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#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 */
  33static 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
  49static 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 */
  77static 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
 108static struct thermal_governor thermal_gov_fair_share = {
 109        .name           = "fair_share",
 110        .throttle       = fair_share_throttle,
 111};
 112
 113int thermal_gov_fair_share_register(void)
 114{
 115        return thermal_register_governor(&thermal_gov_fair_share);
 116}
 117
 118void thermal_gov_fair_share_unregister(void)
 119{
 120        thermal_unregister_governor(&thermal_gov_fair_share);
 121}
 122
 123
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