drivers/thermal/gov_fair_share.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  fair_share.c - A simple weight based Thermal governor
   4  *
   5  *  Copyright (C) 2012 Intel Corp
   6  *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
   7  *
   8  *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   9  *
  10  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  11  */
  12
  13 #include <linux/thermal.h>
  14 #include "thermal_trace.h"
  15
  16 #include "thermal_core.h"
  17
  18 /**
  19  * get_trip_level: - obtains the current trip level for a zone
  20  * @tz:         thermal zone device
  21  */
  22 static int get_trip_level(struct thermal_zone_device *tz)
  23 {
  24         struct thermal_trip trip;
  25         int count;
  26
  27         for (count = 0; count < tz->num_trips; count++) {
  28                 __thermal_zone_get_trip(tz, count, &trip);
  29                 if (tz->temperature < trip.temperature)
  30                         break;
  31         }
  32
  33         /*
  34          * count > 0 only if temperature is greater than first trip
  35          * point, in which case, trip_point = count - 1
  36          */
  37         if (count > 0)
  38                 trace_thermal_zone_trip(tz, count - 1, trip.type);
  39
  40         return count;
  41 }
  42
  43 static long get_target_state(struct thermal_zone_device *tz,
  44                 struct thermal_cooling_device *cdev, int percentage, int level)
  45 {
  46         return (long)(percentage * level * cdev->max_state) / (100 * tz->num_trips);
  47 }
  48
  49 /**
  50  * fair_share_throttle - throttles devices associated with the given zone
  51  * @tz: thermal_zone_device
  52  * @trip: trip point index
  53  *
  54  * Throttling Logic: This uses three parameters to calculate the new
  55  * throttle state of the cooling devices associated with the given zone.
  56  *
  57  * Parameters used for Throttling:
  58  * P1. max_state: Maximum throttle state exposed by the cooling device.
  59  * P2. percentage[i]/100:
  60  *      How 'effective' the 'i'th device is, in cooling the given zone.
  61  * P3. cur_trip_level/max_no_of_trips:
  62  *      This describes the extent to which the devices should be throttled.
  63  *      We do not want to throttle too much when we trip a lower temperature,
  64  *      whereas the throttling is at full swing if we trip critical levels.
  65  *      (Heavily assumes the trip points are in ascending order)
  66  * new_state of cooling device = P3 * P2 * P1
  67  */
  68 static int fair_share_throttle(struct thermal_zone_device *tz, int trip)
  69 {
  70         struct thermal_instance *instance;
  71         int total_weight = 0;
  72         int total_instance = 0;
  73         int cur_trip_level = get_trip_level(tz);
  74
  75         lockdep_assert_held(&tz->lock);
  76
  77         list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
  78                 if (instance->trip != trip)
  79                         continue;
  80
  81                 total_weight += instance->weight;
  82                 total_instance++;
  83         }
  84
  85         list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
  86                 int percentage;
  87                 struct thermal_cooling_device *cdev = instance->cdev;
  88
  89                 if (instance->trip != trip)
  90                         continue;
  91
  92                 if (!total_weight)
  93                         percentage = 100 / total_instance;
  94                 else
  95                         percentage = (instance->weight * 100) / total_weight;
  96
  97                 instance->target = get_target_state(tz, cdev, percentage,
  98                                                     cur_trip_level);
  99
 100                 mutex_lock(&cdev->lock);
 101                 __thermal_cdev_update(cdev);
 102                 mutex_unlock(&cdev->lock);
 103         }
 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 THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);