snapgear Manual
SnapGear Linux for LEON
Manual: SnapGear Linux for LEON
LINUX-SNAPGEAR
Version 1.39.0
April 2009
Written by Daniel Hellström
Kungsgatan 12
411 19 Göteborg
Sweden
www.aeroflex.com/gaisler
tel +46 31 7758650
fax +46 31 421407
LINUX-SNAPGEAR
2
Table of Contents
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
INTRODUCTION..............................................................................................................................5
LEON Linux.......................................................................................................................................5
SnapGear Linux..................................................................................................................................5
Boot loader for LEON Linux...............................................................................................................5
LEON simulator to speed up the development process........................................................................5
Obtaining the software.........................................................................................................................6
Supported hardware.............................................................................................................................6
Support................................................................................................................................................6
2
2.1
2.2
2.3
2.4
INSTALLING GNU TOOLCHAIN AND LEON LINUX..................................................................7
Selecting Toolchain.............................................................................................................................7
Installing the toolchain........................................................................................................................7
Installing SnapGear for LEON Linux 2.0............................................................................................8
Installing SnapGear for LEON Linux 2.6............................................................................................8
3
3.1
3.2
3.2.1
3.2.2
3.2.3
3.3
3.4
3.4.1
3.5
3.5.1
3.5.2
3.5.3
3.5.4
3.5.5
3.5.6
3.5.7
3.5.8
3.5.9
3.5.10
3.5.11
3.5.12
3.5.13
3.5.14
3.5.15
3.5.16
3.5.17
3.5.18
3.5.19
3.6
3.6.1
3.6.2
3.6.3
3.6.4
3.6.5
3.6.6
3.6.7
3.6.8
3.7
3.8
CONFIGURING LINUX....................................................................................................................9
Processor type and MMU....................................................................................................................9
C library............................................................................................................................................10
Static vs Dynamic linking..................................................................................................................10
Toolchains for Linux 2.6...................................................................................................................10
Toolchains for Linux 2.0...................................................................................................................10
Kernel version...................................................................................................................................10
Configuring the boot loader...............................................................................................................11
Symmetric multi-processing..............................................................................................................12
Configuring the 2.6.x kernel..............................................................................................................13
LEON processor type........................................................................................................................13
Symmetric multi-processing support.................................................................................................13
Gaisler AMBA Plug&Play procfs support.........................................................................................13
GRLIB APBUART (LEON3)...........................................................................................................14
LEON Serial (LEON2)......................................................................................................................14
GRLIB GRETH 10/100/1000............................................................................................................14
GRLIB OpenCores Ethernet MAC....................................................................................................14
SMC 91x Ethernet MAC...................................................................................................................14
GRLIB GRETH 10/100/1000 over PCI.............................................................................................15
GRLIB OpenCores I2C-master.........................................................................................................15
GRLIB PCI support...........................................................................................................................15
GRLIB GRPS2..................................................................................................................................15
GRLIB SPICTRL..............................................................................................................................15
GRLIB GRACECTRL......................................................................................................................15
GRLIB GRUSBHC...........................................................................................................................16
GRLIB GRUSBDC...........................................................................................................................16
GRLIB GRVGA................................................................................................................................16
GRLIB ATA Controller....................................................................................................................17
Non-standard PAGESIZE support.....................................................................................................18
Configuring the 2.0.x kernel..............................................................................................................18
LEON processor type........................................................................................................................18
GRLIB APBUART (LEON3)...........................................................................................................19
LEON Serial (LEON2)......................................................................................................................19
GRLIB GRETH 10/100 Ethernet MAC.............................................................................................19
GRLIB OpenCores 10/100 Ethernet MAC........................................................................................19
SMC 91C111 10/100 Ethernet MAC.................................................................................................19
GRLIB VGA text frame buffer support.............................................................................................20
GRLIB GRPS2 PS/2 interface/keyboard...........................................................................................20
Applications included in ROMFS......................................................................................................20
Template configurations....................................................................................................................21
4
BUILDING SNAPGEAR.................................................................................................................22
LINUX-SNAPGEAR
3
5
5.1
5.2
5.3
ADDING CUSTOM APPLICATIONS.............................................................................................23
Creating an application......................................................................................................................23
Setting up compilation directives.......................................................................................................23
Including application to file system...................................................................................................23
6
6.1
6.2
6.2.1
6.2.2
6.2.3
6.3
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.3.7
6.4
6.5
6.5.1
6.5.2
DEBUGGING LINUX-2.6 AND APPLICATIONS.........................................................................24
Debugging symbols...........................................................................................................................24
Debugging the kernel........................................................................................................................24
Configuring GRLIB for kernel debugging........................................................................................25
Using GRMON.................................................................................................................................25
GRMON Example: debugging the Linux kernel...............................................................................25
Debugging userspace applications.....................................................................................................29
Setting up a debugging environment.................................................................................................29
GDB introduction..............................................................................................................................29
Starting GDB server on target...........................................................................................................30
Connecting with GDB to gdbserver...................................................................................................30
GDB example usage..........................................................................................................................30
DDD and GDB..................................................................................................................................33
Insight...............................................................................................................................................33
Using NFS to simplify application updates........................................................................................33
Console output when debugging........................................................................................................34
Redirecting output to NFS share........................................................................................................34
TELNET over TCP/IP network.........................................................................................................34
7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
PS/2 KEYBOARD AND VGA CONSOLE......................................................................................35
Hardware configuration.....................................................................................................................35
Configuring the boot loader and main SnapGear options..................................................................35
Configuring the Linux kernel............................................................................................................35
Configuring SnapGear Applications..................................................................................................36
Building the kernel and applications.................................................................................................36
Setting up /etc/inittab.........................................................................................................................36
Building again with inittab and rc.sh.................................................................................................37
Running on hardware........................................................................................................................37
8
8.1
8.2
8.3
8.4
8.5
ROOT FILE SYSTEM OVER ETHERNET USING NFS................................................................38
Setting up NFS server on PC.............................................................................................................38
Configuring the boot loader and main SnapGear options...................................................................38
Configuring the Linux kernel............................................................................................................39
Building kernel and boot loader........................................................................................................39
Running on hardware........................................................................................................................40
9
9.1
9.2
9.3
9.4
9.5
9.6
ROOT FILE SYSTEM OVER ETHERNET USING ATA OVER ETHERNET..............................41
Setting up ATAoE Server..................................................................................................................41
Configuring the boot loader and main SnapGear options...................................................................41
Configuring the Linux kernel............................................................................................................42
Configuring the vendor/user applications .........................................................................................42
Building kernel, boot loader, and kinit..............................................................................................43
Running on hardware........................................................................................................................43
10
10.1
10.2
10.3
10.4
ROOT FILE SYSTEM ON COMPACTFLASH USING XILINX SYSTEM ACE..........................44
Setting up the root filesystem............................................................................................................44
Configuring the boot loader and main SnapGear options..................................................................44
Configuring the Linux kernel............................................................................................................44
Running on hardware........................................................................................................................45
11
RUNNING GRLINUX/SPLACK FROM AN ATA HARD DISK...................................................46
LINUX-SNAPGEAR
4
11.1
11.2
11.3
Installing the kernel onto flash..........................................................................................................46
Preparing the hard drive....................................................................................................................46
Running splack..................................................................................................................................47
12
12.1
12.2
12.3
12.4
12.5
12.6
12.7
12.8
INSTALLING DEBIAN 3.1 ON LEON LINUX..............................................................................48
Preparing LEON target......................................................................................................................48
Installing Debian installation utility to PC and LEON target.............................................................49
Downloading Debian binaries using PC............................................................................................49
Installing Debain binaries from LEON target....................................................................................49
Adding a serial console to Debian......................................................................................................50
Changing root directory and booting Debian.....................................................................................50
Adding a telnet server to Debian........................................................................................................50
Installing X.org X11 Server...............................................................................................................51
13
13.1
13.2
13.3
13.4
USING THE I2C DEVICE INTERFACE TO INITIALIZE A DVI TRANSMITTER....................52
Kernel configuration.........................................................................................................................52
DVI transmitter initialization.............................................................................................................52
Example application..........................................................................................................................53
Building the application....................................................................................................................53
14
SUPPORT.........................................................................................................................................54
LINUX-SNAPGEAR
1
5
INTRODUCTION
LINUX support for LEON2 and LEON3 is provided through a special version of the SnapGear Embedded Linux
distribution. SnapGear Linux is a full source package, containing kernel, libraries and application code for rapid
development of embedded Linux systems. The LEON port of SnapGear supports both MMU and non-MMU
LEON configurations, as well as the optional V8 mul/div instructions and floating-point unit (FPU). A single crosscompilation tool-chain is provided which is capable of compiling the kernel and applications for any configuration.
LEON Linux has support for symmetric multi-processing (SMP), it has not been extensively tested yet, but work is
in progress.
1.1
LEON Linux
There are two different versions of the Linux kernel in the Gaisler SnapGear distribution, namely 2.6.x and
2.0.x. The 2.0 version is modified for use with MMU-less LEON systems, it is called micro controller Linux –
µCLinux. 2.6.x has support for MMU systems only, the kernel is from kernel.org with LEON specific patches
and additional drivers mainly for GRLIB hardware.
The Linux kernel can be configured using a graphical interface. One can remove drivers and features to save
space. On LEON3 systems the AMBA plug&play information is used to detect devices and load their respective
software drivers. LEON2 uses hard coded addresses to find its devices. During configuration the processor type
is selected, LEON2 or LEON3, it is done from the Linux kernel configuration GUI and in the main SnapGear
GUI.
Multi processor LEON3 systems are supported by Linux 2.6.21.1, symmetric multi-processing support (SMP)
can be enabled through the Linux kernel configuration.
The Linux kernel can be used for other projects that need not be based on SnapGear. The boot loader will still
be needed but it is possible to create custom projects with custom file systems. Even though it is out of the
scope of this document, it is described how to set up Linux with other distributions via NFS.
1.2
SnapGear Linux
SnapGear Linux is a full source package, containing kernel, libraries and application code for rapid development of
embedded Linux systems. It is configured from a graphical interface similar to the Linux 2.4 kernel configuration
utility.
1.3
Boot loader for LEON Linux
A small boot loader has been incorporated into the SnapGear Linux software distribution, it is designed especially
for the LEON processors, both SMP and uniprocessor systems. It is capable of passing arguments to any of the
Linux kernels and initialize low level hardware. The main purpose of the boot loader should be to initialize basic
hardware, such as memory controllers and console output for debugging, before launching LEON Linux.
The SnapGear graphical interface as been extended to allow users to set boot loader parameters in an easy fashion.
The boot loader is stored in a non-volatile memory at the address where the LEON processor reads its first
instructions to be executed, usually stored in flash at address 0.
During the development process GRMON may be used to load the resulting image into RAM directly, thus
bypassing the flash. This shortens the development time drastically. Using this method only the last part of the boot
loader is executed, it is often referred to as “stage 2”. Instead, GRMON initializes the hardware before running
stage 2.
1.4
LEON simulator to speed up the development process
There are simulators available for LEON and most of its peripherals, TSIM and the multiprocessor simulator
GRSIM. See www.gaisler.com for more information about simulators.
LINUX-SNAPGEAR
1.5
6
Obtaining the software
The Software is free of charge and distributed under the GPL licence. The software bundle can be downloaded from
Gaisler's homepage: www.gaisler.com under the downloads section.
1.6
Supported hardware
Below is a list of supported hardware in addition to the standard kernel:
● LEON2, with or without MMU, FPU, MUL/DIV.
● LEON3, with or without MMU, FPU, MUL/DIV.
● LEON3 multi processor systems, SMP
● Non-standard page size, larger that 4KBytes
● APBUART
● GPTIMER
● GRETH 10/100 and Gbit
● OpenCores 10/100 Ethernet MAC
● SMC91x 10/100 Ethernet MAC
● APBPS2
● APBVGA
● GRACECTRL
● GRUSBHC
● GRUSBDC
● GRVGA
● ATACTRL
● GRPCI
● GRETH over PCI
● GR/OpenCores I2CMST
● SPICTRL
Note that new hardware is being added constantly.
1.7
Support
For support, contact the Gaisler Research support team at [email protected]
LINUX-SNAPGEAR
2
7
INSTALLING GNU TOOLCHAIN AND LEON LINUX
SnapGear has been split up into two different distributions, one for Linux 2.6 development and one for Linux 2.0
development.
The toolchain is a composition of several utilities used in the compilation process. It is intended to be used with
Linux only, the most important utilities are the GNU GCC compiler and linker. The toolchain is a cross-compiler
toolchain making it possible to compile LEON SPARC Linux binaries on an ordinary PC running Linux. The
toolchains are distributed as a binary package freely available at www.gaisler.com.
2.1
Selecting Toolchain
For Linux 2.0 selecting toolchain is simple, as only one is available, the sparc-linux-3.2.2. For Linux 2.6 however,
one select toolchain based on what C Library is going to be used, installing multiple toolchains cause no harm. The
two toolchains available for Linux 2.6 are sparc-linux-3.4.4 and sparc-uclinux as indicated by the table below. The
next chapter gives a short introduction to the two different C Libraries.
Name
Description
Location
sparc-linux-3.2.2
Linux 2.0 and 2.6 GNU LibC toolchain
linux/linux-2.0/toolchains/sparc-linux-3.2.2
sparc-linux-3.4.4
Linux 2.6 GNU LibC toolchain
linux/linux-2.6/toolchains/sparc-linux-3.4.4
sparc-uclinux-3.4.4
Linux 2.6 µClibC toolchain
linux/linux-2.6/toolchains/sparc-uclinux-3.4.4
Table 2.1: Toolchain description
The locations described in table 2.1 are all relative to the Gaisler FTP site ftp://ftp.gaisler.com/gaisler.com.
2.2
Installing the toolchain
The installation process for the different toolchains is the same, it is only the names and paths that differ. All
toolchains must be installed to /opt and the path to the toolchain binary directory (/opt/sparc-[uc]-linux-3.x.x/bin)
added to the shell PATH variable. Below is an example of how to install the sparc-linux-3.2.2 toolchain.
Install by extracting the toolchain into /opt:
$ mkdir /opt
$ cd /opt
$ tar -jxf /path/to/toolchain/sparc-linux-1.0.0.tar.bz2
Add the toolchain to the PATH variable preferably in a shell start up script. For bash shells the following is added
to ~/.profile:
export PATH=$PATH:/opt/sparc-linux/bin
After installing the toolchain it is possible to cross compile applications for SPARC LEON Linux:
args.c:
int main(int argc, char *argv[]){
printf(“%s: you passed %d argument(s)\n”,argv[0],argc-1);
return 0;
}
Compile args by running:
LINUX-SNAPGEAR
8
$ sparc-linux-gcc -o args args.c
or
$ sparc-uclinux-gcc -o args args.c
From the ELF header it can be read that the output binary is a SPARC binary:
$ file args
args: ELF 32-bit MSB executable, SPARC, version 1 (SYSV), dynamically
linked (uses shared libs), not stripped
Running the binary on a SPARC Linux host results in:
$ ./args Gaisler
./args: you passed 1 argument(s)
2.3
Installing SnapGear for LEON Linux 2.0
Install the SnapGear distribution by extracting it:
$
$
$
$
mkdir ~/linux
cd ~/linux
tar -xjf /path/to/dist/snapgear-2.0-p36.tar.bz2
ls
snapgear-2.0-p36
2.4
Installing SnapGear for LEON Linux 2.6
Install the SnapGear distribution by extracting it:
$
$
$
$
mkdir ~/linux
cd ~/linux
tar -xjf /path/to/dist/snapgear-2.6-p36.tar.bz2
ls
snapgear-2.6-p36
LINUX-SNAPGEAR
3
9
CONFIGURING LINUX
SnapGear comes with an easy to use graphical interface similar to the Linux kernel's configuration utility. From the
GUI it is possible to select processor, Linux version, C library and what applications will be included into the root
file system (ROMFS image) accessed by Linux during runtime. It is also possible to configure the boot loader
parameters and configure the Linux kernel.
The GUI can be launched by doing a 'make xconfig'. The main configuration menu should appear:
Illustration 3.1: SnapGear main configuration GUI
3.1
Processor type and MMU
Selecting processor is mandatory, the boot loader needs to know how to initialize low level hardware, which in
some cases are processor dependant. It is also important to select MMU support if memory protection hardware is
available for use.
MMU provides memory protection between kernel and user space, and also in between user space processes. With
MMU a faulty process cannot affect another process memory in a destructive manner as may be the case without
MMU.
Linux 2.6 cannot run without MMU, whereas µCLinux runs without MMU, indicated in the table below.
Version / MMU
MMU
MMU-less
2.0.x
N/A
µCLinux 2.0.x
2.6.x
Linux 2.6
N/A
Table 3.1: Linux and MMU
Illustration 3.2: Vendor/Product Selection
LINUX-SNAPGEAR
3.2
10
C library
Two different C libraries are available for selection from the graphical “xconfig” utility. The libraries differ in
binary size and one of them, µClibC, supports MMU-less systems. Table 3.2 outlines which C library is available
for which version of Linux. For configurations that supply their own root filesystem outside of SnapGear (such as
via NFS), a 'none' option is also provided to entirely omit the compilation of a C system library.
Version / LibC
LibC (GNU)
µController LibC
µCLinux 2.0.x
N/A
Small footprint
Linux 2.6.x
Normal footprint
Small footprint
Table 3.2: LibC selection possibilities
3.2.1
Static vs Dynamic linking
When linking an application static, all code used from libraries are included into the output binary. This makes the
binary bigger. Linking all binaries static will make the same code appear in multiple locations (in each binary that
uses it) both in the file system and in main memory during execution.
Dynamic linking however, runs a dynamic linker during the start of the application on the target hardware, this
results in smaller main memory usage as code is shared between applications. Since the same code may appear in
different addresses in different applications, the code must be position independent. Generating position
independent machine code makes the code a bit slower and slightly bigger, it is done by passing the argument
-fPIC to the GNU compiler.
The more applications a file system has, the more space can be saved using dynamically linked binaries. Depending
on needs and resources, different embedded systems choose different linking strategies.
3.2.2
Toolchains for Linux 2.6
The available SPARC LEON toolchains for Linux 2.6 both contains a precompiled C Library. The library has been
built four times for CPUs with different combinations of FPU and mul/div hardware. Two different toolchains are
available the sparc-linux toolchain includes the GNU C library whereas the sparc-uclinux toolchain has µClibC
built in. The two toolchains are based on GCC 3.4.4. Installing both toolchains will not conflict. See previous
chapter for installation instructions.
3.2.3
Toolchains for Linux 2.0
For Linux 2.0 there are one toolchain available, based on GCC 3.2.2. For Linux 2.0 SnapGear projects the
toolchain's C Library isn't used, but the µClibC Library included in the SnapGear release. See installation
instructions in previous chapter.
3.3
Kernel version
Linux kernel version can be selected from the Kernel/Library sub menu. As described earlier in the introduction
there are two variants of the Linux kernel within the SnapGear LEON Linux distribution. One is intended to be
used with MMU-less systems and the other is based on an older version of the Linux kernel, 2.0. For MMU based
systems, Linux 2.6.x is available.
LINUX-SNAPGEAR
11
Illustration 3.3: Kernel, LibC and application selection menu
3.4
Configuring the boot loader
The boot loader sets up low level hardware before entering the Linux kernel. The parameters of the boot loader can
be set using the main SnapGear GUI. Below is a description of available boot loader parameters.
LINUX-SNAPGEAR
12
Name
Description
SPARC v8, MUL/DIV
When “Yes” the compiler emits hardware integer multiplier
instruction. If the LEON processor has been configured without
hardware multiplier select “No”, the compiler will then generate
SPARC v7 compatible code instead (without any MUL or DIV
instructions).
FPU support
Select “Yes” if LEON has a Floating point unit (FPU).
Clock frequency
The frequency is needed for the boot loader to calculate timing
values. Value is in kHz.
Baudrate
The baud rate of the first serial terminal. Typically 38400 baud. It
is favourable to use the same baud rate for the Linux kernel.
UART Loopback on
Enables the loopback mode of the UART, every character sent
will be recieved.
UART hardware flowctrl
Hardware flow control will be used.
In memory root file system
Romfs. Read only root file system. Created from snapgearpxx/romfs. This option is valid for Linux 2.0.x.
Initramfs. A read and write root file system put in main memory.
See linux-2.6.x/Documentation/filesystems/ ramfs-rootfsinitramfs.txt for more information.
Custom, an initramfs is created, similar to initramfs. The
difference is that with this option one can make an file system
externally and provide a description how it is created. The
description is a text file as described in the Linux kernel
documentation at linux-2.6.x/ Documentation/filesystems/ramfsrootfs-initramfs.txt.
None. When specified the linker doesn't include the any root file
system. This means that Linux must read the root file system
from an alternative location, for example NFS or ATA-disk.
Custom initramfs source
The text file used to create an custom filesystem, not necessarily
based on SnapGear. See linux-2.6.x/ Documentation/filesystems/
ramfs-rootfs-initramfs.txt for details.
Kernel command line
The kernel parameters is specified by a string. The string is
interpreted by Linux during the boot sequence. See linux2.6.x/Documentation/kernel-parameters.txt for details.
Default: console=ttyS0,34800
Note: When using Linux 2.0.x the kernel command line is set
from within the kernel configuration tool under "General setup".
ROM bank size
Bank size of flash
ROM rws
Number of ROM/Flash read wait states
ROM wws
Number of ROM/Flash write wait states
Enable write cycles to PROM
Boot loader makes it possible to write to FLASH without
tampering with memory configuration registers.
RAM type
RAM type to be used. SRAM or SDRAM
Alternative physical kernel address
It is possible to manually select an address where the kernel will
be started from. The base address of the stack can be changed
as well.
One can this way make room for a custom data area, the Linux
kernel will only use the memory between the kernel base address
and the stack base.
Table 3.3: Boot loader parameters
3.4.1
Symmetric multi-processing
Multi LEON3 processor systems is supported by the boot loader. The multi processor support is controlled from
within the Linux 2.6.x kernel configuration GUI, once SMP is enabled the boot loader's SMP support is also
LINUX-SNAPGEAR
13
included when built the next time.
See 2.6.x configuration section.
3.5
Configuring the 2.6.x kernel
From the graphical interface it is possible to configure the selected kernel by selecting “y” at “Customize Kernel
Settings” and saving the new settings. After the main GUI has been closed and settings have been saved a second
GUI will appear that is specific for the kernel selected. The kernel configuration GUI for Linux 2.6 is shown below.
Details on how to configure the kernel can be found in the linux-2.6.x/Documentation directory. In later chapters
some common configurations will be presented.
The following sections will be used to describe some of the Linux kernel's settings specific to LEON Linux.
Features and drivers often depend on other features, the dependencies is sometimes not trivial. The dependencies
can be seen in a C programming similar syntax by enabling “Show debug info” from the Option menu. The
dependency can be seen down to the right by selecting the feature in question.
Illustration 3.4: Linux 2.6.x GUI configuration utility
3.5.1
LEON processor type
The configuration of the processor type is done separately for the Linux boot loader and the kernel itself. This is
done to eliminate the kernel's dependency on SnapGear, LEON Linux can be used without SnapGear.
LEON must always be selected but LEON_3 is only selected for LEON3 targets. Selecting LEON_3 will result in
binary unable to run on LEON2 processors and vice versa.
Certain hardware is only available for LEON3, their drivers will be invisible when LEON2 is selected.
3.5.2
Symmetric multi-processing support
LEON Linux has support for multi processor systems, SMP can be enabled for LEON3 systems under “General
machine setup”. The LEON Linux boot loader is updated to initialize the SMP system correctly automatically when
enabling SMP from the Linux kernel configuration GUI.
SMP is only available for LEON3 processors.
3.5.3
Gaisler AMBA Plug&Play procfs support
Procfs is a “pseudo file system” that is normally mounted onto /proc. The procfs is directly linked to the kernel's
internals and can display information relevant to the system's operation. Enabling AMBA_PROC makes a directory
LINUX-SNAPGEAR
14
/proc/bus/amba appear that can display information about devices on the AMBA bus.
Illustration 3.5AMBA procfs support
3.5.4
GRLIB APBUART (LEON3)
If a serial UART is to be used select GRLIB_GAISLER_APBUART, be sure to select
GRLIB_GAISLER_APBUART_CONSOLE if one of the serial controllers are interfaced to a console. One of the
serial terminals can be set up as the system console via the kernel boot parameter, ex: console=ttyS0,38400 selects
the first serial channel to act as the system console. The serial terminals will be available under /dev/ttySx.
Illustration 3.6: APBUART and GRETH Linux configuration.
3.5.5
LEON Serial (LEON2)
For LEON2 systems the serial driver can be found under “Character devices / Serial drivers”. Selecting
SERIAL_LEON enables the serial driver, the serial devices can be used to communicate over the serial line with an
Illustration 3.7: Serial support for LEON2
arbitrary protocol. The serial lines can be accessed from /dev/ttySx.
3.5.6
GRLIB GRETH 10/100/1000
Select GRLIB_GAISLER_GRETH to enable the 10/100 Ethernet MAC or for GRLIB professional users, the
10/100/1000 Ethernet MAC.
The Ethernet MAC address of the GRETH MAC can also be edited directly from the GUI. The address is made out
of an unique 6 byte sequence. One can edit the 24 most significant bits (MSB) and the 24 least significant bits
(LSB) from GRLIB_GAISLER_GRETH_MACXSB.
“Networking”, “Network devices” and “TCP/IP” must be selected for standard network communication to be
available.
3.5.7
GRLIB OpenCores Ethernet MAC
In the same way as the GRETH is configured the OpenCores MAC can be selected and it's MAC address can be
edited. The OpenCores MAC is found under “General machine setup / .. / Vendor OpenCores”.
3.5.8
SMC 91x Ethernet MAC
The SMC91x driver can be found under “Network device support / Ethernet 10/100”. The Ethernet MAC address
must be configured to an unique address as previous MAC controllers.
The chip is not a Plug&Play AMBA device and can therefore not be automatically detected by the driver. Both
address and IRQ number must be given to the driver for it to operate correctly.
LINUX-SNAPGEAR
3.5.9
15
GRLIB GRETH 10/100/1000 over PCI
Select GRETH_PCI from “Network device support / Ethernet 10/100” to include a driver for Gaisler Ethernet
MAC connected via PCI. Usually GRETH is connected via the AMBA interface and is included as previously
described.
PCI support must also be enabled, see the sub section GRLIB PCI support below.
3.5.10
GRLIB OpenCores I2C-master
Enable “I2C support” and “I2C support / I2C Hardware Bus support / OpenCores I2C Controller”. The driver will
use the GRLIB wrapper's interface when the kernel is configured to run on a Leon SoC. To use the I2C bus,
selections should also be made under “I2C support / I2C Algorithms” and “I2C support / Miscellaneous I2C Chip
support”, depending on which peripherals that are present in the system. Section 13 contains an example that
utilizes the I2C character interface to write directly to an I2C device.
3.5.11
GRLIB PCI support
GRPCI is a bridge between the AMBA bus and the PCI bus. The GRPCI core is mainly used to connect off chip
controllers to the LEON system. It can be enabled by selecting “PCI support” under “General machine setup”.
Once the GRPCI driver detects the GRPCI core by probing the AMBA Plug&Play bus, it initializes the core and
starts scanning the PCI bus for additional controllers.
3.5.12
GRLIB GRPS2
Keyboard and mouse drivers are available for the Gaisler PS/2 controller. One can enable GRPS2 under “input
device / Hardware I/O ports”. Input devices that use the PS/2 driver such as keyboard and mouse drivers are enabled
under “Input device support”, MOUSE_PS2, INPUT_MOUSEDEV and INPUT_KEYBOARD.
Illustration 3.8: Adding support for GRPS2 controller.
To separate keyboard and mouse PS/2 devices from each other the IRQ number of the keyboard must be specified.
This is because the PS/2 controllers are identical to the kernel. PS/2 controllers found with an IRQ not matching the
keyboard IRQ number are assumed to be a PS/2 controller connected to a mouse.
The default keyboard IRQ number may be overridden by the kernel command line option:
grps2=kbdirq:irqno
3.5.13
(irqno=0..15)
GRLIB SPICTRL
The Gaisler SPI controller is enabled by selecting “SPI support” and “SPI support / Gaisler Research SPI
Controller”. The driver automatically detects the number of available slave select lines.
Adding support for specific SPI devices requires editing of the SPI initialization code found in linux-2.6.21.1/arch/
sparc/kernel/leon_spic.c. This is necessary since the available SPI devices are normally hard coded in platform
specific code, and GRLIB is used in a wide range of systems.
The current initialization code contains an example where a M25P05 SPI Flash memory is connected to the first
slave select line on SPI bus 1. To enable support for this specific memory device, select “Memory Technology
Devices / Self-contained MTD device drivers / Support for M25 SPI Flash”. To add support for another type of SPI
device, modify the example and configure support for the SPI device in question.
3.5.14
GRLIB GRACECTRL
Support for the System ACE Interface Controller is enabled under “Device Drivers / Block devices / Xilinx
SystemACE Support”. This driver enables interaction with CompactFlash memory devices. A device can be
accessed via /dev/xsysace, with the first partition at /dev/xsysace1.
LINUX-SNAPGEAR
3.5.15
16
GRLIB GRUSBHC
Support for GRUSBHC is enabled under “USB support / Support for Host-side USB”. Depending on the core's
configuration, the applicable host controller drivers are “EHCI HCD (2.0) support” and “UHCI HCD (most Intel
and VIA) support”.
Illustration 3.9: Adding support for USB 2.0 host controller.
To enable support for USB storage devices, “SCSI / SCSI device support” and “SCSI / SCSI disk support” must
first be enabled. USB connected human interface devices such as mice and keyboards are also supported. Enable
“USB / USB Human Interface Device (full HID) support”, and INPUT_KEYBOARD and INPUT_MOUSE under
“Input device support”.
3.5.16
GRLIB GRUSBDC
Support for GRUSBDC is enabled under “USB support / USB Gadget Support / USB Peripheral Controller”.
The driver only supports the core's DMA mode so if this is not enabled in the core in the current system the
driver will not work.
To be able to use the driver a gadget driver also has to be enabled. This is done in “USB support / USB Gadget
Support / USB Gadget Drivers”. The core has been tested with Gadget Zero, GadgetFs and EthernetGadget.
3.5.17
GRLIB GRVGA
GRLIB SVGA controller can be used in Linux using the frame buffer video driver written for GRVGA. XWindows and/or a frame buffer console can be run on top of the frame buffer driver. Normally one want mouse or
at least a keyboard together with the graphical interface, GRPS2 can be used to connect keyboard and mouse
devices.
One may need to consider bus bandwidth when selecting resolution and bit depth. The GRVGA controller will
cause heavy bus loads for high resolution on slower buses. Each word in the frame buffer will be read 60 times on a
system with 60 Hertz vertical refresh rate.
From the “Graphics support” menu one can enable the GRVGA frame buffer driver.
Illustration 3.10: Adding Frame Buffer driver.
When using the SVGA controller to provide console interface to the system the resolution, bit depth and other
parameters can be set from the kernel parameters. Table 3.4 lists available arguments to the driver.
The Mem_size parameter can be calculated as resolution times bit depth in bytes. For example 614400 bytes video
LINUX-SNAPGEAR
17
buffer makes a resolution of 640x480 8-bit, 640x480 16-bit and 800x600 8-bit resolution possible, however
800x600 16-bit would not fit into the memory as that would need 960000 bytes.
The last argument, fb_addr, can be utilized to control where in the memory the framebuffer should be placed. This
is useful for systems that have been designed with a dedicated memory for the framebuffer. Normally this argument
does not have to be specified, in which case the driver will allocate space from the main memory to use for the
framebuffer.
Order
Value
Custom/All
Description
0
video=grvga:
All
Needed to select frame buffer driver
1
Custom
All
Select one of the values to the left. When full control is
needed specify the custom mode.
When custom mode is selected arguments 2-10 are
needed in addition to 11 and 12.
[email protected]
[email protected]
[email protected]
800x480
[email protected]
2
Pixelclock
Custom
Pixelclock in ns.
3
xres
Custom
Horizontal resolution in pixels.
4
rmargin
Custom
Horizontal Front porch in pixels.
5
hsync_len
Custom
Horizontal Sync length in pixels.
6
lmargin
Custom
Horizontal Back porch in pixels.
7
yres
Custom
Vertical resolution in lines.
8
llmargin
Custom
Vertical Front porch in lines.
9
vsync_len
Custom
Vertical Sync length in lines.
10
umargin
Custom
Vertical Back porch in lines.
11
bit_per_pixel
All
Pixel depth in bits: 8,16,32-bits
12
Mem_size
All
Frame buffer memory size in bytes.
13
fb_addr
All
Specify a physical address for the framebuffer. (This
argument is optional.)
Table 3.4: GRVGA kernel parameter arguments
Below is an example how to configure the GRSVGA using 1024x768 resolution, 60Hz vertical refresh rate, 8-bits
pixel depth and 800kb video buffer. The system console will be displayed on virtual terminal zero /dev/tty0 which
is connected to the framebuffer /dev/fb0 instead of a serial terminal.
console=tty0 video=grvga:[email protected],8,786432
[email protected] is a predefined mode by the driver, however a custom mode can be entered, see the table above and
kernel documentation for more details.
When using the GRLIB SVGA controller with a DVI transmitter, additional initialization of the transmitter may be
required. Please see section 13 for an example on how to initialize a DVI transmitter over I2C.
3.5.18
GRLIB ATA Controller
Gaisler ATA controller can interface a hard disk or a compact flash card. Devices can be accessed from /dev/hda.
The ATACTRL can be selected from “ATA/.. support” menu.
The ATA controller depend upon the PCI subsystem to function correctly, PCI can be included from “General
Machine Setup”.
LINUX-SNAPGEAR
18
Illustration 3.11: Enabling ATACTRL.
Once the ATA controller is enabled the IDE devices that needs to be supported are to be selected, most commonly
the IDE/ATA-2 DISK support is selected.
3.5.18.1 DMA Extension
The DMA extension of the GRLIB ATA controller can be enabled by selecting BLK_DEV_IDEPCI,
BLK_DEV_IDEDMA_PCI in addition to the options described for the standard ATA controller.
Note that enabling the DMA extension does not disable the standard ATA controller driver.
3.5.19
Non-standard PAGESIZE support
Support to MMU hardware that supports PAGESIZE other than the default 4k is enabled via option “General
machine setup” → “Running on SoC 'Leon' → “Pagesize extra bits”. The default is the standard 4kb page size, but
can be changed to 8k and 16k. Note that special hardware is needed for page sizes different than 4kb. It is possible
to check whether if a system has non-standard page size or not by typing “mmu” in GRMON. If the system support
a non-standard page size the active page size will be printed out.
3.6
Configuring the 2.0.x kernel
From the graphical interface it is possible to configure the selected kernel by selecting “y” at “Customize Kernel
Settings” and saving the new settings. After the main GUI has been closed and settings been saved a second GUI
will appear that is specific for the kernel selected. The kernel configuration GUI for Linux 2.0 is shown below.
Details on how to configure the kernel can be found in the linux-2.0.x/Documentation directory.
The following sections will be used to describe some of the Linux kernel's settings specific to LEON Linux.
3.6.1
LEON processor type
The configuration of the processor type is done separately for the Linux boot loader and the kernel itself. This is
done to eliminate the kernel's dependency on SnapGear, LEON Linux can be used without SnapGear.
Certain hardware is only available for LEON3, their drivers will be invisible when LEON2 is selected.
Illustration 3.12: Linux 2.0.x kernel configuration utility
LINUX-SNAPGEAR
3.6.2
19
GRLIB APBUART (LEON3)
Select GRLIB_GAISLER_APBUART to include a UART driver for APBUART. One of the serial terminals can
be set up as the system console via the kernel boot parameter, ex: console=ttyS0,38400 selects the first serial
channel to act as the system console.
The serial terminals will be available by accessing /dev/ttySx.
3.6.3
LEON Serial (LEON2)
From “Character devices” sub menu the LEON2 UART driver can be enabled. It allows user space to communicate
with an arbitrary protocol over the serial line terminal interface /dev/ttySx.
This driver uses hard coded addresses instead of probing the AMBA bus for Plug&Play information. This driver is
Illustration 3.14: Platform set up
Illustration 3.13: LEON3 AMBA device
configuration
intended for use with LEON2 only, LEON3 uses the AMBA Plug&Play information.
3.6.4
GRLIB GRETH 10/100 Ethernet MAC
Select GRLIB_GAISLER_GRETH to enable the 10/100 Ethernet MAC.
The Ethernet MAC address of the GRETH MAC can be edited directly from the GUI. The address is made out of
an unique 6 byte sequence. Byte 0 is the most significant byte. The Ethernet hardware address can be found by
running /sbin/ifconfig on a UNIX machine.
3.6.5
GRLIB OpenCores 10/100 Ethernet MAC
OpenCores 10/100 Ethernet MAC modified for the AMBA bus included in GRLIB can be used by enabling the
driver under “Leon3 AMBA / Vendor Opencores“.
The Ethernet address must be set to an unique 6-byte network identifier.
The driver can force the Ethernet MAC to operate on a 100MHz signalling frequency by setting “Set MII to
100mb”.
3.6.6
SMC 91C111 10/100 Ethernet MAC
After enabling “Networking support” from the “General setup” sub menu the SMC driver can be enabled under
“Network device support”. The base address, IRQ and Ethernet address is configurable. The Ethernet address must
be unique on the network.
The base address and the IRQ number can be found by examining the hardware set up of the target board, typically
LINUX-SNAPGEAR
20
found in the user manual or the schematics.
3.6.7
GRLIB VGA text frame buffer support
The VGA text frame buffer make it possible to output text onto a standard monitor. The programming interface
used to access the AMBA VGA graphics controller is called frame buffer. The frame buffer has hardware device
drivers called frame buffer drivers, the Gaisler VGA controller has a frame buffer driver that can be included into
the kernel from the AMBA configuration menu, but first frame buffer support needs to be enabled. Enable
“Console support” and “Frame buffer” under “General setup”, this makes the “VGA support” able to select.
3.6.8
GRLIB GRPS2 PS/2 interface/keyboard
Illustration 3.15: General setup, console on frame
buffer
The PS/2 driver is dependent on the VGA driver, see the section above on how to include the VGA driver. The
main purpose of the PS/2 driver is to provide the ability to interface a keyboard. Both the PS/2 driver and the PS/2
keyboard driver must be enabled to be able to use the keyboard. The keyboard supported is an AT keyboard.
Illustration 3.16: AMBA PS/2 driver
3.7
Applications included in ROMFS
Apart from the Linux kernel the SnapGear RAD environment consist of applications in the snapgear-pxx/user
directory that can be included into the root file system. The root file system is a read only file system that will be
copied and decompressed into RAM during the boot process.
Custom applications can be easily integrated into the directory structure and SnapGear. The steps involving adding
custom applications is described in a separate chapter.
From the main SnapGear GUI one can make a third GUI pop up after the main SnapGear GUI closes. This is
similar to what was earlier described for the Linux kernel. One simply selects “y” at “Customize Vendor/User
Settings” under “Kernel/Library/Defs Selection” and press “Quit and Save”.
BusyBox is a small footprint replacement for traditional UNIX core applications such as ls, find, mount etc.
BusyBox is highly configurable and can be configured from the BusyBox sub menu as shown below.
LINUX-SNAPGEAR
21
Illustration 3.17: SnapGear application configuration main menu
Since SnapGear supports both the 2.0.x and the 2.6.x kernels and some of the applications needs certain kernel
interfaces, they may only be compiled for one of the kernels. A typical example of this is the flash support in
Linux, from Linux 2.4 and onwards a new interface called MTD (memory technology devices) has been
introduced. Linux 2.0 lacks the MTD interface and therefore cannot run applications that depend upon the MTD
interface. Flash utilities can be found under “Flash Tools”.
Illustration 3.19: Flash Tools, MTD utilities
3.8
Illustration 3.18: BusyBox configuration
Template configurations
The “Template configurations” from the SnapGear main menu are provided as an source of examples. It contains
prepared Linux kernel, boot loader and SnapGear application configurations. However it does not include setting
and script files such as inittab and rcS.
Some of the prepared configuration files has been created for a certain template design. The template designs can
be found in the design directory in GRLIB. These configuration files has been used to generate the images found in
ftp://ftp.gaisler.com/gaisler.com/anonftp/linux/images.
It is also possible to add custom configurations easily by creating a directory under
vendor/gaisler/target/templates/config_dir and putting the snapgear-pxx/.config into the config_dir named
vendor.config and snapgear-pxx/linux-x.x.x/.config named linux.config. The configuration files will automatically
be copied into their respective directory upon selection. The template name config_dir may not contain '-'
characters.
LINUX-SNAPGEAR
4
22
BUILDING SNAPGEAR
After configuring the kernel and the applications it is possible to compile and build the SnapGear LEON Linux
distribution. There are two very important options passed to the build scripts, the FPU and SPARCV8 options found
in “Gaisler/Leon2/3/MMU options”.
Disabling the FPU makes the compiler replace the FPU instructions with software routines that calculates the
answer without needing a FPU. The compiler is run with the argument -msoft-float.
SPARC v8 processors have support for hardware integer multiplier/divider through the instructions MUL and DIV
instructions whereas SPARC v7 hasn't. LEON is a highly configurable processor, it can be compiled with or
without hardware integer multiplier support. To make the compiler generate code without MUL and DIV
instruction select “n” for the v8 option. The compiler will generate code compatible with SPARC v7 if started with
-mcpu=v7.
SnapGear is configured and compiled with:
make xconfig
make dep
make
#
#
#
#
config GUI
only Linux 2.0.x needs this
compile kernel, libraries, boot loader, applications
and make images.
The resulting image produced during the build stage is put in snapgear-pxx/images.
Image
Function
image.dsu
RAM image, with partial boot loader
$ grmon nb
grmon> load image.dsu
grmon> run
image.flashbz
Compressed Flash/PROM Image, with complete boot loader.
$ grmon -nb
grmon> flash erase 0 0x00300000
grmon> flash load image.flashbz
grmon> run 0
image.tsim
TSIM LEON simulator image, if MMU is used TSIM must also support MMU.
$ tsim-leon3
tsim> load image.tsim
tsim> run
Table 4.1: Images available
The images can be downloaded and run using GRMON as shown in table 4.1. Be sure to invoke GRMON with the
-nb option so that Linux can take care of traps instead of having GRMON stop the execution.
LINUX-SNAPGEAR
5
23
ADDING CUSTOM APPLICATIONS
Custom applications can be added into the SnapGear projects in several ways, the simplest ways is to add the source
code to the already prepared custom directory, snapgear-pxx/user/custom. It is also rather easy to modify the menu
of the SnapGear Application menu and add a new application to the GUI. It also possible to copy a binary compiled
outside of the SnapGear distribution folders. This chapter shows the simplest possible alternative, adding an
application to the user/custom directory.
5.1
Creating an application
A simple application that print out the number of arguments it was invoked is saved to user/custom/args.c:
#include <stdio.h>
int main(int argc, char *argv[]){
printf("%s: you passed %d arguments\n",argv[0],argc);
return 0;
}
5.2
Setting up compilation directives
For the application to be compiled one must add it to user/custom/Makefile. The Makefile may be edited as
follows.
Add these 4 lines:
EXEC9 = args
OBJS9 = args.o
$(EXEC9): $(OBJS9)
$(CC) $(LDFLAGS) -o [email protected] $(OBJS9) $(LDLIBS$([email protected]))
Add $(EXEC9) to the end of the all statement:
all: $(EXEC1)...$(EXEC5) $(EXEC6) $(EXEC8) $(EXEC9) INSMODEXE
5.3
Including application to file system
From the “Core Applications” it is possible to enable custom applications, the make utilities will enter the
user/custom directory and compile it as described by user/custom/Makefile.
Illustration 5.1: Custom applications
LINUX-SNAPGEAR
6
24
DEBUGGING LINUX-2.6 AND APPLICATIONS
This section discusses different debugging methods used when debugging Linux 2.6.x userspace applications and
the kernel itself.
GRMON is documented in detail in the GRMON manual available at http://www.gaisler.com/doc/grmon.pdf.
When debugging with GRMON the SPARC v8 Architecture manual may come in handy for instruction definition
and the SPARC assembler conventions used by the C-compiler. The SPARC v8 manual is available at
http://gaisler.com/doc/sparcv8.pdf.
GRLIB IP core documentation is very use full when debugging the kernel and writing new drivers, it can be found
at http://gaisler.com/products/grlib/grip.pdf.
GDB documentation is available at http://sourceware.org/gdb/documentation.
6.1
Debugging symbols
In order to translate assembler instructions into C-code, debugging symbols and an application that can read
debugging symbols are needed. The application sparc-linux-objdump part of the binutils package provided with
the toolchain can provide us with information about compiled applications (ELF-binaries).
Debug symbols is made by GCC (sparc-linux-gcc) during compile time when at least one of the flags -g, -g3,
-ggdb, -gstabs are given. The debug symbols enlarges the output binary, but the debug symbols can be removed stripped - with the sparc-linux-strip utility prior to usage. An example of how the debugging information can be
created, viewed and removed:
$
$
$
$
$
sparc-linux-gcc -g3 userapp.c -o userapp
sparc-linux-objdump -S userapp > userapp.S
sparc-linux-objdump -x userapp > userapp.x
sparc-linux-strip -s userapp
less userapp.S
#
#
#
#
#
create app and syms
deasm binary
list sections
remove syms
view output
Debuggers can read the debug information directly from the binary making some of the steps above unnecessary.
The GDB server run on the target, later discussed, does not need debug information, to save space the binary is
stripped with sparc-linux-strip.
Debugging information can be enabled in SnapGear from the "Application Configuration/Debug Builds/build
debugable applications".
6.2
Debugging the kernel
In practice, hardware debug support of some kind is needed when debugging the kernel. It is possible to debug the
kernel using various other methods such as inserting printk calls in the kernel code or using the /proc filesystem.
See the chapter "Debugging Techniques" in "Linux Device Drivers" for more information about debugging
techniques. However these methods are rather time consuming and may change the behaviour and the execution
path. Using a hardware controlling debugger gives the user a completely new way of controlling and monitoring the
execution. Hardware debuggers such as GRMON vastly accelerates the development process. It is possible to read
and manipulate both processor and core registers, walk the MMU page set up, view cache content, list previous
instructions (instruction trace) just to list a few.
The kernel's addresses are static and can be known on before hand whereas multiple user space
applications/threads may have the same virtual address making it impractical in many cases to use hardware
debuggers. Using a software debugger like GDB run natively or a GDB server acting as a server for remote GDB
connections is preferred when debugging userspace applications.
LINUX-SNAPGEAR
6.2.1
25
Configuring GRLIB for kernel debugging
It is assumed that hardware breakpoints/watchpoints and the instruction trace buffer have been enabled in the
GRLIB xconfig during system configuration. Depending on the complexity of the problem to be debugged the
number of breakpoints and the trace buffer length to select may vary. In the template design of the GRXC3S-1500
board the trace buffer can be enabled from "Processor/Debug Support Unit/Instruction trace buffer" and hardware
breakpoints from "Processor/Integer Unit/Hardware watchpoints" in GRLIB xconfig (cd designs/leon3-grxc3s1500; make xconfig).
GRMON can verify the debugging support available by running the command 'info sys', below is a design with 2
hardware breakpoints (2 hwbp) and a 128 instruction deep trace buffer (itrace 128).
$ grmon -jtag
grmon> info sys
...
02.01:004
Gaisler Research
LEON3 Debug Support Unit (ver 0x1)
ahb: 90000000 - a0000000
AHB trace 128 lines, stack pointer 0x43fffff0
CPU#0 win 8, hwbp 2, itrace 128, V8 mul/div, srmmu, lddel 1,
GRFPU-lite
icache 1 * 1 kbyte, 32 byte/line
dcache 1 * 1 kbyte, 32 byte/line
...
6.2.2
Using GRMON
GRMON can be used to debug the Linux kernel, it is primarily an assembler debugger but it is C-symbol aware.
Symbols created by gcc when compiling C code with the -g flag are automatically loaded by GRMON after a
successful load file command, but is also possible to load symbols manually by issuing the command symbol file.
The symbols last loaded are matched first.
During the image creating process in SnapGear (make) the image/ directory is populated with various images:
image, image.dis, image.dsu. The image.dsu is to be loaded into RAM and run, image contain the debug
information of the Linux kernel's virtual addresses and image.dis is a plain text file containing the disassembly of
image.
Starting GRMON with the -nb flag is essential so that Linux can handle traps correctly. The trace buffer can be
enabled by the command 'tm both' and later listed by inst.
Breakpoints trigger when the processor fetches an instruction at the given breakpoint address. Hardware
breakpoints are inserted with 'hbreak address' or 'hbreak symbol' . Inserting breakpoints with break instead hbreak
causes GRMON to insert an instruction (ta 1). Hardware breakpoints is preferred when working with virtual
addresses or debugging non writeable areas. GRMON stop the processor from executing further when a breakpoint
is reached, the exact state can be observed and manipulated. Breakpoints triggers on addresses the processor
executes, in this case virtual addresses.
The watchpoints implemented in GRLIB have support for stopping the processor when an address is being accessed
by the software, all variants if the instructions ld or st are supported. As with hardware breakpoints watchpoints
trigger on the address the processor accesses before MMU translation, thus virtual addresses is to be used when
debugging the Linux kernel and its applications with GRMON. Watchpoints need hardware assistance to work, this
cannot be done in software.
The architecture independent starting point of the kernel is at start_kernel, at this point the kernel is executing in
virtual address space.
6.2.3
GRMON Example: debugging the Linux kernel
Below is an example of how the first call to printk can be debugged. By setting a hardware breakpoint on printk the
processor halts after the save instruction has been executed. Viewing the INS registers one can inspect the
arguments passed to the printk function. See SPARC v8 manual for SPARC calling conventions. From the printk
C-prototype we know that the first argument must hold a pointer to a format string, thus i0 register holds a pointer
to a string.
LINUX-SNAPGEAR
26
The register content can be viewed by the command reg. From the output of reg one can see that i0 is 0xF0227510.
Listing the memory, with vmem, around the virtual address 0xF0227510 reveals that the argument passed to printk
was "PROMLIB: Sun Boot Prom Version %d Revision %d".
A virtual address can easily be translated to a physical address by doing a "MMU page table walk" with the
GRMON command walk. In the example below the virtual address 0xF0227510 is translated into 0x40227510 by
the MMU. Listing the memory content, this time with mem instead of vmem, confirms that the memory content is
the same for the physical address as the virtual address.
By looking at the previous 20 instructions of the trace buffer it is easy to see that the instruction call is executed two
instructions before entering printk. As expected the call address is the address of printk. In the delay slot or is
executed. Searching for 0xf0031e18 in image.dis tells us that the caller is prom_init, from the string passed to
printk is seems reasonable.
As printk processes the string for output it must access the characters at some point or another, that point can be
found be setting a watchpoint at a character address. To demonstrate the watchpoint functionality the processor is
stopped when accessing the character S in the string. A watchpoint it set to 0xF0227519(S). As the execution
continues it can be observed that the processor is stopped at the space character, the character just before S, this is
because watchpoints must be aligned to a 32-bit boundary, GRMON does this for us.
The GRMON command bt, short for backtrace, show the current call history, from it one can see that prom_init
called printk which called vprintk and so on.
LINUX-SNAPGEAR
27
$ grmon -jtag
grlib> tm both
combined instruction/AHB tracing
grlib> lo image.dsu
section: .stage2 at 0x40000000, size 10240 bytes
section: .vmlinux at 0x40004000, size 3670272 bytes
total size: 3680512 bytes (226.5 kbit/s)
read 5814 symbols
entry point: 0x40000000
grlib> symbol image
read 5805 symbols
entry point: 0xf0004000
grlib> hbreak printk
grlib> run
breakpoint 1
printk (0xf0031e1c)
grlib> reg
0:
1:
2:
3:
4:
5:
6:
7:
INS
F0227510
00000000
00000000
F0000C7C
00000000
00000000
F000FF38
F0266124
psr: F3401FE6
pc: f0031e1c
npc: f0031e20
grlib> dis
f0031e10
f0031e14
f0031e18
f0031e1c
f0031e20
f0031e24
f0031e28
f0031e2c
f0031e30
f0031e34
f0031e38
f0031e3c
f0031e40
f0031e44
f0031e48
f0031e4c
LOCALS
F0399000
40000400
00000000
00000000
00000000
00000000
00000000
00000000
OUTS
F02275E0
00000000
00000000
00000140
00000000
00000001
F000FED0
F02666BC
GLOBALS
00000000
00000002
F31010E3
F0000D94
F0237000
00000000
F000E000
F0000C7C
wim: 00000001
tbr: F0004050
mov %i0, %o0
st %i1, [%fp + 0x48]
0xf0031e10
81c3e008
01000000
9de3bf98
90100018
f227a048
f427a04c
f627a050
f827a054
fa27a058
40000004
9207a048
81c7e008
91e80008
9de3bf58
113c0e2d
d2022000
y: 00000000
retl
nop
save %sp, -104, %sp
mov %i0, %o0
st %i1, [%fp + 0x48]
st %i2, [%fp + 0x4c]
st %i3, [%fp + 0x50]
st %i4, [%fp + 0x54]
st %i5, [%fp + 0x58]
call 0xf0031e44
add %fp, 72, %o1
ret
restore %o0, %o0
save %sp, -168, %sp
sethi %hi(0xf038b400), %o0
ld [%o0], %o1
grlib> vmem 0xF0227510
40227510 50524f4d 4c49423a
40227520 74205072 6f6d2056
40227530 64205265 76697369
40227540 61766169 6c61626c
2053756e
65727369
6f6e2025
65000000
20426f6f
6f6e2025
640a0000
00000000
PROMLIB: Sun Boo
t Prom Version %
d Revision %d...
available.......
LINUX-SNAPGEAR
28
grlib> walk 0xF0227510
Tablewalk: (f0)(8)(27)
+ctx(0):40002000 ctx->4000241
+region(f0):400027c0 region->400007e
segment->400007e
page->400007e
= 40227510(pte:400007e)
grlib> mem
40227510
40227520
40227530
40227540
0x40227510
50524f4d 4c49423a
74205072 6f6d2056
64205265 76697369
61766169 6c61626c
grlib> inst 20
time
address
9303794 f02666d4
9303806 f02666d8
9303807 f02666dc
9303808 f02666e0
9303819 f02666e4
9303820 f02666e8
9303833 f02666ec
9303845 f02666f0
9303850 f02666f4
9303851 f0266724
9303861 f0266728
9303862 f026672c
9303900 f0266114
9303925 f0266118
9303944 f026611c
9303955 f0266120
9303965 f0266124
9303973 f0266128
9303983 f0031e18
9303990 f0031e1c
2053756e
65727369
6f6e2025
65000000
20426f6f
6f6e2025
640a0000
00000000
PROMLIB: Sun Boo
t Prom Version %
d Revision %d...
available.......
instruction
result
cmp %o0
[00000000]
bne 0xf0266700
[00000000]
mov 320, %o3
[00000140]
sethi %hi(0xf0399000), %o0 [f0399000]
ld [%o0 + 0x3c0], %o2
[00000000]
sethi %hi(0xf0227400), %o0 [f0227400]
orcc %o2, %o1
[00000000]
be 0xf0266724
[00000000]
or %o0, 0x1e0, %o0
[f02275e0]
nop
[00000000]
ret
[f0266728]
restore
[00000000]
ld [%l0 + 0x34c], %o0
[f0000c7c]
ld [%o0 + 0x4], %o1
[00000000]
ld [%l1 + 0x354], %o2
[00000000]
sethi %hi(0xf0227400), %o0 [f0227400]
call 0xf0031e18
[f0266124]
or %o0, 0x110, %o0
[f0227510]
save %sp, -104, %sp
[f000fed0]
mov %i0, %o0
[trapped]
grlib> watch 0xF0227519
grlib> cont
watchpoint 1
vsnprintf + 0x68 (0xf010edb0)
grlib> reg
0:
1:
2:
3:
4:
5:
6:
7:
INS
F038B000
00000400
F0227518
F000FF80
00000000
00000000
F000FDC0
F010F348
psr: F3901FE3
pc: f010edb0
npc: f010edb4
LOCALS
00000000
F038B3F8
00000000
F038AFF8
00000000
00000000
00000000
00000000
OUTS
0000003A
0000003A
FFFFFFFF
F00001D4
00000000
00000000
F000FD48
F01109B8
GLOBALS
00000000
00000002
F3401FE5
F0000D94
F0237000
00000000
F000E000
F0000C7C
wim: 00000001
tbr: F0004050
ldub [%i2], %o1
sll %o1, 24, %o0
grlib> vmem 0xF0227518 0x10
40227518 2053756e 20426f6f
74205072
6f6d2056
y: 00000000
Sun Boot Prom V
LINUX-SNAPGEAR
6.3
29
Debugging userspace applications
Debugging user space applications is different from kernel debugging. One can still use GRMON the same way as
for kernel debugging but is only effective in simpler debugging cases. When debugging userspace applications a
native GDB debugger, executing on the LEON target, may be used to debug applications using the serial console
for input. This is similar to debugging PC applications and not described here. The CPU may be heavily loaded
since GDB share the CPU with the application, also application sources and debug binaries are required at the target
when debugging natively.
For targets having a serial port or a network connection it is possible to debug Linux applications remote. The
debugging interface is presented on a PC offloading the target CPU. The most common solution is to use a GDB
TCP/IP server (gdbserver) exporting control to a remote PC running GDB (sparc-linux-gdb) compiled for target
binaries (SPARC).
GRMON must be started with the flag -nswb in order to instruct GRMON not to interfere with the debugging
process or else software breakpoints result in GRMON taking over CPU, note that this is only needed when
debugging userspace applications not when debugging the kernel.
6.3.1
Setting up a debugging environment
Together with the sparc-linux toolchain (version 1.0.1 and onwards) comes bin/sparc-linux-gdb and bin/sparclinux-insight. sparc-linux-gdb is GDB built for PC Linux able to read/debug SPARC Linux binaries.
The Data Display Debugger (DDD) is a graphical front end for GDB, it is available in any standard distribution.
DDD is optional as GDB can be used effectively in text mode.
The GDB TCP/IP server can be built within SnapGear by enabling it from the Application Configuration Utility
under "Miscellaneous Applications/gdbserver".
With GRMON version 1.1.23 the flag -nswb was added, it clears bit 3 (BS) in the DSU control register so that
GRMON won't interfere with the software breakpoints (ta 0x1).
6.3.2
GDB introduction
GDB is a debugger able to debug multiple languages including C and SPARC assembly. In this text GDB is used to
access a GDB server running on the target board debugging. GDB needs
●
Binaries of the application and optionally the used libraries
●
Sources used to compile the binaries
●
The IP number of the target, can be found with "target$ /sbin/ifconfig"
●
gdbserver running on the target (part of SnapGear)
●
The gdbserver also need the binary but with or without debug information. Debug information is not
needed by the GDB server.
depending on what to debug. The libraries and their source code may not be needed. When debugging LibC the
sources and libraries are of course needed.
See the previous section "Debugging symbols" on how to create binaries with debugging information.
6.3.2.1
Adding additional source search paths
Sometimes GDB can not list the C-code, that may be due to missing debug information (not even searching for C-
LINUX-SNAPGEAR
30
code) or it can not find the source files mentioned in the debug information. It is not recommended to change the
source files after the debug binary has been created.
If the binary is compiled on the same computer running sparc-linux-gdb one need not to add additional paths
normally. The path information is coded into the binary, however when running GDB on a different computer than
the build host the path information is invalid and it may be needed to add additional search paths. Search paths can
be added with the '-d dir1:dir2:dir3' flag passed to GDB.
6.3.3
Starting GDB server on target
Assuming that the compilation of gdbserver has been successful and that GRMON has been started with the flag
-nswb the GDB server can be started with the following command at the target:
target$ gdbserver :1234 app arg1 arg2
Where 1234 is the TCP/IP port, app is the application to be debugged and arg1 and arg2 are the arguments to app.
Note: The debugged application does not have to include any debugging information. It can be stripped.
6.3.4
Connecting with GDB to gdbserver
Below is an example of how to start GDB on the PC and connecting to the target, the target board IP address is
assumed to be 192.168.0.52, the TCP port 1234.
pc$ cd sources
pc$ sparc-linux-gdb ./app_with_debug_info
(gdb) target remote 192.168.0.52:1234
6.3.5
GDB example usage
Configuring SnapGear with glibc-from-compiler, linux-2.6.21.1, with gdbserver,
pc$ make xconfig
Building SnapGear,
pc$ make
The binary application is recompiled manually with debugging symbols,
pc$ file romfs/bin/testsin
romfs/bin/testsin: ELF 32-bit MSB executable, SPARC, version 1 (SYSV),
dynamically linked (uses shared libs), stripped
pc$ cd user/custom
pc$ sparc-linux-gcc -lm -g3 testsin.c -o testsin-g
pc$ file testsin-g
testsin-g: ELF 32-bit MSB executable, SPARC, version 1 (SYSV),
dynamically linked (uses shared libs), not stripped
The serial console is connected to a terminal emulator such as minicom or hyper terminal with 38400baud 8N1.
Running the image images/image.dsu from RAM on target LEON board using GRMON,
pc$ grmon -jtag -nb -nswb
grmon> lo images/images.dsu
grmon> run
On the terminal emulator connected to LEON Linux target,
target$ gdbserver :1223 /bin/testsin
Process /bin/testsin created; pid = 28
Starting GDB on the PC and testing that GDB finds the sources,
LINUX-SNAPGEAR
31
sparc-linux-gdb testsin-g
GNU gdb 6.4.0.20051202-cvs
Copyright 2005 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.
details.
Type "show warranty" for
This GDB was configured as "--host=i686-pc-linux-gnu --target=sparclinux"...
(gdb) list
1
#include <math.h>
2
#include <stdlib.h>
3
4
int main(int argc,char **argv) {
5
double i = 0.00;
6
int j = 0;
7
printf("testsin:\n");
8
while (i < 100.0) {
9
double v = sin(i);
10
printf("float:sin(%f)=%f\n",i,v);
Connecting GDB to the remote gdbserver,
(gdb) tar rem 192.168.0.80:1223
Remote debugging using 192.168.0.80:1223
0x50001c20 in ?? ()
Setting breakpoints,
(gdb) break 7
Breakpoint 1 at 0x10440: file testsin.c, line 7.
(gdb) break 10
Breakpoint 2 at 0x10494: file testsin.c, line 10.
Running application with cont instead of run since application already has been started and paused on the target
side,
(gdb) cont
Continuing.
Breakpoint 1, main (argc=1, argv=0xefbd1ed4) at testsin.c:7
7
printf("testsin:\n");
Stepping one C-line with next, as the printf call is executed the output appears on the target console,
(gdb) next
8
while (i < 100.0) {
Running the loop four times,
LINUX-SNAPGEAR
32
(gdb) cont
Continuing.
Breakpoint 2, main (argc=1, argv=0xefbd1ed4) at testsin.c:10
10
printf("float:sin(%f)=%f\n",i,v);
(gdb) cont
Continuing.
Breakpoint 2, main (argc=1, argv=0xefbd1ed4) at testsin.c:10
10
printf("float:sin(%f)=%f\n",i,v);
(gdb) cont
Continuing.
Breakpoint 2, main (argc=1, argv=0xefbd1ed4) at testsin.c:10
10
printf("float:sin(%f)=%f\n",i,v);
(gdb) cont
Continuing.
Breakpoint 2, main (argc=1, argv=0xefbd1ed4) at testsin.c:10
10
printf("float:sin(%f)=%f\n",i,v);
(gdb) cont
Continuing.
Breakpoint 2, main (argc=1, argv=0xefbd1ed4) at testsin.c:10
10
printf("float:sin(%f)=%f\n",i,v);
(gdb) print i
$1 = 5
The output on the LEON target terminal is now,
Sash command shell (version 1.1.1)
/> gdbserver :1223 /bin/testsin
Process /bin/testsin created; pid = 26
Remote debugging using :1223
testsin:
float:sin(0.000000)=0.000000
float:sin(1.000000)=0.841471
float:sin(2.000000)=0.909297
float:sin(3.000000)=0.141120
float:sin(4.000000)=-0.756802
One can change the execution flow by manipulating variables within the loop. The integer i set to 90, the
breakpoints are removed and the application are continued to is endpoint,
(gdb) set variable i=90
(gdb) delete
Delete all breakpoints? (y or n) y
(gdb) cont
Continuing.
Program exited normally.
Finally the LEON target's console output was,
LINUX-SNAPGEAR
33
Sash command shell (version 1.1.1)
/> gdbserver :1223 /bin/testsin
Process /bin/testsin created; pid = 26
Remote debugging using :1223
testsin:
float:sin(0.000000)=0.000000
float:sin(1.000000)=0.841471
float:sin(2.000000)=0.909297
float:sin(3.000000)=0.141120
float:sin(4.000000)=-0.756802
float:sin(90.000000)=-0.958924
float:sin(91.000000)=0.105988
float:sin(92.000000)=-0.779466
float:sin(93.000000)=-0.948282
float:sin(94.000000)=-0.245252
float:sin(95.000000)=0.683262
float:sin(96.000000)=0.983588
float:sin(97.000000)=0.379608
float:sin(98.000000)=-0.573382
float:sin(99.000000)=-0.999207
exit testsin
Child exited with retcode = 0
Child exited with status 0
GDBserver exiting
/>
6.3.6
DDD and GDB
DDD is a graphical frontend run alongside with GDB. DDD launches GDB and provides us with direct access to
the GDB console and the ability to display information about the debugged application. DDD is compiled for PC
Linux and uses a socket protocol to connect to the local GDB (sparc-linux-gdb). GDB is responsible for SPARC
specific operations and therefore DDD needs not to be recompiled for SPARC binaries.
pc$ ddd --debugger sparc-linux-gdb app_debug
(ddd-gdb) target remote target:port
(ddd-gdb) b main
(ddd-gdb) cont
Most Linux distributions distribute DDD as a precompiled binary package, in many cases it is installed by default.
See http://www.gnu.org/software/ddd for more information about DDD.
6.3.7
Insight
Insight comes with version 1.0.1 or later of sparc-linux toolchains. Insight is a graphical debugging interface on top
of GDB. It is started by running sparc-linux-insight.
See http://sourceware.org/insight for more information on how to use insight.
6.4
Using NFS to simplify application updates
During development one i often needed to update the application and rerun it. Using the standard procedure is very
inefficient, rebuild the image, reprogram the flash and reboot. With GRMON the flash i not needed to be updated,
the image can be run directly from RAM saving a great deal of time. However, there are occasions where even
rebooting may be troublesome. Sharing the files over NFS may be a good alternative to rebooting and rebuilding all
SnapGear. Only the development files/binaries need to updated, not all SnapGear.
LINUX-SNAPGEAR
34
Perhaps the easiest way is to create a script file in the SnapGear image which mounts NFS after boot, yet another
way is to edit the rcS file in vendors/leon3mmu/rcS to mount automatically on start up.
See your distribution manual how to set up an NFS sharer, normally you edit /etc/exports and run 'exportfs -r' .
The same problem is faced in the chapter "Root Filesystem over Ethernet using NFS".
Good practice is to mount the exported directory on to the server PC to verify that the NFS share is set up correctly
(even if this works it may be wrong). After network and NFS server has been set up on the target one can simply
mount the NFS share into an empty local directory with:
target$ mkdir /nfs
target$ mount -t nfs -o rw,nolock workstation:/export/leonshare
6.5
Console output when debugging
The console is of great help when debugging applications, but often it limits the execution speed or put in another
way the console can not output enough information. There are ways to speed up the console output, two techniques
are discussed here.
6.5.1
Redirecting output to NFS share
The console output can be redirected to a file by the shell. The shell simply connects the application's stdout to a
file. For this to work the shell needs to support redirection, only tiny shells doesn't support redirection. It is also
possible to redirect stderr to file. See 'man stdin' and 'man bash' for more info. Embedded storage is often limited
in size and speed and would fill up the flash device rapidly. Instead a NFS server can be used to place the execution
log over the network.
$ mount -t nfs -rw logserver:/export/logs /nfslogs
$ app > 2>&1 /nfslogs/out_10sep2007.log
6.5.2
TELNET over TCP/IP network
Logging onto the target with telnet is an easier solution, all that has to be done is to set up a telnet server on the
target. A telnet server (telnetd) is available in SnapGear from the SnapGear Application configuration utility under
Network Applications.
pc$ telnet target
username: root
pass: *****
Welcome to SPARC LEON3 Linux
[email protected]# app
LINUX-SNAPGEAR
7
35
PS/2 KEYBOARD AND VGA CONSOLE
This is an example of how to configure the Linux 2.6.x kernel, set up init and it's settings file inittab, the boot
loader's parameters, and the kernel command line.
The software can be run on a GR-XC3S-1500 Spartan-1500 board available at www.gaisler.com.
7.1
Hardware configuration
The hardware set up is based on the template design of GR-XC3S-1500 and modified as in table 7.1.
Hardware / Controller
Function
LEON3 with MMU, HW MUL/DIV and FPU
SPARC v8 Processor with memory protection logic and
floating point unit.
GRVGA
SVGA controller
GRPS2
PS/2 controller connected to keyboard
Table 7.1: Hardware in addition to GR-XC3S-1500 template design
7.2
Configuring the boot loader and main SnapGear options
Start SnapGear main GUI and configure as in table 7.2:
$ make xconfig
Name
Value
Vendor / Product Selection
Vendor
Gaisler
Gaisler Product
Leon3mmu
Gaisler Leon2/3/mmu options
SPARC v8
Yes
FPU support
Yes
Clock frequency
40MHz
Baudrate
38400
In memory root filesystem
initramfs
Kernel command line
console=tty0 video=grvga:[email protected],8,307200
Kernel/Library/Defaults Section
Kernel Version
Linux 2.6.x
Libc Version
Glibc-from-compiler
Customize Kernel Settings
Yes
Customize Vendor/User Settings
Yes
Table 7.2: Boot loader configuration
7.3
Configuring the Linux kernel
Apart from the default configuration support for frame buffer on Gaisler VGA controller and input driver for
Gaisler PS/2 controller is enabled, as in table 7.3.
LINUX-SNAPGEAR
Name
36
Function
Graphics Support
FB
Frame buffer sub system
FB_GRVGA
Frame buffer driver for GRVGA controller
FRAMEBUFFER_CONSOLE
Frame buffer console support
FONTS
Compiled in fonts
FONT_8x16
8x16 Font support
LOGO
Add boot logo support
LOGO_LINUX_CLUT224
Include a coloured Linux logo
Input devices
SERIO_LEON3
Driver for Gaisler PS/2 controller
SERIO_LEON3_KEYB_IRQ
The IRQ number of assigned to the PS/2 controller
connected to the keyboard
INPUT_KEYBOARD
Keyboard sub system
KEYBOARD_ATKBD
AT-keyboard driver
Table 7.3: Kernel configuration
7.4
Configuring SnapGear Applications
Below is a description of how the SnapGear ROMFS can be configured:
Name
Function
BusyBox
Init
First application that gets started after boot
Init: use inittab
Make init read /etc/inittab for settings
Table 7.4: SnapGear configuration
7.5
Building the kernel and applications
Building the kernel, libraries and applications can be done as follows:
$ make
7.6
Setting up /etc/inittab
Init reads the /etc/inittab, line after line at start up and launches the /etc/rc.sh system initialization script and
spawns applications on each console as set up. Inittab can be created by typing:
LINUX-SNAPGEAR
37
$ cat << EOM > romfs/etc/inittab
# System initialization script
::sysinit:/etc/rc.sh
# Make serial terminal have a console
ttyS0::respawn:/bin/sh
# Make consoles appear via frame buffer
tty1::respawn:/bin/sh
tty2::respawn:-/bin/sh
tty3::askfirst:-/bin/sh
EOM
rc.sh can be typed in as follows:
$ cat << EOM > romfs/etc/rc.sh
#!/bin/sh
mount -t proc none /proc
mount -t sysfs none /sys
mount -t devpts devpts /dev/pts
hostname sparky
/sbin/ifconfig lo up 127.0.0.1 netmask 255.0.0.0
route add 127.0.0.1 dev lo
EOM
For the new script to be able to run one must add execution permission to it:
$ chmod +x romfs/etc/rc.sh
7.7
Building again with inittab and rc.sh
Since changes has been made only to the file system one can rebuild the images without having to recompile
kernel, libraries and applications.
$ make image
After building the images the image can be found at images/image.dsu. Note that image.flashbz does not function
correctly since the boot loader's SDRAM and flash settings hasn't been set up properly.
7.8
Running on hardware
The far most simplest method of testing the image is to run it using GRMON as follows. Depending on what debug
interface is available the parameters to GRMON may differ, see GRMON documentation for details:
$ cd images
$ grmon -jtag -nb
grmon> load image.dsu
grmon> run
When everything is working as planned the connected monitor will first display a small penguin, kernel messages
and then launch a shell on tty1, tty2 and the serial terminal (ttyS0). It is possible to switch between tty1-3 by
pressing ALT+F1/F2/F3 at the connected PS/2 keyboard.
LINUX-SNAPGEAR
8
38
ROOT FILE SYSTEM OVER ETHERNET USING NFS
Often during development it is favourable to use NFS as root file system as it is a tedious process reprogramming
the flash each time a change is made, and also there is no need in rebuilding the romfs image. Settings can be
preserved after system reboot.
Setting up root over NFS involves two steps, installing the NFS server on the PC and configuring the LEON Linux
image. The NFS server is assumed to be installed and therefore not described other than with an example entry
applied to /etc/exports, it make the NFS server export the root file system to the LEON board.
8.1
Setting up NFS server on PC
As previously mentioned the NFS server is assumed already to be installed, however an entry to /etc/exports
sharing the root file system should be added similar to what described. Adding the following line to the /etc/exports
makes the server share the /export/rootfs directory. The NFS server is forced to reread the settings file by invoking
“exportfs -r”.
/export/rootfs 192.168.0.0/255.255.255.0 (rw,async,no_root_squash,insecure)
In this example we export /export/rootfs which is a SnapGear ROMFS file system. The directory is exported to any
computer using the IP address 192.168.0.X.
$ su
# mkdir /export
# cp -rpd ~daniel/snapgear-pxx/romfs /export/rootfs
# echo “/export/rootfs 192.168.0.0/255.255.255.0
(rw,async,no_root_squash,insecure)” >>/tmp/exports
# exportfs -r
# exit
$
It is also possible to base the root file system on other distributions for example on splack or creating one from
scratch. A common source of failure is that the initialization scripts, run during boot, assumes that the file system is
of ext2 or ext3 type, but it's not. This can usually easily be removed.
8.2
Configuring the boot loader and main SnapGear options
The important thing when running the root file system over NFS is to set up the kernel boot parameter to point to
the NFS share to be used as root and the network settings such as IP address, netmask and gateway.
To avoid building the image with the unused ROMFS root file system the “In-memory root filesystem” option from
the “Gaisler Leon2/3/mmu options” is set to “none”. The settings in the SnapGear application GUI does not effect
the build process once “In-memory root filesystem” is set to “none”.
An example configuration is outlined in table 8.1, the PC NFS server has the IP address 192.168.0.20 and the target
LEON board is configured to 192.168.0.203.
LINUX-SNAPGEAR
39
Name
Value
Vendor / Product Selection
Vendor
Gaisler
Gaisler Product
Leon3mmu
Gaisler Leon2/3/mmu options
SPARC v8
Yes
FPU support
Yes
Clock frequency
40MHz
Baudrate
38400
In-memory root filesystem
NONE
Kernel command line
console=ttyS0,38400 root=/dev/nfs
nfsroot=192.168.0.20:/export/rootfs,nfsvers=3
ip=192.168.0.203:192.168.0.20:192.168.0.1:255.255.255.0:grxc3
s_daniel:eth0:
Kernel/Library/Defaults Section
Kernel Version
Linux 2.6.x
Customize Kernel Settings
Yes
Table 8.1: SnapGear main configuration
8.3
Configuring the Linux kernel
In addition to the default settings of the Linux 2.6.x kernel add the features described by table 8.2.
Name
Function
Networking
NET
Networking support
INET
TCP/IP protocol
IP_PNP
IP settings can be set from kernel command line
UNIX
UNIX domain sockets, needed by Debian's logging facilities.
Device Drivers / Network device support
NETDEVICES
Enables the network device driver interface
General machine setup / GRLIB: AMBA / Gaisler
GRLIB_GAISLER_GRETH
Add Gaisler Ethernet 10/100/1000 driver.
Select a unique Ethernet address in the MSB and LSB fields.
Device Drivers / Block Devices
BLK_DEV_INITRD
Disable ROMFS RAM root file system
File systems / Network file systems
NFS_FS
Network file system support
NFS_V3
Support for version 3 of the NFS protocol
ROOT_NFS
Add support for root file system over NFS
Table 8.2: Kernel configuration for NFS root FS
8.4
Building kernel and boot loader
As previously described,
LINUX-SNAPGEAR
40
$ make
The image will be available for download to the target board from images/image.dsu.
8.5
Running on hardware
The far most simplest method of testing the image is to run it using GRMON as follows. Depending on what debug
interface is available the parameters to GRMON may differ, see GRMON documentation for details:
$ cd images
$ grmon -jtag -nb
grmon> load image.dsu
grmon> run
The NFS share can be tested by changing or adding files at the PC side and watch as they appear on the LEON
Linux target.
LINUX-SNAPGEAR
9
41
ROOT FILE SYSTEM OVER ETHERNET USING ATA OVER ETHERNET
A network root filesystem can also be provided using ATA-Over-Ethernet on Linux 2.6. This setup requires two
steps: creating an ATAoE server that exports a block device containing the root filesystem, and configuring the
LEON to boot using the exported ATAoE root block device.
ATAoE block devices may be formatted with an arbitrary filesystem. For example, well-supported Linux
filesystems such as ext3 or xfs may be used. The ATAoE server must be on the same Ethernet Local Area Network
as the LEON.
9.1
Setting up ATAoE Server
The ATAoE server, vblade, can be run on any supported Unix system, including Linux and FreeBSD. Vblade can
be obtained at http://aoetools.sourceforge.net .Installation documentation is included with vblade, although typing
'make' followed by 'make install' (as root) should be sufficient for Linux systems.
With vblade installed, the next step is to configure the block device that will be exported by vblade. The block
device may be in one of two formats: a flat file or an actual block device. We will first show how to configure a
block device for vblade, as this is the easier of the two options. This example formats the block device /dev/hdb
using ext3, and then copies a SnapGear root filesystem to /dev/hdb.
#
#
#
#
mke2fs -j /dev/hdb
mount /dev/hdb /mnt/tmp
cp -rpd ~daniel/snapgear-pxx/romfs /mnt/tmp
umount /mnt/tmp
Now we will show how to configure a flat file to be used as a vblade-exported block device. In this example, we
create a 4GB flat file /rootfs.img formatted with ext3 containing a SnapGear root filesystem.
#
#
#
#
#
#
dd if=/dev/zero of=/rootfs.img bs=1024 count=4000000
losetup /dev/loop0 /rootfs.img
mount /dev/loop0 /mnt/tmp
cp -rpd ~daniel/snapgear-pxx/romfs /mnt/tmp
umount /mnt/tmp
losetup -d /dev/loop0
Make sure that the vblade-exported root block device has been unmounted (and in the case of a flat file, that losetup
-d has detached the file from any loopback devices) before running vblade. Now run vblade:
# vbladed eth0 0 0 eth0 /path/to/root-device
In this example, vblade is run with shelf 0 slot 0 over Ethernet network interface eth0, exporting the device at /path/
to/root-device. To use the devices set up by our examples, we could replace /path/to/root-device with /dev/hdb or
/rootfs.img, respectively. The shelf and slot numbers are used for naming purposes – they allow the server to run
multiple vblades. As long as each block device is exported with a different shelf or slot number, the client can
select which of the exported block devices it wishes to access. In our examples we will use shelf 0 slot 0 as we are
not using multiple vblade servers.
The ATAoE server is now operational and its output will be sent via syslog to /var/log/messages. Note that because
vblade operates over Ethernet and not TCP/IP, it does not bind to a port, nor is it accessible from any machine
outside of the local LAN. For more information on ATA over Ethernet, see linux-2.6.x/Documentation/aoe/aoe.txt.
9.2
Configuring the boot loader and main SnapGear options
To mount a root filesystem using ATAoE, we must use Linux 2.6.x with an initramfs initial root filesystem. This
filesystem should contain only the klibc utility, kinit. This utility will automatically parse the options we pass to the
Linux kernel, mount the ATAoE block device, and switch the root filesystem over to the filesystem on the ATAoE
mount.
LINUX-SNAPGEAR
42
An example configuration is outlined in the following table. The ATAoE server has slot and shelf number 0, and
the target LEON board is configured to 192.168.0.203. Note that the ip= option may be omitted, as ATAoE requires
only Ethernet and will function even if the LEON does not have a valid IP address. However, LEON system using
ATAoE typically enable TCP/IP.
Name
Value
Vendor / Product Selection
Vendor
Gaisler
Gaisler Product
Leon3mmu
Gaisler Leon2/3/mmu options
SPARC v8
Yes
FPU support
Yes
Clock frequency
40MHz
Baudrate
38400
In-memory root filesystem
Initramfs
Init pathname
/bin/kinit
Kernel command line
console=ttyS0,38400 root=/dev/etherd/e0.0
ip=192.168.0.203:192.168.0.20:192.168.0.1:255.255.255.0:grxc3
s_daniel:eth0:
Kernel/Library/Defaults Section
Kernel Version
Linux 2.6.x
Customize Kernel Settings
Yes
Customize Vendor/User Settings
Yes
Libc version
None
9.3
Configuring the Linux kernel
In addition to the default settings of the Linux 2.6.x kernel add the features described by the following table.
Name
Function
Networking
NET
Networking support
INET
TCP/IP protocol
IP_PNP
Disable IP PnP – kinit will provide this functionality for us
Device Drivers / Network device support
NETDEVICES
Enables the network device driver interface
General machine setup / GRLIB: AMBA / Gaisler
GRLIB_GAISLER_GRETH
Add Gaisler Ethernet 10/100/1000 driver.
Select a unique Ethernet address in the MSB and LSB fields.
Device Drivers / Block Devices
BLK_DEV_INITRD
Disable INITRD support
ATA_OVER_ETH
Add ATA Over Ethernet block device support
File systems / Network file systems
EXT3_FS
9.4
Ext3 journalling filesystem support
Configuring the vendor/user applications
At a bare minimum, klibc/kinit support must be enabled for ATAoE root to work. Furthermore, we recommend
LINUX-SNAPGEAR
43
disabling all other applications, as there will be no need for them. This is because kinit immediately switches the
root filesystem to the ATAoE block device at startup, and does not invoke or require any other applications or
libraries. Configuring a root filesystem with only klibc/kinit, while not strictly required, will result in a much
shorter build time and a much smaller initial root filesystem.
Name
Function
Core Applications
Custom tests app
Disable custom tests app
Shell Program
Other
Network Applications
arp
Disable arp
portmap
Disable portmap
tcpd
Disable tcpd
Busybox
Busybox
Disable Busybox
Miscellaneous Configuration
RAMFS Image
None
klibc
build klibc
Enable klibc support
kinit
Enable kinit
Statically link all binaries
(Optional) Should result in a slightly smaller size for kinit – there's only one
binary so static linking actually doesn't waste space in this case
9.5
Building kernel, boot loader, and kinit
As previously described,
$ make
The image will be available for download to the target board from images/image.dsu.
9.6
Running on hardware
The simplest method of testing the image is to run it using GRMON as follows. Depending on what debug interface
is available the parameters to GRMON may differ, see GRMON documentation for details:
$ cd images
$ grmon -jtag -nb
grmon> load image.dsu
grmon> run
LINUX-SNAPGEAR
10
44
ROOT FILE SYSTEM ON COMPACTFLASH USING XILINX SYSTEM ACE
A root file system can be provided using a CompactFlash card and Xilinx' System ACE Compact Flash solution. To
access the System ACE controller the Leon3/GRLIB system needs to contain the GRACECTRL core and the Linux
kernel needs to include the Xilinx System ACE block device driver.
10.1
Setting up the root filesystem
The CompactFlash device may be arranged as any normal root file system and the device may be formatted with an
arbitrary filesystem. For example, well-supported Linux filesystems such as ext3 or xfs may be used. When
building the system the user should make sure that devices under the /dev/ directory are properly created and that
/etc/fstab is set up correctly.
At the time of writing the Xilinx System ACE block device has not been assigned a number by LANANA and is
accessed via a major number 254, which is allocated for experimental use. To be able to access a CompactFlash
device and its three first partitions it is recommended that the following devices are created:
#
#
#
#
mknod
mknod
mknod
mknod
10.2
<rootfs
<rootfs
<rootfs
<rootfs
mount
mount
mount
mount
point>/dev/xsysace b 254 0
point>/dev/xsysace1 b 254 1
point>/dev/xsysace2 b 254 2
point>/dev/xsysace3 b 254 3
Configuring the boot loader and main SnapGear options
An example configuration is outlined in the following table. The root file system is mounted from the device with
major number 254 (which is the Xilinx System ACE block device) and partition 1. To mount the root file system
from the second partition, the root argument on the kernel command line should be changed to root=254:2..
Name
Value
Vendor / Product Selection
Vendor
Gaisler
Gaisler Product
Leon3mmu
Gaisler Leon2/3/mmu options
SPARC v8
Yes
FPU support
Yes
Clock frequency
40MHz
Baudrate
38400
In-memory root filesystem
none
Init pathname
/sbin/init
Kernel command line
console=ttyS0,38400 root=254:1 rw
Kernel/Library/Defaults Section
Kernel Version
Linux 2.6.x
Customize Kernel Settings
Yes
Customize Vendor/User Settings
No
Libc version
None
Table 10.1: SnapGear options
10.3
Configuring the Linux kernel
In addition to the default settings of the Linux 2.6.x kernel add the features described by the following table.
LINUX-SNAPGEAR
Name
45
Function
General Setup
BLK_DEV_INITRD
Disable INITRD support
Device Drivers / Block Devices
XILINX_SYSACE
Enable Xilinx SystemACE support
File systems / Network file systems
Select the file systems that needs to be supported.
Table 10.2: Linux kernel configuration
10.4
Running on hardware
The simplest method of testing the image is to run it using GRMON as follows. Depending on what debug interface
is available the parameters to GRMON may differ, see GRMON documentation for details:
$ cd images
$ grmon -jtag -nb
grmon> load image.dsu
grmon> run
The CompactFlash device driver will not finish its initialization if a CompactFlash card is not inserted, or detected,
during boot up.
LINUX-SNAPGEAR
11
46
RUNNING GRLINUX/SPLACK FROM AN ATA HARD DISK
Splack is a distribution based on the SPARC version of slackware, it is prepared especially for demonstrating the
ATA interface. The GRLinux include tested bitfiles for various boards, a precompiled kernel with the appropriate
features to run the root file system from a hard drive, and a temporary image for preparing the hard drive with
splack. The splack distribution was compiled with support for FPU and integer multiplier.
The kernel needs support for Gaisler ATA controller when accessing the root file system from an ATA disk or
compact flash.
11.1
Installing the kernel onto flash
The precompiled kernel is loaded onto the boot PROM of the board, GRMON can be used to program the
PROM/Flash.
$ grmon -jtag
grmon> flash erase all
grmon> flash load image.flashbz
The boot loader is the first to be executed, it copies the kernel into main memory and before it starts the execution
of the kernel, the kernel command line string is made available. The kernel needs to know what partition on the
disk to search for the file system, that can be provided through the kernel command line:
root=/dev/hda1
The example boot line above make the kernel search the first partition on the first disk for a valid file system. In
principle the configuration is similar to a NFS root file system as described earlier, instead of telling the kernel the
IP address of the server and the location of the share on that server, the kernel is fed with hard disk and partition
number.
11.2
Preparing the hard drive
The preparation of the hard drive can be made using a PC computer, or as described below by using the target
hardware. Another image besides the flash image has been create for a single purpose, preparing the hard drive
from the target hardware using NFS to access the splack distribution. This image is called image-nomount.dsu.
Booting the Linux kernel can be done as follows:
$ grmon -jtag -nb
grmon> load image-nomount.dsu
grmon> run
In order to copy the splack distribution onto the disk one must be able to access it. In this example NFS is used to
access the splack distribution:
# mount -t nfs 192.168.0.32:/home/daniel /mnt/nfs
In order for the kernel to read from the hard disk one should create a partition table and a partition on the hard drive
with a file system which the kernel can read the root file system from, EXT2 typically (type 0x83). One can edit
the partition table and create new partitions with fdisk, it can be started as follows:
LINUX-SNAPGEAR
47
# fdisk /dev/hda
n
p
o
w
add a new partition
print the partition table
create a new empty DOS partition table
write table to disk and exit
When a partition has been created it is possible to format it using the mke2fs utility, and copy the splack distribution
to the newly created file system:
# mke2fs /dev/hda1
# mount -t /dev/hda1 /mnt/hd
# cd /mnt/hd
# tar -zxpf /mnt/nfs/splack-1.0.tar.gz
# cd ..
# umount /mnt/hd
# umount /mnt/nfs
11.3
Running splack
If not already connected, connect the hard drive to the target board. Make sure a terminal emulator is connected to
the serial port at 38400 baud. The first boot after power up will fail on the lattice board because the DDR RAM
needs to be manually reset. Push the reset button and the kernel should boot and mount the CF disk.
The root password is set to "qwerqwer".
One must always terminate the system using the 'shutdown -h' command before switching of the power. This will
sync the file systems, otherwise data can get corrupted or lost. Before it is okay to turn power off (or reset it) a
message will be printed at the console:
Shutdown: hda
Power down.
LINUX-SNAPGEAR
12
48
INSTALLING DEBIAN 3.1 ON LEON LINUX
Debian is a widely used Linux distribution freely available at www.debian.org. Debian is available platforms,
including SPARC. Debian binaries expect FPU and hardware integer multiplier to be available. For further
installation information refer to the installation manual at Debian's homepage.
Normally, when installing Debian, installation diskettes or compact discs are used to boot Debian Installation
program. However, installing Debian on LEON involves a different approach where it is installed from an UNIX
host directly onto a disk or a NFS share. The Installation procedure is split in two stages, first Debian binaries are
downloaded and verified from the internet the second stage involves running the binaries on a LEON target board
doing the “real” installation and configuration.
In this example Debian is installed onto a NFS share that will later become the root file system of the LEON board.
The LEON board is a low-cost GR-XC3S-1500 board from www.gaisler.com.
12.1
Preparing LEON target
Preparing the LEON target to run the installation binaries is done similar to a NFS root file system set up as
described previous, the important applications and kernel configuration is listed in two tables below. The LEON
system consist of a kernel that is using a NFS share with BusyBox as it's root file system.
The BusyBox root file system is exported from a PC as /export/busybox and the Debian root file system is placed
in /export/busybox/debian.
Name
Function
Networking
NET
Networking support
INET
TCP/IP protocol
IP_PNP
IP settings can be set from kernel command line
Device Drivers / Network device support
NETDEVICES
Enables the network device driver interface
General machine setup / GRLIB: AMBA / Gaisler
GRLIB_GAISLER_GRETH
Add Gaisler Ethernet 10/100/1000 driver.
Select a unique Ethernet address in the MSB and LSB fields.
Device Drivers / Block Devices
BLK_DEV_INITRD
Disable ROMFS RAM root file system
File systems / Network file systems
NFS_FS
Network file system support
NFS_V3
Support for version 3 of the NFS protocol
ROOT_NFS
Add support for root file system over NFS
Table 12.1: Kernel configuration for Debian and install program
Name
Function
Core Applications
Bash
Shell to parse Debian scripts
BusyBox
ar, cat, chmod, chown, chroot, find, grep, gunzip, head, init, ln, md5sum, mkdir, mv, printf, rm, sed, sleep, sort,
sync, tar, touch, tr, umount, wc
Table 12.2: Root file system mounted via NFS
LINUX-SNAPGEAR
12.2
49
Installing Debian installation utility to PC and LEON target
The utility that is able to download, extract and install Debian is called debootstrap. It can be downloaded from
Debian's homepage. Since debootstrap is run from the PC as well as the LEON target two versions are needed to
be downloaded, the SPARC version for the LEON and the i386 version for the PC. Unless of course running on
Solaris.
It is assumed that the Debian package manager is not available. Download and install debootstrap on a non-debian
machine as root:
$
$
$
$
$
$
$
BUSYBOXLINUX=/export/busybox_rootfs
DEBOOT=debootstrap_0.2.45-0.2_i386.deb
TMPDIR=/tmp/debinst
ARCH=sparc
INSTDIR=$BUSYBOXLINUX/debian
DISTNAME=sarge
MIRROR=ftp://ftp.se.debian.org/debian
$ mkdir -p $TMPDIR/work
$ cd $TMPDIR
$ wget http://ftp.se.debian.org/debian/pool/main/d/debootstrap/$DEBOOT
$ cd work
$ ar -xf $TMPDIR/$DEBOOT
$ cd /
$ tar -zxvf $TMPDIR/work/data.tar.gz
Download and install debootstrap to LEON BusyBox root file system:
$ DEBOOT=debootstrap_0.2.45-0.2_sparc.deb
$ mkdir -p $TMPDIR/work_sparc
$ cd $TMPDIR
$ wget http://ftp.se.debian.org/debian/pool/main/d/debootstrap/$DEBOOT
$ cd work_sparc
$ ar -xf $TMPDIR/$DEBOOT
$ cd $BUSYBOXLINUX
$ tar -zxvf $TMPDIR/work_sparc/data.tar.gz
The two debootstrap applications should now be working both for the LEON target and the PC.
12.3
Downloading Debian binaries using PC
Downloading Debian binaries to PC:
$ mkdir -p $INSTDIR
/usr/sbin/debootstrap --download-only --arch $ARCH $DISTNAME $INSTDIR
$MIRROR
12.4
Installing Debain binaries from LEON target
The LEON target is able to access the binaries downloaded by the PC in the previous step by entering the /debian
directory. Invoking the Debian installation utility debootstrap with the correct parameters makes it continue the
installation process, this step may take some time to complete:
LINUX-SNAPGEAR
50
/usr/sbin/debootstrap sarge /debian
12.5
Adding a serial console to Debian
Even though the system console may be the serial terminal no shell is given unless explicitly telling init to launch
one. This can be done as previously described by editing the /etc/inittab in the Debian root file system. Add or
uncomment:
T0:234:respawn:/sbin/getty -L ttyS0 38400 vt100
Getty will present us with a login prompt at serial channel 0. One must make sure there is a valid serial terminal
device node for getty to open in /dev/ttyS0. If the device is missing it can be created by mknod:
# cd $INSTDIR/dev
# mknod ttyS0 c 4 64
In case of trouble booting Debian it may be of good practice to change the run level to 1 or 2 in inittab before
booting:
# The default runlevel.
id:2:initdefault:
12.6
Changing root directory and booting Debian
Before booting the kernel command line needs to be updated to reflect the new root file system. Enter the “make
xconfig” GUI and update the kernel command line to include the debian directory:
nfsroot=192.168.0.20:/export/busybox_rootfs/debian
Make the configuration, rebuild the image and run the image:
$
$
$
$
$
12.7
make xconfig
make image
grmon -jtag -nb
load images/image.dsu
run
Adding a telnet server to Debian
During the development process it often comes in handy with a telnet terminal. The telnet terminal isn't limited by
the bandwidth as the serial terminal, making it to an excellent choice when running or debugging new applications.
The easiest way of installing applications in Debian is using the apt-get utility. The apt-get utility can be setup to
fetch binaries from close mirror servers by editing /etc/apt/sources.list. Setting it up on the LEON target:
# echo deb ftp://ftp.se.debian.org/debian stable main contrib non-free
> /etc/apt/sources.list
# apt-get update
Installing telnet server can be done as follows:
# apt-get install telnetd
It is generally an good idea to have a look in the /etc/inetd.conf and verifying that telnetd is correctly configured.
To make the telnet server appear on the network inetd may need to be restarted to reread it's configuration file,
sometimes it is enough sending inetd it the SIGHUP signal.
LINUX-SNAPGEAR
12.8
51
Installing X.org X11 Server
The graphical X server is normally operated using keyboard and mouse. See the chapter "PS/2 and VGA" on how
to setup the monitor and PS/2 keyboard. The peripherals and monitor/GRVGA is setup in /etc/X11/xorg.conf
installed with apt-get.
Installing the graphical X server, fbset (a frame buffer utility), X fonts and xterm terminal emulator is similar to
installing the telnet server in the previous section:
#
#
#
#
apt-get
apt-get
apt-get
apt-get
install
install
install
install
xserver-xorg
xfonts-base
fbset
xterm
Configure the X server by editing /etc/X11/xorg.conf.
After setting up the X server properly it is possible to start the server with extra debug output by adding the option verbose [level]:
$ X -verbose 3
LINUX-SNAPGEAR
13
52
USING THE I2C DEVICE INTERFACE TO INITIALIZE A DVI TRANSMITTER
This section describes how to use the I2C device interface to initialize a Chrontel 7301C DVI transmitter. The
description is relevant if running a design with an external DVI transmitter that needs to be initialized and it is also
relevant as an example on how to interact directly with I2C devices.
13.1
Kernel configuration
The Linux kernel distributed with SnapGear does not contain support for initializing a CH7301C DVI transmitter
and the transmitter often needs to be initialized before the correct video output can be obtained. To resolve this
issue, a user space program which talks directly to the transmitter can be used. To be able to communicate directly
with the DVI transmitter, the following selections must be made in the Linux kernel configuration:
Name
Function
Device Drivers / I2C support
I2C
I2C support
I2C_CHARDEV
I2C device interface
IP_PNP
IP settings can be set from kernel command line
Device Drivers / I2C support / I2C Hardware Bus support
I2C_OCORES
OpenCores I2C Controller
Table 13.1: Linux kernel configuration selections for I2C device interface support
After the kernel has been rebuilt, the system has support for accessing I2C devices via the /dev/i2c-<devnum>
files. The device files are created by the SnapGear scripts, if an external root file system is used the devices may
have to be created.
13.2
DVI transmitter initialization
The listing in section 13.3 contains a program that will initialize a Chrontel 7301C DVI transmitter. This
transmitter is placed on, among others, the Xilinx ML50x development boards. The application's default values are
suitable for the ML505, ML506 and ML507 boards. The ML501 may require a change in the sample delays. It is
recommended to put the application in your distribution's init scripts, so that it is run on each boot. Please consult
your distribution's documentation for a description on how to do this.
The application always opens /dev/i2c-0. Depending on the system configuration and start sequence this may not be
the I2C adapter that connects to the DVI transmitter. To dynamically select the correct transmitter an application
should first probe the contents under /sys/class/i2c-dev/.
The register addresses and their values are kept in pairs ({address, value}) in the configtable array. Some of the
affected registers are listed in table 13.2 below. Please refer to the DVI transmitter datasheet for a complete
description of the registers.
Register address
Register name
Comment
0x1d
Input clock register
The four least significant bits in this register contains a
field to adjust the delay used when latching data.
0x1f
Input data format register
Default value is suitable for leon3-xilinx-ml50x designs.
This value may need to be changed if another colour
depth is desirable.
0x21
DAC control register
Note that the define DVI in the application selects if the
device should be initialized for a VGA or DVI output.
Table 13.2: Chrontel CH7301C registers affected by example application
LINUX-SNAPGEAR
13.3
53
Example application
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <linux/i2c-dev.h>
/* Define DVI if you want DVI output */
/* #define DVI */
static char configtable[11][2] = {{0x1c, 0x04},{0x1d, 0x45},
{0x1e, 0xc0},{0x1f, 0x9a},
#ifdef DVI
{0x21, 0x00},
#else
{0x21, 0x09},
#endif
{0x33, 0x08},{0x34, 0x16},{0x36, 0x60},{0x48, 0x18},{0x49, 0xc0},
{0x56, 0x0}
};
int main(void)
{
int i, file, adapter_nr = 0;
char filename[20];
int i2c_addr = 0x76; /* DVI transmitter address */
sprintf(filename, "/dev/i2c-%d", adapter_nr);
if ((file = open(filename, O_RDWR)) < 0) {
printf("Could not open device: %s\n", strerror(errno));
exit(1);
}
if (ioctl(file, I2C_SLAVE, i2c_addr) < 0) {
printf("Could not set slave address: %s\n", strerror(errno));
exit(1);
}
for (i = 0; i < 11; i++) {
if (write(file, configtable[i], 2) != 2) {
printf("error: i2c register write %d failed!\n", i);
exit(1);
}
}
return 0;
}
13.4
Building the application
The application can be compiled with natively with (to cross-compile, use sparc-linux-gcc and add the -static flag
for portability):
gcc -Wall -o i2c_dvi_init i2c_dvi_init.c
The required define I2C_SLAVE is defined in the kernel header file i2c-dev.h. Since this file may be missing on
the build system it can be convenient to work around the missing define with:
gcc -Wall -DI2C_SLAVE=0x0703 -o i2c_dvi_init i2c_dvi_init.c
LINUX-SNAPGEAR
14
54
SUPPORT
For support, contact the Gaisler Research support team at [email protected]
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement