Commit ef1d87e0 authored by Keerthy's avatar Keerthy Committed by Zhang Rui
Browse files

thermal: core: Add a back up thermal shutdown mechanism 



orderly_poweroff is triggered when a graceful shutdown
of system is desired. This may be used in many critical states of the
kernel such as when subsystems detects conditions such as critical
temperature conditions. However, in certain conditions in system
boot up sequences like those in the middle of driver probes being
initiated, userspace will be unable to power off the system in a clean
manner and leaves the system in a critical state. In cases like these,
the /sbin/poweroff will return success (having forked off to attempt
powering off the system. However, the system overall will fail to
completely poweroff (since other modules will be probed) and the system
is still functional with no userspace (since that would have shut itself
off).

However, there is no clean way of detecting such failure of userspace
powering off the system. In such scenarios, it is necessary for a backup
workqueue to be able to force a shutdown of the system when orderly
shutdown is not successful after a configurable time period.

Reported-by: default avatarNishanth Menon <nm@ti.com>
Signed-off-by: default avatarKeerthy <j-keerthy@ti.com>
Acked-by: default avatarEduardo Valentin <edubezval@gmail.com>
Signed-off-by: default avatarZhang Rui <rui.zhang@intel.com>
parent e441fd68

Documentation/thermal/sysfs-api.txt

+21 −0
Original line number Original line Diff line number Diff line
@@ -582,3 +582,24 @@ platform data is provided, this uses the step_wise throttling policy. 
This function serves as an arbitrator to set the state of a cooling

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

device. It sets the cooling device to the deepest cooling state if

possible.

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

+17 −0
Original line number Original line Diff line number Diff line
@@ -15,6 +15,23 @@ menuconfig THERMAL 




if THERMAL

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

config THERMAL_HWMON

	bool

	bool

	prompt "Expose thermal sensors as hwmon device"

	prompt "Expose thermal sensors as hwmon device"

drivers/thermal/thermal_core.c

+53 −0
Original line number Original line Diff line number Diff line
@@ -324,6 +324,54 @@ static void handle_non_critical_trips(struct thermal_zone_device *tz, 
		       def_governor->throttle(tz, 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.

 */

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,

static void handle_critical_trips(struct thermal_zone_device *tz,

				  int trip, enum thermal_trip_type trip_type)

				  int trip, enum thermal_trip_type trip_type)

{

{
@@ -346,6 +394,11 @@ static void handle_critical_trips(struct thermal_zone_device *tz, 
			  tz->temperature / 1000);

			  tz->temperature / 1000);

		mutex_lock(&poweroff_lock);

		mutex_lock(&poweroff_lock);

		if (!power_off_triggered) {

		if (!power_off_triggered) {

			/*

			 * Queue a backup emergency shutdown in the event of

			 * orderly_poweroff failure

			 */

			thermal_emergency_poweroff();

			orderly_poweroff(true);

			orderly_poweroff(true);

			power_off_triggered = true;

			power_off_triggered = true;

		}

		}

CRA Git | Maintained and supported by SUSTech CRA and CCSE