drivers/thermal/step_wise.c

   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  */
  52 static 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
  91 static 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
 102 static 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  */
 161 static 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
 180 static struct thermal_governor thermal_gov_step_wise = {
 181         .name           = "step_wise",
 182         .throttle       = step_wise_throttle,
 183         .owner          = THIS_MODULE,
 184 };
 185
 186 static int __init thermal_gov_step_wise_init(void)
 187 {
 188         return thermal_register_governor(&thermal_gov_step_wise);
 189 }
 190
 191 static 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 */
 197 fs_initcall(thermal_gov_step_wise_init);
 198 module_exit(thermal_gov_step_wise_exit);
 199
 200 MODULE_AUTHOR("Durgadoss R");
 201 MODULE_DESCRIPTION("A step-by-step thermal throttling governor");
 202 MODULE_LICENSE("GPL");