actually, leo supports RTC_ALARM through both dex and pcom (and the emulated lk version which isn't quite efficient).
Code:
DEX_SET_ALARM_RTC = 0x84,
PCOM_SET_RTC_ALARM = 0xD,
but i've tested the PCOM command and it don't seem to work (works totally fine on an old MSM7k device), the current leo kernels already have support for wake_after which uses the pcom command, you could try and swap it with dex and see if it makes any difference.
To test it on your device:
Code:
su
echo 'time' > /sys/module/pm/parameters/wakeup_after
where time = <unknown time spec, MSM7k's unit is seconds but cotulla mentioned it appears to be milliseconds>, I tried 300, 600, 60000. expecting them to be 300s, 600s, 1s resoectively.