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 <[email protected]>
   7  *
   8  *  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   9  *
  10  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  11  */
  12
  13 #include <linux/thermal.h>
  14 #include "thermal_trace.h"
  15
  16 #include "thermal_core.h"
  17
  18 static int get_trip_level(struct thermal_zone_device *tz)
  19 {
  20         const struct thermal_trip_desc *level_td = NULL;
  21         const struct thermal_trip_desc *td;
  22         int trip_level = -1;
  23
  24         for_each_trip_desc(tz, td) {
  25                 if (td->threshold > tz->temperature)
  26                         continue;
  27
  28                 trip_level++;
  29
  30                 if (!level_td || td->threshold > level_td->threshold)
  31                         level_td = td;
  32         }
  33
  34         /*  Bail out if the temperature is not greater than any trips. */
  35         if (trip_level < 0)
  36                 return 0;
  37
  38         trace_thermal_zone_trip(tz, thermal_zone_trip_id(tz, &level_td->trip),
  39                                 level_td->trip.type);
  40
  41         return trip_level;
  42 }
  43
  44 /**
  45  * fair_share_throttle - throttles devices associated with the given zone
  46  * @tz: thermal_zone_device
  47  * @td: trip point descriptor
  48  * @trip_level: number of trips crossed by the zone temperature
  49  *
  50  * Throttling Logic: This uses three parameters to calculate the new
  51  * throttle state of the cooling devices associated with the given zone.
  52  *
  53  * Parameters used for Throttling:
  54  * P1. max_state: Maximum throttle state exposed by the cooling device.
  55  * P2. weight[i]/total_weight:
  56  *      How 'effective' the 'i'th device is, in cooling the given zone.
  57  * P3. trip_level/max_no_of_trips:
  58  *      This describes the extent to which the devices should be throttled.
  59  *      We do not want to throttle too much when we trip a lower temperature,
  60  *      whereas the throttling is at full swing if we trip critical levels.
  61  * new_state of cooling device = P3 * P2 * P1
  62  */
  63 static void fair_share_throttle(struct thermal_zone_device *tz,
  64                                 const struct thermal_trip_desc *td,
  65                                 int trip_level)
  66 {
  67         struct thermal_instance *instance;
  68         int total_weight = 0;
  69         int nr_instances = 0;
  70
  71         list_for_each_entry(instance, &td->thermal_instances, trip_node) {
  72                 total_weight += instance->weight;
  73                 nr_instances++;
  74         }
  75
  76         list_for_each_entry(instance, &td->thermal_instances, trip_node) {
  77                 struct thermal_cooling_device *cdev = instance->cdev;
  78                 u64 dividend;
  79                 u32 divisor;
  80
  81                 dividend = trip_level;
  82                 dividend *= cdev->max_state;
  83                 divisor = tz->num_trips;
  84                 if (total_weight) {
  85                         dividend *= instance->weight;
  86                         divisor *= total_weight;
  87                 } else {
  88                         divisor *= nr_instances;
  89                 }
  90                 instance->target = div_u64(dividend, divisor);
  91
  92                 thermal_cdev_update_nocheck(cdev);
  93         }
  94 }
  95
  96 static void fair_share_manage(struct thermal_zone_device *tz)
  97 {
  98         int trip_level = get_trip_level(tz);
  99         const struct thermal_trip_desc *td;
 100
 101         lockdep_assert_held(&tz->lock);
 102
 103         for_each_trip_desc(tz, td) {
 104                 const struct thermal_trip *trip = &td->trip;
 105
 106                 if (trip->temperature == THERMAL_TEMP_INVALID ||
 107                     trip->type == THERMAL_TRIP_CRITICAL ||
 108                     trip->type == THERMAL_TRIP_HOT)
 109                         continue;
 110
 111                 fair_share_throttle(tz, td, trip_level);
 112         }
 113 }
 114
 115 static struct thermal_governor thermal_gov_fair_share = {
 116         .name   = "fair_share",
 117         .manage = fair_share_manage,
 118 };
 119 THERMAL_GOVERNOR_DECLARE(thermal_gov_fair_share);