Commit c5727e70 authored by Ram Chandrasekar's avatar Ram Chandrasekar Committed by popcornmix
Browse files

drivers: thermal: step_wise: add support for hysteresis 



From: Ram Chandrasekar <rkumbako@codeaurora.org>

Step wise governor increases the mitigation level when the temperature
goes above a threshold and will decrease the mitigation when the
temperature falls below the threshold. If it were a case, where the
temperature hovers around a threshold, the mitigation will be applied
and removed at every iteration. This reaction to the temperature is
inefficient for performance.

The use of hysteresis temperature could avoid this ping-pong of
mitigation by relaxing the mitigation to happen only when the
temperature goes below this lower hysteresis value.

Signed-off-by: default avatarRam Chandrasekar <rkumbako@codeaurora.org>
Signed-off-by: default avatarLina Iyer <ilina@codeaurora.org>
parent 67689145

drivers/thermal/step_wise.c

+23 −10
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ 
 *       for this trip point

 *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit

 *       for this trip point

 * If the temperature is lower than a trip point,

 * If the temperature is lower than a hysteresis temperature,

 *    a. if the trend is THERMAL_TREND_RAISING, do nothing

 *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling

 *       state for this trip point, if the cooling state already
@@ -127,7 +127,7 @@ static void update_passive_instance(struct thermal_zone_device *tz, 


static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)

{

	int trip_temp;

	int trip_temp, hyst_temp;

	enum thermal_trip_type trip_type;

	enum thermal_trend trend;

	struct thermal_instance *instance;
@@ -135,22 +135,23 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip) 
	int old_target;



	if (trip == THERMAL_TRIPS_NONE) {

		trip_temp = tz->forced_passive;

		hyst_temp = trip_temp = tz->forced_passive;

		trip_type = THERMAL_TRIPS_NONE;

	} else {

		tz->ops->get_trip_temp(tz, trip, &trip_temp);

		hyst_temp = trip_temp;

		if (tz->ops->get_trip_hyst) {

			tz->ops->get_trip_hyst(tz, trip, &hyst_temp);

			hyst_temp = trip_temp - hyst_temp;

		}

		tz->ops->get_trip_type(tz, trip, &trip_type);

	}



	trend = get_tz_trend(tz, trip);



	if (tz->temperature >= trip_temp) {

		throttle = true;

		trace_thermal_zone_trip(tz, trip, trip_type);

	}



	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",

				trip, trip_type, trip_temp, trend, throttle);

	dev_dbg(&tz->device,

		"Trip%d[type=%d,temp=%d,hyst=%d]:trend=%d,throttle=%d\n",

		trip, trip_type, trip_temp, hyst_temp, trend, throttle);



	mutex_lock(&tz->lock);
@@ -159,6 +160,18 @@ static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip) 
			continue;



		old_target = instance->target;

		throttle = false;

		/*

		 * Lower the mitigation only if the temperature

		 * goes below the hysteresis temperature.

		 */

		if (tz->temperature >= trip_temp ||

		   (tz->temperature >= hyst_temp &&

		   old_target != THERMAL_NO_TARGET)) {

			throttle = true;

			trace_thermal_zone_trip(tz, trip, trip_type);

		}



		instance->target = get_target_state(instance, trend, throttle);

		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",

					old_target, (int)instance->target);