Linux Receiving ACPI "Time and Alarm Device" Driver
The Linux kernel ACPI TAD driver implements the wake-up capabilities of the ACPI 6.2 specification. Via sysfs, users can manage wake-up timers of the TAD, including setting/checking/clearing timers. The timers can transition the system from S3/S4/S5 to the S0 state after a set time period elapses.
The TAD driver allows controlling all tunables from sysfs, TAD information spans platform reboots / power state transitions, and is much more featureful than say the real-time clock wake-up option you may find from your motherboard BIOS.
Linux PM subsystem maintainer Rafael Wysocki spearheaded this driver at Intel. A look at the various tunables via sysfs can be found via this documentation for those trying to grasp the scope of ACPI Time and Alarm Device.
This code is queued in Wysocki's power management -next tree for introduction with the Linux 4.17 kernel.