thermal: Use generic HW-protection shutdown API

The hardware shutdown function was exported from kernel/reboot for
other subsystems to use. Logic is copied from the thermal_core. The
protection mutex is replaced by an atomic_t to allow calls also from
an IRQ context. Also the WARN() was replaced by pr_emerg() based on
discussions here:
https://lore.kernel.org/lkml/YJuPwAZroVZ%2Fw633@alley/
and here:
https://lore.kernel.org/linux-iommu/20210331093104.383705-4-geert+renesas@glider.be/

Use the exported API instead of implementing own just for the
thermal_core.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/5531e89d9e710f5d10e7cdce3ee58957335b9e03.1622628333.git.matti.vaittinen@fi.rohmeurope.comSigned-off-by: Mark Brown <broonie@kernel.org>

Documentation/driver-api/thermal/sysfs-api.rst

@@ -740,21 +740,15 @@ possible.
 5. thermal_emergency_poweroff
 =============================
 
-On an event of critical trip temperature crossing. Thermal framework
-allows the system to shutdown gracefully by calling orderly_poweroff().
-In the event of a failure of orderly_poweroff() to shut down the system
-we are in danger of keeping the system alive at undesirably high
-temperatures. To mitigate this high risk scenario we program a work
-queue to fire after a pre-determined number of seconds to start
-an emergency shutdown of the device using the kernel_power_off()
-function. In case kernel_power_off() fails then finally
-emergency_restart() is called in the worst case.
+On an event of critical trip temperature crossing the thermal framework
+shuts down the system by calling hw_protection_shutdown(). The
+hw_protection_shutdown() first attempts to perform an orderly shutdown
+but accepts a delay after which it proceeds doing a forced power-off
+or as last resort an emergency_restart.
 
 The delay should be carefully profiled so as to give adequate time for
-orderly_poweroff(). In case of failure of an orderly_poweroff() the
-emergency poweroff kicks in after the delay has elapsed and shuts down
-the system.
+orderly poweroff.
 
-If set to 0 emergency poweroff will not be supported. So a carefully
-profiled non-zero positive value is a must for emergency poweroff to be
-triggered.
+If the delay is set to 0 emergency poweroff will not be supported. So a
+carefully profiled non-zero positive value is a must for emergency
+poweroff to be triggered.

drivers/thermal/thermal_core.c

@@ -36,10 +36,8 @@ static LIST_HEAD(thermal_governor_list);
 
 static DEFINE_MUTEX(thermal_list_lock);
 static DEFINE_MUTEX(thermal_governor_lock);
-static DEFINE_MUTEX(poweroff_lock);
 
 static atomic_t in_suspend;
-static bool power_off_triggered;
 
 static struct thermal_governor *def_governor;
 
@@ -327,70 +325,18 @@ static void handle_non_critical_trips(struct thermal_zone_device *tz, int trip)
 		       def_governor->throttle(tz, trip);
 }
 
-/**
- * thermal_emergency_poweroff_func - emergency poweroff work after a known delay
- * @work: work_struct associated with the emergency poweroff function
- *
- * This function is called in very critical situations to force
- * a kernel poweroff after a configurable timeout value.
- */
-static void thermal_emergency_poweroff_func(struct work_struct *work)
-{
-	/*
-	 * We have reached here after the emergency thermal shutdown
-	 * Waiting period has expired. This means orderly_poweroff has
-	 * not been able to shut off the system for some reason.
-	 * Try to shut down the system immediately using kernel_power_off
-	 * if populated
-	 */
-	WARN(1, "Attempting kernel_power_off: Temperature too high\n");
-	kernel_power_off();
-
-	/*
-	 * Worst of the worst case trigger emergency restart
-	 */
-	WARN(1, "Attempting emergency_restart: Temperature too high\n");
-	emergency_restart();
-}
-
-static DECLARE_DELAYED_WORK(thermal_emergency_poweroff_work,
-			    thermal_emergency_poweroff_func);
-
-/**
- * thermal_emergency_poweroff - Trigger an emergency system poweroff
- *
- * This may be called from any critical situation to trigger a system shutdown
- * after a known period of time. By default this is not scheduled.
- */
-static void thermal_emergency_poweroff(void)
+void thermal_zone_device_critical(struct thermal_zone_device *tz)
 {
-	int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS;
 	/*
 	 * poweroff_delay_ms must be a carefully profiled positive value.
-	 * Its a must for thermal_emergency_poweroff_work to be scheduled
+	 * Its a must for forced_emergency_poweroff_work to be scheduled.
 	 */
-	if (poweroff_delay_ms <= 0)
-		return;
-	schedule_delayed_work(&thermal_emergency_poweroff_work,
-			      msecs_to_jiffies(poweroff_delay_ms));
-}
+	int poweroff_delay_ms = CONFIG_THERMAL_EMERGENCY_POWEROFF_DELAY_MS;
 
-void thermal_zone_device_critical(struct thermal_zone_device *tz)
-{
 	dev_emerg(&tz->device, "%s: critical temperature reached, "
 		  "shutting down\n", tz->type);
 
-	mutex_lock(&poweroff_lock);
-	if (!power_off_triggered) {
-		/*
-		 * Queue a backup emergency shutdown in the event of
-		 * orderly_poweroff failure
-		 */
-		thermal_emergency_poweroff();
-		orderly_poweroff(true);
-		power_off_triggered = true;
-	}
-	mutex_unlock(&poweroff_lock);
+	hw_protection_shutdown("Temperature too high", poweroff_delay_ms);
 }
 EXPORT_SYMBOL(thermal_zone_device_critical);
 
@@ -1538,7 +1484,6 @@ static int __init thermal_init(void)
 	ida_destroy(&thermal_cdev_ida);
 	mutex_destroy(&thermal_list_lock);
 	mutex_destroy(&thermal_governor_lock);
-	mutex_destroy(&poweroff_lock);
 	return result;
 }
 postcore_initcall(thermal_init);