linux/drivers/thermal/fair_share.c
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   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 */
  36static 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
  52static 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 */
  80static 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
 111static struct thermal_governor thermal_gov_fair_share = {
 112        .name           = "fair_share",
 113        .throttle       = fair_share_throttle,
 114        .owner          = THIS_MODULE,
 115};
 116
 117static int __init thermal_gov_fair_share_init(void)
 118{
 119        return thermal_register_governor(&thermal_gov_fair_share);
 120}
 121
 122static 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 */
 128fs_initcall(thermal_gov_fair_share_init);
 129module_exit(thermal_gov_fair_share_exit);
 130
 131MODULE_AUTHOR("Durgadoss R");
 132MODULE_DESCRIPTION("A simple weight based thermal throttling governor");
 133MODULE_LICENSE("GPL");
 134
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