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 #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  */
  49 static 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
 101 static 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
 112 static 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  */
 174 static 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
 193 static struct thermal_governor thermal_gov_step_wise = {
 194         .name           = "step_wise",
 195         .throttle       = step_wise_throttle,
 196 };
 197
 198 int thermal_gov_step_wise_register(void)
 199 {
 200         return thermal_register_governor(&thermal_gov_step_wise);
 201 }
 202
 203 void thermal_gov_step_wise_unregister(void)
 204 {
 205         thermal_unregister_governor(&thermal_gov_step_wise);
 206 }