Texas Instruments | Power Management of KS2 Device (Rev. C) | Application notes | Texas Instruments Power Management of KS2 Device (Rev. C) Application notes

Texas Instruments Power Management of KS2 Device (Rev. C) Application notes
Application Report
SPRABX9C – February 2014 – Revised July 2016
Power Management of KeyStone II Devices
ABSTRACT
This application report lists the steps to enable Class 0 Temperature Compensation (Class 0 TC) mode of
SmartReflex™ Subsystem (SRSS) module available on such devices.
For features that apply to various Keystone II devices, see Section 2.
1
2
3
4
Contents
SmartReflex ..................................................................................................................
Device Applicability ..........................................................................................................
Frequently Asked Questions for SRSS Class 0 TC Mode .............................................................
References ...................................................................................................................
1
SmartReflex
1.1
Acronyms
1
4
4
5
Table 1. Acronyms
Acronyms
Definitions
TCI6630K2L,
66AK2L0x,
TCI6638K2K
TCI6636K2H,
66AK2Hxx, 66AK2E0x,
AM5K2E0x
Keystone II architecture Devices from Texas Instruments.
AVS
Adaptive Voltage Scaling
CVDD
Adjustable voltage supply used by core logic on Keystone II devices.
PAPLL
Pll for PA module on device
PSC
Power Sleep Controller on device
MCSDK
Multi Core Software Development Kit
R
Read Only Register
RW
Read/Write Register
SRSS
Smart Reflex Subsystem on device
SRSS Base
Base Address of SRSS module on device
TC
Temperature Compensation
TPS544Bxx
PMBus compatible voltage regulator from Texas Instruments.
VID
SmartReflex VID Value Mapping - Hardware Design Guide for KeyStone II Devices (SPRABV0)
SmartReflex is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
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1
SmartReflex
1.2
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Smart Reflex Class 0
Keystone II devices have Smart Reflex Class 0 operation mode enabled by default. In this mode, the
SmartReflex module determines value for CVDD voltage using adaptive voltage scaling (AVS) to
compensate for variations in performance from die to die, and from wafer to wafer. Adaptive voltage
scaling (AVS) is the adaptation or modification of the supply voltage for a processor voltage-domain given
the process strength.
For more detailed information, see the CVDD section in the Hardware Design Guide for KeyStone II
Devices (SPRABV0).
1.3
Smart Reflex Class 0 With Temperature Compensation Mode
On supported Keystone II devices the voltage on CVDD or AVS rail can be set dynamically based on the
device temperature. Smart Reflex module on these devices needs to be enabled to support this feature.
By default, the Smart Reflex module on these devices is setup for Class 0 mode of operation. To enable
the Class 0 with Temperature Compensation mode, additional steps are needed after device boot. When
this feature is enabled, the Smart Reflex module senses the instantaneous temperature of the device from
on die sensors and determines appropriate voltage for the device. Steps to enable SRSS module for this
mode are mentioned in the next section. Detection of voltage change request and setting the appropriate
voltage are not covered here. MCSDK release supporting this feature would cover enabling, detection as
well as response handling.
A comparison of CVDD voltage with Class 0 temperature compensation enabled is shown in Figure 1. It
shows the reduction is voltage at higher temperatures versus the corresponding voltage value for a Class
0 only mode.
The voltage values and number of steps shown in Figure 1 are only for example purpose. Different device
will have different voltage and number of steps based on its process strength.
Class 0 Temperature Compensation Voltage
1.02
1
Voltage
0.98
Class 0 Only
0.96
0.94
0.92
Class 0 TC
0.9
0.88
35
55
75
95
115
135
Temperature
Figure 1. Class 0 Temperature Compensation Voltage
2
Power Management of KeyStone II Devices
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SmartReflex
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1.3.1
Steps to Enable SRSS Class0 Temperature Compensation Mode
1. Relevant Registers:
The following are registers relevant for the Class 0 TC setup. Perform Read Modify Write and change
only the value of required fields within the registers.
Table 2. Registers Relevant for Class 0 TC Setup
Register Name
SRSS_TEMP_CTL0_REG
Read/Write
Register Width
(Bits)
Base Address
Within SOC
Address Offset Within
Module
Reset Value/
Comments
RW
32
SRSS Base
0x0000 001C
0x0
SRSS_TEMP_STAT0_REG
R
32
SRSS Base
0x0000 0028
0x0
SRSS_TEMP_STAT1_REG
R
32
SRSS Base
0x0000 002C
0x0
VPRM_STATUS0_REG
R
32
SRSS Base
0x0000 0088
0x0
2. Setup Parameters: (Thresholds for temperature, and so forth)
(a) All Keystone II devices have this programmed by default. No additional setup is needed.
3. Enable Temperature Sensors:
Keystone II devices have two on die sensors tm0 and tm1 that can be configured in order to be used
by SRSS in the class 0 TC mode to sense temperature. These can be enabled by writing to
SRSS_TEMP_CTL0_REG’s bits[1:0].
(a) Smart Reflex Sensor Power Domain should be turned on by programming the PSC (Power Sleep
Controller) module.
(b) SRSS_TEMP_CTL0_REG[0] = srss_tm0_en,
Used for Temperature Sensor 0 SRSS_TEMP_CTL0_REG[1] = srss_tm1_en, used for
Temperature Sensor 1
0: Temperature Monitor disabled locally
1: Temperature Monitor enabled locally
(c) PAPLL should be Configured and kept on for sensors to work.
(d) Only one of the two available sensors can be used at a time by the SRSS state machine to initiate
voltage change.
SRSS_TEMP_CTL0_REG[19] = srss_tempm_sel
0: Select tm0 as the source of temperature-comparison used to compare vs threshold points.
1: Select tm1 as the source of temperature-comparison used to compare vs threshold points
All Keystone II devices have this bit programmed by default to 0.
(e) Reading Temperature Value
Enabled sensor’s temperature can be read in Signed two compliment formats in the following
register:
SRSS_TEMP_STAT0_REG[7:0] = srss_tm0_temp
SRSS_TEMP_STAT0_REG[23:16] = srss_tm1_temp
4. Enable SRSS Temperature Compensation mode
(a) Make sure the SRSS state machine is not in State S0 or S1 by reading VPRM_STATUS0_REG
VPRM_STATUS0_REG[2:0] = VID_FSM_STATUS
Reflects the status of the VID FSM posting the voltage change request to the SMPS:
“0x0” FSM in state S0
“0x1” FSM in state S1
(b) The final step is to enable the State machine to be in Class 0 TC mode by the following write:
SRSS_TEMP_CTL0_REG[2] = srss_c0temp_en = 1b1
SR-Class0 temperature compensated
5. Read temperature compensated voltage (VID)
When Class0-TC mode is enabled, the suggested value of the voltage (based on the temperature of
the device) is reflected in the following register field:
SRSS_TEMP_STAT1_REG[29:24] = srss_tempthp_vctl[5:0]
This value is the temperature compensated and calculated SR-Class0 voltage target in the 6-bit VID
interface format.
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Device Applicability
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6. Detecting voltage change request:
(a) Read VID change by monitoring SRSS register
(b) Interrupt triggered
7. Updating the Voltage output of the voltage controller (for example, TPS544Cxx type regulator)
(a) VCNTLID bus
(b) Generic I2C bus
Software support to be added MCSDK 3.1.0 onwards.
2
Device Applicability
Various Keystone II architecture devices support different features offered by Smart Reflex module. Some
devices support only a select few features like allowing instantaneous temperature of device sensors to be
read. Table 3 shows the various devices and SRSS features supported by them. Please note that for
using supported device features appropriate software steps might be needed and refer to relevant
sections in this document to enable those.
Table 3. Supporting Devices
Supporting Devices
TCI6630K2L
66AK2L0x
TCI6638K2K
TCI6636K2H
66AK2Hxx
66AK2E0x
AM5K2E0x
Relevant Sections
SRSS Class 0
Yes
Yes
Yes
Section 1.2
SRSS Class 0 TC
Yes
No
Yes
Section 1.3
Temperature Read
Yes
Yes
Yes
Section 1.3.1 (3)
Feature
3
Frequently Asked Questions for SRSS Class 0 TC Mode
1. Question: What is the voltage change step size when the device crosses a temperature threshold?
Answer: Voltage step sizes are device specific and are preprogrammed in the device. Two different
devices of same ‘Device Type’ may have different voltage step sizes.
2. Question: What is the expected maximum and minimum voltage values?
Answer: Device can request any voltage between the CVDD range mentioned in the device-specific
data sheet. Requested voltage will never exceed this bound.
3. Question: How many temperature threshold/ranges are expected in a device?
Answer: SRSS can support up to five threshold points making it six temperature ranges max.
Threshold points utilized are specific to device and not all threshold points would be necessarily used
by every device.
4. Question: Does every device have the same number of temperature ranges/thresholds and voltage
values?
Answer: Not necessarily, the number of temperature ranges and temperature thresholds can vary
from device to device.
5. Question: Usage of SRSS temperature reading in other applications?
Answer: SRSS temperature sensors are primarily meant to be used by SRSS and not for application
software use. Although the temperature reading from SRSS temperature sensors closely represents
the device temperature the use of these readings in users/application software, precise device
temperature measurement is not recommended.
6. Question: What happens if applied voltage to device does not match the SRSS suggested value?
Answer: When the applied CVDD value does not match the SRSS recommended value, the device
would be out of power spec but still functional as long as the applied voltage is higher or equal to the
SRSS recommended value and is within the range specified for that device.
4
Power Management of KeyStone II Devices
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References
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7. Question: What is expected voltage ramp up time requirement to ensure the silicon function and
performance, minimal or maximal time requirement?
Answer: Supply Max Rise/Fall Time: Applied voltage should reach new value within 10 msec.
Supply Min Rise/Fall Time: >10 µSec
8. Question: Does Smart-Reflex Class0 work as a temperature compensator for DSP core rail in
accordance with the measured DSP temperature, not with the DSP load?
Or, do the temperature values represent the temperature of DSP or ARM core?
Answer: Smart-Reflex Class 0 TC mode takes into account the instantaneous device temperature,
and this instantaneous temperature does not necessarily correspond to temperature of DSP or ARM
core.
9. Question: Do VID values mean the DSP temperature?
Answer: VID values are enumerated voltage values that represent the recommended voltage for
device by the SRSS module of that device. VID to voltage conversion is mentioned in the Hardware
Design Guide for KeyStone II Devices (SPRABV0).
10. Question: What is the expected power saving with SRSS class 0 TC mode?
Answer: In general with SRSS class 0 TC mode enabled, the CVDD voltage at higher temperatures
will be lower than without class 0 TC mode enabled, this should result in power saving at higher
temperature. Exact saving will depend on device and device load.
11. Question: Is it ok to apply fixed voltage before SRSS class 0 TC mode is enabled?
Answer: By default the device will boot is SRSS Class 0 only mode and will request a fixed voltage
value and that should be applied to device until SRSS class 0 TC mode is enabled. As long as device
is supplied with CVDD voltage value higher or equal to the SRSS recommended value and is within
the range of Data Sheet limits, device will not be harmed. Only drawback of not using SRSS class 0
TC is that device might be out of power specification during that duration.
4
References
•
Hardware Design Guide for KeyStone II Devices (SPRABV0)
SPRABX9C – February 2014 – Revised July 2016
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Revision History
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Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from B Revision (January 2016) to C Revision ............................................................................................... Page
•
•
6
Changed K2L to KS2 throughout the document....................................................................................... 1
Updated Table 3 ........................................................................................................................... 4
Revision History
SPRABX9C – February 2014 – Revised July 2016
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