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         dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
  57
  58         switch (trend) {
  59         case THERMAL_TREND_RAISING:
  60                 if (throttle) {
  61                         cur_state = cur_state < instance->upper ?
  62                                     (cur_state + 1) : instance->upper;
  63                         if (cur_state < instance->lower)
  64                                 cur_state = instance->lower;
  65                 }
  66                 break;
  67         case THERMAL_TREND_RAISE_FULL:
  68                 if (throttle)
  69                         cur_state = instance->upper;
  70                 break;
  71         case THERMAL_TREND_DROPPING:
  72                 if (cur_state == instance->lower) {
  73                         if (!throttle)
  74                                 cur_state = -1;
  75                 } else {
  76                         cur_state -= 1;
  77                         if (cur_state > instance->upper)
  78                                 cur_state = instance->upper;
  79                 }
  80                 break;
  81         case THERMAL_TREND_DROP_FULL:
  82                 if (cur_state == instance->lower) {
  83                         if (!throttle)
  84                                 cur_state = -1;
  85                 } else
  86                         cur_state = instance->lower;
  87                 break;
  88         default:
  89                 break;
  90         }
  91
  92         return cur_state;
  93 }
  94
  95 static void update_passive_instance(struct thermal_zone_device *tz,
  96                                 enum thermal_trip_type type, int value)
  97 {
  98         /*
  99          * If value is +1, activate a passive instance.
 100          * If value is -1, deactivate a passive instance.
 101          */
 102         if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
 103                 tz->passive += value;
 104 }
 105
 106 static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
 107 {
 108         long trip_temp;
 109         enum thermal_trip_type trip_type;
 110         enum thermal_trend trend;
 111         struct thermal_instance *instance;
 112         bool throttle = false;
 113         int old_target;
 114
 115         if (trip == THERMAL_TRIPS_NONE) {
 116                 trip_temp = tz->forced_passive;
 117                 trip_type = THERMAL_TRIPS_NONE;
 118         } else {
 119                 tz->ops->get_trip_temp(tz, trip, &trip_temp);
 120                 tz->ops->get_trip_type(tz, trip, &trip_type);
 121         }
 122
 123         trend = get_tz_trend(tz, trip);
 124
 125         if (tz->temperature >= trip_temp)
 126                 throttle = true;
 127
 128         dev_dbg(&tz->device, "Trip%d[type=%d,temp=%ld]:trend=%d,throttle=%d\n",
 129                                 trip, trip_type, trip_temp, trend, throttle);
 130
 131         mutex_lock(&tz->lock);
 132
 133         list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 134                 if (instance->trip != trip)
 135                         continue;
 136
 137                 old_target = instance->target;
 138                 instance->target = get_target_state(instance, trend, throttle);
 139                 dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
 140                                         old_target, (int)instance->target);
 141
 142                 /* Activate a passive thermal instance */
 143                 if (old_target == THERMAL_NO_TARGET &&
 144                         instance->target != THERMAL_NO_TARGET)
 145                         update_passive_instance(tz, trip_type, 1);
 146                 /* Deactivate a passive thermal instance */
 147                 else if (old_target != THERMAL_NO_TARGET &&
 148                         instance->target == THERMAL_NO_TARGET)
 149                         update_passive_instance(tz, trip_type, -1);
 150
 151
 152                 instance->cdev->updated = false; /* cdev needs update */
 153         }
 154
 155         mutex_unlock(&tz->lock);
 156 }
 157
 158 /**
 159  * step_wise_throttle - throttles devices asscciated with the given zone
 160  * @tz - thermal_zone_device
 161  * @trip - the trip point
 162  * @trip_type - type of the trip point
 163  *
 164  * Throttling Logic: This uses the trend of the thermal zone to throttle.
 165  * If the thermal zone is 'heating up' this throttles all the cooling
 166  * devices associated with the zone and its particular trip point, by one
 167  * step. If the zone is 'cooling down' it brings back the performance of
 168  * the devices by one step.
 169  */
 170 static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
 171 {
 172         struct thermal_instance *instance;
 173
 174         thermal_zone_trip_update(tz, trip);
 175
 176         if (tz->forced_passive)
 177                 thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
 178
 179         mutex_lock(&tz->lock);
 180
 181         list_for_each_entry(instance, &tz->thermal_instances, tz_node)
 182                 thermal_cdev_update(instance->cdev);
 183
 184         mutex_unlock(&tz->lock);
 185
 186         return 0;
 187 }
 188
 189 static struct thermal_governor thermal_gov_step_wise = {
 190         .name           = "step_wise",
 191         .throttle       = step_wise_throttle,
 192 };
 193
 194 int thermal_gov_step_wise_register(void)
 195 {
 196         return thermal_register_governor(&thermal_gov_step_wise);
 197 }
 198
 199 void thermal_gov_step_wise_unregister(void)
 200 {
 201         thermal_unregister_governor(&thermal_gov_step_wise);
 202 }