drivers/thermal/gov_step_wise.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  step_wise.c - A step-by-step Thermal throttling 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 <linux/minmax.h>
  15 #include "thermal_trace.h"
  16
  17 #include "thermal_core.h"
  18
  19 /*
  20  * If the temperature is higher than a trip point,
  21  *    a. if the trend is THERMAL_TREND_RAISING, use higher cooling
  22  *       state for this trip point
  23  *    b. if the trend is THERMAL_TREND_DROPPING, do nothing
  24  * If the temperature is lower than a trip point,
  25  *    a. if the trend is THERMAL_TREND_RAISING, do nothing
  26  *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
  27  *       state for this trip point, if the cooling state already
  28  *       equals lower limit, deactivate the thermal instance
  29  */
  30 static unsigned long get_target_state(struct thermal_instance *instance,
  31                                 enum thermal_trend trend, bool throttle)
  32 {
  33         struct thermal_cooling_device *cdev = instance->cdev;
  34         unsigned long cur_state;
  35
  36         /*
  37          * We keep this instance the way it is by default.
  38          * Otherwise, we use the current state of the
  39          * cdev in use to determine the next_target.
  40          */
  41         cdev->ops->get_cur_state(cdev, &cur_state);
  42         dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
  43
  44         if (!instance->initialized) {
  45                 if (throttle)
  46                         return clamp(cur_state + 1, instance->lower, instance->upper);
  47
  48                 return THERMAL_NO_TARGET;
  49         }
  50
  51         if (throttle) {
  52                 if (trend == THERMAL_TREND_RAISING)
  53                         return clamp(cur_state + 1, instance->lower, instance->upper);
  54         } else if (trend == THERMAL_TREND_DROPPING) {
  55                 if (cur_state <= instance->lower)
  56                         return THERMAL_NO_TARGET;
  57
  58                 /*
  59                  * If 'throttle' is false, no mitigation is necessary, so
  60                  * request the lower state for this instance.
  61                  */
  62                 return instance->lower;
  63         }
  64
  65         return instance->target;
  66 }
  67
  68 static void thermal_zone_trip_update(struct thermal_zone_device *tz,
  69                                      const struct thermal_trip_desc *td,
  70                                      int trip_threshold)
  71 {
  72         const struct thermal_trip *trip = &td->trip;
  73         enum thermal_trend trend = get_tz_trend(tz, trip);
  74         int trip_id = thermal_zone_trip_id(tz, trip);
  75         struct thermal_instance *instance;
  76         bool throttle = false;
  77
  78         if (tz->temperature >= trip_threshold) {
  79                 throttle = true;
  80                 trace_thermal_zone_trip(tz, trip_id, trip->type);
  81         }
  82
  83         dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
  84                 trip_id, trip->type, trip_threshold, trend, throttle);
  85
  86         list_for_each_entry(instance, &td->thermal_instances, trip_node) {
  87                 int old_target;
  88
  89                 old_target = instance->target;
  90                 instance->target = get_target_state(instance, trend, throttle);
  91
  92                 dev_dbg(&instance->cdev->device, "old_target=%d, target=%ld\n",
  93                         old_target, instance->target);
  94
  95                 if (instance->initialized && old_target == instance->target)
  96                         continue;
  97
  98                 instance->initialized = true;
  99
 100                 scoped_guard(cooling_dev, instance->cdev) {
 101                         instance->cdev->updated = false; /* cdev needs update */
 102                 }
 103         }
 104 }
 105
 106 static void step_wise_manage(struct thermal_zone_device *tz)
 107 {
 108         const struct thermal_trip_desc *td;
 109         struct thermal_instance *instance;
 110
 111         lockdep_assert_held(&tz->lock);
 112
 113         /*
 114          * Throttling Logic: Use the trend of the thermal zone to throttle.
 115          * If the thermal zone is 'heating up', throttle all of the cooling
 116          * devices associated with each trip point by one step. If the zone
 117          * is 'cooling down', it brings back the performance of the devices
 118          * by one step.
 119          */
 120         for_each_trip_desc(tz, td) {
 121                 const struct thermal_trip *trip = &td->trip;
 122
 123                 if (trip->temperature == THERMAL_TEMP_INVALID ||
 124                     trip->type == THERMAL_TRIP_CRITICAL ||
 125                     trip->type == THERMAL_TRIP_HOT)
 126                         continue;
 127
 128                 thermal_zone_trip_update(tz, td, td->threshold);
 129         }
 130
 131         for_each_trip_desc(tz, td) {
 132                 list_for_each_entry(instance, &td->thermal_instances, trip_node)
 133                         thermal_cdev_update(instance->cdev);
 134         }
 135 }
 136
 137 static struct thermal_governor thermal_gov_step_wise = {
 138         .name   = "step_wise",
 139         .manage = step_wise_manage,
 140 };
 141 THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);