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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); | |
191b0754 MDG |
32 | |
33 | if (!tz->ops->get_trip_hyst) { | |
34 | pr_warn_once("Undefined get_trip_hyst for thermal zone %s - " | |
35 | "running with default hysteresis zero\n", tz->type); | |
36 | trip_hyst = 0; | |
37 | } else | |
38 | tz->ops->get_trip_hyst(tz, trip, &trip_hyst); | |
e4dbf98f | 39 | |
17e8351a | 40 | dev_dbg(&tz->device, "Trip%d[temp=%d]:temp=%d:hyst=%d\n", |
e4dbf98f PF |
41 | trip, trip_temp, tz->temperature, |
42 | trip_hyst); | |
43 | ||
44 | mutex_lock(&tz->lock); | |
45 | ||
46 | list_for_each_entry(instance, &tz->thermal_instances, tz_node) { | |
47 | if (instance->trip != trip) | |
48 | continue; | |
49 | ||
50 | /* in case fan is in initial state, switch the fan off */ | |
51 | if (instance->target == THERMAL_NO_TARGET) | |
52 | instance->target = 0; | |
53 | ||
54 | /* in case fan is neither on nor off set the fan to active */ | |
55 | if (instance->target != 0 && instance->target != 1) { | |
56 | pr_warn("Thermal instance %s controlled by bang-bang has unexpected state: %ld\n", | |
57 | instance->name, instance->target); | |
58 | instance->target = 1; | |
59 | } | |
60 | ||
61 | /* | |
62 | * enable fan when temperature exceeds trip_temp and disable | |
63 | * the fan in case it falls below trip_temp minus hysteresis | |
64 | */ | |
65 | if (instance->target == 0 && tz->temperature >= trip_temp) | |
66 | instance->target = 1; | |
67 | else if (instance->target == 1 && | |
68 | tz->temperature < trip_temp - trip_hyst) | |
69 | instance->target = 0; | |
70 | ||
71 | dev_dbg(&instance->cdev->device, "target=%d\n", | |
72 | (int)instance->target); | |
73 | ||
74 | instance->cdev->updated = false; /* cdev needs update */ | |
75 | } | |
76 | ||
77 | mutex_unlock(&tz->lock); | |
78 | } | |
79 | ||
80 | /** | |
81 | * bang_bang_control - controls devices associated with the given zone | |
82 | * @tz - thermal_zone_device | |
83 | * @trip - the trip point | |
84 | * | |
85 | * Regulation Logic: a two point regulation, deliver cooling state depending | |
86 | * on the previous state shown in this diagram: | |
87 | * | |
88 | * Fan: OFF ON | |
89 | * | |
90 | * | | |
91 | * | | |
92 | * trip_temp: +---->+ | |
93 | * | | ^ | |
94 | * | | | | |
95 | * | | Temperature | |
96 | * (trip_temp - hyst): +<----+ | |
97 | * | | |
98 | * | | |
99 | * | | |
100 | * | |
101 | * * If the fan is not running and temperature exceeds trip_temp, the fan | |
102 | * gets turned on. | |
103 | * * In case the fan is running, temperature must fall below | |
104 | * (trip_temp - hyst) so that the fan gets turned off again. | |
105 | * | |
106 | */ | |
107 | static int bang_bang_control(struct thermal_zone_device *tz, int trip) | |
108 | { | |
109 | struct thermal_instance *instance; | |
110 | ||
111 | thermal_zone_trip_update(tz, trip); | |
112 | ||
113 | mutex_lock(&tz->lock); | |
114 | ||
115 | list_for_each_entry(instance, &tz->thermal_instances, tz_node) | |
116 | thermal_cdev_update(instance->cdev); | |
117 | ||
118 | mutex_unlock(&tz->lock); | |
119 | ||
120 | return 0; | |
121 | } | |
122 | ||
123 | static struct thermal_governor thermal_gov_bang_bang = { | |
124 | .name = "bang_bang", | |
125 | .throttle = bang_bang_control, | |
126 | }; | |
127 | ||
128 | int thermal_gov_bang_bang_register(void) | |
129 | { | |
130 | return thermal_register_governor(&thermal_gov_bang_bang); | |
131 | } | |
132 | ||
133 | void thermal_gov_bang_bang_unregister(void) | |
134 | { | |
135 | thermal_unregister_governor(&thermal_gov_bang_bang); | |
136 | } |