drivers/thermal/fair_share.c

   1 /*
   2  *  fair_share.c - A simple weight based Thermal 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 #include <trace/events/thermal.h>
  27
  28 #include "thermal_core.h"
  29
  30 /**
  31  * get_trip_level: - obtains the current trip level for a zone
  32  * @tz:         thermal zone device
  33  */
  34 static int get_trip_level(struct thermal_zone_device *tz)
  35 {
  36         int count = 0;
  37         int trip_temp;
  38         enum thermal_trip_type trip_type;
  39
  40         if (tz->trips == 0 || !tz->ops->get_trip_temp)
  41                 return 0;
  42
  43         for (count = 0; count < tz->trips; count++) {
  44                 tz->ops->get_trip_temp(tz, count, &trip_temp);
  45                 if (tz->temperature < trip_temp)
  46                         break;
  47         }
  48
  49         /*
  50          * count > 0 only if temperature is greater than first trip
  51          * point, in which case, trip_point = count - 1
  52          */
  53         if (count > 0) {
  54                 tz->ops->get_trip_type(tz, count - 1, &trip_type);
  55                 trace_thermal_zone_trip(tz, count - 1, trip_type);
  56         }
  57
  58         return count;
  59 }
  60
  61 static long get_target_state(struct thermal_zone_device *tz,
  62                 struct thermal_cooling_device *cdev, int percentage, int level)
  63 {
  64         unsigned long max_state;
  65
  66         cdev->ops->get_max_state(cdev, &max_state);
  67
  68         return (long)(percentage * level * max_state) / (100 * tz->trips);
  69 }
  70
  71 /**
  72  * fair_share_throttle - throttles devices associated with the given zone
  73  * @tz - thermal_zone_device
  74  *
  75  * Throttling Logic: This uses three parameters to calculate the new
  76  * throttle state of the cooling devices associated with the given zone.
  77  *
  78  * Parameters used for Throttling:
  79  * P1. max_state: Maximum throttle state exposed by the cooling device.
  80  * P2. percentage[i]/100:
  81  *      How 'effective' the 'i'th device is, in cooling the given zone.
  82  * P3. cur_trip_level/max_no_of_trips:
  83  *      This describes the extent to which the devices should be throttled.
  84  *      We do not want to throttle too much when we trip a lower temperature,
  85  *      whereas the throttling is at full swing if we trip critical levels.
  86  *      (Heavily assumes the trip points are in ascending order)
  87  * new_state of cooling device = P3 * P2 * P1
  88  */
  89 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
  90 {
  91         struct thermal_instance *instance;
  92         int total_weight = 0;
  93         int total_instance = 0;
  94         int cur_trip_level = get_trip_level(tz);
  95
  96         mutex_lock(&tz->lock);
  97
  98         list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
  99                 if (instance->trip != trip)
 100                         continue;
 101
 102                 total_weight += instance->weight;
 103                 total_instance++;
 104         }
 105
 106         list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 107                 int percentage;
 108                 struct thermal_cooling_device *cdev = instance->cdev;
 109
 110                 if (instance->trip != trip)
 111                         continue;
 112
 113                 if (!total_weight)
 114                         percentage = 100 / total_instance;
 115                 else
 116                         percentage = (instance->weight * 100) / total_weight;
 117
 118                 instance->target = get_target_state(tz, cdev, percentage,
 119                                                     cur_trip_level);
 120
 121                 instance->cdev->updated = false;
 122                 thermal_cdev_update(cdev);
 123         }
 124
 125         mutex_unlock(&tz->lock);
 126         return 0;
 127 }
 128
 129 static struct thermal_governor thermal_gov_fair_share = {
 130         .name           = "fair_share",
 131         .throttle       = fair_share_throttle,
 132 };
 133
 134 int thermal_gov_fair_share_register(void)
 135 {
 136         return thermal_register_governor(&thermal_gov_fair_share);
 137 }
 138
 139 void thermal_gov_fair_share_unregister(void)
 140 {
 141         thermal_unregister_governor(&thermal_gov_fair_share);
 142 }
 143