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1 | Generic Thermal Sysfs driver How To |
2 | ========================= | |
3 | ||
4 | Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com> | |
5 | ||
6 | Updated: 2 January 2008 | |
7 | ||
8 | Copyright (c) 2008 Intel Corporation | |
9 | ||
10 | ||
11 | 0. Introduction | |
12 | ||
13 | The generic thermal sysfs provides a set of interfaces for thermal zone devices (sensors) | |
14 | and thermal cooling devices (fan, processor...) to register with the thermal management | |
15 | solution and to be a part of it. | |
16 | ||
543a9561 | 17 | This how-to focuses on enabling new thermal zone and cooling devices to participate |
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18 | in thermal management. |
19 | This solution is platform independent and any type of thermal zone devices and | |
20 | cooling devices should be able to make use of the infrastructure. | |
21 | ||
22 | The main task of the thermal sysfs driver is to expose thermal zone attributes as well | |
23 | as cooling device attributes to the user space. | |
24 | An intelligent thermal management application can make decisions based on inputs | |
25 | from thermal zone attributes (the current temperature and trip point temperature) | |
26 | and throttle appropriate devices. | |
27 | ||
28 | [0-*] denotes any positive number starting from 0 | |
29 | [1-*] denotes any positive number starting from 1 | |
30 | ||
31 | 1. thermal sysfs driver interface functions | |
32 | ||
33 | 1.1 thermal zone device interface | |
34 | 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, int trips, | |
35 | void *devdata, struct thermal_zone_device_ops *ops) | |
36 | ||
37 | This interface function adds a new thermal zone device (sensor) to | |
38 | /sys/class/thermal folder as thermal_zone[0-*]. | |
39 | It tries to bind all the thermal cooling devices registered at the same time. | |
40 | ||
41 | name: the thermal zone name. | |
42 | trips: the total number of trip points this thermal zone supports. | |
43 | devdata: device private data | |
543a9561 | 44 | ops: thermal zone device call-backs. |
203d3d4a | 45 | .bind: bind the thermal zone device with a thermal cooling device. |
543a9561 | 46 | .unbind: unbind the thermal zone device with a thermal cooling device. |
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47 | .get_temp: get the current temperature of the thermal zone. |
48 | .get_mode: get the current mode (user/kernel) of the thermal zone. | |
49 | "kernel" means thermal management is done in kernel. | |
50 | "user" will prevent kernel thermal driver actions upon trip points | |
51 | so that user applications can take charge of thermal management. | |
52 | .set_mode: set the mode (user/kernel) of the thermal zone. | |
53 | .get_trip_type: get the type of certain trip point. | |
54 | .get_trip_temp: get the temperature above which the certain trip point | |
55 | will be fired. | |
56 | ||
57 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | |
58 | ||
59 | This interface function removes the thermal zone device. | |
60 | It deletes the corresponding entry form /sys/class/thermal folder and unbind all | |
61 | the thermal cooling devices it uses. | |
62 | ||
63 | 1.2 thermal cooling device interface | |
64 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | |
65 | void *devdata, struct thermal_cooling_device_ops *) | |
66 | ||
67 | This interface function adds a new thermal cooling device (fan/processor/...) to | |
68 | /sys/class/thermal/ folder as cooling_device[0-*]. | |
69 | It tries to bind itself to all the thermal zone devices register at the same time. | |
70 | name: the cooling device name. | |
71 | devdata: device private data. | |
543a9561 | 72 | ops: thermal cooling devices call-backs. |
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73 | .get_max_state: get the Maximum throttle state of the cooling device. |
74 | .get_cur_state: get the Current throttle state of the cooling device. | |
75 | .set_cur_state: set the Current throttle state of the cooling device. | |
76 | ||
77 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | |
78 | ||
79 | This interface function remove the thermal cooling device. | |
80 | It deletes the corresponding entry form /sys/class/thermal folder and unbind | |
81 | itself from all the thermal zone devices using it. | |
82 | ||
83 | 1.3 interface for binding a thermal zone device with a thermal cooling device | |
84 | 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, | |
85 | int trip, struct thermal_cooling_device *cdev); | |
86 | ||
87 | This interface function bind a thermal cooling device to the certain trip point | |
88 | of a thermal zone device. | |
89 | This function is usually called in the thermal zone device .bind callback. | |
90 | tz: the thermal zone device | |
91 | cdev: thermal cooling device | |
92 | trip: indicates which trip point the cooling devices is associated with | |
93 | in this thermal zone. | |
94 | ||
95 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | |
96 | int trip, struct thermal_cooling_device *cdev); | |
97 | ||
98 | This interface function unbind a thermal cooling device from the certain trip point | |
99 | of a thermal zone device. | |
100 | This function is usually called in the thermal zone device .unbind callback. | |
101 | tz: the thermal zone device | |
102 | cdev: thermal cooling device | |
103 | trip: indicates which trip point the cooling devices is associated with | |
104 | in this thermal zone. | |
105 | ||
106 | 2. sysfs attributes structure | |
107 | ||
108 | RO read only value | |
109 | RW read/write value | |
110 | ||
111 | All thermal sysfs attributes will be represented under /sys/class/thermal | |
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112 | |
113 | Thermal zone device sys I/F, created once it's registered: | |
114 | |thermal_zone[0-*]: | |
115 | |-----type: Type of the thermal zone | |
116 | |-----temp: Current temperature | |
117 | |-----mode: Working mode of the thermal zone | |
118 | |-----trip_point_[0-*]_temp: Trip point temperature | |
119 | |-----trip_point_[0-*]_type: Trip point type | |
120 | ||
121 | Thermal cooling device sys I/F, created once it's registered: | |
122 | |cooling_device[0-*]: | |
123 | |-----type : Type of the cooling device(processor/fan/...) | |
124 | |-----max_state: Maximum cooling state of the cooling device | |
125 | |-----cur_state: Current cooling state of the cooling device | |
126 | ||
127 | ||
128 | These two dynamic attributes are created/removed in pairs. | |
129 | They represent the relationship between a thermal zone and its associated cooling device. | |
130 | They are created/removed for each | |
543a9561 | 131 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution. |
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132 | |
133 | |thermal_zone[0-*] | |
134 | |-----cdev[0-*]: The [0-*]th cooling device in the current thermal zone | |
135 | |-----cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
136 | ||
137 | ||
138 | *************************** | |
139 | * Thermal zone attributes * | |
140 | *************************** | |
141 | ||
142 | type Strings which represent the thermal zone type. | |
143 | This is given by thermal zone driver as part of registration. | |
144 | Eg: "ACPI thermal zone" indicates it's a ACPI thermal device | |
145 | RO | |
3152fb9f | 146 | Required |
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147 | |
148 | temp Current temperature as reported by thermal zone (sensor) | |
3152fb9f | 149 | Unit: millidegree Celsius |
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150 | RO |
151 | Required | |
152 | ||
543a9561 | 153 | mode One of the predefined values in [kernel, user] |
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154 | This file gives information about the algorithm |
155 | that is currently managing the thermal zone. | |
156 | It can be either default kernel based algorithm | |
157 | or user space application. | |
158 | RW | |
159 | Optional | |
160 | kernel = Thermal management in kernel thermal zone driver. | |
161 | user = Preventing kernel thermal zone driver actions upon | |
162 | trip points so that user application can take full | |
163 | charge of the thermal management. | |
164 | ||
165 | trip_point_[0-*]_temp The temperature above which trip point will be fired | |
3152fb9f | 166 | Unit: millidegree Celsius |
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167 | RO |
168 | Optional | |
169 | ||
170 | trip_point_[0-*]_type Strings which indicate the type of the trip point | |
543a9561 | 171 | E.g. it can be one of critical, hot, passive, |
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172 | active[0-*] for ACPI thermal zone. |
173 | RO | |
174 | Optional | |
175 | ||
176 | cdev[0-*] Sysfs link to the thermal cooling device node where the sys I/F | |
177 | for cooling device throttling control represents. | |
178 | RO | |
179 | Optional | |
180 | ||
543a9561 | 181 | cdev[0-*]_trip_point The trip point with which cdev[0-*] is associated in this thermal zone |
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182 | -1 means the cooling device is not associated with any trip point. |
183 | RO | |
184 | Optional | |
185 | ||
186 | ****************************** | |
187 | * Cooling device attributes * | |
188 | ****************************** | |
189 | ||
190 | type String which represents the type of device | |
191 | eg: For generic ACPI: this should be "Fan", | |
192 | "Processor" or "LCD" | |
193 | eg. For memory controller device on intel_menlow platform: | |
194 | this should be "Memory controller" | |
195 | RO | |
3152fb9f | 196 | Required |
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197 | |
198 | max_state The maximum permissible cooling state of this cooling device. | |
199 | RO | |
200 | Required | |
201 | ||
202 | cur_state The current cooling state of this cooling device. | |
203 | the value can any integer numbers between 0 and max_state, | |
204 | cur_state == 0 means no cooling | |
205 | cur_state == max_state means the maximum cooling. | |
206 | RW | |
207 | Required | |
208 | ||
209 | 3. A simple implementation | |
210 | ||
211 | ACPI thermal zone may support multiple trip points like critical/hot/passive/active. | |
212 | If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time, | |
543a9561 | 213 | it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all. |
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214 | It has one processor and one fan, which are both registered as thermal_cooling_device. |
215 | If the processor is listed in _PSL method, and the fan is listed in _AL0 method, | |
216 | the sys I/F structure will be built like this: | |
217 | ||
218 | /sys/class/thermal: | |
219 | ||
220 | |thermal_zone1: | |
221 | |-----type: ACPI thermal zone | |
3152fb9f | 222 | |-----temp: 37000 |
203d3d4a | 223 | |-----mode: kernel |
3152fb9f | 224 | |-----trip_point_0_temp: 100000 |
203d3d4a | 225 | |-----trip_point_0_type: critical |
3152fb9f | 226 | |-----trip_point_1_temp: 80000 |
203d3d4a | 227 | |-----trip_point_1_type: passive |
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228 | |-----trip_point_2_temp: 70000 |
229 | |-----trip_point_2_type: active0 | |
230 | |-----trip_point_3_temp: 60000 | |
231 | |-----trip_point_3_type: active1 | |
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232 | |-----cdev0: --->/sys/class/thermal/cooling_device0 |
233 | |-----cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
234 | |-----cdev1: --->/sys/class/thermal/cooling_device3 | |
235 | |-----cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
236 | ||
237 | |cooling_device0: | |
238 | |-----type: Processor | |
239 | |-----max_state: 8 | |
240 | |-----cur_state: 0 | |
241 | ||
242 | |cooling_device3: | |
243 | |-----type: Fan | |
244 | |-----max_state: 2 | |
245 | |-----cur_state: 0 |