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
  27 #include "thermal_core.h"
  28
  29 /**
  30  * get_trip_level: - obtains the current trip level for a zone
  31  * @tz:         thermal zone device
  32  */
  33 static int get_trip_level(struct thermal_zone_device *tz)
  34 {
  35         int count = 0;
  36         unsigned long trip_temp;
  37
  38         if (tz->trips == 0 || !tz->ops->get_trip_temp)
  39                 return 0;
  40
  41         for (count = 0; count < tz->trips; count++) {
  42                 tz->ops->get_trip_temp(tz, count, &trip_temp);
  43                 if (tz->temperature < trip_temp)
  44                         break;
  45         }
  46         return count;
  47 }
  48
  49 static long get_target_state(struct thermal_zone_device *tz,
  50                 struct thermal_cooling_device *cdev, int weight, int level)
  51 {
  52         unsigned long max_state;
  53
  54         cdev->ops->get_max_state(cdev, &max_state);
  55
  56         return (long)(weight * level * max_state) / (100 * tz->trips);
  57 }
  58
  59 /**
  60  * fair_share_throttle - throttles devices asscciated with the given zone
  61  * @tz - thermal_zone_device
  62  *
  63  * Throttling Logic: This uses three parameters to calculate the new
  64  * throttle state of the cooling devices associated with the given zone.
  65  *
  66  * Parameters used for Throttling:
  67  * P1. max_state: Maximum throttle state exposed by the cooling device.
  68  * P2. weight[i]/100:
  69  *      How 'effective' the 'i'th device is, in cooling the given zone.
  70  * P3. cur_trip_level/max_no_of_trips:
  71  *      This describes the extent to which the devices should be throttled.
  72  *      We do not want to throttle too much when we trip a lower temperature,
  73  *      whereas the throttling is at full swing if we trip critical levels.
  74  *      (Heavily assumes the trip points are in ascending order)
  75  * new_state of cooling device = P3 * P2 * P1
  76  */
  77 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
  78 {
  79         const struct thermal_zone_params *tzp;
  80         struct thermal_cooling_device *cdev;
  81         struct thermal_instance *instance;
  82         int i;
  83         int cur_trip_level = get_trip_level(tz);
  84
  85         if (!tz->tzp || !tz->tzp->tbp)
  86                 return -EINVAL;
  87
  88         tzp = tz->tzp;
  89
  90         for (i = 0; i < tzp->num_tbps; i++) {
  91                 if (!tzp->tbp[i].cdev)
  92                         continue;
  93
  94                 cdev = tzp->tbp[i].cdev;
  95                 instance = get_thermal_instance(tz, cdev, trip);
  96                 if (!instance)
  97                         continue;
  98
  99                 instance->target = get_target_state(tz, cdev,
 100                                         tzp->tbp[i].weight, cur_trip_level);
 101
 102                 instance->cdev->updated = false;
 103                 thermal_cdev_update(cdev);
 104         }
 105         return 0;
 106 }
 107
 108 static struct thermal_governor thermal_gov_fair_share = {
 109         .name           = "fair_share",
 110         .throttle       = fair_share_throttle,
 111 };
 112
 113 int thermal_gov_fair_share_register(void)
 114 {
 115         return thermal_register_governor(&thermal_gov_fair_share);
 116 }
 117
 118 void thermal_gov_fair_share_unregister(void)
 119 {
 120         thermal_unregister_governor(&thermal_gov_fair_share);
 121 }
 122