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 update_passive_instance(struct thermal_zone_device *tz,
72				enum thermal_trip_type type, int value)
73{
74	/*
75	 * If value is +1, activate a passive instance.
76	 * If value is -1, deactivate a passive instance.
77	 */
78	if (type == THERMAL_TRIP_PASSIVE)
79		tz->passive += value;
80}
81
82static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip_id)
83{
84	const struct thermal_trip *trip = &tz->trips[trip_id];
85	enum thermal_trend trend;
86	struct thermal_instance *instance;
87	bool throttle = false;
88	int old_target;
89
90	trend = get_tz_trend(tz, trip_id);
91
92	if (tz->temperature >= trip->temperature) {
93		throttle = true;
94		trace_thermal_zone_trip(tz, trip_id, trip->type);
95	}
96
97	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
98		trip_id, trip->type, trip->temperature, trend, throttle);
99
100	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
101		if (instance->trip != trip)
102			continue;
103
104		old_target = instance->target;
105		instance->target = get_target_state(instance, trend, throttle);
106		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
107					old_target, (int)instance->target);
108
109		if (instance->initialized && old_target == instance->target)
110			continue;
111
112		/* Activate a passive thermal instance */
113		if (old_target == THERMAL_NO_TARGET &&
114			instance->target != THERMAL_NO_TARGET)
115			update_passive_instance(tz, trip->type, 1);
116		/* Deactivate a passive thermal instance */
117		else if (old_target != THERMAL_NO_TARGET &&
118			instance->target == THERMAL_NO_TARGET)
119			update_passive_instance(tz, trip->type, -1);
120
121		instance->initialized = true;
122		mutex_lock(&instance->cdev->lock);
123		instance->cdev->updated = false; /* cdev needs update */
124		mutex_unlock(&instance->cdev->lock);
125	}
126}
127
128/**
129 * step_wise_throttle - throttles devices associated with the given zone
130 * @tz: thermal_zone_device
131 * @trip: trip point index
132 *
133 * Throttling Logic: This uses the trend of the thermal zone to throttle.
134 * If the thermal zone is 'heating up' this throttles all the cooling
135 * devices associated with the zone and its particular trip point, by one
136 * step. If the zone is 'cooling down' it brings back the performance of
137 * the devices by one step.
138 */
139static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
140{
141	struct thermal_instance *instance;
142
143	lockdep_assert_held(&tz->lock);
144
145	thermal_zone_trip_update(tz, trip);
146
147	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
148		thermal_cdev_update(instance->cdev);
149
150	return 0;
151}
152
153static struct thermal_governor thermal_gov_step_wise = {
154	.name		= "step_wise",
155	.throttle	= step_wise_throttle,
156};
157THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);
158