1 // SPDX-License-Identifier: GPL-2.0-only
3 * step_wise.c - A step-by-step Thermal throttling governor
5 * Copyright (C) 2012 Intel Corp
8 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
10 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
13 #include <linux/thermal.h>
14 #include <linux/minmax.h>
15 #include "thermal_trace.h"
17 #include "thermal_core.h"
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
30 static unsigned long get_target_state(struct thermal_instance *instance,
31 enum thermal_trend trend, bool throttle)
33 struct thermal_cooling_device *cdev = instance->cdev;
34 unsigned long cur_state;
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.
41 cdev->ops->get_cur_state(cdev, &cur_state);
42 dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
44 if (!instance->initialized) {
46 return clamp(cur_state + 1, instance->lower, instance->upper);
48 return THERMAL_NO_TARGET;
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;
59 * If 'throttle' is false, no mitigation is necessary, so
60 * request the lower state for this instance.
62 return instance->lower;
65 return instance->target;
68 static void thermal_zone_trip_update(struct thermal_zone_device *tz,
69 const struct thermal_trip *trip,
72 enum thermal_trend trend = get_tz_trend(tz, trip);
73 int trip_id = thermal_zone_trip_id(tz, trip);
74 struct thermal_instance *instance;
75 bool throttle = false;
77 if (tz->temperature >= trip_threshold) {
79 trace_thermal_zone_trip(tz, trip_id, trip->type);
82 dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
83 trip_id, trip->type, trip_threshold, trend, throttle);
85 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
88 if (instance->trip != trip)
91 old_target = instance->target;
92 instance->target = get_target_state(instance, trend, throttle);
94 dev_dbg(&instance->cdev->device, "old_target=%d, target=%ld\n",
95 old_target, instance->target);
97 if (instance->initialized && old_target == instance->target)
100 instance->initialized = true;
102 mutex_lock(&instance->cdev->lock);
103 instance->cdev->updated = false; /* cdev needs update */
104 mutex_unlock(&instance->cdev->lock);
108 static void step_wise_manage(struct thermal_zone_device *tz)
110 const struct thermal_trip_desc *td;
111 struct thermal_instance *instance;
113 lockdep_assert_held(&tz->lock);
116 * Throttling Logic: Use the trend of the thermal zone to throttle.
117 * If the thermal zone is 'heating up', throttle all of the cooling
118 * devices associated with each trip point by one step. If the zone
119 * is 'cooling down', it brings back the performance of the devices
122 for_each_trip_desc(tz, td) {
123 const struct thermal_trip *trip = &td->trip;
125 if (trip->temperature == THERMAL_TEMP_INVALID ||
126 trip->type == THERMAL_TRIP_CRITICAL ||
127 trip->type == THERMAL_TRIP_HOT)
130 thermal_zone_trip_update(tz, trip, td->threshold);
133 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
134 thermal_cdev_update(instance->cdev);
137 static struct thermal_governor thermal_gov_step_wise = {
139 .manage = step_wise_manage,
141 THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);