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e4dbf98f PF |
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 | { | |
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 | */ | |
102 | static 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 | ||
118 | static struct thermal_governor thermal_gov_bang_bang = { | |
119 | .name = "bang_bang", | |
120 | .throttle = bang_bang_control, | |
121 | }; | |
122 | ||
123 | int thermal_gov_bang_bang_register(void) | |
124 | { | |
125 | return thermal_register_governor(&thermal_gov_bang_bang); | |
126 | } | |
127 | ||
128 | void thermal_gov_bang_bang_unregister(void) | |
129 | { | |
130 | thermal_unregister_governor(&thermal_gov_bang_bang); | |
131 | } |