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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 <[email protected]>
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, use a lower cooling state
24 * for this trip point, but keep the cooling state above the applicable
25 * minimum
26 * If the temperature is lower than a trip point,
27 * a. if the trend is THERMAL_TREND_RAISING, do nothing
28 * b. if the trend is THERMAL_TREND_DROPPING, use the minimum applicable
29 * cooling state for this trip point, or if the cooling state already
30 * equals lower limit, deactivate the thermal instance
31 */
32static unsigned long get_target_state(struct thermal_instance *instance,
33 enum thermal_trend trend, bool throttle)
34{
35 struct thermal_cooling_device *cdev = instance->cdev;
36 unsigned long cur_state;
37
38 /*
39 * We keep this instance the way it is by default.
40 * Otherwise, we use the current state of the
41 * cdev in use to determine the next_target.
42 */
43 cdev->ops->get_cur_state(cdev, &cur_state);
44 dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
45
46 if (!instance->initialized) {
47 if (throttle)
48 return clamp(cur_state + 1, instance->lower, instance->upper);
49
50 return THERMAL_NO_TARGET;
51 }
52
53 if (throttle) {
54 if (trend == THERMAL_TREND_RAISING)
55 return clamp(cur_state + 1, instance->lower, instance->upper);
56
57 /*
58 * If the zone temperature is falling, the cooling level can
59 * be reduced, but it should still be above the lower state of
60 * the given thermal instance to pull the temperature further
61 * down.
62 */
63 if (trend == THERMAL_TREND_DROPPING)
64 return clamp(cur_state - 1,
65 min(instance->lower + 1, instance->upper),
66 instance->upper);
67 } else if (trend == THERMAL_TREND_DROPPING) {
68 /*
69 * If 'throttle' is false, no mitigation is necessary and
70 * passive polling is already deactivated, so clear this
71 * instance state by returning THERMAL_NO_TARGET.
72 */
73 return THERMAL_NO_TARGET;
74 }
75
76 return instance->target;
77}
78
79static void thermal_zone_trip_update(struct thermal_zone_device *tz,
80 const struct thermal_trip_desc *td,
81 int trip_threshold)
82{
83 bool throttle = tz->temperature >= trip_threshold;
84 const struct thermal_trip *trip = &td->trip;
85 enum thermal_trend trend = get_tz_trend(tz, trip);
86 int trip_id = thermal_zone_trip_id(tz, trip);
87 struct thermal_instance *instance;
88
89 if (throttle)
90 trace_thermal_zone_trip(tz, trip_id, trip->type);
91
92 dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
93 trip_id, trip->type, trip_threshold, trend, throttle);
94
95 list_for_each_entry(instance, &td->thermal_instances, trip_node) {
96 int old_target;
97
98 old_target = instance->target;
99 instance->target = get_target_state(instance, trend, throttle);
100
101 dev_dbg(&instance->cdev->device, "old_target=%d, target=%ld\n",
102 old_target, instance->target);
103
104 if (instance->initialized && old_target == instance->target)
105 continue;
106
107 instance->initialized = true;
108
109 scoped_guard(cooling_dev, instance->cdev) {
110 instance->cdev->updated = false; /* cdev needs update */
111 }
112 }
113}
114
115static void step_wise_manage(struct thermal_zone_device *tz)
116{
117 const struct thermal_trip_desc *td;
118 struct thermal_instance *instance;
119
120 lockdep_assert_held(&tz->lock);
121
122 /*
123 * Throttling Logic: Use the trend of the thermal zone to throttle.
124 * If the thermal zone is 'heating up', throttle all of the cooling
125 * devices associated with each trip point by one step. If the zone
126 * is 'cooling down', it brings back the performance of the devices
127 * by one step.
128 */
129 for_each_trip_desc(tz, td) {
130 const struct thermal_trip *trip = &td->trip;
131
132 if (trip->temperature == THERMAL_TEMP_INVALID ||
133 trip->type == THERMAL_TRIP_CRITICAL ||
134 trip->type == THERMAL_TRIP_HOT)
135 continue;
136
137 thermal_zone_trip_update(tz, td, td->threshold);
138 }
139
140 for_each_trip_desc(tz, td) {
141 list_for_each_entry(instance, &td->thermal_instances, trip_node)
142 thermal_cdev_update(instance->cdev);
143 }
144}
145
146static struct thermal_governor thermal_gov_step_wise = {
147 .name = "step_wise",
148 .manage = step_wise_manage,
149};
150THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);