Power management with STM32MP15x and OpenAMP_TTY_echo_wakeup example

[AHayo.1]

Hi,

I did some power measurements with a Joulescope which measures the full power given to the card (no distinction between VDD, VDDCORE, etc.) - we chose this way for first measurements without card's resistors modification.

I mostly followed the same steps as explained in the AN5284 application note.

• For point 3.1 with CoreMark, I've same iterations per seconds and a much higher power measurement which is normal as I measure the full system. But the difference between 1 or 2 core is the same as in the document.
• For point 3.3 with data acquisition : Here again, I have higher power measurement but it's still consistent as the ratio of power reduction is the same than in theorie.

Then I was interested in point 4.3 (various low power modes) but I did get results I don't understand. Know that I changed the /etc/systemd/sleep.conf as explained here and used the systemctl suspend commend for MPU.

• When the card is idle (just powered on, but no program running) : 3060 mW
•  When the card do a for loop : 3160 mW -> ok
• When doing the LP-STOP : 574 mW -> ok
• When doing Standby DDR : 906mW -> ??
• When doing Standby DDR OFF : 1178 mW -> ???

Isn't the Standby supposed to be more power saving than Stop ?

I tried to power measure the OpenAMP_TTY_echo_wakeup example as well :

• card idle : 2640 mW
• First scenario : stopping MCU -> 2620 mW (ok small gain)
• Second scenario ("*delay" & systemctl suspend) : 703 mW
• Third and fourth with Stop : 615mW
• Fifth scenario with Standby : 1191 mW

So should I suppose that Standby is less power saving than Stop ? I though Standby is more power saving because on chapter 4.1 it's written that in standby VDDCORE is off whereas in Stop it's on.

How do I know in which mode I am between Stop, LP-Stop and LPLV-Stop ? Is there some logging about it ? Or should I just read the flags in the code ?

Best regards !

[PatrickF]

Hi,

I assume you use STM32MP157C-EV1 mother-board (MB1262)+ daughter-board (MB1263) + display + camera.

Measurements from AN5284 section 3.4 were done using only the MB1263 alone (with some instrumentation to measure individual supplies).

I think the strange behavior is coming from MB1262 were some part are not well controlled in low power. This board was not optimized for low power.

Maybe you could try using only the MB1263 board (should boot from SD-Card or eMMC with same Started package).

Regards.

[AHayo.1]

Hi,

Thanks for answer !

I'm using STM32MP157A-EV1 with weston environment yes.

> Maybe you could try using only the MB1263 board

May I ask you how you achieve that ?

The problème is that I'll need the camera for my application. Do you think it's possible to lower power consumption by changing the device tree to disable for example peripherals I don't need (like the display) ?

Would there be some other ways I could try or is it a lost cause ?

Best regards !

[PatrickF]

You could use the MB1263C board in standalone. Simply unplug it (ensure the board is not powered before doing it). Starter Package will work from eMMC or SD-Card without change.

EV1 platform is not a good candidate for checking power consumption, there is no SW solution for that.

It might be possible to depopulate some MB1262 component, but I fear it is risky and might create a lot of issue. You could first check without the display board (it is easily removable too), it might be guilty of most power.

When using MB1263C in standalone, your could use an USB camera (most Linux compatible camera will work out of the box with Starter Package).

Regards.

[AHayo.1]

Ok !

For me the MB1263 doesn't have USB port. Or aren't we thinking about the same product ?

Best regards !

Edit : are you maybe referring to the STM32MP157C-DK2 ?