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 	enum thermal_trend trend;
85 	struct thermal_instance *instance;
86 	struct thermal_trip trip;
87 	bool throttle = false;
88 	int old_target;
89 
90 	__thermal_zone_get_trip(tz, trip_id, &trip);
91 
92 	trend = get_tz_trend(tz, trip_id);
93 
94 	if (tz->temperature >= trip.temperature) {
95 		throttle = true;
96 		trace_thermal_zone_trip(tz, trip_id, trip.type);
97 	}
98 
99 	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
100 				trip_id, trip.type, trip.temperature, trend, throttle);
101 
102 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
103 		if (instance->trip != trip_id)
104 			continue;
105 
106 		old_target = instance->target;
107 		instance->target = get_target_state(instance, trend, throttle);
108 		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
109 					old_target, (int)instance->target);
110 
111 		if (instance->initialized && old_target == instance->target)
112 			continue;
113 
114 		/* Activate a passive thermal instance */
115 		if (old_target == THERMAL_NO_TARGET &&
116 			instance->target != THERMAL_NO_TARGET)
117 			update_passive_instance(tz, trip.type, 1);
118 		/* Deactivate a passive thermal instance */
119 		else if (old_target != THERMAL_NO_TARGET &&
120 			instance->target == THERMAL_NO_TARGET)
121 			update_passive_instance(tz, trip.type, -1);
122 
123 		instance->initialized = true;
124 		mutex_lock(&instance->cdev->lock);
125 		instance->cdev->updated = false; /* cdev needs update */
126 		mutex_unlock(&instance->cdev->lock);
127 	}
128 }
129 
130 /**
131  * step_wise_throttle - throttles devices associated with the given zone
132  * @tz: thermal_zone_device
133  * @trip: trip point index
134  *
135  * Throttling Logic: This uses the trend of the thermal zone to throttle.
136  * If the thermal zone is 'heating up' this throttles all the cooling
137  * devices associated with the zone and its particular trip point, by one
138  * step. If the zone is 'cooling down' it brings back the performance of
139  * the devices by one step.
140  */
141 static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
142 {
143 	struct thermal_instance *instance;
144 
145 	lockdep_assert_held(&tz->lock);
146 
147 	thermal_zone_trip_update(tz, trip);
148 
149 	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
150 		thermal_cdev_update(instance->cdev);
151 
152 	return 0;
153 }
154 
155 static struct thermal_governor thermal_gov_step_wise = {
156 	.name		= "step_wise",
157 	.throttle	= step_wise_throttle,
158 };
159 THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);
160