1/*
  2 *  step_wise.c - A step-by-step Thermal throttling governor
  3 *
  4 *  Copyright (C) 2012 Intel Corp
  5 *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
  6 *
  7 *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  8 *
  9 *  This program is free software; you can redistribute it and/or modify
 10 *  it under the terms of the GNU General Public License as published by
 11 *  the Free Software Foundation; version 2 of the License.
 12 *
 13 *  This program is distributed in the hope that it will be useful, but
 14 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 15 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 16 *  General Public License for more details.
 17 *
 18 *  You should have received a copy of the GNU General Public License along
 19 *  with this program; if not, write to the Free Software Foundation, Inc.,
 20 *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
 21 *
 22 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 23 */
 24
 25#include <linux/thermal.h>
 26
 27#include "thermal_core.h"
 28
 29/*
 30 * If the temperature is higher than a trip point,
 31 *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
 32 *       state for this trip point
 33 *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
 34 *       state for this trip point
 35 *    c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
 36 *       for this trip point
 37 *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
 38 *       for this trip point
 39 * If the temperature is lower than a trip point,
 40 *    a. if the trend is THERMAL_TREND_RAISING, do nothing
 41 *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
 42 *       state for this trip point, if the cooling state already
 43 *       equals lower limit, deactivate the thermal instance
 44 *    c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
 45 *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
 46 *       if the cooling state already equals lower limit,
 47 *       deactive the thermal instance
 48 */
 49static unsigned long get_target_state(struct thermal_instance *instance,
 50				enum thermal_trend trend, bool throttle)
 51{
 52	struct thermal_cooling_device *cdev = instance->cdev;
 53	unsigned long cur_state;
 54	unsigned long next_target;
 55
 56	/*
 57	 * We keep this instance the way it is by default.
 58	 * Otherwise, we use the current state of the
 59	 * cdev in use to determine the next_target.
 60	 */
 61	cdev->ops->get_cur_state(cdev, &cur_state);
 62	next_target = instance->target;
 63	dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
 64
 65	switch (trend) {
 66	case THERMAL_TREND_RAISING:
 67		if (throttle) {
 68			next_target = cur_state < instance->upper ?
 69				    (cur_state + 1) : instance->upper;
 70			if (next_target < instance->lower)
 71				next_target = instance->lower;
 72		}
 73		break;
 74	case THERMAL_TREND_RAISE_FULL:
 75		if (throttle)
 76			next_target = instance->upper;
 77		break;
 78	case THERMAL_TREND_DROPPING:
 79		if (cur_state == instance->lower) {
 80			if (!throttle)
 81				next_target = THERMAL_NO_TARGET;
 82		} else {
 83			next_target = cur_state - 1;
 84			if (next_target > instance->upper)
 85				next_target = instance->upper;
 86		}
 87		break;
 88	case THERMAL_TREND_DROP_FULL:
 89		if (cur_state == instance->lower) {
 90			if (!throttle)
 91				next_target = THERMAL_NO_TARGET;
 92		} else
 93			next_target = instance->lower;
 94		break;
 95	default:
 96		break;
 97	}
 98
 99	return next_target;
100}
101
102static void update_passive_instance(struct thermal_zone_device *tz,
103				enum thermal_trip_type type, int value)
104{
105	/*
106	 * If value is +1, activate a passive instance.
107	 * If value is -1, deactivate a passive instance.
108	 */
109	if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
110		tz->passive += value;
111}
112
113static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
114{
115	long trip_temp;
116	enum thermal_trip_type trip_type;
117	enum thermal_trend trend;
118	struct thermal_instance *instance;
119	bool throttle = false;
120	int old_target;
121
122	if (trip == THERMAL_TRIPS_NONE) {
123		trip_temp = tz->forced_passive;
124		trip_type = THERMAL_TRIPS_NONE;
125	} else {
126		tz->ops->get_trip_temp(tz, trip, &trip_temp);
127		tz->ops->get_trip_type(tz, trip, &trip_type);
128	}
129
130	trend = get_tz_trend(tz, trip);
131
132	if (tz->temperature >= trip_temp)
133		throttle = true;
134
135	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%ld]:trend=%d,throttle=%d\n",
136				trip, trip_type, trip_temp, trend, throttle);
137
138	mutex_lock(&tz->lock);
139
140	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
141		if (instance->trip != trip)
142			continue;
143
144		old_target = instance->target;
145		instance->target = get_target_state(instance, trend, throttle);
146		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
147					old_target, (int)instance->target);
148
149		if (old_target == instance->target)
150			continue;
151
152		/* Activate a passive thermal instance */
153		if (old_target == THERMAL_NO_TARGET &&
154			instance->target != THERMAL_NO_TARGET)
155			update_passive_instance(tz, trip_type, 1);
156		/* Deactivate a passive thermal instance */
157		else if (old_target != THERMAL_NO_TARGET &&
158			instance->target == THERMAL_NO_TARGET)
159			update_passive_instance(tz, trip_type, -1);
160
161
162		instance->cdev->updated = false; /* cdev needs update */
163	}
164
165	mutex_unlock(&tz->lock);
166}
167
168/**
169 * step_wise_throttle - throttles devices asscciated with the given zone
170 * @tz - thermal_zone_device
171 * @trip - the trip point
172 * @trip_type - type of the trip point
173 *
174 * Throttling Logic: This uses the trend of the thermal zone to throttle.
175 * If the thermal zone is 'heating up' this throttles all the cooling
176 * devices associated with the zone and its particular trip point, by one
177 * step. If the zone is 'cooling down' it brings back the performance of
178 * the devices by one step.
179 */
180static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
181{
182	struct thermal_instance *instance;
183
184	thermal_zone_trip_update(tz, trip);
185
186	if (tz->forced_passive)
187		thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
188
189	mutex_lock(&tz->lock);
190
191	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
192		thermal_cdev_update(instance->cdev);
193
194	mutex_unlock(&tz->lock);
195
196	return 0;
197}
198
199static struct thermal_governor thermal_gov_step_wise = {
200	.name		= "step_wise",
201	.throttle	= step_wise_throttle,
202};
203
204int thermal_gov_step_wise_register(void)
205{
206	return thermal_register_governor(&thermal_gov_step_wise);
207}
208
209void thermal_gov_step_wise_unregister(void)
210{
211	thermal_unregister_governor(&thermal_gov_step_wise);
212}