step_wise.c 6.7 KB
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/*
 *  step_wise.c - A step-by-step Thermal throttling governor
 *
 *  Copyright (C) 2012 Intel Corp
 *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
 *
 *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; version 2 of the License.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/thermal.h>
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#include <trace/events/thermal.h>
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#include "thermal_core.h"

/*
 * If the temperature is higher than a trip point,
 *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
 *       state for this trip point
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 *    b. if the trend is THERMAL_TREND_DROPPING, do nothing
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 *    c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
 *       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,
 *    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
 *       equals lower limit, deactivate the thermal instance
 *    c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
 *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
 *       if the cooling state already equals lower limit,
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 *       deactivate the thermal instance
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 */
static unsigned long get_target_state(struct thermal_instance *instance,
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				enum thermal_trend trend, bool throttle)
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{
	struct thermal_cooling_device *cdev = instance->cdev;
	unsigned long cur_state;
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	unsigned long next_target;
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	/*
	 * We keep this instance the way it is by default.
	 * Otherwise, we use the current state of the
	 * cdev in use to determine the next_target.
	 */
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	cdev->ops->get_cur_state(cdev, &cur_state);
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	next_target = instance->target;
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	dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
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	if (!instance->initialized) {
		if (throttle) {
			next_target = (cur_state + 1) >= instance->upper ?
					instance->upper :
					((cur_state + 1) < instance->lower ?
					instance->lower : (cur_state + 1));
		} else {
			next_target = THERMAL_NO_TARGET;
		}

		return next_target;
	}

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	switch (trend) {
	case THERMAL_TREND_RAISING:
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		if (throttle) {
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			next_target = cur_state < instance->upper ?
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				    (cur_state + 1) : instance->upper;
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			if (next_target < instance->lower)
				next_target = instance->lower;
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		}
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		break;
	case THERMAL_TREND_RAISE_FULL:
		if (throttle)
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			next_target = instance->upper;
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		break;
	case THERMAL_TREND_DROPPING:
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		if (cur_state <= instance->lower) {
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			if (!throttle)
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				next_target = THERMAL_NO_TARGET;
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		} else {
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			if (!throttle) {
				next_target = cur_state - 1;
				if (next_target > instance->upper)
					next_target = instance->upper;
			}
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		}
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		break;
	case THERMAL_TREND_DROP_FULL:
		if (cur_state == instance->lower) {
			if (!throttle)
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				next_target = THERMAL_NO_TARGET;
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		} else
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			next_target = instance->lower;
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		break;
	default:
		break;
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	}

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	return next_target;
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}

static void update_passive_instance(struct thermal_zone_device *tz,
				enum thermal_trip_type type, int value)
{
	/*
	 * If value is +1, activate a passive instance.
	 * If value is -1, deactivate a passive instance.
	 */
	if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
		tz->passive += value;
}

static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
{
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	int trip_temp;
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	enum thermal_trip_type trip_type;
	enum thermal_trend trend;
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	struct thermal_instance *instance;
	bool throttle = false;
	int old_target;
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	if (trip == THERMAL_TRIPS_NONE) {
		trip_temp = tz->forced_passive;
		trip_type = THERMAL_TRIPS_NONE;
	} else {
		tz->ops->get_trip_temp(tz, trip, &trip_temp);
		tz->ops->get_trip_type(tz, trip, &trip_type);
	}

	trend = get_tz_trend(tz, trip);

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	if (tz->temperature >= trip_temp) {
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		throttle = true;
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		trace_thermal_zone_trip(tz, trip, trip_type);
	}
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	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
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				trip, trip_type, trip_temp, trend, throttle);

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	mutex_lock(&tz->lock);

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	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
		if (instance->trip != trip)
			continue;

		old_target = instance->target;
		instance->target = get_target_state(instance, trend, throttle);
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		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
					old_target, (int)instance->target);
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		if (instance->initialized && old_target == instance->target)
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			continue;

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		/* Activate a passive thermal instance */
		if (old_target == THERMAL_NO_TARGET &&
			instance->target != THERMAL_NO_TARGET)
			update_passive_instance(tz, trip_type, 1);
		/* Deactivate a passive thermal instance */
		else if (old_target != THERMAL_NO_TARGET &&
			instance->target == THERMAL_NO_TARGET)
			update_passive_instance(tz, trip_type, -1);

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		instance->initialized = true;
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		mutex_lock(&instance->cdev->lock);
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		instance->cdev->updated = false; /* cdev needs update */
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		mutex_unlock(&instance->cdev->lock);
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	}
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	mutex_unlock(&tz->lock);
}

/**
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 * step_wise_throttle - throttles devices associated with the given zone
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 * @tz - thermal_zone_device
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 * @trip - trip point index
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 *
 * Throttling Logic: This uses the trend of the thermal zone to throttle.
 * If the thermal zone is 'heating up' this throttles all the cooling
 * devices associated with the zone and its particular trip point, by one
 * step. If the zone is 'cooling down' it brings back the performance of
 * the devices by one step.
 */
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static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
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{
	struct thermal_instance *instance;

	thermal_zone_trip_update(tz, trip);

	if (tz->forced_passive)
		thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);

	mutex_lock(&tz->lock);

	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
		thermal_cdev_update(instance->cdev);

	mutex_unlock(&tz->lock);

	return 0;
}

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static struct thermal_governor thermal_gov_step_wise = {
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	.name		= "step_wise",
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	.throttle	= step_wise_throttle,
};

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int thermal_gov_step_wise_register(void)
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{
	return thermal_register_governor(&thermal_gov_step_wise);
}

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void thermal_gov_step_wise_unregister(void)
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{
	thermal_unregister_governor(&thermal_gov_step_wise);
}