blob: c5dd76b2ee74fb930654a7ce000f44262a40198e [file] [log] [blame]
Peter Feuerere4dbf982014-07-22 17:37:13 +02001/*
2 * gov_bang_bang.c - A simple thermal throttling governor using hysteresis
3 *
4 * Copyright (C) 2014 Peter Feuerer <peter@piie.net>
5 *
6 * Based on step_wise.c with following Copyrights:
7 * Copyright (C) 2012 Intel Corp
8 * Copyright (C) 2012 Durgadoss R <durgadoss.r@intel.com>
9 *
10 *
11 * This program is free software; you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation, version 2.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
18 * the GNU General Public License for more details.
19 *
20 */
21
22#include <linux/thermal.h>
23
24#include "thermal_core.h"
25
26static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip)
27{
28 long trip_temp;
29 unsigned long trip_hyst;
30 struct thermal_instance *instance;
31
32 tz->ops->get_trip_temp(tz, trip, &trip_temp);
33 tz->ops->get_trip_hyst(tz, trip, &trip_hyst);
34
35 dev_dbg(&tz->device, "Trip%d[temp=%ld]:temp=%d:hyst=%ld\n",
36 trip, trip_temp, tz->temperature,
37 trip_hyst);
38
39 mutex_lock(&tz->lock);
40
41 list_for_each_entry(instance, &tz->thermal_instances, tz_node) {
42 if (instance->trip != trip)
43 continue;
44
45 /* in case fan is in initial state, switch the fan off */
46 if (instance->target == THERMAL_NO_TARGET)
47 instance->target = 0;
48
49 /* in case fan is neither on nor off set the fan to active */
50 if (instance->target != 0 && instance->target != 1) {
51 pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n",
52 instance->name, instance->target);
53 instance->target = 1;
54 }
55
56 /*
57 * enable fan when temperature exceeds trip_temp and disable
58 * the fan in case it falls below trip_temp minus hysteresis
59 */
60 if (instance->target == 0 && tz->temperature >= trip_temp)
61 instance->target = 1;
62 else if (instance->target == 1 &&
63 tz->temperature < trip_temp - trip_hyst)
64 instance->target = 0;
65
66 dev_dbg(&instance->cdev->device, "target=%d\n",
67 (int)instance->target);
68
69 instance->cdev->updated = false; /* cdev needs update */
70 }
71
72 mutex_unlock(&tz->lock);
73}
74
75/**
76 * bang_bang_control - controls devices associated with the given zone
77 * @tz - thermal_zone_device
78 * @trip - the trip point
79 *
80 * Regulation Logic: a two point regulation, deliver cooling state depending
81 * on the previous state shown in this diagram:
82 *
83 * Fan: OFF ON
84 *
85 * |
86 * |
87 * trip_temp: +---->+
88 * | | ^
89 * | | |
90 * | | Temperature
91 * (trip_temp - hyst): +<----+
92 * |
93 * |
94 * |
95 *
96 * * If the fan is not running and temperature exceeds trip_temp, the fan
97 * gets turned on.
98 * * In case the fan is running, temperature must fall below
99 * (trip_temp - hyst) so that the fan gets turned off again.
100 *
101 */
102static int bang_bang_control(struct thermal_zone_device *tz, int trip)
103{
104 struct thermal_instance *instance;
105
106 thermal_zone_trip_update(tz, trip);
107
108 mutex_lock(&tz->lock);
109
110 list_for_each_entry(instance, &tz->thermal_instances, tz_node)
111 thermal_cdev_update(instance->cdev);
112
113 mutex_unlock(&tz->lock);
114
115 return 0;
116}
117
118static struct thermal_governor thermal_gov_bang_bang = {
119 .name = "bang_bang",
120 .throttle = bang_bang_control,
121};
122
123int thermal_gov_bang_bang_register(void)
124{
125 return thermal_register_governor(&thermal_gov_bang_bang);
126}
127
128void thermal_gov_bang_bang_unregister(void)
129{
130 thermal_unregister_governor(&thermal_gov_bang_bang);
131}