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203d3d4a | 1 | Generic Thermal Sysfs driver How To |
38bb0849 | 2 | =================================== |
203d3d4a ZR |
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 | ||
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13 | The generic thermal sysfs provides a set of interfaces for thermal zone |
14 | devices (sensors) and thermal cooling devices (fan, processor...) to register | |
15 | with the thermal management solution and to be a part of it. | |
203d3d4a | 16 | |
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17 | This how-to focuses on enabling new thermal zone and cooling devices to |
18 | participate in thermal management. | |
19 | This solution is platform independent and any type of thermal zone devices | |
20 | and cooling devices should be able to make use of the infrastructure. | |
203d3d4a | 21 | |
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22 | The main task of the thermal sysfs driver is to expose thermal zone attributes |
23 | as well as cooling device attributes to the user space. | |
24 | An intelligent thermal management application can make decisions based on | |
25 | inputs from thermal zone attributes (the current temperature and trip point | |
26 | temperature) and throttle appropriate devices. | |
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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 | |
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34 | 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, |
35 | int trips, 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-*]. It tries to bind all the | |
39 | 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 | |
44 | ops: thermal zone device call-backs. | |
45 | .bind: bind the thermal zone device with a thermal cooling device. | |
46 | .unbind: unbind the thermal zone device with a thermal cooling device. | |
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. | |
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56 | |
57 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | |
58 | ||
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59 | This interface function removes the thermal zone device. |
60 | It deletes the corresponding entry form /sys/class/thermal folder and | |
61 | unbind all the thermal cooling devices it uses. | |
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62 | |
63 | 1.2 thermal cooling device interface | |
64 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | |
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65 | void *devdata, struct thermal_cooling_device_ops *) |
66 | ||
67 | This interface function adds a new thermal cooling device (fan/processor/...) | |
68 | to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself | |
69 | to all the thermal zone devices register at the same time. | |
70 | name: the cooling device name. | |
71 | devdata: device private data. | |
72 | ops: thermal cooling devices call-backs. | |
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. | |
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76 | |
77 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | |
78 | ||
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79 | This interface function remove the thermal cooling device. |
80 | It deletes the corresponding entry form /sys/class/thermal folder and | |
81 | unbind itself from all the thermal zone devices using it. | |
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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, | |
38bb0849 | 85 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 86 | |
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87 | This interface function bind a thermal cooling device to the certain trip |
88 | point 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. | |
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94 | |
95 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | |
38bb0849 | 96 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 97 | |
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98 | This interface function unbind a thermal cooling device from the certain |
99 | trip point of a thermal zone device. This function is usually called in | |
100 | 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. | |
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105 | |
106 | 2. sysfs attributes structure | |
107 | ||
108 | RO read only value | |
109 | RW read/write value | |
110 | ||
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111 | Thermal sysfs attributes will be represented under /sys/class/thermal. |
112 | Hwmon sysfs I/F extension is also available under /sys/class/hwmon | |
113 | if hwmon is compiled in or built as a module. | |
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114 | |
115 | Thermal zone device sys I/F, created once it's registered: | |
e9ae7107 | 116 | /sys/class/thermal/thermal_zone[0-*]: |
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117 | |---type: Type of the thermal zone |
118 | |---temp: Current temperature | |
119 | |---mode: Working mode of the thermal zone | |
120 | |---trip_point_[0-*]_temp: Trip point temperature | |
121 | |---trip_point_[0-*]_type: Trip point type | |
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122 | |
123 | Thermal cooling device sys I/F, created once it's registered: | |
e9ae7107 | 124 | /sys/class/thermal/cooling_device[0-*]: |
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125 | |---type: Type of the cooling device(processor/fan/...) |
126 | |---max_state: Maximum cooling state of the cooling device | |
127 | |---cur_state: Current cooling state of the cooling device | |
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128 | |
129 | ||
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130 | Then next two dynamic attributes are created/removed in pairs. They represent |
131 | the relationship between a thermal zone and its associated cooling device. | |
132 | They are created/removed for each successful execution of | |
133 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. | |
203d3d4a | 134 | |
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135 | /sys/class/thermal/thermal_zone[0-*]: |
136 | |---cdev[0-*]: [0-*]th cooling device in current thermal zone | |
137 | |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
203d3d4a | 138 | |
e9ae7107 | 139 | Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
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140 | the generic thermal driver also creates a hwmon sysfs I/F for each _type_ |
141 | of thermal zone device. E.g. the generic thermal driver registers one hwmon | |
142 | class device and build the associated hwmon sysfs I/F for all the registered | |
143 | ACPI thermal zones. | |
144 | ||
e9ae7107 | 145 | /sys/class/hwmon/hwmon[0-*]: |
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146 | |---name: The type of the thermal zone devices |
147 | |---temp[1-*]_input: The current temperature of thermal zone [1-*] | |
148 | |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] | |
149 | ||
e9ae7107 | 150 | Please read Documentation/hwmon/sysfs-interface for additional information. |
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151 | |
152 | *************************** | |
153 | * Thermal zone attributes * | |
154 | *************************** | |
155 | ||
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156 | type |
157 | Strings which represent the thermal zone type. | |
158 | This is given by thermal zone driver as part of registration. | |
159 | E.g: "acpitz" indicates it's an ACPI thermal device. | |
160 | In order to keep it consistent with hwmon sys attribute; this should | |
161 | be a short, lowercase string, not containing spaces nor dashes. | |
162 | RO, Required | |
163 | ||
164 | temp | |
165 | Current temperature as reported by thermal zone (sensor). | |
166 | Unit: millidegree Celsius | |
167 | RO, Required | |
168 | ||
169 | mode | |
170 | One of the predefined values in [kernel, user]. | |
171 | This file gives information about the algorithm that is currently | |
172 | managing the thermal zone. It can be either default kernel based | |
173 | algorithm or user space application. | |
174 | kernel = Thermal management in kernel thermal zone driver. | |
175 | user = Preventing kernel thermal zone driver actions upon | |
176 | trip points so that user application can take full | |
177 | charge of the thermal management. | |
178 | RW, Optional | |
179 | ||
180 | trip_point_[0-*]_temp | |
181 | The temperature above which trip point will be fired. | |
182 | Unit: millidegree Celsius | |
183 | RO, Optional | |
184 | ||
185 | trip_point_[0-*]_type | |
186 | Strings which indicate the type of the trip point. | |
187 | E.g. it can be one of critical, hot, passive, active[0-*] for ACPI | |
188 | thermal zone. | |
189 | RO, Optional | |
190 | ||
191 | cdev[0-*] | |
192 | Sysfs link to the thermal cooling device node where the sys I/F | |
193 | for cooling device throttling control represents. | |
194 | RO, Optional | |
195 | ||
196 | cdev[0-*]_trip_point | |
197 | The trip point with which cdev[0-*] is associated in this thermal | |
198 | zone; -1 means the cooling device is not associated with any trip | |
199 | point. | |
200 | RO, Optional | |
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201 | |
202 | passive | |
203 | Attribute is only present for zones in which the passive cooling | |
204 | policy is not supported by native thermal driver. Default is zero | |
205 | and can be set to a temperature (in millidegrees) to enable a | |
206 | passive trip point for the zone. Activation is done by polling with | |
207 | an interval of 1 second. | |
208 | Unit: millidegrees Celsius | |
3d8e3ad8 | 209 | Valid values: 0 (disabled) or greater than 1000 |
29226ed3 | 210 | RW, Optional |
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211 | |
212 | ***************************** | |
213 | * Cooling device attributes * | |
214 | ***************************** | |
215 | ||
216 | type | |
217 | String which represents the type of device, e.g: | |
218 | - for generic ACPI: should be "Fan", "Processor" or "LCD" | |
219 | - for memory controller device on intel_menlow platform: | |
220 | should be "Memory controller". | |
221 | RO, Required | |
222 | ||
223 | max_state | |
224 | The maximum permissible cooling state of this cooling device. | |
225 | RO, Required | |
226 | ||
227 | cur_state | |
228 | The current cooling state of this cooling device. | |
229 | The value can any integer numbers between 0 and max_state: | |
230 | - cur_state == 0 means no cooling | |
231 | - cur_state == max_state means the maximum cooling. | |
232 | RW, Required | |
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233 | |
234 | 3. A simple implementation | |
235 | ||
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236 | ACPI thermal zone may support multiple trip points like critical, hot, |
237 | passive, active. If an ACPI thermal zone supports critical, passive, | |
238 | active[0] and active[1] at the same time, it may register itself as a | |
239 | thermal_zone_device (thermal_zone1) with 4 trip points in all. | |
240 | It has one processor and one fan, which are both registered as | |
241 | thermal_cooling_device. | |
242 | ||
243 | If the processor is listed in _PSL method, and the fan is listed in _AL0 | |
244 | method, the sys I/F structure will be built like this: | |
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245 | |
246 | /sys/class/thermal: | |
247 | ||
248 | |thermal_zone1: | |
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249 | |---type: acpitz |
250 | |---temp: 37000 | |
251 | |---mode: kernel | |
252 | |---trip_point_0_temp: 100000 | |
253 | |---trip_point_0_type: critical | |
254 | |---trip_point_1_temp: 80000 | |
255 | |---trip_point_1_type: passive | |
256 | |---trip_point_2_temp: 70000 | |
257 | |---trip_point_2_type: active0 | |
258 | |---trip_point_3_temp: 60000 | |
259 | |---trip_point_3_type: active1 | |
260 | |---cdev0: --->/sys/class/thermal/cooling_device0 | |
261 | |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
262 | |---cdev1: --->/sys/class/thermal/cooling_device3 | |
263 | |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
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264 | |
265 | |cooling_device0: | |
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266 | |---type: Processor |
267 | |---max_state: 8 | |
268 | |---cur_state: 0 | |
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269 | |
270 | |cooling_device3: | |
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271 | |---type: Fan |
272 | |---max_state: 2 | |
273 | |---cur_state: 0 | |
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274 | |
275 | /sys/class/hwmon: | |
276 | ||
277 | |hwmon0: | |
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278 | |---name: acpitz |
279 | |---temp1_input: 37000 | |
280 | |---temp1_crit: 100000 |