LXR linux/drivers/thermal/fair

   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 */
  34static 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
  61static 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 */
  89static 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        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
  97                if (instance->trip != trip)
  98                        continue;
  99
 100                total_weight += instance->weight;
 101                total_instance++;
 102        }
 103
 104        list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
 105                int percentage;
 106                struct thermal_cooling_device *cdev = instance->cdev;
 107
 108                if (instance->trip != trip)
 109                        continue;
 110
 111                if (!total_weight)
 112                        percentage = 100 / total_instance;
 113                else
 114                        percentage = (instance->weight * 100) / total_weight;
 115
 116                instance->target = get_target_state(tz, cdev, percentage,
 117                                                    cur_trip_level);
 118
 119                instance->cdev->updated = false;
 120                thermal_cdev_update(cdev);
 121        }
 122        return 0;
 123}
 124
 125static struct thermal_governor thermal_gov_fair_share = {
 126        .name           = "fair_share",
 127        .throttle       = fair_share_throttle,
 128};
 129
 130int thermal_gov_fair_share_register(void)
 131{
 132        return thermal_register_governor(&thermal_gov_fair_share);
 133}
 134
 135void thermal_gov_fair_share_unregister(void)
 136{
 137        thermal_unregister_governor(&thermal_gov_fair_share);
 138}
 139
 140