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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  26
  27 #include <linux/module.h>
  28 #include <linux/thermal.h>
  29
  30 #include "thermal_core.h"
  31
  32 /**
  33  * get_trip_level: - obtains the current trip level for a zone
  34  * @tz:         thermal zone device
  35  */
  36 static int get_trip_level(struct thermal_zone_device *tz)
  37 {
  38         int count = 0;
  39         unsigned long trip_temp;
  40
  41         if (tz->trips == 0 || !tz->ops->get_trip_temp)
  42                 return 0;
  43
  44         for (count = 0; count < tz->trips; count++) {
  45                 tz->ops->get_trip_temp(tz, count, &trip_temp);
  46                 if (tz->temperature < trip_temp)
  47                         break;
  48         }
  49         return count;
  50 }
  51
  52 static long get_target_state(struct thermal_zone_device *tz,
  53                 struct thermal_cooling_device *cdev, int weight, int level)
  54 {
  55         unsigned long max_state;
  56
  57         cdev->ops->get_max_state(cdev, &max_state);
  58
  59         return (long)(weight * level * max_state) / (100 * tz->trips);
  60 }
  61
  62 /**
  63  * fair_share_throttle - throttles devices asscciated with the given zone
  64  * @tz - thermal_zone_device
  65  *
  66  * Throttling Logic: This uses three parameters to calculate the new
  67  * throttle state of the cooling devices associated with the given zone.
  68  *
  69  * Parameters used for Throttling:
  70  * P1. max_state: Maximum throttle state exposed by the cooling device.
  71  * P2. weight[i]/100:
  72  *      How 'effective' the 'i'th device is, in cooling the given zone.
  73  * P3. cur_trip_level/max_no_of_trips:
  74  *      This describes the extent to which the devices should be throttled.
  75  *      We do not want to throttle too much when we trip a lower temperature,
  76  *      whereas the throttling is at full swing if we trip critical levels.
  77  *      (Heavily assumes the trip points are in ascending order)
  78  * new_state of cooling device = P3 * P2 * P1
  79  */
  80 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
  81 {
  82         const struct thermal_zone_params *tzp;
  83         struct thermal_cooling_device *cdev;
  84         struct thermal_instance *instance;
  85         int i;
  86         int cur_trip_level = get_trip_level(tz);
  87
  88         if (!tz->tzp || !tz->tzp->tbp)
  89                 return -EINVAL;
  90
  91         tzp = tz->tzp;
  92
  93         for (i = 0; i < tzp->num_tbps; i++) {
  94                 if (!tzp->tbp[i].cdev)
  95                         continue;
  96
  97                 cdev = tzp->tbp[i].cdev;
  98                 instance = get_thermal_instance(tz, cdev, trip);
  99                 if (!instance)
 100                         continue;
 101
 102                 instance->target = get_target_state(tz, cdev,
 103                                         tzp->tbp[i].weight, cur_trip_level);
 104
 105                 instance->cdev->updated = false;
 106                 thermal_cdev_update(cdev);
 107         }
 108         return 0;
 109 }
 110
 111 static struct thermal_governor thermal_gov_fair_share = {
 112         .name           = "fair_share",
 113         .throttle       = fair_share_throttle,
 114         .owner          = THIS_MODULE,
 115 };
 116
 117 static int __init thermal_gov_fair_share_init(void)
 118 {
 119         return thermal_register_governor(&thermal_gov_fair_share);
 120 }
 121
 122 static void __exit thermal_gov_fair_share_exit(void)
 123 {
 124         thermal_unregister_governor(&thermal_gov_fair_share);
 125 }
 126
 127 /* This should load after thermal framework */
 128 fs_initcall(thermal_gov_fair_share_init);
 129 module_exit(thermal_gov_fair_share_exit);
 130
 131 MODULE_AUTHOR("Durgadoss R");
 132 MODULE_DESCRIPTION("A simple weight based thermal throttling governor");
 133 MODULE_LICENSE("GPL");