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
  55        cdev->ops->get_cur_state(cdev, &cur_state);
  56
  57        switch (trend) {
  58        case THERMAL_TREND_RAISING:
  59                if (throttle) {
  60                        cur_state = cur_state < instance->upper ?
  61                                    (cur_state + 1) : instance->upper;
  62                        if (cur_state < instance->lower)
  63                                cur_state = instance->lower;
  64                }
  65                break;
  66        case THERMAL_TREND_RAISE_FULL:
  67                if (throttle)
  68                        cur_state = instance->upper;
  69                break;
  70        case THERMAL_TREND_DROPPING:
  71                if (cur_state == instance->lower) {
  72                        if (!throttle)
  73                                cur_state = -1;
  74                } else {
  75                        cur_state -= 1;
  76                        if (cur_state > instance->upper)
  77                                cur_state = instance->upper;
  78                }
  79                break;
  80        case THERMAL_TREND_DROP_FULL:
  81                if (cur_state == instance->lower) {
  82                        if (!throttle)
  83                                cur_state = -1;
  84                } else
  85                        cur_state = instance->lower;
  86                break;
  87        default:
  88                break;
  89        }
  90
  91        return cur_state;
  92}
  93
  94static void update_passive_instance(struct thermal_zone_device *tz,
  95                                enum thermal_trip_type type, int value)
  96{
  97        /*
  98         * If value is +1, activate a passive instance.
  99         * If value is -1, deactivate a passive instance.
 100         */
 101        if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
 102                tz->passive += value;
 103}
 104
 105static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
 106{
 107        long trip_temp;
 108        enum thermal_trip_type trip_type;
 109        enum thermal_trend trend;
 110        struct thermal_instance *instance;
 111        bool throttle = false;
 112        int old_target;
 113
 114        if (trip == THERMAL_TRIPS_NONE) {
 115                trip_temp = tz->forced_passive;
 116                trip_type = THERMAL_TRIPS_NONE;
 117        } else {
 118                tz->ops->get_trip_temp(tz, trip, &trip_temp);
 119                tz->ops->get_trip_type(tz, trip, &trip_type);
 120        }
 121
 122        trend = get_tz_trend(tz, trip);
 123
 124        if (tz->temperature >= trip_temp)
 125                throttle = true;
 126
 127        mutex_lock(&tz->lock);
 128
 129        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 130                if (instance->trip != trip)
 131                        continue;
 132
 133                old_target = instance->target;
 134                instance->target = get_target_state(instance, trend, throttle);
 135
 136                /* Activate a passive thermal instance */
 137                if (old_target == THERMAL_NO_TARGET &&
 138                        instance->target != THERMAL_NO_TARGET)
 139                        update_passive_instance(tz, trip_type, 1);
 140                /* Deactivate a passive thermal instance */
 141                else if (old_target != THERMAL_NO_TARGET &&
 142                        instance->target == THERMAL_NO_TARGET)
 143                        update_passive_instance(tz, trip_type, -1);
 144
 145
 146                instance->cdev->updated = false; /* cdev needs update */
 147        }
 148
 149        mutex_unlock(&tz->lock);
 150}
 151
 152/**
 153 * step_wise_throttle - throttles devices asscciated with the given zone
 154 * @tz - thermal_zone_device
 155 * @trip - the trip point
 156 * @trip_type - type of the trip point
 157 *
 158 * Throttling Logic: This uses the trend of the thermal zone to throttle.
 159 * If the thermal zone is 'heating up' this throttles all the cooling
 160 * devices associated with the zone and its particular trip point, by one
 161 * step. If the zone is 'cooling down' it brings back the performance of
 162 * the devices by one step.
 163 */
 164static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
 165{
 166        struct thermal_instance *instance;
 167
 168        thermal_zone_trip_update(tz, trip);
 169
 170        if (tz->forced_passive)
 171                thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
 172
 173        mutex_lock(&tz->lock);
 174
 175        list_for_each_entry(instance, &tz->thermal_instances, tz_node)
 176                thermal_cdev_update(instance->cdev);
 177
 178        mutex_unlock(&tz->lock);
 179
 180        return 0;
 181}
 182
 183static struct thermal_governor thermal_gov_step_wise = {
 184        .name           = "step_wise",
 185        .throttle       = step_wise_throttle,
 186};
 187
 188int thermal_gov_step_wise_register(void)
 189{
 190        return thermal_register_governor(&thermal_gov_step_wise);
 191}
 192
 193void thermal_gov_step_wise_unregister(void)
 194{
 195        thermal_unregister_governor(&thermal_gov_step_wise);
 196}
 197
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