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→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>
*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)
** 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 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 an idle condition (that is there are no user applications ready to run nor interrupt requests to serve).
** RS232 transceiver is shutdown via unused processor's GPIO
**RS485 polarization network has been removed.
====Generic idle====
In this case the default governor (<code>interactive</code>) is used.
[1] '''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 board 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>.
====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
</pre>
===Deep-sleep mode (aka suspend)===
The same test bed described in the [[#Idle configurations|Idle configuration]] section has been used.