From 3fc58056cba3cb56f20f98432de2c144f3d07308 Mon Sep 17 00:00:00 2001 From: Ram Chandrasekar Date: Mon, 7 May 2018 11:54:08 -0600 Subject: [PATCH] drivers: thermal: step_wise: add support for hysteresis 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: Ram Chandrasekar Signed-off-by: Lina Iyer --- drivers/thermal/gov_step_wise.c | 34 ++++++++++++++++++++++++--------- 1 file changed, 25 insertions(+), 9 deletions(-) --- a/drivers/thermal/gov_step_wise.c +++ b/drivers/thermal/gov_step_wise.c @@ -25,7 +25,7 @@ * 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 @@ -97,7 +97,7 @@ static void update_passive_instance(stru 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; @@ -107,21 +107,37 @@ static void thermal_zone_trip_update(str tz->ops->get_trip_temp(tz, trip, &trip_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); + 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); - dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n", - trip, trip_type, trip_temp, trend, throttle); + trend = get_tz_trend(tz, trip); + + 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); list_for_each_entry(instance, &tz->thermal_instances, tz_node) { if (instance->trip != 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);