Wake on Real Time Clock (set alarm)

To use wake on RTC, you can run the command below.

sleeptime_seconds=30
RTC=/sys/class/rtc/rtc0/wakealarm; echo 0>$RTC && echo +${sleeptime_seconds} >$RTC && systemctl suspend

You can also run the following to enter suspend to RAM.

rtcwake -s 10 -m mem

For HMX, rtc1 will also work.

rtcwake -s 10 -m mem -d /dev/rtc1