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#include <trace/events/thermal.h>
 27
 28#include "thermal_core.h"
 29
 30/*
 31 * If the temperature is higher than a trip point,
 32 *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
 33 *       state for this trip point
 34 *    b. if the trend is THERMAL_TREND_DROPPING, do nothing
 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 *       deactivate 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	if (!instance->initialized) {
 66		if (throttle) {
 67			next_target = (cur_state + 1) >= instance->upper ?
 68					instance->upper :
 69					((cur_state + 1) < instance->lower ?
 70					instance->lower : (cur_state + 1));
 71		} else {
 72			next_target = THERMAL_NO_TARGET;
 73		}
 74
 75		return next_target;
 76	}
 77
 78	switch (trend) {
 79	case THERMAL_TREND_RAISING:
 80		if (throttle) {
 81			next_target = cur_state < instance->upper ?
 82				    (cur_state + 1) : instance->upper;
 83			if (next_target < instance->lower)
 84				next_target = instance->lower;
 85		}
 86		break;
 87	case THERMAL_TREND_RAISE_FULL:
 88		if (throttle)
 89			next_target = instance->upper;
 90		break;
 91	case THERMAL_TREND_DROPPING:
 92		if (cur_state <= instance->lower) {
 93			if (!throttle)
 94				next_target = THERMAL_NO_TARGET;
 95		} else {
 96			if (!throttle) {
 97				next_target = cur_state - 1;
 98				if (next_target > instance->upper)
 99					next_target = instance->upper;
100			}
101		}
102		break;
103	case THERMAL_TREND_DROP_FULL:
104		if (cur_state == instance->lower) {
105			if (!throttle)
106				next_target = THERMAL_NO_TARGET;
107		} else
108			next_target = instance->lower;
109		break;
110	default:
111		break;
112	}
113
114	return next_target;
115}
116
117static void update_passive_instance(struct thermal_zone_device *tz,
118				enum thermal_trip_type type, int value)
119{
120	/*
121	 * If value is +1, activate a passive instance.
122	 * If value is -1, deactivate a passive instance.
123	 */
124	if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
125		tz->passive += value;
126}
127
128static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
129{
130	int trip_temp;
131	enum thermal_trip_type trip_type;
132	enum thermal_trend trend;
133	struct thermal_instance *instance;
134	bool throttle = false;
135	int old_target;
136
137	if (trip == THERMAL_TRIPS_NONE) {
138		trip_temp = tz->forced_passive;
139		trip_type = THERMAL_TRIPS_NONE;
140	} else {
141		tz->ops->get_trip_temp(tz, trip, &trip_temp);
142		tz->ops->get_trip_type(tz, trip, &trip_type);
143	}
144
145	trend = get_tz_trend(tz, trip);
146
147	if (tz->temperature >= trip_temp) {
148		throttle = true;
149		trace_thermal_zone_trip(tz, trip, trip_type);
150	}
151
152	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
153				trip, trip_type, trip_temp, trend, throttle);
154
155	mutex_lock(&tz->lock);
156
157	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
158		if (instance->trip != trip)
159			continue;
160
161		old_target = instance->target;
162		instance->target = get_target_state(instance, trend, throttle);
163		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
164					old_target, (int)instance->target);
165
166		if (instance->initialized && old_target == instance->target)
167			continue;
168
169		/* Activate a passive thermal instance */
170		if (old_target == THERMAL_NO_TARGET &&
171			instance->target != THERMAL_NO_TARGET)
172			update_passive_instance(tz, trip_type, 1);
173		/* Deactivate a passive thermal instance */
174		else if (old_target != THERMAL_NO_TARGET &&
175			instance->target == THERMAL_NO_TARGET)
176			update_passive_instance(tz, trip_type, -1);
177
178		instance->initialized = true;
179		mutex_lock(&instance->cdev->lock);
180		instance->cdev->updated = false; /* cdev needs update */
181		mutex_unlock(&instance->cdev->lock);
182	}
183
184	mutex_unlock(&tz->lock);
185}
186
187/**
188 * step_wise_throttle - throttles devices associated with the given zone
189 * @tz - thermal_zone_device
190 * @trip - trip point index
191 *
192 * Throttling Logic: This uses the trend of the thermal zone to throttle.
193 * If the thermal zone is 'heating up' this throttles all the cooling
194 * devices associated with the zone and its particular trip point, by one
195 * step. If the zone is 'cooling down' it brings back the performance of
196 * the devices by one step.
197 */
198static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
199{
200	struct thermal_instance *instance;
201
202	thermal_zone_trip_update(tz, trip);
203
204	if (tz->forced_passive)
205		thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
206
207	mutex_lock(&tz->lock);
208
209	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
210		thermal_cdev_update(instance->cdev);
211
212	mutex_unlock(&tz->lock);
213
214	return 0;
215}
216
217static struct thermal_governor thermal_gov_step_wise = {
218	.name		= "step_wise",
219	.throttle	= step_wise_throttle,
220};
221
222int thermal_gov_step_wise_register(void)
223{
224	return thermal_register_governor(&thermal_gov_step_wise);
225}
226
227void thermal_gov_step_wise_unregister(void)
228{
229	thermal_unregister_governor(&thermal_gov_step_wise);
230}