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 */
30static 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 unsigned long next_target;
36
37 /*
38 * We keep this instance the way it is by default.
39 * Otherwise, we use the current state of the
40 * cdev in use to determine the next_target.
41 */
42 cdev->ops->get_cur_state(cdev, &cur_state);
43 next_target = instance->target;
44 dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
45
46 if (!instance->initialized) {
47 if (throttle) {
48 next_target = clamp((cur_state + 1), instance->lower, instance->upper);
49 } else {
50 next_target = THERMAL_NO_TARGET;
51 }
52
53 return next_target;
54 }
55
56 if (throttle) {
57 if (trend == THERMAL_TREND_RAISING)
58 next_target = clamp((cur_state + 1), instance->lower, instance->upper);
59 } else {
60 if (trend == THERMAL_TREND_DROPPING) {
61 if (cur_state <= instance->lower)
62 next_target = THERMAL_NO_TARGET;
63 else
64 next_target = clamp((cur_state - 1), instance->lower, instance->upper);
65 }
66 }
67
68 return next_target;
69}
70
71static void thermal_zone_trip_update(struct thermal_zone_device *tz,
72 const struct thermal_trip *trip)
73{
74 int trip_id = thermal_zone_trip_id(tz, trip);
75 enum thermal_trend trend;
76 struct thermal_instance *instance;
77 bool throttle = false;
78 int old_target;
79
80 trend = get_tz_trend(tz, trip);
81
82 if (tz->temperature >= trip->temperature) {
83 throttle = true;
84 trace_thermal_zone_trip(tz, trip: trip_id, trip_type: trip->type);
85 }
86
87 dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
88 trip_id, trip->type, trip->temperature, trend, throttle);
89
90 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
91 if (instance->trip != trip)
92 continue;
93
94 old_target = instance->target;
95 instance->target = get_target_state(instance, trend, throttle);
96 dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
97 old_target, (int)instance->target);
98
99 if (instance->initialized && old_target == instance->target)
100 continue;
101
102 if (old_target == THERMAL_NO_TARGET &&
103 instance->target != THERMAL_NO_TARGET) {
104 /* Activate a passive thermal instance */
105 if (trip->type == THERMAL_TRIP_PASSIVE)
106 tz->passive++;
107 } else if (old_target != THERMAL_NO_TARGET &&
108 instance->target == THERMAL_NO_TARGET) {
109 /* Deactivate a passive thermal instance */
110 if (trip->type == THERMAL_TRIP_PASSIVE)
111 tz->passive--;
112 }
113
114 instance->initialized = true;
115 mutex_lock(&instance->cdev->lock);
116 instance->cdev->updated = false; /* cdev needs update */
117 mutex_unlock(lock: &instance->cdev->lock);
118 }
119}
120
121/**
122 * step_wise_throttle - throttles devices associated with the given zone
123 * @tz: thermal_zone_device
124 * @trip: trip point
125 *
126 * Throttling Logic: This uses the trend of the thermal zone to throttle.
127 * If the thermal zone is 'heating up' this throttles all the cooling
128 * devices associated with the zone and its particular trip point, by one
129 * step. If the zone is 'cooling down' it brings back the performance of
130 * the devices by one step.
131 */
132static int step_wise_throttle(struct thermal_zone_device *tz,
133 const struct thermal_trip *trip)
134{
135 struct thermal_instance *instance;
136
137 lockdep_assert_held(&tz->lock);
138
139 thermal_zone_trip_update(tz, trip);
140
141 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
142 thermal_cdev_update(instance->cdev);
143
144 return 0;
145}
146
147static struct thermal_governor thermal_gov_step_wise = {
148 .name = "step_wise",
149 .throttle = step_wise_throttle,
150};
151THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);
152

source code of linux/drivers/thermal/gov_step_wise.c