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 <trace/events/thermal.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  *    c. if the trend is THERMAL_TREND_RAISE_FULL, use upper limit
25  *       for this trip point
26  *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit
27  *       for this trip point
28  * If the temperature is lower than a trip point,
29  *    a. if the trend is THERMAL_TREND_RAISING, do nothing
30  *    b. if the trend is THERMAL_TREND_DROPPING, use lower cooling
31  *       state for this trip point, if the cooling state already
32  *       equals lower limit, deactivate the thermal instance
33  *    c. if the trend is THERMAL_TREND_RAISE_FULL, do nothing
34  *    d. if the trend is THERMAL_TREND_DROP_FULL, use lower limit,
35  *       if the cooling state already equals lower limit,
36  *       deactivate the thermal instance
37  */
38 static unsigned long get_target_state(struct thermal_instance *instance,
39 				enum thermal_trend trend, bool throttle)
40 {
41 	struct thermal_cooling_device *cdev = instance->cdev;
42 	unsigned long cur_state;
43 	unsigned long next_target;
44 
45 	/*
46 	 * We keep this instance the way it is by default.
47 	 * Otherwise, we use the current state of the
48 	 * cdev in use to determine the next_target.
49 	 */
50 	cdev->ops->get_cur_state(cdev, &cur_state);
51 	next_target = instance->target;
52 	dev_dbg(&cdev->device, "cur_state=%ld\n", cur_state);
53 
54 	if (!instance->initialized) {
55 		if (throttle) {
56 			next_target = clamp((cur_state + 1), instance->lower, instance->upper);
57 		} else {
58 			next_target = THERMAL_NO_TARGET;
59 		}
60 
61 		return next_target;
62 	}
63 
64 	switch (trend) {
65 	case THERMAL_TREND_RAISING:
66 		if (throttle) {
67 			next_target = clamp((cur_state + 1), instance->lower, instance->upper);
68 		}
69 		break;
70 	case THERMAL_TREND_DROPPING:
71 		if (cur_state <= instance->lower) {
72 			if (!throttle)
73 				next_target = THERMAL_NO_TARGET;
74 		} else {
75 			if (!throttle) {
76 				next_target = clamp((cur_state - 1), instance->lower, instance->upper);
77 			}
78 		}
79 		break;
80 	default:
81 		break;
82 	}
83 
84 	return next_target;
85 }
86 
87 static void update_passive_instance(struct thermal_zone_device *tz,
88 				enum thermal_trip_type type, int value)
89 {
90 	/*
91 	 * If value is +1, activate a passive instance.
92 	 * If value is -1, deactivate a passive instance.
93 	 */
94 	if (type == THERMAL_TRIP_PASSIVE)
95 		tz->passive += value;
96 }
97 
98 static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
99 {
100 	int trip_temp;
101 	enum thermal_trip_type trip_type;
102 	enum thermal_trend trend;
103 	struct thermal_instance *instance;
104 	bool throttle = false;
105 	int old_target;
106 
107 	tz->ops->get_trip_temp(tz, trip, &trip_temp);
108 	tz->ops->get_trip_type(tz, trip, &trip_type);
109 
110 	trend = get_tz_trend(tz, trip);
111 
112 	if (tz->temperature >= trip_temp) {
113 		throttle = true;
114 		trace_thermal_zone_trip(tz, trip, trip_type);
115 	}
116 
117 	dev_dbg(&tz->device, "Trip%d[type=%d,temp=%d]:trend=%d,throttle=%d\n",
118 				trip, trip_type, trip_temp, trend, throttle);
119 
120 	mutex_lock(&tz->lock);
121 
122 	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
123 		if (instance->trip != trip)
124 			continue;
125 
126 		old_target = instance->target;
127 		instance->target = get_target_state(instance, trend, throttle);
128 		dev_dbg(&instance->cdev->device, "old_target=%d, target=%d\n",
129 					old_target, (int)instance->target);
130 
131 		if (instance->initialized && old_target == instance->target)
132 			continue;
133 
134 		/* Activate a passive thermal instance */
135 		if (old_target == THERMAL_NO_TARGET &&
136 			instance->target != THERMAL_NO_TARGET)
137 			update_passive_instance(tz, trip_type, 1);
138 		/* Deactivate a passive thermal instance */
139 		else if (old_target != THERMAL_NO_TARGET &&
140 			instance->target == THERMAL_NO_TARGET)
141 			update_passive_instance(tz, trip_type, -1);
142 
143 		instance->initialized = true;
144 		mutex_lock(&instance->cdev->lock);
145 		instance->cdev->updated = false; /* cdev needs update */
146 		mutex_unlock(&instance->cdev->lock);
147 	}
148 
149 	mutex_unlock(&tz->lock);
150 }
151 
152 /**
153  * step_wise_throttle - throttles devices associated with the given zone
154  * @tz: thermal_zone_device
155  * @trip: trip point index
156  *
157  * Throttling Logic: This uses the trend of the thermal zone to throttle.
158  * If the thermal zone is 'heating up' this throttles all the cooling
159  * devices associated with the zone and its particular trip point, by one
160  * step. If the zone is 'cooling down' it brings back the performance of
161  * the devices by one step.
162  */
163 static int step_wise_throttle(struct thermal_zone_device *tz, int trip)
164 {
165 	struct thermal_instance *instance;
166 
167 	thermal_zone_trip_update(tz, trip);
168 
169 	mutex_lock(&tz->lock);
170 
171 	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
172 		thermal_cdev_update(instance->cdev);
173 
174 	mutex_unlock(&tz->lock);
175 
176 	return 0;
177 }
178 
179 static struct thermal_governor thermal_gov_step_wise = {
180 	.name		= "step_wise",
181 	.throttle	= step_wise_throttle,
182 };
183 THERMAL_GOVERNOR_DECLARE(thermal_gov_step_wise);
184