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1 | /* |
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 | ||
26 | static void thermal_zone_trip_update(struct thermal_zone_device *tz, int trip) | |
27 | { | |
17e8351a | 28 | int trip_temp, trip_hyst; |
e4dbf98f PF |
29 | struct thermal_instance *instance; |
30 | ||
31 | tz->ops->get_trip_temp(tz, trip, &trip_temp); | |
32 | tz->ops->get_trip_hyst(tz, trip, &trip_hyst); | |
33 | ||
17e8351a | 34 | dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n", |
e4dbf98f PF |
35 | trip, trip_temp, tz->temperature, |
36 | trip_hyst); | |
37 | ||
38 | mutex_lock(&tz->lock); | |
39 | ||
40 | list_for_each_entry(instance, &tz->thermal_instances, tz_node) { | |
41 | if (instance->trip != trip) | |
42 | continue; | |
43 | ||
44 | /* in case fan is in initial state, switch the fan off */ | |
45 | if (instance->target == THERMAL_NO_TARGET) | |
46 | instance->target = 0; | |
47 | ||
48 | /* in case fan is neither on nor off set the fan to active */ | |
49 | if (instance->target != 0 && instance->target != 1) { | |
50 | pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n", | |
51 | instance->name, instance->target); | |
52 | instance->target = 1; | |
53 | } | |
54 | ||
55 | /* | |
56 | * enable fan when temperature exceeds trip_temp and disable | |
57 | * the fan in case it falls below trip_temp minus hysteresis | |
58 | */ | |
59 | if (instance->target == 0 && tz->temperature >= trip_temp) | |
60 | instance->target = 1; | |
61 | else if (instance->target == 1 && | |
62 | tz->temperature < trip_temp - trip_hyst) | |
63 | instance->target = 0; | |
64 | ||
65 | dev_dbg(&instance->cdev->device, "target=%d\n", | |
66 | (int)instance->target); | |
67 | ||
68 | instance->cdev->updated = false; /* cdev needs update */ | |
69 | } | |
70 | ||
71 | mutex_unlock(&tz->lock); | |
72 | } | |
73 | ||
74 | /** | |
75 | * bang_bang_control - controls devices associated with the given zone | |
76 | * @tz - thermal_zone_device | |
77 | * @trip - the trip point | |
78 | * | |
79 | * Regulation Logic: a two point regulation, deliver cooling state depending | |
80 | * on the previous state shown in this diagram: | |
81 | * | |
82 | * Fan: OFF ON | |
83 | * | |
84 | * | | |
85 | * | | |
86 | * trip_temp: +---->+ | |
87 | * | | ^ | |
88 | * | | | | |
89 | * | | Temperature | |
90 | * (trip_temp - hyst): +<----+ | |
91 | * | | |
92 | * | | |
93 | * | | |
94 | * | |
95 | * * If the fan is not running and temperature exceeds trip_temp, the fan | |
96 | * gets turned on. | |
97 | * * In case the fan is running, temperature must fall below | |
98 | * (trip_temp - hyst) so that the fan gets turned off again. | |
99 | * | |
100 | */ | |
101 | static int bang_bang_control(struct thermal_zone_device *tz, int trip) | |
102 | { | |
103 | struct thermal_instance *instance; | |
104 | ||
105 | thermal_zone_trip_update(tz, trip); | |
106 | ||
107 | mutex_lock(&tz->lock); | |
108 | ||
109 | list_for_each_entry(instance, &tz->thermal_instances, tz_node) | |
110 | thermal_cdev_update(instance->cdev); | |
111 | ||
112 | mutex_unlock(&tz->lock); | |
113 | ||
114 | return 0; | |
115 | } | |
116 | ||
117 | static struct thermal_governor thermal_gov_bang_bang = { | |
118 | .name = "bang_bang", | |
119 | .throttle = bang_bang_control, | |
120 | }; | |
121 | ||
122 | int thermal_gov_bang_bang_register(void) | |
123 | { | |
124 | return thermal_register_governor(&thermal_gov_bang_bang); | |
125 | } | |
126 | ||
127 | void thermal_gov_bang_bang_unregister(void) | |
128 | { | |
129 | thermal_unregister_governor(&thermal_gov_bang_bang); | |
130 | } |