say differently, U-Boot will automatically start the
image by jumping to its entry point (given by the -e option to mkimage) after loading it. If you want
to prevent automatic execution, just set the environment variable "autostart" to "no"
("setenv autostart no") before running bootm.
14.2.19. How can I create an uImage from a ELF file
Question:
I would like to run a standard distribution kernel on my target, but I can find only ELF kernel images
or even RPM files. How can I use these?
Answer:
If you have just the kernel ELF file, this may be difficult, as you will usually also need a bunch of
kernel modules that the distribution of your choice probably bundles with this kernel file. Try to
locate and install these first.
If you have a kernel RPM, this usually includes both the kernel ELF file and the required modules.
Install these in the ELDK root file system so you can use this for example mounted over NFS. The
following example uses a Fedora kernel RPM on a 4xxFP target:
$ cd /tmp/
$ wget http://download.fedora.redhat.com/pub/fedora/linux/updates/11/ppc/kernel-2.6.30.9-90
After downloading the RPM we install it (manually using "rpm2cpio" and "cpio" in the root of
the ELDK file system, "/opt/eldk/ppc_4xxFP/" :
$ cd /opt/eldk/ppc_4xxFP/
$ rpm2cpio /tmp/kernel-2.6.30.9-90.fc11.ppc.rpm | sudo cpio -vidum
14.2.19. How can I create an uImage from a ELF file
171
This installs a lot of kernel modules in "./lib/modules/" and a kernel ELF file in "./boot" :
$ ls -l boot
total 8792
-rw-r--r-- 1 root root 1226119 Oct 17 17:31 System.map-2.6.30.9-90.fc11.ppc
-rw-r--r-- 1 root root
96224 Oct 17 17:31 config-2.6.30.9-90.fc11.ppc
-rwxr-xr-x 1 root root 7673768 Oct 17 18:20 vmlinuz-2.6.30.9-90.fc11.ppc
Now convert the ELF kernel image into an uImage file:
$ ppc_4xxFP-objcopy -O binary boot/vmlinuz-2.6.30.9-90.fc11.ppc /tmp/vmlinux.bin
$ gzip -v9 /tmp/vmlinux.bin
/tmp/vmlinux.bin:
58.1% -- replaced with /tmp/vmlinux.bin.gz
$ mkimage -A ppc -O linux -T kernel -C gzip \
> -a 0x00000000 -e 0x00000000 \
> -n Linux-2.6.30.9-90.fc11.ppc \
> -d /tmp/vmlinux.bin.gz /tftpboot/uImage-2.6.30.9-90.fc11.ppc
Image Name:
Linux-2.6.30.9-90.fc11.ppc
Created:
Sun Nov 1 17:00:37 2009
Image Type:
PowerPC Linux Kernel Image (gzip compressed)
Data Size:
3187431 Bytes = 3112.73 kB = 3.04 MB
Load Address: 0x00000000
Entry Point: 0x00000000
There you go.
Note: you still need the Device Tree Blob for your specific target board. This usually does not
come with any of the standard distributions. Also, you may find that you need a ramdisk image to get
some modules loaded that might be needed to mount your root file system.
14.2.20. My standalone program does not work
Question:
I tried adding some new code to the hellow_world.c demo program. This works well as soon as I
only add code to the existing hello_world() function, but as soon as I add some functions of my own,
things go all haywire: the code of the hello_world() function does not get executed correctly, and my
new function gets called with unexpected arguments. What's wrong?
Answer:
You probably failed to notice that any code you add to the example program may shift the entry point
address. You should check this using the nm program:
$ ${CROSS_COMPILE}nm -n examples/hello_world
0000000000040004 T testfunc
0000000000040058 T hello_world
000000000004016c t dummy
...
As you can see, the entry point (function hello_world()) is no longer at 0x40004 as it was before and
as it's documented. Instead, it is now at 0x40058. So you have to start your standalone program at this
address, and everything should work well.
14.2.21. Linux hangs after uncompressing the
kernel
14.2.21. Linux hangs after uncompressing the kernel
172
Question:
I am using U-Boot with a Linux kernel version Y (Y < 2.4.5-pre5), but the last message I see is
Uncompressing Kernel Image ... OK
Then the system hangs.
Answer:
Most probably you pass bad parameters to the Linux kernel.
There are several possible reasons:
◊ Bad device tree; for example, check that the memory map set up by the boot loader (like
mapping of IMMR, PCI addresses etc.) is consistent with what is encoded in your device tree
specification.
Here some possible reasons for older Linux kernel versions:
Linux:
arch/ppc:
◊ arch/ppc: Bad definition of the bd_info structure
You must make sure that your machine specific header file (for instance
include/asm-ppc/tqm8xx.h) includes the same definition of the Board Information structure as
we define in include/ppcboot.h, and make sure that your definition of IMAP_ADDR uses the
same value as your U-Boot configuration in CFG_IMMR.
◊ Bad clock information
Before kernel version 2.4.5-pre5 (BitKeeper Patch 1.1.1.6, 22MAY2001) the kernel expected
the clock information in MHz, but recent kernels expect it in Hz instead. U-Boot passes the
clock information in Hz by default. To switch to the old behaviour, you can set the
environment variable "clocks_in_mhz" in U-Boot:
=> setenv clocks_in_mhz 1
=> saveenv
For recent kernel the "clocks_in_mhz" variable must not be set. If it is present in your environment, you
can delete it as follows:
=> setenv clocks_in_mhz
=> saveenv
A common error is to try "setenv clocks_in_mhz 0" or to some other value - this will not work,
as the value of the variable is not important at all. It is the existence of the variable that will be checked.
•
♦ Inconsistent memory map
Some boards may need corrct mappings for some special hardware devices like BCSR (Board
Control and Status Registers) etc. Verify that the mappings expected by Linux match those
created by U-Boot.
14.2.22. How can I implement automatic software
updates?
Question:
How I can use U-Boot to make it easy for my end users to upgrade the firmware of the device?
14.2.22. How can I implement automatic software updates?
173
Answer:
This depends mainly on how you intend to distribute your software updates, and which physical
interfaces are present (or usable for this purpose) on your device. Typically you will either distribute
the software over the network, or you can use soMe type of storage device like USB mass storage
device (memory stick etc.), SD cards etc.
U-Boot already supports such a feature on several boards. You will probably have to adapt the code
and/or the actual behaviour to your specific hardware and/or requirements. Please see here for a
starting point:
Network:
When auto-update support over TFTP is enabled, U-Boot will test in the initialization sequence if a
specific image file is present on the TFTP server. If this is the case, the image will be downloaded
and, if it is considered ok, installed into flash. For details, please read doc/README.update and/or
see commits 4bae9090 and e83cc063.
USB:
Several boards implement this feature, all in a slightly different way; see board/trab/auto_update.c,
board/mcc200/auto_update.c and board/esd/common/auto_update.c.
With this feature enabled, U-Boot will check during the init sequence if a USB mass storage device is
plugged in, if this contains a readable file system, and check if this contains one or more known image
files. Additionally it is possible to check if the image versions on the USB device are more recent than
those already stored in flash. If all programmed criteria match, and if the images can be read without
error, the content of the on-board storage (flash, NAND, etc.) gets automatically updated. Adaption
for other storage devices (like SD card etc.) should be trivial to implement.
14.3. Linux
14.3.1. Linux crashes randomly
Question:
On my board, Linux crashes randomly or has random exceptions (especially floating point exceptions
if it is a Power Architecture® processor). Why?
Answer:
Quite likely your SDRAM initialization is bad. See UBootCrashAfterRelocation for more
information.
On a Power Architecture®, the instructions beginning with 0xFF are floating point instructions. When
your memory subsystem fails, the Power Architecture® is reading bad values (0xFF) and thus
executing illegal floating point instructions.
14.3.2. Linux crashes when uncompressing the
kernel
Question:
When I try to boot Linux, it crashes during uncompressing the kernel image:
=> bootm 100000
## Booting image at 00100000 ...
14.3.2. Linux crashes when uncompressing the kernel
174
Image Name: Linux-2.4.25
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 1003065 Bytes = 979.6 kB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Uncompressing Kernel Image ... Error: inflate() returned -3
GUNZIP ERROR - must RESET board to recover
Answer:
Your kernel image is quite big - nearly 1 MB compressed; when it gets uncompressed it will need 2.5
... 3 MB, starting at address 0x0000. But your compressed image was stored at 1 MB (0x100000), so
the uncompressed code will overwrite the (remaining) compressed image. The solution is thus simple:
just use a higher address to download the compressed image into RAM. For example, try:
=> bootm 400000
14.3.3. Linux Post Mortem Analysis
You may find yourself in a situation where the Linux kernel crashes or hangs without any output on the
console. The first attempt to get more information in such a situation is a Post Mortem dump of the log buffer
- often the Linux kernel has already collected useful information in its console I/O buffer which just does not
get printed because the kernel does not run until successful initialization of the console port.
Proceed as follows:
1. Find out the virtual address of the log buffer; For 2.4 Linux kernels search for "log_buf":
2.4 Linux:
bash$ grep log_buf System.map
c0182f54 b log_buf
Here the virtual address of the buffer is 0xC0182F54
For 2.6 kernels "__log_buf" must be used:
bash$ grep __log_buf System.map
c02124c4 b __log_buf
Here the virtual address of the buffer is 0xC02124C4
2. Convert to physical address: on Power Architecture® systems, the kernel is usually configured for a
virtual address of kernel base (CONFIG_KERNEL_START) of 0xC0000000. Just subtract this value
from the address you found. In our case we get:
physical address = 0xC0182F54 - 0xC0000000 = 0x00182F54
3. Reset your board - do not power-cycle it!
4. Use your boot loader (you're running U-Boot, right?) to print a memory dump of that memory area:
=> md 0x00182F54
This whole operation is based on the assumption that your boot loader does not overwrite the RAM contents U-Boot will take care not to destroy such valuable information.
14.3.3. Linux Post Mortem Analysis
175
14.3.4. Linux kernel register usage
For the Power Architecture® architecture, the Linux kernel uses the following registers:
R1:
stack pointer
R2:
pointer to task_struct for the current task
R3-R4:
parameter passing and return values
R5-R10:
parameter passing
R13:
small data area pointer
R30:
GOT pointer
R31:
frame pointer
A function can use r0 and r3 - r12 without saving and restoring them. r13 - r31 have to be preserved so
they must be saved and restored when you want to use them. Also, cr2 - cr4 must be preserved, while cr0,
cr1, cr5 - cr7, lr, ctr and xer can be used without saving & restoring them. [ Posted Tue, 15 Jul 2003
by Paul Mackerras to linuxppc-embedded@lists.linuxppc.org ].
See also the (E)ABI specifications for the Power Architecture® architecture, Developing PowerPC Embedded
Application Binary Interface (EABI) Compliant Programs
14.3.5. Linux Kernel Ignores my bootargs
Question:
Why doesn't the kernel use the command-line options I set in the "bootargs" environment variable in
U-Boot when I boot my target system?
Answer:
This problem is typical for ARM systems only. The following discussion is ARM-centric:
First, check to ensure that you have configured your U-Boot build so that CONFIG_CMDLINE_TAG
is enabled. (Other tags like CONFIG_SETUP_MEMORY_TAGS or CONFIG_INITRD_TAG may be
needed, too.) This ensures that u-boot will boot the kernel with a command-line tag that incorporates
the kernel options you set in the "bootargs" environment variable.
If you have the CONFIG_CMDLINE_TAG option configured, the problem is almost certainly with
your kernel build. You have to instruct the kernel to pick up the boot tags at a certain address. This is
done in the machine descriptor macros, which are found in the processor start-up C code for your
architecture. For the Intel DBPXA250 "Lubbock" development board, the machine descriptor
macros are located at the bottom of the file arch/arm/mach-pxa/lubbock.c, and they look
like this:
MACHINE_START(LUBBOCK, "Intel DBPXA250 Development Platform")
MAINTAINER("MontaVista Software Inc.")
BOOT_MEM(0xa0000000, 0x40000000, io_p2v(0x40000000))
FIXUP(fixup_lubbock)
MAPIO(lubbock_map_io)
INITIRQ(lubbock_init_irq)
14.3.5. Linux Kernel Ignores my bootargs
176
MACHINE_END
The machine descriptor macros for your machine will be located in a similar file in your kernel source
tree. Having located your machine descriptor macros, the next step is to find out where U-Boot puts
the kernel boot tags in memory for your architecture. On the Lubbock, this address turns out to be the
start of physical RAM plus 0x100, or 0xa0000100. Add the "BOOT_PARAMS" macro with this
address to your machine descriptor macros; the result should look something like this:
MACHINE_START(LUBBOCK, "Intel DBPXA250 Development Platform")
MAINTAINER("MontaVista Software Inc.")
BOOT_PARAMS(0xa0000100)
BOOT_MEM(0xa0000000, 0x40000000, io_p2v(0x40000000))
FIXUP(fixup_lubbock)
MAPIO(lubbock_map_io)
INITIRQ(lubbock_init_irq)
MACHINE_END
If there is already a BOOT_PARAMS macro in your machine descriptor macros, modify it so that it
has the correct address. Then, rebuild your kernel and re-install it on your target. Now the kernel
should be able to pick up the kernel options you have set in the "bootargs" environment variable.
14.3.6. Cannot configure Root Filesystem over NFS
Question:
I want to configure my system with root filesystem over NFS, but I cannot find any such
configuration option.
Answer:
What you are looking for is the CONFIG_ROOT_NFS configuration option, which depends on
CONFIG_IP_PNP.
To enable root filesystem over NFS you must enable the "IP: kernel level
autoconfiguration" option in the "Networking options" menu first.
14.3.7. Linux Kernel Panics because "init" process
dies
Question:
I once had a running system but suddenly, without any changes, the Linux kernel started crashing
because the "init" process was dying each time I tried to boot the system, for example like that:
...
VFS: Mounted root (nfs filesystem).
Freeing unused kernel memory: 140k init
init has generated signal 11 but has no handler for it
Kernel panic - not syncing: Attempted to kill init!
Answer:
You probably run your system with the root file system mounted over NFS. Change into the root
directory of your target file system, and remove the file "etc/ld.so.cache". That should fix this
problem:
# cd /opt/eldk/ppc_6xx/
# rm -f etc/ld.so.cache
Explanation:
14.3.7. Linux Kernel Panics because "init" process dies
177
Normally, the file "etc/ld.so.cache" contains a compiled list of system libraries. This file is
used by the dynamic linker/loader ld.so to cache library information. If it does not exist, rebuilt
automatically. For some reason, a corrupted or partial file was written to your root file system. This
corrupt file then confused the dynamic linker so that it crashed when trying to start the init process.
Question:
I cannot boot into my freshly installed ELDK Root-NFS because init dies with an unhandled signal
like this:
Freeing unused kernel memory: 124k init
PHY: e0103320:00 - Link is Up - 100/Full
init has generated signal 4 but has no handler for it
Kernel panic - not syncing: Attempted to kill init!
Rebooting in 1 seconds..
Answer:
Your CPU does not have a floating point unit, your kernel has no math emulation
(CONFIG_MATH_EMULATION) enabled but you still try to boot into a rootfilesystem intended for
FPU systems.
This is to be expected for example if you try to use a ppc_6xx rootfilesystem on an 8xx system.
14.3.8. Unable to open an initial console
Question:
The Linux kernel boots, but then hangs after printing: "Warning: unable to open an initial console".
Answer:
Most probably you have one or missing entries in the /dev directory in your root filesystem. If you
are using the ELDK's root filesystem over NFS, you probably forgot to run the ELDK_MAKEDEV and
ELDK_FIXOWNER scripts as described in 3.7. Mounting Target Components via NFS.
14.3.9. System hangs when entering User Space
(ARM)
Question:
The Linux kernel boots, but then the system hangs after printing: "Freeing init memory: 120K".
I'm using the root file system from ELDK 4.2 (or later) on an ARM system.
Answer:
ELDK 4.2 (and later) for ARM provide an EABI compliant User Space environment. You must
enable EABI support in your Linux kernel configuration, or the system will hang as described. Your
kernel's ".config" file should contain "CONFIG_AEABI=y" for this.
14.3.10. Mounting a Filesystem over NFS hangs
forever
Question:
14.3.10. Mounting a Filesystem over NFS hangs forever
178
We use the SELF ramdisk image that comes with the ELDK. When we try to mount a filesystem over
NFS from the server, for example:
# mount -t nfs 192.168.1.1:/target/home /home
the command waits nearly 5 minutes in uninterruptable sleep. Then the mount finally succeeds.
What's wrong?
Answer:
The default configuration of the SELF was not designed to mount additional filesystems with file
locking over NFS, so no portmap deamon is running, which is causing your problems. There are two
solutions for the problem:
1. Add the portmap deamon (/sbin/portmap) to the target filesystem and start it as part of
the init scripts.
2. Tell the "mount" program and the kernel that you don't need file locking by passing the
"nolock" option to the mount call, i. e. use
# mount -o nolock -t nfs 192.168.1.1:/target/home /home
Explanation:
If you call the mount command like above (i. e. without the "nolock" option) an RPC call to the
"portmap" deamon will be attempted which is required to start a lockd kernel thread which is
necessary if you want to use file locking on the NFS filesystem. This call will fail only after a very
long timeout.
14.3.11. Ethernet does not work in Linux
Question:
Ethernet does not work on my board. But everything is fine when I use the ethernet interface in
U-Boot (for example by performing a TFTP download). This is a bug in U-Boot, right?
Answer:
No. It's a bug in the Linux ethernet driver.
In some cases the Linux driver fails to set the MAC address. That's a buggy driver then - Linux
ethernet drivers are supposed to read the MAC address at startup. On ->open, they are supposed to
reprogram the MAC address back into the chip (but not the EEPROM, if any) whether or not the
address has been changed.
In general, a Linux driver shall not make any assumptions about any initialization being done (or not
done) by a boot loader; instead, that driver is responsible for performing all of the necessary
initialization itself.
And U-Boot shall not touch any hardware it does not access itself. If you don't use the ethernet
interface in U-Boot, it won't be initialized by U-Boot.
A pretty extensive discussion of this issue can be found in the thread ATAG for MAC address on the
ARM Linux mailing list. archive 1 archive 2
Some current methods for handling the MAC address programming:
• use custom ATAGs (ARM systems)
• use a Flattened Device Tree (if your arch/port supports it)
14.3.11. Ethernet does not work in Linux
179
• parse the U-Boot environment directly
• pass it via the command line
If your device driver does not support one of these sources directly, then do it yourself:
• add an init board hook
• program it from user space (`ifconfig hw ...`)
• for people who need to do NFS root or similar, then use initramfs -- this is what it was designed for !
14.3.12. Loopback interface does not work
Question:
When I boot Linux I get a "socket: Address family not supported by protocol"
error message when I try to configure the loopback interface. What's wrong?
Answer:
This is most probably a problem with your kernel configuration. Make sure that the
CONFIG_PACKET option is selected.
14.3.13. Linux kernel messages are not printed on
the console
Question:
I expect to see some Linux kernel messages on the console, but there aren't any.
Answer:
This is absolutely normal when using the ELDK with root filesystem over NFS. The ELDK startup
routines will start the syslog daemon, which will collect all kernel messages and write them into a
logfile ( /var/log/messages ).
If you want to see the messages at the console, either run "tail -f /var/log/messages &"
on the console window, or stop the syslog daemon by issuing a "/etc/rc.d/init.d/syslog
stop" command. Another alternative is to increase the console_loglevel of the kernel (any
message with log level less than console_loglevel will be printed to the console). With the
following command the console_loglevel could be set at runtime: "echo 8 >
/proc/sys/kernel/printk". Now all messages are displayed on the console.
14.3.14. Linux ignores input when using the
framebuffer driver
Question:
When using the framebuffer driver the console output goes to the LCD display, but I cannot input
anything. What's wrong?
Answer:
You can define "console devices" using the console= boot argument. Add something like this to your
bootargs setting:
14.3.14. Linux ignores input when using the framebuffer driver
180
... console=tty0 console=ttyS0,${baudrate} ...
This will ensure that the boot messages are displayed on both the framebuffer (/dev/tty0) and the serial
console (/dev/ttyS0); the last device named in a console= option will be the one that takes input,
too, so with the settings above you can use the serial console to enter commands etc. For a more
detailed description see
http://www.tldp.org/HOWTO/Remote-Serial-Console-HOWTO/configure-kernel.html
14.3.15. How to switch off the screen saver and the
blinking cursor?
Question:
I'm using a splash screen on my frame buffer display, but it is disturbed by a blinking cursor, and after
a while the screen is blanked. How can I prevent this?
Answer:
Screen saver and blinking cursor can be turned off (and on) using escape sequences.
To turn off the screen saver, send the sequence "\E[9;0]" to the terminal ="/dev/tty1". For
example, output the content of file "/etc/blank_off" in one of your init scripts:
# cat /etc/blank_off
To turn off the blinking cursor, send the sequence "\E[?25l\E[?1c" to the terminal. For
example, copy the content of file "/etc/init_tty" to the terminal:
# cat /etc/init_tty
For details, please see "man 4 console_codes" .
14.3.16. BogoMIPS Value too low
Question:
We are only seeing 263.78 bogomips on a MPC5200 running at 396 MHz.
Doesn't this seem way to low ?? With a 603e core I'd expect 1 bogomip per MHz or better.
Answer:
No, the values you see is correct. Please keep in mind that there is a good reason for the name
BogoMIPS.
On Power Architecture®, the bogomips calculation is measuring the speed of a dbnz instruction. On
some processors like the MPC8xx it takes 2 clocks per dbnz instruction, and you get 1
BogoMIP/MHz. The MPC5200 takes 3 clocks per dbnz in this loop, so you get .67 BogoMIP/MHz.
See also The frequently asked questions about BogoMips (note: this document is somewhat outdated).
Question:
But I have a MPC8572 running at 1.5GHz, amd it shows only 150 bogomips. This cannot be correct?
Answer:
This value is indeed correct.
"With recent kernels, when build with ARCH=powerpc, we now use the hardware timebase instead of
bogus processor loops for short timings. Thus our bogomips value is no longer the speed at which the
processor runs empty loops, but the actual processor timebase value as obtained after calibration at
14.3.16. BogoMIPS Value too low
181
boot. " - Benjamin Herrenschmidt
14.3.17. Linux Kernel crashes when using a
ramdisk image
Question:
I have a Power Architecture® board with 1 GiB of RAM (or more). It works fine with root file system
over NFS, but it will crash when I try to use a ramdisk.
Answer:
Check where your ramdisk image gets loaded to. In the standard configuration, the Linux kernel can
access only 768 MiB of RAM, so your ramdisk image must be loaded below this limit. Check your
boot messages. You are hit by this problem when U-Boot reports something like this:
Loading Ramdisk to 3fdab000, end 3ff2ff9d ... OK
and then Linux shows a message like this:
mem_pieces_remove: [3fdab000,3ff2ff9d) not in any region
To fix, just tell U-Boot to load the ramdisk image below the 768 MB limit:
=> setenv initrd_high 30000000
14.3.18. Ramdisk Greater than 4 MB Causes
Problems
Question:
I built a ramdisk image which is bigger than 4 MB. I run into problems when I try to boot Linux with
this image, while other (smaller) ramdisk images work fine.
Answer:
The Linux kernel has a default maximum ramdisk size of 4096 kB. To boot with a bigger ramdisk
image, you must raise this value. There are two methods:
◊ Dynamical adjustment using boot arguments:
You can pass a boot argument ramdisk_size=<size-in-kB> to the Linux kernel to
overwrite the configured maximum. Note that this argument needs to be before any root
argument. A flexible way to to this is using U-Boot environment variables. For instance, to
boot with a ramdisk image of 6 MB (6144 kB), you can define:
=> setenv rd_size 6144
=> setenv bootargs ... ramdisk_size=\${rd_size} ...
=> saveenv
If you later find out that you need an even bigger ramdisk image, or that a smaller one is sufficient, all that
needs changing is the value of the "rd_size" environment variable.
•
♦ Increasing the Linux kernel default value:
When configuring your Linux kernel, adjust the value of the
14.3.18. Ramdisk Greater than 4 MB Causes Problems
182
CONFIG_BLK_DEV_RAM_SIZE parameter so that it contains a number equal or larger than
your ramdisk (in kB). (In the 2.4 kernel series, you'll find this setting under the "Block
devices" menu choice while, in the 2.6 series, it will be under "Device drivers" -> "Block
devices".)
14.3.19. Combining a Kernel and a Ramdisk into a
Multi-File Image
Question:
I used to build a zImage.initrd file which combined the Linux kernel with a ramdisk image. Can
I do something similar with U-Boot?
Answer:
Yes, you can create "Multi-File Images" which contain several images, typically an OS (Linux) kernel
image and one or more data images like RAMDisks. This construct is useful for instance when you
want to boot over the network using BOOTP etc., where the boot server provides just a single image
file, but you want to get for instance an OS kernel and a RAMDisk image.
The typical way to build such an image is:
bash$ mkimage -A ppc -O Linux -T multi -C gzip \
-n 'Linux Multiboot-Image' -e 0 -a 0 \
-d vmlinux.gz:ramdisk_image.gz pMulti
See also the usage message you get when you call "mkimage" without arguments.
14.3.20. Adding Files to Ramdisk is Non Persistent
Quetsion:
I want to add some files to my ramdisk, but every time I reboot I lose all my changes. What can I do?
Answer:
To add your files or modifications permanently, you have to rebuild the ramdisk image. You may
check out the sources of our SELF package (Simple Embedded Linux Framework) to see how this can
be done, see for example ftp://ftp.denx.de/pub/LinuxPPC/usr/src/SELF/ or check out the sources for
ELDK (module eldk_build from our CVS server, see http://www.denx.de/re/linux.html.
See also section 14.4.1. How to Add Files to a SELF Ramdisk for another way to change the ramdisk
image.
For further hints about the creation and use of initial ramdisk images see also the file
Documentation/initrd.txt in your Linux kernel source directory.
14.3.21. Kernel Configuration for PCMCIA
Question:
Which kernel configuration options are relevant to support PCMCIA cards under Linux?
Answer:
14.3.21. Kernel Configuration for PCMCIA
183
The following kernel configuration options are required to support miscellaneous PCMCIA card types
with Linux and the PCMCIA CS package:
◊ PCMCIA IDE cards (CF and true-IDE)
To support the IDE CardService client, the kernel has to be configured with general ATA IDE
support. The MPC8xx IDE support (CONFIG_BLK_DEV_MPC8XX_IDE flag) must be
turned off.
◊ PCMCIA modem cards
The kernel has to be configured with standard serial port support (CONFIG_SERIAL flag).
After the kernel bootup the following preparation is needed:
bash# mknod /dev/ttySp0 c 240 64
This creates a new special device for the modem card; please note that /dev/ttyS0 ... S4 and
TTY_MAJOR 4 are already used by the standard 8xx UART driver). /dev/ttySp0 becomes
available for use as soon as the CardServices detect and initialize the PCMCIA modem card.
◊ PCMCIA Wireless LAN cards
Enable the "Network device support" --> "Wireless LAN (non-hamradio)" --> "Wireless
LAN (non-hamradio)" option in the kernel configuration (CONFIG_NET_RADIO flag).
14.3.22. Configure Linux for PCMCIA Cards using
the Card Services package
The following kernel configuration options are required to support miscellaneous PCMCIA card types with
Linux and the PCMCIA CS package:
1. PCMCIA IDE cards (CompactFlash and true-IDE)
General setup -> Support for hot-pluggable devices (enable: Y) -> PCMCIA/CardBus support ->
PCMCIA/CardBus support (enable: M) -> MPC8XX PCMCIA host bridge support (select)
2. PCMCIA Modem Cards
3. PCMCIA Network Cards
4. PCMCIA WLAN Cards
Build and install modules in target root filesystem, shared over NFS:
bash$ make modules modules_install INSTALL_MOD_PATH=/opt/eldk/ppc_8xx
Adjust PCMCIA configuration file (/opt/eldk/ppc_8xx/etc/sysconfig/pcmcia):
PCMCIA=yes
PCIC=m8xx_pcmcia
PCIC_OPTS=
CORE_OPTS=
CARDMGR_OPTS=
Start PCMCIA Card Services:
bash-2.05# sh /etc/rc.d/init.d/pcmcia start
14.3.23. Configure Linux for PCMCIA Cards without
the Card Services package
14.3.23. Configure Linux for PCMCIA Cards without the Card Services package
184
For "disk" type PC Cards (FlashDisks, CompactFlash, Hard Disk Adapters - basically anything that looks like
an ordinary IDE drive), an alternative solution is available: direct support within the Linux kernel. This has
the big advantage of minimal memory footprint, but of course it comes with a couple of disadvantages, too:
• It works only with "disk" type PC Cards - no support for modems, network cards, etc; for these you
still need the PCMCIA Card Services package.
• There is no support for "hot plug", i. e. you cannot insert or remove the card while Linux is running.
(Well, of course you can do this, but either you will not be able to access any card inserted, or when
you remove a card you will most likely crash the system. Don't do it - you have been warned!)
• The code relies on initialization of the PCMCIA controller by the firmware (of course U-Boot will do
exactly what's required).
On the other hand these are no real restrictions for use in an Embedded System.
To enable the "direct IDE support" you have to select the following Linux kernel configuration options:
CONFIG_IDE=y
CONFIG_BLK_DEV_IDE=y
CONFIG_BLK_DEV_IDEDISK=y
CONFIG_IDEDISK_MULTI_MODE=y
CONFIG_BLK_DEV_MPC8xx_IDE=y
CONFIG_BLK_DEV_IDE_MODES=y
and, depending on which partition types and languages you want to support:
CONFIG_PARTITION_ADVANCED=y
CONFIG_MAC_PARTITION=y
CONFIG_MSDOS_PARTITION=y
CONFIG_NLS=y
CONFIG_NLS_DEFAULT="y"
CONFIG_NLS_ISO8859_1=y
CONFIG_NLS_ISO8859_15=y
With these options you will see messages like the following when you boot the Linux kernel:
...
Uniform Multi-Platform E-IDE driver Revision: 6.31
ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx
PCMCIA slot B: phys mem e0000000...ec000000 (size 0c000000)
Card ID:
CF 128MB CH
Fixed Disk Card
IDE interface
[silicon] [unique] [single] [sleep] [standby] [idle] [low power]
hda: probing with STATUS(0x50) instead of ALTSTATUS(0x41)
hda: CF 128MB, ATA DISK drive
ide0 at 0xc7000320-0xc7000327,0xc3000106 on irq 13
hda: 250368 sectors (128 MB) w/16KiB Cache, CHS=978/8/32
Partition check:
hda: hda1 hda2 hda3 hda4
...
You can now access your PC Card "disk" like any normal IDE drive. If you start with a new drive, you have
to start by creating a new partition table. For Power Architecture® systems, there are two commonly used
options:
14.3.23.1. Using a MacOS Partition Table
A MacOS partition table is the "native" partition table format on Power Architecture® systems; most desktop
Power Architecture® systems use it, so you may prefer it when you have Power Architecture® development
14.3.23.1. Using a MacOS Partition Table
185
systems around.
To format your "disk" drive with a MacOS partition table you can use the pdisk command:
We start printing the help menu, re-initializing the partition table and then printing the new, empty partition
table so that we know the block numbers when we want to create new partitions:
# pdisk /dev/hda
Edit /dev/hda Command (? for help): ?
Notes:
Base and length fields are blocks, which vary in size between media.
The base field can be <nth>p; i.e. use the base of the nth partition.
The length field can be a length followed by k, m, g or t to indicate
kilo, mega, giga, or tera bytes; also the length can be <nth>p; i.e. use
the length of the nth partition.
The name of a partition is descriptive text.
Commands are:
h
help
p
print the partition table
P
(print ordered by base address)
i
initialize partition map
s
change size of partition map
c
create new partition (standard MkLinux type)
C
(create with type also specified)
n
(re)name a partition
d
delete a partition
r
reorder partition entry in map
w
write the partition table
q
quit editing (don't save changes)
Command (? for help): i
map already exists
do you want to reinit? [n/y]: y
Command (? for help): p
Partition map (with 512 byte blocks) on '/dev/hda'
#:
type name
length
base
( size )
1: Apple_partition_map Apple
63 @ 1
2:
Apple_Free Extra 1587536 @ 64
(775.2M)
Device block size=512, Number of Blocks=1587600 (775.2M)
DeviceType=0x0, DeviceId=0x0
At first we create two small partitions that will be used to store a Linux boot image; a compressed Linux
kernel is typically around 400 ... 500 kB, so chosing a partition size of 2 MB is more than generous. 2 MB
coresponds to 4096 disk blocks of 512 bytes each, so we enter:
Command (? for help): C
First block: 64
Length in blocks: 4096
Name of partition: boot0
Type of partition: PPCBoot
Command (? for help): p
Partition map (with 512 byte blocks) on '/dev/hda'
#:
type name
length
base
( size )
1: Apple_partition_map Apple
63 @ 1
2:
PPCBoot boot0
4096 @ 64
( 2.0M)
3:
Apple_Free Extra 1583440 @ 4160
(773.2M)
Device block size=512, Number of Blocks=1587600 (775.2M)
DeviceType=0x0, DeviceId=0x0
To be able to select between two kernel images (for instance when we want to do a field upgrade of the Linux
kernel) we create a second boot partition of exactly the same size:
Command (? for help): C
14.3.23.1. Using a MacOS Partition Table
186
First block: 4160
Length in blocks: 4096
Name of partition: boot1
Type of partition: PPCBoot
Command (? for help): p
Partition map (with 512 byte blocks) on '/dev/hda'
#:
type name
length
base
( size )
1: Apple_partition_map Apple
63 @ 1
2:
PPCBoot boot0
4096 @ 64
( 2.0M)
3:
PPCBoot boot1
4096 @ 4160
( 2.0M)
4:
Apple_Free Extra 1579344 @ 8256
(771.2M)
Device block size=512, Number of Blocks=1587600 (775.2M)
DeviceType=0x0, DeviceId=0x0
Now we create a swap partition - 64 MB should be more than sufficient for our Embedded System; 64 MB
means 64*1024*2 = 131072 disk blocks of 512 bytes:
Command (? for help): C
First block: 8256
Length in blocks: 131072
Name of partition: swap
Type of partition: swap
Command (? for help): p
Partition map (with 512 byte blocks) on '/dev/hda'
#:
type name
length
base
( size )
1: Apple_partition_map Apple
63 @ 1
2:
PPCBoot boot0
4096 @ 64
( 2.0M)
3:
PPCBoot boot1
4096 @ 4160
( 2.0M)
4:
swap swap
131072 @ 8256
( 64.0M)
5:
Apple_Free Extra 1448272 @ 139328 (707.2M)
Device block size=512, Number of Blocks=1587600 (775.2M)
DeviceType=0x0, DeviceId=0x0
Finally, we dedicate all the remaining space to the root partition:
Command (? for help): C
First block: 139328
Length in blocks: 1448272
Name of partition: root
Type of partition: Linux
Command (? for help): p
Partition map (with 512 byte blocks) on '/dev/hda'
#:
type name
length
base
( size )
1: Apple_partition_map Apple
63 @ 1
2:
PPCBoot boot0
4096 @ 64
( 2.0M)
3:
PPCBoot boot1
4096 @ 4160
( 2.0M)
4:
swap swap
131072 @ 8256
( 64.0M)
5:
Linux root
1448272 @ 139328 (707.2M)
Device block size=512, Number of Blocks=1587600 (775.2M)
DeviceType=0x0, DeviceId=0x0
To make our changes permanent we must write the new partition table to the disk, before we quit the pdisk
program:
Command (? for help): w
Writing the map destroys what was there before. Is that okay? [n/y]: y
hda: [mac] hda1 hda2 hda3 hda4 hda5
hda: [mac] hda1 hda2 hda3 hda4 hda5
Command (? for help): q
Now we can initialize the swap space and the filesystem:
# mkswap /dev/hda4
Setting up swapspace version 1, size = 67104768 bytes
14.3.23.1. Using a MacOS Partition Table
187
# mke2fs /dev/hda5
mke2fs 1.19, 13-Jul-2000 for EXT2 FS 0.5b, 95/08/09
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
90624 inodes, 181034 blocks
9051 blocks (5.00%) reserved for the super user
First data block=0
6 block groups
32768 blocks per group, 32768 fragments per group
15104 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
14.3.23.2. Using a MS-DOS Partition Table
The MS-DOS partition table is especially common on PC type computers, which these days means nearly
everywhere. You will prefer this format if you want to exchange your "disk" media with any PC type host
system.
The fdisk command is used to create MS-DOS type partition tables; to create the same partitioning scheme as
above you would use the following commands:
# fdisk /dev/hda
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel. Changes will remain in memory only,
until you decide to write them. After that, of course, the previous
content won't be recoverable.
The number of cylinders for this disk is set to 1575.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
Command (m for help): m
Command action
a
toggle a bootable flag
b
edit bsd disklabel
c
toggle the dos compatibility flag
d
delete a partition
l
list known partition types
m
print this menu
n
add a new partition
o
create a new empty DOS partition table
p
print the partition table
q
quit without saving changes
s
create a new empty Sun disklabel
t
change a partition's system id
u
change display/entry units
v
verify the partition table
w
write table to disk and exit
x
extra functionality (experts only)
Command (m for help): n
Command action
e
extended
p
primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-1575, default 1):
Using default value 1
14.3.23.2. Using a MS-DOS Partition Table
188
Last cylinder or +size or +sizeM or +sizeK (1-1575, default 1575): +2M
Command (m for help): p
Disk /dev/hda: 16 heads, 63 sectors, 1575 cylinders
Units = cylinders of 1008 * 512 bytes
Device Boot
Start
End
Blocks
Id System
/dev/hda1
1
5
2488+ 83 Linux
Command (m for help): n
Command action
e
extended
p
primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (6-1575, default 6):
Using default value 6
Last cylinder or +size or +sizeM or +sizeK (6-1575, default 1575): +2M
Command (m for help): p
Disk /dev/hda: 16 heads, 63 sectors, 1575 cylinders
Units = cylinders of 1008 * 512 bytes
Device Boot
Start
End
Blocks
Id System
/dev/hda1
1
5
2488+ 83 Linux
/dev/hda2
6
10
2520
83 Linux
Command (m for help): n
Command action
e
extended
p
primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (11-1575, default 11):
Using default value 11
Last cylinder or +size or +sizeM or +sizeK (11-1575, default 1575): +64M
Command (m for help): t
Partition number (1-4): 3
Hex code (type L to list codes): 82
Changed system type of partition 3 to 82 (Linux swap)
Command (m for help): p
Disk /dev/hda: 16 heads, 63 sectors, 1575 cylinders
Units = cylinders of 1008 * 512 bytes
Device Boot
Start
End
Blocks
Id System
/dev/hda1
1
5
2488+ 83 Linux
/dev/hda2
6
10
2520
83 Linux
/dev/hda3
11
141
66024
82 Linux swap
Note that we had to use the t command to mark this partition as swap space.
Command (m for help): n
Command action
e
extended
p
primary partition (1-4)
p
Partition number (1-4): 4
First cylinder (142-1575, default 142):
Using default value 142
Last cylinder or +size or +sizeM or +sizeK (142-1575, default 1575):
Using default value 1575
Command (m for help): p
Disk /dev/hda: 16 heads, 63 sectors, 1575 cylinders
Units = cylinders of 1008 * 512 bytes
Device Boot
Start
End
Blocks
Id System
/dev/hda1
1
5
2488+ 83 Linux
/dev/hda2
6
10
2520
83 Linux
/dev/hda3
11
141
66024
82 Linux swap
/dev/hda4
142
1575
722736
83 Linux
Command (m for help): w
14.3.23.2. Using a MS-DOS Partition Table
189
The partition table has been altered!
Calling ioctl() to re-read partition table.
hda: hda1 hda2 hda3 hda4
hda: hda1 hda2 hda3 hda4
WARNING: If you have created or modified any DOS 6.x
partitions, please see the fdisk manual page for additional
information.
Syncing disks.
Now we are ready to initialize the partitions:
# mkswap /dev/hda3
Setting up swapspace version 1, size = 67604480 bytes
# mke2fs /dev/hda4
mke2fs 1.19, 13-Jul-2000 for EXT2 FS 0.5b, 95/08/09
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
90432 inodes, 180684 blocks
9034 blocks (5.00%) reserved for the super user
First data block=0
6 block groups
32768 blocks per group, 32768 fragments per group
15072 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
14.3.24. Boot-Time Configuration of MTD Partitions
Instead of defining a static partition map as described in section Memory Technology Devices you can define
the partitions for your flash memory at boot time using command line arguments. To do that you have to
enable the CONFIG_MTD_CMDLINE_PARTS kernel configuration option. With this option enabled, the
kernel will recognize a command line argument mtdparts and decode it as follows:
mtdparts=<mtddef>[;<mtddef]
<mtddef> := <mtd-id>:<partdef>[,<partdef>]
<partdef> := <size>[@offset][<name>][ro]
<mtd-id> := unique id used in mapping driver/device (number of flash bank)
<size>
:= standard linux memsize OR "-" to denote all remaining space
<name>
:= '(' NAME ')'
For example, instead of using a static partition map like this:
0x00000000-0x00060000
0x00060000-0x00080000
0x00080000-0x000A0000
0x000A0000-0x000C0000
0x000C0000-0x001C0000
0x001C0000-0x005C0000
0x005C0000-0x01000000
:
:
:
:
:
:
:
"U-Boot"
"Environment 1"
"Environment 2"
"ASIC Images"
"Linux Kernel"
"Ramdisk Image"
"User Data"
you can pass a command line argument as follows:
mtdparts=0:384k(U-Boot),128k(Env1),128k(Env2),128k(ASIC),1M(Linux),4M(Ramdisk),-(User_Data)
14.3.24. Boot-Time Configuration of MTD Partitions
190
14.3.25. Use NTP to synchronize system time
against RTC
If a system has a real-time clock (RTC) this is often used only to initialize the system time when the system
boots. From then, the system time is running independently. The RTC will probably only be used again at
shutdown to save the current system time. Such a configuration is used in many workstation configurations. It
is useful if time is not really critical, or if the system time is synchronized against some external reference
clock like when using the Network Time Protocol (NTP) to access time servers on the network.
But some systems provide a high-accuracy real-time clock (RTC) while the system clocks are not as accurate,
and sometimes permanent access to the net is not possible or wanted. In such systems it makes more sense to
use the RTC as reference clock (Stratum 1 NTP server - cf. http://www.ntp.org/). To enable this mode of
operation you must edit the NTP daemon's configuration file /etc/ntp.conf in your target's root file
system. Replace the lines
server
fudge
127.127.1.0
# local clock
127.127.1.0 stratum 10
by
server 127.127.43.0
# standard Linux RTC
Then make sure to start the NTP daemon on your target by adding it to the corresponding init scripts and
restart it if it is already running.
The "address" of the RTC (127.127.43.0 in the example above) is not an IP address, but actually used
as an index into an internal array of supported reference clocks in the NTP daemon code. You may need to
check with your ntpd implementation if the example above does not work as expected.
14.3.26. Configure Linux for XIP (Execution In
Place)
This document describes how to setup and use XIP in the kernel and the cramfs filesystem. (A patch to add
XIP support to your kernel can be found at the bottom of this page.)
14.3.26.1. XIP Kernel
To select XIP you must enable the CONFIG_XIP option:
$ cd <xip-linux-root>
$ make menuconfig
...
MPC8xx CPM Options --->
[*] Make a XIP (eXecute in Place) kernel
(40100000) Physical XIP kernel address
(c1100000) Virtual XIP kernel address
(64) Image header size e.g. 64 bytes for PPCBoot
The physical and virtual address of the flash memory used for XIP must be defined statically with the macros
CONFIG_XIP_PHYS_ADDR and CONFIG_XIP_VIRT_ADDR. The virtual address usually points to the end
of the kernel virtual address of the system memory. The physical and virtual address must be aligned relative
to an 8 MB boundary:
14.3.26. Configure Linux for XIP (Execution In Place)
191
CONFIG_XIP_PHYS_ADDR = FLASH-base-address + offset-in-FLASH
CONFIG_XIP_VIRT_ADDR = 0xc0000000 + DRAM-size + offset-in-FLASH
The default configuration parameters shown above are for a system with 16MB of DRAM and the XIP kernel
image located at the physical address 0x40100000 in flash memory.
Note that the FLASH and MTD driver must be disabled.
You can then build the "uImage", copy it to CONFIG_XIP_PHYS_ADDR in flash memory and boot it from
CONFIG_XIP_PHYS_ADDR as usual.
14.3.26.2. Cramfs Filesystem
The cramfs filesystem enhancements:
• They allow cramfs optional direct access to a cramfs image in memory (ram, rom, flash). It eliminates
the unnecessary step of passing data through an intermediate buffer, as compared to accessing the
same image through a memory block device like mtdblock.
• They allow optional cramfs linear root support. This eliminates the requirement of having to provide a
block device to use a linear cramfs image as the root filesystem.
• They provide optional XIP. It extends mkcramfs to store files marked "+t" uncompressed and
page-aligned. Linux can then mmap those files and execute them in-place without copying them
entirely to ram first.
Note: the current implementation can only be used together with a XIP kernel, which provides the appropriate
XIP memory (FLASH) mapping.
To configure a root file system on linear cramfs with XIP select:
$ cd <xip-linux-root>
$ make menuconfig
...
File systems --->"
...
<*> Compressed ROM file system support
[*]
Use linear addressing for cramfs
(40400000) Physical address of linear cramfs
[*]
Support XIP on linear cramfs
[*]
Root file system on linear cramfs
This defines a cramfs filesystem located at the physical address 0x40400000 in FLASH memory.
After building the kernel image "pImage" as usual, you will want to build a filesystem using the mkcramfs
executable (it's located in /scripts/cramfs). If you do not already have a reasonable sized disk directory tree
you will need to make one. The ramdisk directory of SELF (the Simple Embedded Linux Framework from
DENX at ftp.denx.de) is a good starting point. Before you build your cramfs image you must mark the binary
files to be executed in place later on with the "t" permission:
$ mkcramfs -r ramdisk cramfs.img
and copy it to the defined place in FLASH memory.
You can then boot the XIP kernel with the cramfs root filesystem using the boot argument:
$ setenv bootargs root=/dev/cramfs ...
14.3.26.1. XIP Kernel
192
Be aware that cramfs is a read-only filesystem.
14.3.26.3. Hints and Notes
• XIP conserves RAM at the expense of flash. This might be useful if you have a big flash memory and
little RAM.
• Flash memory used for XIP must be readable all the time e.g. this excludes installation and usage the
character device or MTD flash drivers, because they do device probing, sector erase etc.
• The XIP extension is currently only available for PowerQUICC™I 8xx but can easily be extended to
other architectures.
• Currently only up to 8 MB of ROM/Flash are supported.
• The original work was done for the amanda system.
• Special thanks goes to David Petersen for collecting the availible XIP extension sources and
highlighting how to put all the pieces together.
14.3.26.4. Space requirements and RAM saving, an example
For ppc 8xx, all figures are in bytes:
• Normal kernel + linear cramfs (patched):
pImage: 538062
cramfs: 1081344
Mem:
total:
14921728
used:
free:
3866624 11055104
shared: buffers:
2781184
0
cached:
2240512
shared: buffers:
2822144
0
cached:
2240512
• XIP kernel + linear cramfs:
pImage: 1395952
cramfs: 1081344
Mem:
total:
16175104
used:
free:
3940352 12234752
• XIP kernel + XIP cramfs (chmod +t: busybox, initd, libc):
pImage: 1395952
cramfs: 1871872
Mem:
total:
16175104
used:
free:
2367488 13807616
shared: buffers:
610304
0
cached:
671744
The actual RAM saving is here approximately 1.1MB + 1.5M = 2.6 MB.
Have fun with XIP.
Wolfgang Grandegger (wg@denx.de)
• linux-2.4.4-2002-03-21-xip.patch.gz: Linux patches for XIP on MPC8xx
14.3.27. Use SCC UART with Hardware Handshake
Question:
14.3.27. Use SCC UART with Hardware Handshake
193
I am using a SCC port of a MPC8xx / MPC82xx as UART; for the Linux UART driver I have
configured support for hardware handshake. Then I used a null-modem cable to connect the port to
the serial port of my PC. But this does not work. What am I doing wrong?
Answer:
There is absolutely no way to connect a MPC8xx / MPC82xx SCC port to any DTE and use RS-232
standard hardware flow control.
Explanation:
The serial interface of the SCC ports in MPC8xx / MPC82xx processors is designed as a DTE
circuitry and the RS-232 standard hardware flow control can not be used in the DTE to DTE
connection with the null-modem cable (with crossed RTS/CTS signals).
The RS-232 standard specifies a DTE to DCE connection and its hardware handshaking is designed
for this specific task. The hardware flow control signals in the PC (and similar equipment) are
implemented as software readable/writable bits in a control register and therefore may be arbitrary
treated. Unlike that, in the 8xx/82xx the handshake protocol is handled by the CPM microcode. The
meaning of the signals is fixed for the RS-232 standard with no way for user to change it.
In widely spread DTE-to-DTE connections over the so called 'null-modem' cable with the hardware
flow control lines the meaning of the handshake signals is changed with respect to the RS-232
standard. Therefore this approach may not be used with the 8xx/82xx.
Question:
I succeeded in activating hardware handshake on the transmit side of the SCC using the CTS signal.
However I have problems in the receive direction.
Answer:
This is caused by the semantics of the RTS signal as implemented on the SCC controllers: the CPM
will assert this signal when it wants to send out data. This means you cannot use RTS to enable the
transmitter on the other side, because it will be enabled only when the SCC is sending data itself.
Conclusions:
If you want to use 8xx/82xx based equipment in combination with RS-232 hardware control protocol,
you must have a DCE device (modem, plotter, printer, etc) on the other end.
Hardware flow control on a SCC works only in transmit direction; when receiving data the driver has
to be fast enough to prevent data overrun conditions (normally this is no problem though).
14.3.28. How can I access U-Boot environment
variables in Linux?
Question:
I would like to access U-Boot's environment variables from my Linux application. Is this possible?
Answer:
Yes, you can. The environment variables must be stored in flash memory, and your Linux kernel must
support flash access through the MTD layer. In the U-Boot source tree you can find the environment
tools in the directory tools/env, which can be built with command:
make env
14.3.28. How can I access U-Boot environment variables in Linux?
194
For building against older versions of the MTD headers (meaning before v2.6.8-rc1) it is required to pass the
argument "MTD_VERSION=old" to make:
make MTD_VERSION=old env
The resulting binary is called fw_printenv, but actually includes support for setting environment variables
too. To achieve this, the binary behaves according to the name it is invoked as, so you will have to create a
link called fw_setenv to fw_printenv.
These tools work exactly like the U-Boot commands printenv resp. setenv You can either build these
tools with a fixed configuration selected at compile time, or you can configure the tools using the
/etc/fw_env.config configuration file in your target root filesystem. Here is an example configuration
file:
# Configuration file for fw_(printenv/saveenv) utility.
# Up to two entries are valid, in this case the redundand
# environment sector is assumed present.
#########################################################################
# For TQM8xxL modules:
#########################################################################
# MTD device name
Device offset
Env. size
Flash sector size
/dev/mtd0
0x8000
0x4000
0x4000
/dev/mtd0
0xC000
0x4000
0x4000
#########################################################################
# For NSCU:
#########################################################################
# MTD device name
Device offset
Env. size
Flash sector size
#/dev/mtd1
0x0000
0x8000
0x20000
#/dev/mtd2
0x0000
0x8000
0x20000
#########################################################################
# For LWMON
#########################################################################
# MTD device name
Device offset
Env. size
Flash sector size
#/dev/mtd1
0x0000
0x2000
0x40000
14.3.29. The appWeb server hangs OR /dev/random
hangs
Question:
I try to run the appWeb server, but it hangs, because read accesses to /dev/random hang forever.
What's wrong?
Answer:
Your configuration of the Linux kernel does not contain drivers that feed enough entropy for
/dev/random. Often mouse or keyboard drivers are used for this purpose, so on an embedded
system without such devices /dev/random may not provide enough random numbers for your
application.
Workaround:
As a quick workaround you can use /dev/urandom instead; i. e. try the following commands on
your system:
# cd /dev
14.3.29. The appWeb server hangs OR /dev/random hangs
195
# rm -f random
# ln -s urandom random
Solution:
The correct solution for the problem is of course to feed sufficient entropy into /dev/random. To
do so you can modify one or more appropriate device drivers on your system; for example if you
know that there is sufficient traffic on network or on a serial port than adding SA_SAMPLE_RANDOM
to the 3rd argument when calling the request_irq() function in your ethernet and/or serial
driver(s) will cause the inter-interrupt times to be used to build up entropy for /dev/random.
14.3.30. Swapping over NFS
In case that the available memory is not sufficient, i.e. for compiling the X.org server, and no hard-drive can
be attached to the system it is possible to swap over NFS, although it is not quite straightforward.
Usually one would create a blank file, mkswap it and simply do a swapon swapfile. Doing this on a filesystem
mounted over NFS, i.e. the ELDK root filesystem, fails however.
With one level of indirection we can trick the kernel into doing it anyway. First we create a filesystem image
(ext2 will do) on the NFS filesystem and mount it with the aid of the loopback device. Then we create a blank
swapfile inside of this filesystem and turn on swapping:
bash-2.05b# mount
/dev/nfs on / type nfs (rw)
none on /proc type proc (rw)
bash-2.05b# cd /tmp
bash-2.05b# dd if=/dev/zero of=ext2.img bs=1M count=66
66+0 records in
66+0 records out
bash-2.05b# mkfs.ext2 ext2.img
mke2fs 1.27 (8-Mar-2002)
ext2.img is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
16920 inodes, 67584 blocks
3379 blocks (5.00%) reserved for the super user
First data block=1
9 block groups
8192 blocks per group, 8192 fragments per group
1880 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345
Writing inode tables: done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 26 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
bash-2.05b# for i in `seq 0 9` ; do mknod /dev/loop$i b 7 $i ; done
bash-2.05b# mkdir /mnt2
bash-2.05b# mount -o loop ext2.img /mnt2
bash-2.05b# cd /mnt2
bash-2.05b# dd if=/dev/zero of=swapfile bs=1M count=62
62+0 records in
62+0 records out
bash-2.05b# mkswap swapfile
Setting up swapspace version 1, size = 65007 kB
14.3.30. Swapping over NFS
196
bash-2.05b# free
total
used
Mem:
14556
14260
-/+ buffers/cache:
4372
Swap:
0
0
bash-2.05b# swapon swapfile
bash-2.05b# free
total
used
Mem:
14556
14172
-/+ buffers/cache:
4368
Swap:
63480
0
bash-2.05b#
free
296
10184
0
shared
0
buffers
772
cached
9116
free
384
10188
63480
shared
0
buffers
784
cached
9020
Because the ELDK right now has no device nodes for the loopback driver we create them along the way. It
goes without saying that the loop driver has to be included in the kernel configuration. You can check this by
looking for a driver for major number 7 (block devices) in /proc/devices.
14.3.31. Using NFSv3 for NFS Root Filesystem
Question:
My NFS server only allows the protocol in version 3. Even though my kernel has "NFS client support
for NFS version 3" compiled in, I cannot use this as a root filesystem. The boot process stops like this:
Looking up port of RPC 100003/2 on 10.0.0.136
Looking up port of RPC 100005/1 on 10.0.0.136
Root-NFS: Server returned error -22 while mounting /opt/eldk/ppc_6xx
VFS: Unable to mount root fs via NFS, trying floppy.
VFS: Cannot open root device "nfs" or unknown-block(2,0)
Answer:
In addition to the kernel support, you need to specify the "nfsvers=3" option to use NFS protocol
version 3 as a rootfilesystem. So include something like the following in your kernel commandline:
nfsroot=[<server-ip>:]<root-dir>,nfsvers=3
14.3.32. Using and Configuring the SocketCAN
Driver
Question:
When trying to start the SocketCAN interfaces I get error messages like "bit-timing not yet
defined", but when trying to configure the bit timing the directory
"/sys/class/net/can0/can_bittiming" does not exist.
Answer:
The SysFS CAN interface has not been accepted for inclusion into the mainline Linux kernel tree. We
had to switch to a Netlink based interface as described in
"Documentation/networking/can.txt"
You need a recent version of the IPROUTE2 utility suite. You can get and build it as follows:
$ git clone \
git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/iproute2.git
$ cd iproute2
$ make CC=${CROSS_COMPILE}gcc
14.3.32. Using and Configuring the SocketCAN Driver
197
14.3.33. Telnet / SSH (dropbear) server not working
Question:
The telnet server is running on the target but when I try to login I get this error message:
$ telnet 192.168.20.12
telnet 192.168.20.12
Trying 192.168.20.12...
Connected to 192.168.20.12.
Escape character is '^]'.
telnetd: All network ports in use.
Connection closed by foreign host.
The dropbear ssh server fails in a similar fashion:
$ ssh root@192.168.20.12
root@192.168.20.12's password:
PTY allocation request failed on channel 0
shell request failed on channel 0
Answer:
Application software on the target cannot open a PTY (pseudo terminal) to handle the incoming
request. To understand the problem, we have to be aware that the linux kernel and glibc support two
schemes to handle PTYs. The deprecated scheme is hooked to the kernel option
CONFIG_LEGACY_PTYS and at runtime uses (static) device files /dev/ptyxx and /dev/ttyxx
for the master- and the slave ends of the PTYs. For this to work, you need the kernel support and
/dev/[pt]tyxx pairs (where xx usually is a letter in the range p-z followed by a hexadecimal
digit) in the target file system.
The regular support is coupled to the linux kernel option CONFIG_UNIX98_PTYS and the devpts
virtual filesystem which has to be mounted on the target. Together with the device special file
/dev/ptmx this will dynamically create device files for the allocated PTYs below the mount point.
To use it, the device file has to exist and the filesystem needs to be mounted, e.g. like this:
# mkdir /dev/pts
# mknod c 5 2 /dev/ptmx
# mount -t devpts devpts /dev/pts
14.4. Self
14.4.1. How to Add Files to a SELF Ramdisk
It is not always necessary to rebuild a SELF based ramdisk image if you want to modify or to extend it.
Especially during development it is often eaiser to unpack it, modify it, and re-pack it again. To do so, you
have to understand the internal structure of the uRamdisk (resp. pRamdisk) images files as used with the
U-Boot (old: PPCBoot) boot loader:
The uRamdisk image contains two parts:
• a 64 byte U-Boot header
• a (usually gzip compressed) ramdisk image
To modify the contents you have to extract, uncompress and mount the ramdisk image. This can be done as
follows:
14.4.1. How to Add Files to a SELF Ramdisk
198
1. Extract compressed ramdisk image (ramdisk.gz)
bash$ dd if=uRamdisk bs=64 skip=1 of=ramdisk.gz
21876+1 records in
21876+1 records out
2. Uncompress ramdisk image (if it was a compressed one)
bash$ gunzip -v ramdisk.gz
ramdisk.gz:
66.6% -- replaced with ramdisk
3. Mount ramdisk image
bash# mount -o loop ramdisk /mnt/tmp
Now you can add, remove, or modify files in the /mnt/tmp directory. If you are done, you can re-pack the
ramdisk into a U-Boot image:
1. Unmount ramdisk image:
bash# umount /mnt/tmp
2. Compress ramdisk image
bash$ gzip -v9 ramdisk
ramdisk:
66.6% -- replaced with ramdisk.gz
3. Create new U-Boot image (new-uRamdisk)
bash$ mkimage -T ramdisk -C gzip -n 'Simple Embedded Linux Framework' \
> -d ramdisk.gz new-uRamdisk
Image Name:
Simple Embedded Linux Framework
Created:
Sun May 4 13:23:48 2003
Image Type:
PowerPC Linux RAMDisk Image (gzip compressed)
Data Size:
1400121 Bytes = 1367.31 kB = 1.34 MB
Load Address: 0x00000000
Entry Point: 0x00000000
Instead of re-packing into a U-boot ramdisk image you can of course also just extract the contents of the
SELF image and re-use it as base of a (known to be working) root filesystem.
• For example, you can create a JFFS2 filesystem using the mkfs.jffs2 command that comes with
the MTD Tools:
bash# mkfs.jffs2 -r /mnt/tmp -e 0x10000 -o image.jffs2
• Or you can create a CramFS filesystem with mkcramfs:
bash# mkcramfs -r /mnt/tmp image.cramfs
Swapping filesystem endian-ness
...
Everything: 1656 kilobytes
Super block: 76 bytes
CRC: 7f34cae4
14.4.2. How to Increase the Size of the Ramdisk
1. Extract compressed ramdisk image (ramdisk.gz) from U-Boot image:
bash$ dd if=uRamdisk bs=64 skip=1 of=ramdisk.gz
21876+1 records in
21876+1 records out
14.4.2. How to Increase the Size of the Ramdisk
199
2. Uncompress ramdisk image
bash$ gunzip -v ramdisk.gz
ramdisk.gz:
66.6% -- replaced with ramdisk
3. Mount ramdisk image
As root:
bash# mkdir -p /mnt/tmp
bash# mount -o loop ramdisk /mnt/tmp
4. Create new ramdisk image, say 8 MB big:
bash$ dd if=/dev/zero of=new_ramdisk bs=1024k count=8
bash$ /sbin/mke2fs -F -m0 new_ramdisk
bash$ /sbin/tune2fs -c 0 -i 0 new_ramdisk
As root:
bash# mkdir -p /mnt/new
bash# mount -o loop new_ramdisk /mnt/new
5. Copy files from old ramdisk to new ramdisk:
As root:
bash# cd /mnt/tmp
bash# find . -depth -print | cpio -VBpdum /mnt/new
Now you can add, remove, or modify files in the /mnt/new directory. If you are done, you can re-pack
the ramdisk into a U-Boot image:
6. Unmount ramdisk images:
As root:
bash# umount /mnt/tmp
bash# umount /mnt/new
7. Compress new ramdisk image
bash$ gzip -v9 new_ramdisk
ramdisk:
66.6% -- replaced with new_ramdisk.gz
8. Create new U-Boot image (new-uRamdisk)
bash$ mkimage -T ramdisk -C gzip -n 'New Simple Embedded Linux Framework' \
> -d new_ramdisk.gz new_uRamdisk
Image Name:
Simple Embedded Linux Framework
Created:
Sun May 4 13:23:48 2003
Image Type:
PowerPC Linux RAMDisk Image (gzip compressed)
Data Size:
1400121 Bytes = 1367.31 kB = 1.34 MB
Load Address: 0x00000000
Entry Point: 0x00000000
Remember that Linux by default supports only ramdisks up to a size of 4 MB. For bigger ramdisks, you
have to either modify your LInux kernel configuration (parameter CONFIG_BLK_DEV_RAM_SIZE in the
"Block devices" menue), or pass a "ramdisk_size=" boot argument to the Linux kernel.
14.5. RTAI
14.5.1. Conflicts with asm clobber list
Question:
14.5.1. Conflicts with asm clobber list
200
When I try to compile my LInux kernel after applying the RTAI patch, I get a strange "asm-specifier
for variable `__sc_3' conflicts with asm clobber list" error message. What does that mean?
Answer:
You are using an old version of the Linux kernel / RTAI patch in combination with a more recent
version of the cross compiler. Please use a recent kernel tree (and the corresponding RTAI patch), or
apply the attached patch to fix this problem.
See: http://www.denx.de/wiki/pub/DULG/ConflictsWithAsmClobberList/patch
14.6. BDI2000
14.6.1. Where can I find BDI2000 Configuration
Files?
The configuration files provided by Abatron can be found here: ftp://94.230.212.16/bdigdb/config/
A collection of configuration files for the BDI2000 BDM/JTAG debugger by Abatron can be found at
ftp://ftp.denx.de/pub/BDI2000/
A list of FAQ (with answers) can be found at http://www.ultsol.com/faqs.htm
A list of supported flash chips (and the needed matching entries for the config file) can be found at
http://www.abatron.ch/fileadmin/user_upload/products/pdf/flashsupp.pdf
14.6.2. How to Debug Linux Exceptions
Question:
I am trying to single step into a Linux exception handler. This does not seem to work. Setting a
breakpoint does not work either.
Answer:
The problem is bit complex on a MPC8xx target. Debug mode entry is like an exception and therefore
only safe at locations in the code where an exception does not lead to an unrecoverable state. Another
exception can only be accepted if SRR0 and SRR1 are saved. The MSR[RI] should indicate if
currently an exception is safe. MSR[RI] is cleared automatically at exception entry.
The MPC8xx hardware breakpoints do only trigger if MSR[RI] is set in order to prevent
non-recoverable state.
The problem is that the Linux exception handler does not take all this into account. First priority has
speed, therefore neither SRR0 nor SRR1 are saved immediately. Only after EXCEPTION_PROLOG
this registers are saved. Also Linux does not handle the MSR[RI] bit.
Hint: Use STEPMODE HWBP when debugging Linux. This allows the TLB Miss Exception
handler to update the TLB while you are single stepping.
14.6.2. How to Debug Linux Exceptions
201
Conclusion:
You cannot debug Linux exception entry and exit code. Because of speed, DataStoreTLBMiss does
not even make use of EXCEPTION_PROLOG, and SRR0/SRR1 are never saved. Therefore you
cannot debug DataStoreTLBMiss unless you change it's code (save SRR0/SRR1, set MSR[RI].
14.6.3. How to single step through "RFI"
instruction
Question:
I am trying to debug Linux on an IBM 405GP processor. Linux boots fine and I can step through the
code until the "rfi" instruction in head_4xx.S; then I get the following:
- TARGET: target has entered debug mode
Target state
: debug mode
Debug entry cause : JTAG stop request
Current PC
: 0x00000700
Current CR
: 0x28004088
Current MSR
: 0x00000000
Current LR
: 0x000007a8
# Step timeout detected
Answer:
Your single step problem most likely comes from the fact that GDB accesses some non-existent
memory (at least some versions do/did in the past). This exception is stored in some way within the
405 and when you step "rfi" it triggers. This is because some instructions like "rfi" are always
stepped using a hardware breakpoint and not with the JTAG single step feature.
Probably you can step over the "rfi" instruction when using the BDI2000's telnet command
interface instead of GDB.
Similar problems have also been reported when stepping through "mtmsr" or "mfmsr" during
initial boot code. The problem comes also from the fact that GDB accesses non-existent memory
(maybe it tries to read a non-existent stack frame).
To debug the Linux kernel, I recommend that you run to a point where the MMU is on before you
connect with GDB.
To debug boot code where the MMU is off I recommend to use the MMAP feature of the BDI to
prevent illegal memory accesses from GDB.
14.6.4. Setting a breakpoint doesn't work
Question:
I am trying to set a breakpoint using the BDI2000 telnet interface. However, the code does not
stop at the breakpoint.
Answer:
Make sure that the CPU has been stopped before setting the breakpoint. You can verify this by issuing
the "info" command before setting the breakpoint. If the target state is "running" you must use
the "halt" command to stop the CPU before you can successfully set the breakpoint.
14.6.4. Setting a breakpoint doesn't work
202
14.6.5. Remote 'g' packet reply is too long
Question:
I'm trying to debug U-Boot for a PPC4xx processor, but I get the following error:
(gdb) target remote xx.xx.xx.xx:2001
Remote debugging using xx.xx.xx.xx:2001
Remote 'g' packet reply is too long:...
I believe this error is caused by GDB being configured to the wrong architecture. So I did the
following:
$ ppc_4xx-gdb u-boot
...
The target architecture is set automatically (currently powerpc:403)
(gdb) show arch
The target architecture is set automatically (currently powerpc:e500)
(gdb) set arch powerpc:403
The target architecture is assumed to be powerpc:e500
(gdb) show arch
The target architecture is assumed to be powerpc:e500
(gdb) set arch powerpc:common
The target architecture is assumed to be powerpc:e500
(gdb) show arch
The target architecture is assumed to be powerpc:e500
(gdb)
As you see, initially GDB says the target architecture is "powerpc:403". But the "show arch"
command claims it is the "powerpc:e500". And any commands that try to change it from
"powerpc:e500" do not appear to be working.
What's wrong, and why am I not able to change the architecture?
Answer:
Some versions of GDB are hard coded to try and read the architecture from the ELF file and set the
arch based on that at startup. When this happens you cannot change the arch again. In this case it
looks like it has set it incorrectly from the ELF file as "powerpc:e500".
Workaround:
The following procedure can be used to work around the problem:
◊ Start GDB without a file argument, i. e. do not give the the name of the ELF file (here
"u-boot") on the command line
◊ use "set arch" to set the appropriate architecture
◊ use the "add-symbol-file" command to load the ELF file (here "u-boot") manually
◊ double check using "show arch" to make sure the arch hasn't changed; change it back in
case it has
◊ connect to the BDI using the "target remote" commAnd as usual and start debugging
Note:
When you see this problem with the GDB version 6.7-1rh as included with ELDK release 4.2, you
may want to install the update to version 6.7-4rh which can be found here:
ftp://ftp.denx.de/pub/eldk/4.2/ppc-linux-x86/updates/RPMS/gdb-ppc-6.7-4.i386.rpm
14.7. Motorola LITE5200 Board
14.7. Motorola LITE5200 Board
203
14.7.1. LITE5200 Installation Howto
A nice "Application Note: Installing Embedded Linux on the Motorola MPC5200 Lite Evaluation Board"
which covers the installation of U-Boot and Linux can be found at:
http://emsys.denayer.wenk.be/emcam/Linux_on_MPC5200_(UK).pdf
14.7.2. USB does not work on Lite5200 board
Question:
USB does not work on my Lite5200 board. Also, the green LED behind the USB connector remains
always off. Why?
Answer:
This is a hardware problem. The green LED must be on as soon as you power on the Lite5200 board.
As a workaround you can short-circuit resistor R164 (bottom side of the board, close to the USB
connector). Please note that you will probably lose all warranty and/or may ruin the board. You have
been warned.
15. Glossary
ABI
- Application Binary Interface
The convention for register usage and C linkage commonly used on desktop Power Architecture® machines.
Similar, but not identical to the EABI.
Includes binding specific ppc registers to certain fixed purposes, even though there may be no technical
reason to enforce such binding, simplifying the process of linking together two separate sets of object code.
e.g the ABI states that r1 shall be the stack pointer.
BANK
- also "memory bank"
A bank of memory (flash or RAM) consists of all those memory chips on your system that are controlled by
the same chip select signal.
For example, a system might consist of one flash chip with a 8 bit bus interface, which is attached to the CS0
chip select signal, 2 flash chips with a 16 bit bus interface, which are attached to the CS1 chip select signal,
and 2 SDRAM chips with a 16 bit bus interface, which are attached to the CS2 chip select signal.
This setup results in a system with 3 banks of memory:
• 1 bank of flash, 8 bit wide (CS0)
• 1 bank of flash, 32 bit wide (CS1)
• 1 bank of SDRAM, 32 bit wide (CS2)
15. Glossary
204
BDM
- Background Debug Mode
An on-chip debug interface supported by a special hardware port on some processors. It allows to take full
control over the CPU with minimal external hardware, in many cases eliminationg the need for expensive
tools like In-Circuit-Emulators.
BOOTP
- Boot Protocol
A network protocol which can be used to inquire a server about information for the intended system
configuration (like IP address, host name, netmask, name server, routing, name of a boot image, address of
NFS server, etc.
CFI
- Common Flash Interface
CFI is a standard for flash chips that allows to create device independend drivers for such chips.
CPM
- Communications Processor Module
The magic communications co-processor in Motorola PowerQUICC devices. It contains SCCs and SMCs, and
performs SDMA and IDMA.
CPU
- Central Processor Unit
Depending on the context, this may refer to the processor core itself, or the physical processor device
(including peripherals like memory controller, Ethernet controller, UARTs, LCD controller, ..., packaging
etc.) as a single unit. The latter is today often called "system on chip" ("SoC").
CramFs
- Compressed ROM File System
Cramfs is designed to be a simple, small, and compressed file system for ROM based embedded systems.
CramFs is read-only, limited to 256MB file systems (with 16MB files), and doesn't support 16/32 bits uid/gid,
hard links and timestamps.
CVS
- Concurrent Versions System
CVS is a version control system; it can be used to record the history of files, so that it is for instance possible
to retrieve specific versions of a source tree.
BDM
205
DHCP
- Dynamic Host Configuration Protocol
A network protocol which can be used to inquire a server about information for the intended system
configuration (like IP address, host name, netmask, name server, routing, name of a boot image, address of
NFS server, etc.). Sucessor of BOOTP
DMA
- Direct Memory Access
A form a data transfer directly between memory and a peripheral or between memory and memory, without
normal program intervention.
EABI
- Embedded Application Binary Interface
The convention for register usage and C linkage commonly used on embedded Power Architecture®
machines, derived from the ABI.
ELDK
- Embedded Linux Development Kit
A package which contains everything you need to get startet with an Embedded Linux project on your
hardware:
• cross development tools (like compiler, assembler, linker etc.) that are running on a Host system
while generating code for a Target system
• native tools and libraries that can be use to build a system running on the target; they can also be
exported on a NFS server and used as root filesystem for the target
• source code and binary images for PPCBoot and Linux
• Our SELF package as example configuration for an embedded system.
FEC
- Fast Ethernet Controller
The 100 Mbps (100Base) Ethernet controller, present on 'T' devices such as the 860T and 855T.
FTP
- File Transfer Protocol
A protocol that can be used to transfer files over a network.
DHCP
206
GPL
/ LGPL - GNU General Public License/Lesser General Public License
The full license text can be found at http://www.gnu.org/copyleft/gpl.html.
The licenses under which the Linux kernel and much of the utility and library code necessary to build a
complete system may be copied, distributed and modified. Each portion of the software is copyright by its
respected copyright holder, and you must comply with the terms of the license in order to legally copy (and
hence use) it. One significant requirement is that you freely redistribute any modifications you make; if you
can't cope with this, embedded Linux isn't for you.
Host
The computer system which is used for software development. For instance it is used to run the tools of the
ELDK to build software packages.
IDMA
- Independent DMA
A general purpose DMA engine with relatively limited throughput provided by the microcoded CPM, for use
with external peripherals or memory-to-memory transfers.
JFFS
- Journalling Flash File System
JFFS (developed by Axis Communicartion AB, Sweden) is a log-based filesystem on top of the MTD layer; it
promises to keep your filesystem and data in a consistent state even in cases of sudden power-down or system
crashes. That's why it is especially useful for embedded devices where a regular shutdown procedure cannot
always be guaranteed.
JFFS2
- Second version of the Journalling Flash File System
Like JFFS this is a journalling flash filesystem that is based on the MTD layer; it fixes some design problems
of JFFS and adds transparent compression.
JTAG
- Joint Test Action Group
A standard (see "IEEE Standard 1149.1") that defines how to control the pins of JTAG compliant devices.
Here: An on-chip debug interface supported by a special hardware port on some processors. It allows to take
full control over the CPU with minimal external hardware, in many cases eliminationg the need for expensive
tools like In-Circuit-Emulators.
GPL
207
MII
- Media Independent Interface
The IEEE Ethernet standard control interface used to communicate between the Ethernet controller (MAC)
and the external PHY.
MMU
- Memory Management Unit
CPU component which maps kernel- and user-space virtual addresses to physical addresses, and is an integral
part of Linux kernel operation.
MTD
- Memory Technology Devices
The MTD functions in Linux support memory devices like flash or Disk-On-Chip in a device-independend
way so that the higher software layers (like filesystem code) need no knowledge about the actual hardware
properties.
PC
Card
PC Cards are self-contained extension cards especially for laptops and other types of portable computers. In
just about the size of a credit card they provide functions like LAN cards (including wireless LAN), modems,
ISDN cards, or hard disk drives - often "solid-state" disks based on flash chips.
The PC Card technology has been has been developed and standardized by the Personal Computer Memory
Card International Association (PCMCIA), see http://www.pcmcia.org/pccard.htm .
PCMCIA
- Personal Computer Memory Card International Association
PCMCIA is an abbreviation that can stand for several things: the association which defines the standard, the
specification itself, or the devices. The official term for the devices is PC-Card.
PHY
- Physical Interface
The physical layer transceiver which implements the IEEE Ethernet standard interface between the ethernet
wires (twisted pair, 50 ohm coax, etc.) and the ethernet controller (MAC). PHYs are often external
transceivers but may be integrated in the MAC chip or in the CPU.
The PHY is controlled more or less transparently to software via the MII.
MII
208
RTOS
- Real-Time Operating System
SCC
- Serial Communications Controller
The high performance module(s) within the CPM which implement the lowest layer of various serial
protocols, such as Asynchronous serial (UART), 10 Mbps Ethernet, HDLC etc.
SDMA
- Serial DMA
DMA used to transfer data to and from the SCCs.
SELF
- Simple Embedded Linux Framework
A simple default configuration for Embedded Linux systems that is suitable as starting point for building your
own systems. It is based on BusyBox to provide an init process, shell, and many common tools (from cat
and ls to vi), plus some other tools to provide network connectivity, allowing to access the system over the
internet using telnet and FTP services.
SIU
- System Interface Unit
Provides much of the external interfacing logic. It's the other major module on Motorola PowerQUICC
devices alongside the CPU core and CPM.
SMC
- Serial Management Controller
A lower performance version of the SCCs with more limited functionality, particularly useful for serial debug
ports and low throughput serial protocols.
SPI
- Serial Peripheral Interface
A relatively simple synchronous serial interface for connecting low speed external devices using minimal
wires.
S-Record
- Motorola S-Record Format
RTOS
209
Motorola S-records are an industry-standard format for transmitting binary files to target systems and PROM
programmers.
See also: http://pmon.groupbsd.org/Info/srec.htm
Target
The computer system which will be used later in you application environment, for instance an Embedded
System. In many cases it has a different architecture and much more limited resoucres than a typical Host
system, so it is often not possible to develop the software directly (native) on this system.
TFTP
- Trivial File Transfer Protocol
A simple network protocol for file transfer; used in combination with BOOTP or DHCP to load boot images
etc. over the network.
UART
- Universal Asynchronous Receiver Transmitter
Generically, this refers to any device capable of implementing a variety of asynchronous serial protocols, such
as RS-232, HDLC and SDLC. In this context, it refers to the operating mode of the SCCs which provides this
functionality.
UPM
- User Programmable Machine
A highly flexible bus interfacing machine unit allowing external peripherals with an extremely wide variety of
interfacing requirements to be connected directly to the CPU.
YellowDog
More information about the YellowDog GNU/Linux distribution for Power Architecture® systems can be
found at http://www.yellowdoglinux.com.
S-Record
210