Bureaucrats, dave_user, Administrators
4,650
edits
Changes
→Idle configurations
Please note that SBC Lynx platform is extremely flexible{{efn|Consider for example the expandability provided by J45/J52 interfaces.}}, so it is virtually impossible to test for all possible configurations and applications on the market. The use cases here presented should cover most of real-world scenarios. However actual customer's application might require more power than values reported here or customer's use case may be differ significantly with respect to the ones here considered. Therefore, '''application-specific requirements have always to be taken into consideration''' in order to size power supply unit and to implement thermal management properly.
==Use case #1: headless system==
<div id="PSUBlockDiagramHeadless">The following picture shows a simplified block diagram of the measurement system.</div>
[[File:SBCLynx-simplified-PSU-headless.png|thumb|center|600px|Simplified block diagram of the measurement system]]
Two custom power probes have been used:
*power probe #1 is connected to the input power rail (12V) supplying the entire system
*power probe #2 is connected to the input power rail of the PMIC NXP PF3000 (nominal voltage is 3.75V); this, in turn, powers the processor subsystem.
=== Heavy load configurations===
Measurements have been performed on the following platform:
* SBC Lynx rev.A (S-XUBB0110C1R)
* System software: XUELK 1.1.0
** U-Boot: U-Boot 2015.04-xuelk-1.1.0 (Nov 25 2016 - 16:43:19), Build: jenkins-XUELK_U-Boot-8
** Kernel: Linux sbc-lynx 3.14.52-xuelk-1.1.0-00026-g88e5473 #36 SMP PREEMPT Tue Dec 13 15:20:14 CET 2016 armv7l GNU/Linux
*root file system is stored on NAND flash
* processor's LDO is enabled (required to perform voltage scaling).
The following table shows the summary result of data collected at different checkpoints.
{|class="wikitable" style="text-align: center;"
|-
!Checkpoint
!Board power consumption<br>[mW]
!Processor subsystem power consumption<br>[mW]
|-
| U-Boot prompt || 330 || 282
|-
| Linux prompt [1]|| 268 || 230
|-
| StressAppTest || 840 || 721
|-
| Complete Stress Test || 834 || 725
|-
|}
Additional notes and reference:
* U-boot is set run processor at 396MHz
* At Linux prompt, a fixed processor clock frequency of 528MHz has been set (via <code>userspace</code> governor)
* <code>StressAppTest</code> application is used to stress CPU and DDR3L RAM (https://github.com/stressapptest/stressapptest)
* Complete Stress Test includes the following tests:
** <code>StressAppTest</code>
** USB host: read/write/verify operations on a USB memory stick
** USB otg tested as Host: read/write/verify operations on an USB memory stick
** uSD card: read/write/verify operations
** Ethernet: <code>iperf</code> TCP test running
=== Idle configurations ===
* SBC Lynx rev.A (S-XUBB0110C1R)
* System software: XUELK 1.1.0
** U-Boot: U-Boot 2015.04-xuelk-1.1.0 (Nov 25 2016 - 16:43:19), Build: jenkins-XUELK_U-Boot-8
** Kernel: Linux sbc-lynx 3.14.52-xuelk-1.1.0-00026-g88e5473 #36 SMP PREEMPT Tue Dec 13 15:20:14 CET 2016 armv7l GNU/Linux
* root file system stored in NAND flash
* CAN transceiver not present
===Generic idle===
In this case the default governor (<code>interactive</code>) is used.
Ethernet controller and PHY are active (but cable is disconnected).
<pre>
root@sbc-lynx:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
interactive
</pre>
{|class="wikitable" style="text-align: center;"
|-
!Board power consumption ([[#PSUBlockDiagramHeadless|probe #1]])<br>[mW]
!Processor subsystem power consumption ([[#PSUBlockDiagramHeadless|probe #2]]) [1]<br>[mW]
|-
| 206||177
|-
|}
===Optimized idle===
In this case the <code>powersave</code> governor is used. Most importantly, Ethernet interface is disabled, as described in i.MX 6UltraLite Power Consumption Measurement application note.<ref name="AN5170">NXP Semiconductors, ''i.MX 6UltraLite Power Consumption Measurement'', Rev. 1, 04/2016</ref> This allows to reduce power consumption significantly because
* processor's peripheral bus can be disabled as well
* external PHY is put in power-down mode.
{|class="wikitable" style="text-align: center;"
|-
!Average board power consumption ([[#PSUBlockDiagramHeadless|probe #1]])<br>[mW]
!Average processor subsystem power consumption ([[#PSUBlockDiagramHeadless|probe #2]])<br>[mW]
|-
| 71 || 63
|-
|}
<pre>
#!/bin/bash
echo 8 > /proc/sys/kernel/printk
ifconfig eth0 down
echo powersave > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
</pre>
===Deep-sleep mode (aka suspend)===
The same test bed described in the [[#Idle configurations|Idle configuration]] section has been used.
First the system has been configured to set up optimized idle mode, as described [[#Optimized idle|here]].
Then ''deep-sleep mode'' has been enabled by issuing the following commands:
<pre>
root@sbc-lynx:~# echo enabled > /sys/devices/soc0/soc.0/2000000.aips-bus/2000000.spba-bus/2020000.serial/tty/ttymxc0/power/wakeup
root@sbc-lynx:~# echo mem > /sys/power/state</pre>
The first command is used to enable the console UART as wake up source.
The following table recaps the power consumptions measured under this condition.
{|class="wikitable" style="text-align: center;"
|-
!Average board power consumption ([[#PSUBlockDiagramHeadless|probe #1]])<br>[mW]
!Average processor subsystem power consumption ([[#PSUBlockDiagramHeadless|probe #2]])<br>[mW]
|-
| 51||43
|-
|}
Ethernet PHY supports several power-management modes. The most aggressive is the ''slow-oscillator mode''. At the time of this writing, Linux kernel does not support this mode. The ''power-down mode'' is used instead. If ''slow-oscillator mode'' were implemented, about 7mW would be spared.
<br />
<br />
==Use case #2: system equipped with LCD panel==
<div id="PSUBlockDiagram">The following picture shows a simplified block diagram of the measurement system.</div>
[[File:SBCLynx-simplified-PSU.png|thumb|center|400px600px|Simplified block diagram of the measurement system]]
Two custom power probes have been used:
*power probe #2 is connected to the input power rail of the PMIC NXP PF3000 (nominal voltage is 3.75V); this, in turn, powers the processor subsystem.
===Heavy load configurations===Measurements have been performed on the following platform (also denoted as ''testbed1'' in the rest of the document):
* SBC Lynx rev.0 (S-XUBB0000C0R) equipped with a plug-in board for 24-bit RGB LCD interfacing
*LCD p/n: KOE TX11D06vm2Apa (https://www.koe-europe.com/doc/TX11D06VM2APA.pdf)
* System software: [[SBC_Lynx_Embedded_Linux_Kit_AXEL ULite and SBC Lynx Embedded Linux Kit (XUELK)|XUELK 0.9.0]], patched to include 24-bit RGB LCD support
* root file system mounted via NFS over Ethernet connection
* processor's LDO is enabled (required to perform voltage scaling).
The following table shows the summary result of data collected at different checkpoints:
{|class="wikitable" style="text-align: center;"
|-
!Checkpoint
|-
|}
[1] In this condition, Linux kernel spends most of the time in idle state because user space applications and interrupt service routines run for very short periods. However, LCD is turned on (LCD power consumption is about 600mA600mW).
Additional notes and reference:
* U-boot is set to work run processor at 396MHz* At U-boot prompt the LCD interface and circuitry are in turned off state* At Linux prompt, a fixed processor clock frequency of 528MHz has been set (via <code>userspace </code> governor)* All the measures include Ethernet link at 100M, and power requirement for two USB memory sticks and an uSD card* <code>StressAppTest </code> application is used to stress CPU and DDR3 DDR3L RAM (https://github.com/stressapptest/stressapptest)* A 4.3 inches 480x272 LCD is used to test the 24bit parallel video interface output. The LCD backlight is driven by the 12V VIN using an external circuitry at ; brightness is set to 100% brightness
* Complete Stress Test includes the following tests:
** <code>StressAppTest</code>** USB Hosthost: read/write/verify operations on an a USB memory stick** USB otg tested as Host: read/write/verify operations on an USB memory stick** uSD card: read/write/verifyoperations** ETHEthernet: <code>iperf </code> TCP test running at 100Mbps** NAND: stress test with <code>mtd </code> kernel modules.
===Idle configurations===Some power-constrained applications can't afford to make use of [[#Deep-sleep mode (aka suspend)|deep-sleep mode]] when the system "has nothing to do", because wake up process takes may take too long to complete. In such situations aggressive implementation of so-called idle mode can come to help.Basic assumption is that the system spends most of the time in a system an idle condition (that is there are no user applications ready to run nor interrupt requests to serve). Two idle configurations have been tested, detailed in the following sections: generic idle and system idle. System idle is the same nomenclature used NXP official documentation (specifically processor's data sheet<ref name="IMX6ULIEC">Freescale Semiconductor, ''i.MX 6UltraLite Applications Processors for Industrial Products Data Sheet'', Rev. 1, 04/2016</ref> and AN5170 application note<ref name="AN5170">NXP Semiconductors, ''i.MX 6UltraLite Power Consumption Measurement'', Rev. 1, 04/2016</ref>).
Measurements have been performed on the following platform (also denoted as ''testbed2'' in the rest of the document):
* SBC Lynx rev.0 (S-XUBB0000C0R)
* System software: [[SBC_Lynx_Embedded_Linux_Kit_AXEL ULite and SBC Lynx Embedded Linux Kit (XUELK)|XUELK 0.9.0]]
* UBIFS root file system mounted from Flash NAND
* processor's LDO is enabled (required to perform voltage scaling)
* Some HW modifications are required hardware optimizations have been implemented to obtain the minimum minimize power consumption:** CAN Transceiver SN65HVD232 (U4) is removed, beaceuse it doesn't have low power functionalitytransceiver has been turned off** All all the unneeded pull-ups on signals in the VDD_SNVS_IN voltage domain are have been removed** LCD_DATA14 RS232 transceiver is connected to MPUART0_ON signal in order to shutdown RS232 transceivervia unused processor's GPIO* Power monitors: two custom current probes have *RS485 polarization network has been usedremoved.**power probe #1 is connected to the input power rail at 12V====Generic idle====**power probe #2 is connected to the input power rail of the PMIC NXP PF3000; In this, in turn, powers processors subsystem, as depicted in TBD Two idle configurations have been tested, detailed in case the following sections. Nomenclature is the same used in the processor's data sheetdefault governor (<ref name="IMX6ULIEC"code>Freescale Semiconductor, ''i.MX 6UltraLite Applications Processors for Industrial Products Data Sheet'', Rev. 1, 04/2016interactive</refcode>) is used.
<pre>
root@sbc-lynx:~# cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
interactive
</pre>
{|class="wikitable" style="text-align: center;"
|-
!Board power consumption ([[#PSUBlockDiagram|probe #1]]) [1],[2]<br>[mW]!Processor subsystem power consumption ([[#PSUBlockDiagram|probe #2]]) [1],[2]<br>[mW]
|-
| 370 [2]||325 [2]
|-
|}
[1] Power '''24MHz active oscillator power consumption is included'''. As the board under test is equipped with iMX6UL revision 1.0, active oscillator is required to implement the fix described by errata ERR009455. Typical consumption of this oscillator is about 20mW. Future revision of the following parts is excluded:*CAN PHY*RS485 polarization network*RS232 and RS485 transceivers*Ethernet PHYboard will be populated with silicon revision 1.1 or newer. Thus active oscillator will be removed. For more details please refer to ''Chip Errata for the i.MX 6UltraLite''<ref name="IMX6ULCE">Freescale Semiconductor, ''Chip Errata for the i.MX 6UltraLite'', Rev. 0.1, 02/2016</ref>.
|-
!Board power consumption ([[#PSUBlockDiagram|probe #1]]) [1],[2]<br>[mW]!Processor subsystem power consumption ([[#PSUBlockDiagram|probe #2]]) [1],[2]<br>[mW]
|-
| 90 || 72
|-
|}
[1] Power '''24MHz active oscillator power consumption is included'''. As the board under test is equipped with iMX6UL revision 1.0, active oscillator is required to implement the fix described by errata ERR009455. Typical consumption of this oscillator is about 20mW. Future revision of the following parts is excluded:*CAN PHY*RS485 polarization network*RS232 and RS485 transceivers*Ethernet PHYboard will be populated with silicon revision 1.1 or newer. Thus active oscillator will be removed. For more details please refer to ''Chip Errata for the i.MX 6UltraLite''<ref name="IMX6ULCE">Freescale Semiconductor, ''Chip Errata for the i.MX 6UltraLite'', Rev. 0.1, 02/2016</ref>.
<pre>
#!/bin/bash
</pre>
The system automatically switch between low-power idle enters to and normal exits from system idle states mode when needed:
<pre>
root@sbc-lynx:~# ./idle.sh
</pre>
It is worth to remember that the use of <code>powersave</code> governor '''has a drawback in terms of system reactivity''', because processor is relatively slow to get out of the idle condition. This can lead to phenomena such as the UART RX FIFO overrun, shown in the following box{{efn|This is the same issue described [[Linux_and_interrupt_latency_(Axel)#A_real-word_case:_UART_RX_FIFO_overrun|here]].}}. Here is an In this example of an entire , a relatively long command string has been pasted into the serial console leading to the Rx FIFO overrun issueterminal:
<pre>
root@sbc-lynx:~# imx-uart 2020000.serial: Rx FIFO overrun
</pre>
===Deep-sleep mode (aka suspend)===TBD introThe same test bed described in the [[#Idle configurations|Idle configuration]] section has been used.
The following table recaps the power consumptions measured under this condition.{|class="wikitable" style="text-align: center;"
|-
!Board power consumption ([[#PSUBlockDiagram|probe #1]]) [1]<br>[mW]
!Processor subsystem power consumption ([[#PSUBlockDiagram|probe #2]]) [1]<br>[mW]
|-
| 63 57|| 5147
|-
|}
[1] Power consumption of When entering DSM mode, iMX6UL turns 24MHz external active oscillator off. As the following parts board under test is excluded:*CAN PHY*RS485 polarization network*RS232 and RS485 are in shutdown mode*Ethernet linkequipped with iMX6UL revision 1.0, active oscillator is required to implement the fix described by errata ERR009455. For more details please refer to ''Chip Errata for the i.MX 6UltraLite''<ref name="IMX6ULCE">Freescale Semiconductor, ''Chip Errata for the i.MX 6UltraLite'', Rev. 0.1, 02/2016</ref>.
-----