PM / wakeup: Add callback for wake-up change notification
Add a callback to inform a device that its wake-up setting has been
changed. This allows a device to synchronize device configuration with
an external user action.
E.g. on systems using a Rohm BD9571MWV PMIC and a toggle accessory power
switch, the system suspend/resume procedure is:
1. Configure PMIC for DDR backup mode (by software), which changes the
role of the accessory power switch from a power to a wake-up
switch,
2. Switch accessory power switch off (manually), to prepare for system
suspend,
3. Suspend system (by software),
4. Switch accessory power switch on (manually), to wake up the system.
As step 2 involves a manual operation, step 1 cannot be combined
with step 3 and performed in the PMIC's suspend callback (unlike on
systems with a momentary power switch).
Adding the new callback allows to move step 1 to the new callback, to be
performed in response to the user writing "enabled" to the PMIC's
"wakeup" virtual file in sysfs.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Is there a better way to handle this?
Currently step 1 is done in userspace using i2set, which is very
user-unfriendly
(https://elinux.org/R-Car/Boards/Salvator-XS#PSCI_System_Suspend).
v2:
- Improve patch description.
2 files changed
