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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  26
  27#include <linux/module.h>
  28#include <linux/thermal.h>
  29
  30#include "thermal_core.h"
  31
  32/*
  33 * If the temperature is higher than a trip point,
  34 *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
  35 *       state for this trip point
  36 *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
  37 *       state for this trip point
  38 *    c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
  39 *       for this trip point
  40 *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
  41 *       for this trip point
  42 * If the temperature is lower than a trip point,
  43 *    a. if the trend is THERMAL_TREND_RAISING, do nothing
  44 *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
  45 *       state for this trip point, if the cooling state already
  46 *       equals lower limit, deactivate the thermal instance
  47 *    c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
  48 *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
  49 *       if the cooling state already equals lower limit,
  50 *       deactive the thermal instance
  51 */
  52static unsigned long get_target_state(struct thermal_instance *instance,
  53                                enum thermal_trend trend, bool throttle)
  54{
  55        struct thermal_cooling_device *cdev = instance->cdev;
  56        unsigned long cur_state;
  57
  58        cdev->ops->get_cur_state(cdev, &cur_state);
  59
  60        switch (trend) {
  61        case THERMAL_TREND_RAISING:
  62                if (throttle)
  63                        cur_state = cur_state < instance->upper ?
  64                                    (cur_state + 1) : instance->upper;
  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                break;
  77        case THERMAL_TREND_DROP_FULL:
  78                if (cur_state == instance->lower) {
  79                        if (!throttle)
  80                                cur_state = -1;
  81                } else
  82                        cur_state = instance->lower;
  83                break;
  84        default:
  85                break;
  86        }
  87
  88        return cur_state;
  89}
  90
  91static void update_passive_instance(struct thermal_zone_device *tz,
  92                                enum thermal_trip_type type, int value)
  93{
  94        /*
  95         * If value is +1, activate a passive instance.
  96         * If value is -1, deactivate a passive instance.
  97         */
  98        if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
  99                tz->passive += value;
 100}
 101
 102static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
 103{
 104        long trip_temp;
 105        enum thermal_trip_type trip_type;
 106        enum thermal_trend trend;
 107        struct thermal_instance *instance;
 108        bool throttle = false;
 109        int old_target;
 110
 111        if (trip == THERMAL_TRIPS_NONE) {
 112                trip_temp = tz->forced_passive;
 113                trip_type = THERMAL_TRIPS_NONE;
 114        } else {
 115                tz->ops->get_trip_temp(tz, trip, &trip_temp);
 116                tz->ops->get_trip_type(tz, trip, &trip_type);
 117        }
 118
 119        trend = get_tz_trend(tz, trip);
 120
 121        if (tz->temperature >= trip_temp)
 122                throttle = true;
 123
 124        mutex_lock(&tz->lock);
 125
 126        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 127                if (instance->trip != trip)
 128                        continue;
 129
 130                old_target = instance->target;
 131                instance->target = get_target_state(instance, trend, throttle);
 132
 133                /* Activate a passive thermal instance */
 134                if (old_target == THERMAL_NO_TARGET &&
 135                        instance->target != THERMAL_NO_TARGET)
 136                        update_passive_instance(tz, trip_type, 1);
 137                /* Deactivate a passive thermal instance */
 138                else if (old_target != THERMAL_NO_TARGET &&
 139                        instance->target == THERMAL_NO_TARGET)
 140                        update_passive_instance(tz, trip_type, -1);
 141
 142
 143                instance->cdev->updated = false; /* cdev needs update */
 144        }
 145
 146        mutex_unlock(&tz->lock);
 147}
 148
 149/**
 150 * step_wise_throttle - throttles devices asscciated with the given zone
 151 * @tz - thermal_zone_device
 152 * @trip - the trip point
 153 * @trip_type - type of the trip point
 154 *
 155 * Throttling Logic: This uses the trend of the thermal zone to throttle.
 156 * If the thermal zone is 'heating up' this throttles all the cooling
 157 * devices associated with the zone and its particular trip point, by one
 158 * step. If the zone is 'cooling down' it brings back the performance of
 159 * the devices by one step.
 160 */
 161static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
 162{
 163        struct thermal_instance *instance;
 164
 165        thermal_zone_trip_update(tz, trip);
 166
 167        if (tz->forced_passive)
 168                thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
 169
 170        mutex_lock(&tz->lock);
 171
 172        list_for_each_entry(instance, &tz->thermal_instances, tz_node)
 173                thermal_cdev_update(instance->cdev);
 174
 175        mutex_unlock(&tz->lock);
 176
 177        return 0;
 178}
 179
 180static struct thermal_governor thermal_gov_step_wise = {
 181        .name           = "step_wise",
 182        .throttle       = step_wise_throttle,
 183        .owner          = THIS_MODULE,
 184};
 185
 186static int __init thermal_gov_step_wise_init(void)
 187{
 188        return thermal_register_governor(&thermal_gov_step_wise);
 189}
 190
 191static void __exit thermal_gov_step_wise_exit(void)
 192{
 193        thermal_unregister_governor(&thermal_gov_step_wise);
 194}
 195
 196/* This should load after thermal framework */
 197fs_initcall(thermal_gov_step_wise_init);
 198module_exit(thermal_gov_step_wise_exit);
 199
 200MODULE_AUTHOR("Durgadoss R");
 201MODULE_DESCRIPTION("A step-by-step thermal throttling governor");
 202MODULE_LICENSE("GPL");
 203
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