Merge branch 'backup-thermal-shutdown' into next

Documentation/thermal/sysfs-api.txt

···
 This function serves as an arbitrator to set the state of a cooling
 device. It sets the cooling device to the deepest cooling state if
 possible.
+
+6. 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.
+
+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.
+
+If set to 0 emergency poweroff will not be supported. So a carefully
+profiled non-zero positive value is a must for emergerncy poweroff to be
+triggered.

drivers/thermal/Kconfig

···
 
 if THERMAL
 
+config THERMAL_EMERGENCY_POWEROFF_DELAY_MS
+	int "Emergency poweroff delay in milli-seconds"
+	depends on THERMAL
+	default 0
+	help
+	  Thermal subsystem will issue a graceful shutdown when
+	  critical temperatures are reached using orderly_poweroff(). In
+	  case of failure of an orderly_poweroff(), the thermal emergency
+	  poweroff kicks in after a delay has elapsed and shuts down the system.
+	  This config is number of milliseconds to delay before emergency
+	  poweroff kicks in. Similarly to the critical trip point,
+	  the delay should be carefully profiled so as to give adequate
+	  time for orderly_poweroff() to finish on regular execution.
+	  If set to 0 emergency poweroff will not be supported.
+
+	  In doubt, leave as 0.
+
 config THERMAL_HWMON
 	bool
 	prompt "Expose thermal sensors as hwmon device"

drivers/thermal/thermal_core.c

···
 
 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;
 
···
 		       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.
+ */
+void thermal_emergency_poweroff(void)
+{
+	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
+	 */
+	if (poweroff_delay_ms <= 0)
+		return;
+	schedule_delayed_work(&thermal_emergency_poweroff_work,
+			      msecs_to_jiffies(poweroff_delay_ms));
+}
+
 static void handle_critical_trips(struct thermal_zone_device *tz,
 				  int trip, enum thermal_trip_type trip_type)
 {
···
 		dev_emerg(&tz->device,
 			  "critical temperature reached(%d C),shutting down\n",
 			  tz->temperature / 1000);
-		orderly_poweroff(true);
+		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);
 	}
 }
 
···
 {
 	int result;
 
+	mutex_init(&poweroff_lock);
 	result = thermal_register_governors();
 	if (result)
 		goto error;
···
 	ida_destroy(&thermal_cdev_ida);
 	mutex_destroy(&thermal_list_lock);
 	mutex_destroy(&thermal_governor_lock);
+	mutex_destroy(&poweroff_lock);
 	return result;
 }