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
  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
  94 static 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
 105 static 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  */
 164 static 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
 183 static struct thermal_governor thermal_gov_step_wise = {
 184         .name           = "step_wise",
 185         .throttle       = step_wise_throttle,
 186 };
 187
 188 int thermal_gov_step_wise_register(void)
 189 {
 190         return thermal_register_governor(&thermal_gov_step_wise);
 191 }
 192
 193 void thermal_gov_step_wise_unregister(void)
 194 {
 195         thermal_unregister_governor(&thermal_gov_step_wise);
 196 }