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 */
  39static unsigned long get_target_state(struct thermal_instance *instance,
  40                                        enum thermal_trend trend)
  41{
  42        struct thermal_cooling_device *cdev = instance->cdev;
  43        unsigned long cur_state;
  44
  45        cdev->ops->get_cur_state(cdev, &cur_state);
  46
  47        if (trend == THERMAL_TREND_RAISING) {
  48                cur_state = cur_state < instance->upper ?
  49                            (cur_state + 1) : instance->upper;
  50        } else if (trend == THERMAL_TREND_DROPPING) {
  51                cur_state = cur_state > instance->lower ?
  52                            (cur_state - 1) : instance->lower;
  53        }
  54
  55        return cur_state;
  56}
  57
  58static void update_passive_instance(struct thermal_zone_device *tz,
  59                                enum thermal_trip_type type, int value)
  60{
  61        /*
  62         * If value is +1, activate a passive instance.
  63         * If value is -1, deactivate a passive instance.
  64         */
  65        if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
  66                tz->passive += value;
  67}
  68
  69static void update_instance_for_throttle(struct thermal_zone_device *tz,
  70                                int trip, enum thermal_trip_type trip_type,
  71                                enum thermal_trend trend)
  72{
  73        struct thermal_instance *instance;
  74
  75        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
  76                if (instance->trip != trip)
  77                        continue;
  78
  79                instance->target = get_target_state(instance, trend);
  80
  81                /* Activate a passive thermal instance */
  82                if (instance->target == THERMAL_NO_TARGET)
  83                        update_passive_instance(tz, trip_type, 1);
  84
  85                instance->cdev->updated = false; /* cdev needs update */
  86        }
  87}
  88
  89static void update_instance_for_dethrottle(struct thermal_zone_device *tz,
  90                                int trip, enum thermal_trip_type trip_type)
  91{
  92        struct thermal_instance *instance;
  93        struct thermal_cooling_device *cdev;
  94        unsigned long cur_state;
  95
  96        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
  97                if (instance->trip != trip ||
  98                        instance->target == THERMAL_NO_TARGET)
  99                        continue;
 100
 101                cdev = instance->cdev;
 102                cdev->ops->get_cur_state(cdev, &cur_state);
 103
 104                instance->target = cur_state > instance->lower ?
 105                            (cur_state - 1) : THERMAL_NO_TARGET;
 106
 107                /* Deactivate a passive thermal instance */
 108                if (instance->target == THERMAL_NO_TARGET)
 109                        update_passive_instance(tz, trip_type, -1);
 110
 111                cdev->updated = false; /* cdev needs update */
 112        }
 113}
 114
 115static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
 116{
 117        long trip_temp;
 118        enum thermal_trip_type trip_type;
 119        enum thermal_trend trend;
 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        mutex_lock(&tz->lock);
 132
 133        if (tz->temperature >= trip_temp)
 134                update_instance_for_throttle(tz, trip, trip_type, trend);
 135        else
 136                update_instance_for_dethrottle(tz, trip, trip_type);
 137
 138        mutex_unlock(&tz->lock);
 139}
 140
 141/**
 142 * step_wise_throttle - throttles devices asscciated with the given zone
 143 * @tz - thermal_zone_device
 144 * @trip - the trip point
 145 * @trip_type - type of the trip point
 146 *
 147 * Throttling Logic: This uses the trend of the thermal zone to throttle.
 148 * If the thermal zone is 'heating up' this throttles all the cooling
 149 * devices associated with the zone and its particular trip point, by one
 150 * step. If the zone is 'cooling down' it brings back the performance of
 151 * the devices by one step.
 152 */
 153static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
 154{
 155        struct thermal_instance *instance;
 156
 157        thermal_zone_trip_update(tz, trip);
 158
 159        if (tz->forced_passive)
 160                thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
 161
 162        mutex_lock(&tz->lock);
 163
 164        list_for_each_entry(instance, &tz->thermal_instances, tz_node)
 165                thermal_cdev_update(instance->cdev);
 166
 167        mutex_unlock(&tz->lock);
 168
 169        return 0;
 170}
 171
 172static struct thermal_governor thermal_gov_step_wise = {
 173        .name           = "step_wise",
 174        .throttle       = step_wise_throttle,
 175        .owner          = THIS_MODULE,
 176};
 177
 178static int __init thermal_gov_step_wise_init(void)
 179{
 180        return thermal_register_governor(&thermal_gov_step_wise);
 181}
 182
 183static void __exit thermal_gov_step_wise_exit(void)
 184{
 185        thermal_unregister_governor(&thermal_gov_step_wise);
 186}
 187
 188/* This should load after thermal framework */
 189fs_initcall(thermal_gov_step_wise_init);
 190module_exit(thermal_gov_step_wise_exit);
 191
 192MODULE_AUTHOR("Durgadoss R");
 193MODULE_DESCRIPTION("A step-by-step thermal throttling governor");
 194MODULE_LICENSE("GPL");
 195
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