aboutsummaryrefslogtreecommitdiff
path: root/drivers/thermal/gov_bang_bang.c
blob: fc5e5057f0de73bbf5567bc5e14a9a824414a189 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
/*
 *  gov_bang_bang.c - A simple thermal throttling governor using hysteresis
 *
 *  Copyright (C) 2014 Peter Feuerer <peter@piie.net>
 *
 *  Based on step_wise.c with following Copyrights:
 *  Copyright (C) 2012 Intel Corp
 *  Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
 * the GNU General Public License for more details.
 *
 */

#include <linux/thermal.h>

#include "thermal_core.h"

static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
{
	int trip_temp, trip_hyst;
	struct thermal_instance *instance;

	tz->ops->get_trip_temp(tz, trip, &trip_temp);

	if (!tz->ops->get_trip_hyst) {
		pr_warn_once("Undefined get_trip_hyst for thermal zone %s - "
				"running with default hysteresis zero\n", tz->type);
		trip_hyst = 0;
	} else
		tz->ops->get_trip_hyst(tz, trip, &trip_hyst);

	dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n",
				trip, trip_temp, tz->temperature,
				trip_hyst);

	mutex_lock(&tz->lock);

	list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
		if (instance->trip != trip)
			continue;

		/* in case fan is in initial state, switch the fan off */
		if (instance->target == THERMAL_NO_TARGET)
			instance->target = 0;

		/* in case fan is neither on nor off set the fan to active */
		if (instance->target != 0 && instance->target != 1) {
			pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n",
					instance->name, instance->target);
			instance->target = 1;
		}

		/*
		 * enable fan when temperature exceeds trip_temp and disable
		 * the fan in case it falls below trip_temp minus hysteresis
		 */
		if (instance->target == 0 && tz->temperature >= trip_temp)
			instance->target = 1;
		else if (instance->target == 1 &&
				tz->temperature <= trip_temp - trip_hyst)
			instance->target = 0;

		dev_dbg(&instance->cdev->device, "target=%d\n",
					(int)instance->target);

		mutex_lock(&instance->cdev->lock);
		instance->cdev->updated = false; /* cdev needs update */
		mutex_unlock(&instance->cdev->lock);
	}

	mutex_unlock(&tz->lock);
}

/**
 * bang_bang_control - controls devices associated with the given zone
 * @tz - thermal_zone_device
 * @trip - the trip point
 *
 * Regulation Logic: a two point regulation, deliver cooling state depending
 * on the previous state shown in this diagram:
 *
 *                Fan:   OFF    ON
 *
 *                              |
 *                              |
 *          trip_temp:    +---->+
 *                        |     |        ^
 *                        |     |        |
 *                        |     |   Temperature
 * (trip_temp - hyst):    +<----+
 *                        |
 *                        |
 *                        |
 *
 *   * If the fan is not running and temperature exceeds trip_temp, the fan
 *     gets turned on.
 *   * In case the fan is running, temperature must fall below
 *     (trip_temp - hyst) so that the fan gets turned off again.
 *
 */
static int bang_bang_control(struct thermal_zone_device *tz, int trip)
{
	struct thermal_instance *instance;

	thermal_zone_trip_update(tz, trip);

	mutex_lock(&tz->lock);

	list_for_each_entry(instance, &tz->thermal_instances, tz_node)
		thermal_cdev_update(instance->cdev);

	mutex_unlock(&tz->lock);

	return 0;
}

static struct thermal_governor thermal_gov_bang_bang = {
	.name		= "bang_bang",
	.throttle	= bang_bang_control,
};

int thermal_gov_bang_bang_register(void)
{
	return thermal_register_governor(&thermal_gov_bang_bang);
}

void thermal_gov_bang_bang_unregister(void)
{
	thermal_unregister_governor(&thermal_gov_bang_bang);
}