linux/drivers/thermal/step_wise.c
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   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
  64        switch (trend) {
  65        case THERMAL_TREND_RAISING:
  66                if (throttle) {
  67                        next_target = cur_state < instance->upper ?
  68                                    (cur_state + 1) : instance->upper;
  69                        if (next_target < instance->lower)
  70                                next_target = instance->lower;
  71                }
  72                break;
  73        case THERMAL_TREND_RAISE_FULL:
  74                if (throttle)
  75                        next_target = instance->upper;
  76                break;
  77        case THERMAL_TREND_DROPPING:
  78                if (cur_state == instance->lower) {
  79                        if (!throttle)
  80                                next_target = THERMAL_NO_TARGET;
  81                } else {
  82                        next_target = cur_state - 1;
  83                        if (next_target > instance->upper)
  84                                next_target = instance->upper;
  85                }
  86                break;
  87        case THERMAL_TREND_DROP_FULL:
  88                if (cur_state == instance->lower) {
  89                        if (!throttle)
  90                                next_target = THERMAL_NO_TARGET;
  91                } else
  92                        next_target = instance->lower;
  93                break;
  94        default:
  95                break;
  96        }
  97
  98        return next_target;
  99}
 100
 101static void update_passive_instance(struct thermal_zone_device *tz,
 102                                enum thermal_trip_type type, int value)
 103{
 104        /*
 105         * If value is +1, activate a passive instance.
 106         * If value is -1, deactivate a passive instance.
 107         */
 108        if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
 109                tz->passive += value;
 110}
 111
 112static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
 113{
 114        long trip_temp;
 115        enum thermal_trip_type trip_type;
 116        enum thermal_trend trend;
 117        struct thermal_instance *instance;
 118        bool throttle = false;
 119        int old_target;
 120
 121        if (trip == THERMAL_TRIPS_NONE) {
 122                trip_temp = tz->forced_passive;
 123                trip_type = THERMAL_TRIPS_NONE;
 124        } else {
 125                tz->ops->get_trip_temp(tz, trip, &trip_temp);
 126                tz->ops->get_trip_type(tz, trip, &trip_type);
 127        }
 128
 129        trend = get_tz_trend(tz, trip);
 130
 131        if (tz->temperature >= trip_temp)
 132                throttle = true;
 133
 134        mutex_lock(&tz->lock);
 135
 136        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 137                if (instance->trip != trip)
 138                        continue;
 139
 140                old_target = instance->target;
 141                instance->target = get_target_state(instance, trend, throttle);
 142
 143                if (old_target == instance->target)
 144                        continue;
 145
 146                /* Activate a passive thermal instance */
 147                if (old_target == THERMAL_NO_TARGET &&
 148                        instance->target != THERMAL_NO_TARGET)
 149                        update_passive_instance(tz, trip_type, 1);
 150                /* Deactivate a passive thermal instance */
 151                else if (old_target != THERMAL_NO_TARGET &&
 152                        instance->target == THERMAL_NO_TARGET)
 153                        update_passive_instance(tz, trip_type, -1);
 154
 155
 156                instance->cdev->updated = false; /* cdev needs update */
 157        }
 158
 159        mutex_unlock(&tz->lock);
 160}
 161
 162/**
 163 * step_wise_throttle - throttles devices asscciated with the given zone
 164 * @tz - thermal_zone_device
 165 * @trip - the trip point
 166 * @trip_type - type of the trip point
 167 *
 168 * Throttling Logic: This uses the trend of the thermal zone to throttle.
 169 * If the thermal zone is 'heating up' this throttles all the cooling
 170 * devices associated with the zone and its particular trip point, by one
 171 * step. If the zone is 'cooling down' it brings back the performance of
 172 * the devices by one step.
 173 */
 174static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
 175{
 176        struct thermal_instance *instance;
 177
 178        thermal_zone_trip_update(tz, trip);
 179
 180        if (tz->forced_passive)
 181                thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
 182
 183        mutex_lock(&tz->lock);
 184
 185        list_for_each_entry(instance, &tz->thermal_instances, tz_node)
 186                thermal_cdev_update(instance->cdev);
 187
 188        mutex_unlock(&tz->lock);
 189
 190        return 0;
 191}
 192
 193static struct thermal_governor thermal_gov_step_wise = {
 194        .name           = "step_wise",
 195        .throttle       = step_wise_throttle,
 196};
 197
 198int thermal_gov_step_wise_register(void)
 199{
 200        return thermal_register_governor(&thermal_gov_step_wise);
 201}
 202
 203void thermal_gov_step_wise_unregister(void)
 204{
 205        thermal_unregister_governor(&thermal_gov_step_wise);
 206}
 207
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