regulator: allow user configuration of hardware protection action

When the core detects permanent regulator hardware failure or imminent
power failure of a critical supply, it will call hw_protection_shutdown in
an attempt to do a limited orderly shutdown followed by powering off the
system.

This doesn't work out well for many unattended embedded systems that don't
have support for shutdown and that power on automatically when power is
supplied:

- A brief power cycle gets detected by the driver
- The kernel powers down the system and SoC goes into shutdown mode
- Power is restored
- The system remains oblivious to the restored power
- System needs to be manually power cycled for a duration long enough
to drain the capacitors

Allow users to fix this by calling the newly introduced
hw_protection_trigger() instead: This way the hw_protection commandline or
sysfs parameter is used to dictate the policy of dealing with the
regulator fault.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ahmad Fatoum <[e-mail]>
Reviewed-by: Tzung-Bi Shih <[e-mail]>
Reviewed-by: Matti Vaittinen <[e-mail]>
Cc: Benson Leung <[e-mail]>
Cc: Daniel Lezcano <[e-mail]>
Cc: Fabio Estevam <[e-mail]>
Cc: Guenter Roeck <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Liam Girdwood <[e-mail]>
Cc: Lukasz Luba <[e-mail]>
Cc: Mark Brown <[e-mail]>
Cc: Matteo Croce <[e-mail]>
Cc: "Rafael J. Wysocki" <[e-mail]>
Cc: Rob Herring (Arm) <[e-mail]>
Cc: Rui Zhang <[e-mail]>
Cc: Sascha Hauer <[e-mail]>
Cc: "Serge E. Hallyn" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

drivers/regulator/core.c

···
 	if (!reason)
 		return;
 
-	hw_protection_shutdown(reason,
-			       rdev->constraints->uv_less_critical_window_ms);
+	hw_protection_trigger(reason,
+			      rdev->constraints->uv_less_critical_window_ms);
 }
 
 /**

drivers/regulator/irq_helpers.c

···
 reread:
 	if (d->fatal_cnt && h->retry_cnt > d->fatal_cnt) {
 		if (!d->die)
-			return hw_protection_shutdown("Regulator HW failure? - no IC recovery",
-						      REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
+			return hw_protection_trigger("Regulator HW failure? - no IC recovery",
+						     REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
 		ret = d->die(rid);
 		/*
 		 * If the 'last resort' IC recovery failed we will have
 		 * nothing else left to do...
 		 */
 		if (ret)
-			return hw_protection_shutdown("Regulator HW failure. IC recovery failed",
-						      REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
+			return hw_protection_trigger("Regulator HW failure. IC recovery failed",
+						     REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
 
 		/*
 		 * If h->die() was implemented we assume recovery has been
···
 	if (d->fatal_cnt && h->retry_cnt > d->fatal_cnt) {
 		/* If we have no recovery, just try shut down straight away */
 		if (!d->die) {
-			hw_protection_shutdown("Regulator failure. Retry count exceeded",
-					       REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
+			hw_protection_trigger("Regulator failure. Retry count exceeded",
+					      REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
 		} else {
 			ret = d->die(rid);
 			/* If die() failed shut down as a last attempt to save the HW */
 			if (ret)
-				hw_protection_shutdown("Regulator failure. Recovery failed",
-						       REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
+				hw_protection_trigger("Regulator failure. Recovery failed",
+						      REGULATOR_FORCED_SAFETY_SHUTDOWN_WAIT_MS);
 		}
 	}