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Suspend to ram and wakeup by console input?

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I'm using ConnectCore i.mx8qxp board, I'd like to test the suspend-to-ram functions as mentioned here: https://community.arm.com/developer/tools-software/oss-platforms/w/docs/526/system-suspend-to-ram

I followed the instructions as in the document above:

/* Set the wakeup alarm for 30s */
# echo +30 > /sys/class/rtc/rtc0/wakealarm
/* Suspend system to RAM */
# echo -n mem > /sys/power/state
and also `rtcwake -d /dev/rtc0 -s 30 -m mem`.

It seems that the suspend is working fine. (I run ping cmd at the same time and I saw it disconnected).

Now I'd like to test the wake-up from console input.
I am connecting the PC to imx8qxp's debug port, which displays as "ttyLP2" during boot.

Is there a way to config ttyLP2 as a wakeup input?

From some other website, there is an instruction like this:
echo enabled > /sys/devices/platform/imx-uart.0/tty/ttymxc0/power/wakeup echo mem > /sys/power/state
but in my imx8qxp, I didn't find `/sys/devices/platform/imx-uart.0`, maybe in a different path or name?

asked Jul 14, 2021 in Linux by fei4xu New to the Community (3 points)

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1 Answer

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please see:

Wake from suspend
To allow an MCA UART to resume the system from suspend when a character is received (and not lose data), run the following command:

~# echo enabled > /sys/class/tty/ttyMCAx/power/wakeup
where x is the UART index, starting at 0.

An application must be reading from the device or the system will not wake up when a character is received.
answered Sep 13, 2021 by LeonidM Veteran of the Digi Community (4,454 points)