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         dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
  64
  65         switch (trend) {
  66         case THERMAL_TREND_RAISING:
  67                 if (throttle) {
  68                         next_target = cur_state < instance->upper ?
  69                                     (cur_state + 1) : instance->upper;
  70                         if (next_target < instance->lower)
  71                                 next_target = instance->lower;
  72                 }
  73                 break;
  74         case THERMAL_TREND_RAISE_FULL:
  75                 if (throttle)
  76                         next_target = instance->upper;
  77                 break;
  78         case THERMAL_TREND_DROPPING:
  79                 if (cur_state <= instance->lower) {
  80                         if (!throttle)
  81                                 next_target = THERMAL_NO_TARGET;
  82                 } else {
  83                         next_target = cur_state - 1;
  84                         if (next_target > instance->upper)
  85                                 next_target = instance->upper;
  86                 }
  87                 break;
  88         case THERMAL_TREND_DROP_FULL:
  89                 if (cur_state == instance->lower) {
  90                         if (!throttle)
  91                                 next_target = THERMAL_NO_TARGET;
  92                 } else
  93                         next_target = instance->lower;
  94                 break;
  95         default:
  96                 break;
  97         }
  98
  99         return next_target;
 100 }
 101
 102 static void update_passive_instance(struct thermal_zone_device *tz,
 103                                 enum thermal_trip_type type, int value)
 104 {
 105         /*
 106          * If value is +1, activate a passive instance.
 107          * If value is -1, deactivate a passive instance.
 108          */
 109         if (type == THERMAL_TRIP_PASSIVE || type == THERMAL_TRIPS_NONE)
 110                 tz->passive += value;
 111 }
 112
 113 static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
 114 {
 115         long trip_temp;
 116         enum thermal_trip_type trip_type;
 117         enum thermal_trend trend;
 118         struct thermal_instance *instance;
 119         bool throttle = false;
 120         int old_target;
 121
 122         if (trip == THERMAL_TRIPS_NONE) {
 123                 trip_temp = tz->forced_passive;
 124                 trip_type = THERMAL_TRIPS_NONE;
 125         } else {
 126                 tz->ops->get_trip_temp(tz, trip, &trip_temp);
 127                 tz->ops->get_trip_type(tz, trip, &trip_type);
 128         }
 129
 130         trend = get_tz_trend(tz, trip);
 131
 132         if (tz->temperature >= trip_temp)
 133                 throttle = true;
 134
 135         dev_dbg(&tz->device, "Trip%d[type=%d,temp=%ld]:trend=%d,throttle=%d\n",
 136                                 trip, trip_type, trip_temp, trend, throttle);
 137
 138         mutex_lock(&tz->lock);
 139
 140         list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 141                 if (instance->trip != trip)
 142                         continue;
 143
 144                 old_target = instance->target;
 145                 instance->target = get_target_state(instance, trend, throttle);
 146                 dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
 147                                         old_target, (int)instance->target);
 148
 149                 /* Activate a passive thermal instance */
 150                 if (old_target == THERMAL_NO_TARGET &&
 151                         instance->target != THERMAL_NO_TARGET)
 152                         update_passive_instance(tz, trip_type, 1);
 153                 /* Deactivate a passive thermal instance */
 154                 else if (old_target != THERMAL_NO_TARGET &&
 155                         instance->target == THERMAL_NO_TARGET)
 156                         update_passive_instance(tz, trip_type, -1);
 157
 158
 159                 instance->cdev->updated = false; /* cdev needs update */
 160         }
 161
 162         mutex_unlock(&tz->lock);
 163 }
 164
 165 /**
 166  * step_wise_throttle - throttles devices asscciated with the given zone
 167  * @tz - thermal_zone_device
 168  * @trip - the trip point
 169  * @trip_type - type of the trip point
 170  *
 171  * Throttling Logic: This uses the trend of the thermal zone to throttle.
 172  * If the thermal zone is 'heating up' this throttles all the cooling
 173  * devices associated with the zone and its particular trip point, by one
 174  * step. If the zone is 'cooling down' it brings back the performance of
 175  * the devices by one step.
 176  */
 177 static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
 178 {
 179         struct thermal_instance *instance;
 180
 181         thermal_zone_trip_update(tz, trip);
 182
 183         if (tz->forced_passive)
 184                 thermal_zone_trip_update(tz, THERMAL_TRIPS_NONE);
 185
 186         mutex_lock(&tz->lock);
 187
 188         list_for_each_entry(instance, &tz->thermal_instances, tz_node)
 189                 thermal_cdev_update(instance->cdev);
 190
 191         mutex_unlock(&tz->lock);
 192
 193         return 0;
 194 }
 195
 196 static struct thermal_governor thermal_gov_step_wise = {
 197         .name           = "step_wise",
 198         .throttle       = step_wise_throttle,
 199 };
 200
 201 int thermal_gov_step_wise_register(void)
 202 {
 203         return thermal_register_governor(&thermal_gov_step_wise);
 204 }
 205
 206 void thermal_gov_step_wise_unregister(void)
 207 {
 208         thermal_unregister_governor(&thermal_gov_step_wise);
 209 }