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 	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 
71 static 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 
82 static 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  */
139 static 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 
153 static struct thermal_governor thermal_gov_step_wise = {
154 	.name		= "step_wise",
155 	.throttle	= step_wise_throttle,
156 };
157 THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);
158