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 !

[AHayo.1]

Thanks !

So I set back the JP1 and wrote a shell script which starts after boot to try and test out these modes on the MB1263 in standalone mode. I've got the following results :

• CRun : 1020 mW
• LP-Stop : 151 mW
• Standby DDR SR : 87 mW
• Standby DDR off : 69 mW

So yeah, it's definitely better. But still, I'm surprised that we aren't lower in Standby DDR off. It still makes ca. 14mA. Do you really think the LD1 uses 14mA ... ? o.o

[PatrickF]

LED could count for maybe 9-10mA, but you have some also components on STLINK (STM32F103CBT6 in reset which is not OFF, it's LDO, few passives) which could explain the remaining part.

STPMIC1 use some power, as well as Buck3 efficiency to be taken into account (VDD is still on during STANDBY).

You should trust datasheet values and make your own computation of platform power. Not sure the EV1 or DK2 are best for challenging lowest power (not optimized for that).

Regards.

[AHayo.1]

Top, thank you very much for your time !