thermal/core/power_allocator: Update once cooling devices when temp is low

The cooling device state change generates an event, also when there is no
need, because temperature is low and device is not throttled. Avoid to
unnecessary update the cooling device which means also not sending event.
The cooling device state has not changed because the temperature is still
below the first activation trip point value, so we can do this.
Add a tracking mechanism to make sure it updates cooling devices only
once - when the temperature dropps below first trip point.
Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210422114308.29684-4-lukasz.luba@arm.com

drivers/thermal/gov_power_allocator.c

@@ -571,7 +571,7 @@ static void reset_pid_controller(struct power_allocator_params *params)
 	params->prev_err = 0;
 }
 
-static void allow_maximum_power(struct thermal_zone_device *tz)
+static void allow_maximum_power(struct thermal_zone_device *tz, bool update)
 {
 	struct thermal_instance *instance;
 	struct power_allocator_params *params = tz->governor_data;
@@ -594,9 +594,10 @@ static void allow_maximum_power(struct thermal_zone_device *tz)
 		 */
 		cdev->ops->get_requested_power(cdev, &req_power);
 
-		instance->cdev->updated = false;
+		if (update)
+			__thermal_cdev_update(instance->cdev);
+
 		mutex_unlock(&instance->cdev->lock);
-		thermal_cdev_update(instance->cdev);
 	}
 	mutex_unlock(&tz->lock);
 }
@@ -710,6 +711,7 @@ static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
 	int ret;
 	int switch_on_temp, control_temp;
 	struct power_allocator_params *params = tz->governor_data;
+	bool update;
 
 	/*
 	 * We get called for every trip point but we only need to do
@@ -721,9 +723,10 @@ static int power_allocator_throttle(struct thermal_zone_device *tz, int trip)
 	ret = tz->ops->get_trip_temp(tz, params->trip_switch_on,
 				     &switch_on_temp);
 	if (!ret && (tz->temperature < switch_on_temp)) {
+		update = (tz->last_temperature >= switch_on_temp);
 		tz->passive = 0;
 		reset_pid_controller(params);
-		allow_maximum_power(tz);
+		allow_maximum_power(tz, update);
 		return 0;
 	}