Entering deep sleep causes a reset

[asd]

Hi,

I am trying to enter deep sleep on octavo red v1.2 board using:

“echo mem > /sys/power/state”

However, this makes a reset to the board and tf-a says it is due to NRST asserted:

NOTICE:  Model: Octavo OSD32MP1 RED board
INFO:    PMIC version = 0x21
INFO:    Reset reason (0x814):
INFO:      Pad Reset from NRST

I tried the sd card image provided in https://octavosystems.com/octavo_products/osd32mp1-red/.

This issue doesn’t happen on BRK board.

Any idea how can I fix that?

[Neeraj Dantu]

asd,

Verified this behavior on RED v1.2. I will put in an issue with the software team. I suspect that it is a RED specific Debian service(weston?) that is preventing a proper enter into low power state. Please use the OpenSTLinux version to implement the deep sleep state for now. Will update here once I get an update.

Best,

Neeraj

[asd]

Thanks Neeraj,

We tried the OpenSTLinux image and not the debian image.

The issue happens on the latest image provided in the link above.

What we discovered so far, is that if we keep buck4 on (by customizing arm trusted firmware), we are able to enter standby mode.

Do you know what is the connection of buck4 and the reset we are facing?

[Neeraj Dantu]

asd,

It seems like you found a hardware bug on the RED board. I was able to figure out the root cause after a chat with ST’s Engineer:

“TF-A is accurate when reporting the boot reason.”

This meant that NRST was being pulled LOW by another component. eMMC is the only device that has it’s RESET pin tied to NRST and it is powered by BUCK4. This is probably why if you have BUCK4 ON, you are not seeing the faulty behavior.

Once I disconnected eMMC’s RESET from NRST by cutting the trace, I was able to get the RED board into STANDBY without issue.

I was seeing variability in behavior before because I was using SD card interface to boot instead of eMMC. I suggest you use the SD card boot to work with low power modes that turn off BUCK4. I will add an issue to the design team to fix the hardware issue in the next revision.

Best,

Neeraj

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