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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 | |
38bb0849 | 34 | 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, |
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35 | int trips, int mask, void *devdata, |
36 | struct thermal_zone_device_ops *ops) | |
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37 | |
38 | This interface function adds a new thermal zone device (sensor) to | |
39 | /sys/class/thermal folder as thermal_zone[0-*]. It tries to bind all the | |
40 | thermal cooling devices registered at the same time. | |
41 | ||
42 | name: the thermal zone name. | |
43 | trips: the total number of trip points this thermal zone supports. | |
c56f5c03 | 44 | mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable. |
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45 | devdata: device private data |
46 | ops: thermal zone device call-backs. | |
47 | .bind: bind the thermal zone device with a thermal cooling device. | |
48 | .unbind: unbind the thermal zone device with a thermal cooling device. | |
49 | .get_temp: get the current temperature of the thermal zone. | |
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50 | .get_mode: get the current mode (enabled/disabled) of the thermal zone. |
51 | - "enabled" means the kernel thermal management is enabled. | |
52 | - "disabled" will prevent kernel thermal driver action upon trip points | |
38bb0849 | 53 | so that user applications can take charge of thermal management. |
8eaa8d6c | 54 | .set_mode: set the mode (enabled/disabled) of the thermal zone. |
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55 | .get_trip_type: get the type of certain trip point. |
56 | .get_trip_temp: get the temperature above which the certain trip point | |
57 | will be fired. | |
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58 | |
59 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | |
60 | ||
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61 | This interface function removes the thermal zone device. |
62 | It deletes the corresponding entry form /sys/class/thermal folder and | |
63 | unbind all the thermal cooling devices it uses. | |
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64 | |
65 | 1.2 thermal cooling device interface | |
66 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | |
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67 | void *devdata, struct thermal_cooling_device_ops *) |
68 | ||
69 | This interface function adds a new thermal cooling device (fan/processor/...) | |
70 | to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself | |
71 | to all the thermal zone devices register at the same time. | |
72 | name: the cooling device name. | |
73 | devdata: device private data. | |
74 | ops: thermal cooling devices call-backs. | |
75 | .get_max_state: get the Maximum throttle state of the cooling device. | |
76 | .get_cur_state: get the Current throttle state of the cooling device. | |
77 | .set_cur_state: set the Current throttle state of the cooling device. | |
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78 | |
79 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | |
80 | ||
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81 | This interface function remove the thermal cooling device. |
82 | It deletes the corresponding entry form /sys/class/thermal folder and | |
83 | unbind itself from all the thermal zone devices using it. | |
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84 | |
85 | 1.3 interface for binding a thermal zone device with a thermal cooling device | |
86 | 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, | |
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87 | int trip, struct thermal_cooling_device *cdev, |
88 | unsigned long upper, unsigned long lower); | |
203d3d4a | 89 | |
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90 | This interface function bind a thermal cooling device to the certain trip |
91 | point of a thermal zone device. | |
92 | This function is usually called in the thermal zone device .bind callback. | |
93 | tz: the thermal zone device | |
94 | cdev: thermal cooling device | |
95 | trip: indicates which trip point the cooling devices is associated with | |
96 | in this thermal zone. | |
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97 | upper:the Maximum cooling state for this trip point. |
98 | THERMAL_NO_LIMIT means no upper limit, | |
99 | and the cooling device can be in max_state. | |
100 | lower:the Minimum cooling state can be used for this trip point. | |
101 | THERMAL_NO_LIMIT means no lower limit, | |
102 | and the cooling device can be in cooling state 0. | |
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103 | |
104 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | |
38bb0849 | 105 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 106 | |
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107 | This interface function unbind a thermal cooling device from the certain |
108 | trip point of a thermal zone device. This function is usually called in | |
109 | the thermal zone device .unbind callback. | |
110 | tz: the thermal zone device | |
111 | cdev: thermal cooling device | |
112 | trip: indicates which trip point the cooling devices is associated with | |
113 | in this thermal zone. | |
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114 | |
115 | 2. sysfs attributes structure | |
116 | ||
117 | RO read only value | |
118 | RW read/write value | |
119 | ||
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120 | Thermal sysfs attributes will be represented under /sys/class/thermal. |
121 | Hwmon sysfs I/F extension is also available under /sys/class/hwmon | |
122 | if hwmon is compiled in or built as a module. | |
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123 | |
124 | Thermal zone device sys I/F, created once it's registered: | |
e9ae7107 | 125 | /sys/class/thermal/thermal_zone[0-*]: |
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126 | |---type: Type of the thermal zone |
127 | |---temp: Current temperature | |
128 | |---mode: Working mode of the thermal zone | |
129 | |---trip_point_[0-*]_temp: Trip point temperature | |
130 | |---trip_point_[0-*]_type: Trip point type | |
27365a6c | 131 | |---trip_point_[0-*]_hyst: Hysteresis value for this trip point |
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132 | |
133 | Thermal cooling device sys I/F, created once it's registered: | |
e9ae7107 | 134 | /sys/class/thermal/cooling_device[0-*]: |
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135 | |---type: Type of the cooling device(processor/fan/...) |
136 | |---max_state: Maximum cooling state of the cooling device | |
137 | |---cur_state: Current cooling state of the cooling device | |
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138 | |
139 | ||
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140 | Then next two dynamic attributes are created/removed in pairs. They represent |
141 | the relationship between a thermal zone and its associated cooling device. | |
142 | They are created/removed for each successful execution of | |
143 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. | |
203d3d4a | 144 | |
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145 | /sys/class/thermal/thermal_zone[0-*]: |
146 | |---cdev[0-*]: [0-*]th cooling device in current thermal zone | |
147 | |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
203d3d4a | 148 | |
e9ae7107 | 149 | Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
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150 | the generic thermal driver also creates a hwmon sysfs I/F for each _type_ |
151 | of thermal zone device. E.g. the generic thermal driver registers one hwmon | |
152 | class device and build the associated hwmon sysfs I/F for all the registered | |
153 | ACPI thermal zones. | |
154 | ||
e9ae7107 | 155 | /sys/class/hwmon/hwmon[0-*]: |
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156 | |---name: The type of the thermal zone devices |
157 | |---temp[1-*]_input: The current temperature of thermal zone [1-*] | |
158 | |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] | |
159 | ||
e9ae7107 | 160 | Please read Documentation/hwmon/sysfs-interface for additional information. |
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161 | |
162 | *************************** | |
163 | * Thermal zone attributes * | |
164 | *************************** | |
165 | ||
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166 | type |
167 | Strings which represent the thermal zone type. | |
168 | This is given by thermal zone driver as part of registration. | |
169 | E.g: "acpitz" indicates it's an ACPI thermal device. | |
170 | In order to keep it consistent with hwmon sys attribute; this should | |
171 | be a short, lowercase string, not containing spaces nor dashes. | |
172 | RO, Required | |
173 | ||
174 | temp | |
175 | Current temperature as reported by thermal zone (sensor). | |
176 | Unit: millidegree Celsius | |
177 | RO, Required | |
178 | ||
179 | mode | |
8eaa8d6c | 180 | One of the predefined values in [enabled, disabled]. |
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181 | This file gives information about the algorithm that is currently |
182 | managing the thermal zone. It can be either default kernel based | |
183 | algorithm or user space application. | |
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184 | enabled = enable Kernel Thermal management. |
185 | disabled = Preventing kernel thermal zone driver actions upon | |
186 | trip points so that user application can take full | |
187 | charge of the thermal management. | |
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188 | RW, Optional |
189 | ||
190 | trip_point_[0-*]_temp | |
191 | The temperature above which trip point will be fired. | |
192 | Unit: millidegree Celsius | |
193 | RO, Optional | |
194 | ||
195 | trip_point_[0-*]_type | |
196 | Strings which indicate the type of the trip point. | |
197 | E.g. it can be one of critical, hot, passive, active[0-*] for ACPI | |
198 | thermal zone. | |
199 | RO, Optional | |
200 | ||
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201 | trip_point_[0-*]_hyst |
202 | The hysteresis value for a trip point, represented as an integer | |
203 | Unit: Celsius | |
204 | RW, Optional | |
205 | ||
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206 | cdev[0-*] |
207 | Sysfs link to the thermal cooling device node where the sys I/F | |
208 | for cooling device throttling control represents. | |
209 | RO, Optional | |
210 | ||
211 | cdev[0-*]_trip_point | |
212 | The trip point with which cdev[0-*] is associated in this thermal | |
213 | zone; -1 means the cooling device is not associated with any trip | |
214 | point. | |
215 | RO, Optional | |
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216 | |
217 | passive | |
218 | Attribute is only present for zones in which the passive cooling | |
219 | policy is not supported by native thermal driver. Default is zero | |
220 | and can be set to a temperature (in millidegrees) to enable a | |
221 | passive trip point for the zone. Activation is done by polling with | |
222 | an interval of 1 second. | |
223 | Unit: millidegrees Celsius | |
3d8e3ad8 | 224 | Valid values: 0 (disabled) or greater than 1000 |
29226ed3 | 225 | RW, Optional |
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226 | |
227 | ***************************** | |
228 | * Cooling device attributes * | |
229 | ***************************** | |
230 | ||
231 | type | |
232 | String which represents the type of device, e.g: | |
233 | - for generic ACPI: should be "Fan", "Processor" or "LCD" | |
234 | - for memory controller device on intel_menlow platform: | |
235 | should be "Memory controller". | |
236 | RO, Required | |
237 | ||
238 | max_state | |
239 | The maximum permissible cooling state of this cooling device. | |
240 | RO, Required | |
241 | ||
242 | cur_state | |
243 | The current cooling state of this cooling device. | |
244 | The value can any integer numbers between 0 and max_state: | |
245 | - cur_state == 0 means no cooling | |
246 | - cur_state == max_state means the maximum cooling. | |
247 | RW, Required | |
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248 | |
249 | 3. A simple implementation | |
250 | ||
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251 | ACPI thermal zone may support multiple trip points like critical, hot, |
252 | passive, active. If an ACPI thermal zone supports critical, passive, | |
253 | active[0] and active[1] at the same time, it may register itself as a | |
254 | thermal_zone_device (thermal_zone1) with 4 trip points in all. | |
255 | It has one processor and one fan, which are both registered as | |
256 | thermal_cooling_device. | |
257 | ||
258 | If the processor is listed in _PSL method, and the fan is listed in _AL0 | |
259 | method, the sys I/F structure will be built like this: | |
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260 | |
261 | /sys/class/thermal: | |
262 | ||
263 | |thermal_zone1: | |
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264 | |---type: acpitz |
265 | |---temp: 37000 | |
8eaa8d6c | 266 | |---mode: enabled |
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267 | |---trip_point_0_temp: 100000 |
268 | |---trip_point_0_type: critical | |
269 | |---trip_point_1_temp: 80000 | |
270 | |---trip_point_1_type: passive | |
271 | |---trip_point_2_temp: 70000 | |
272 | |---trip_point_2_type: active0 | |
273 | |---trip_point_3_temp: 60000 | |
274 | |---trip_point_3_type: active1 | |
275 | |---cdev0: --->/sys/class/thermal/cooling_device0 | |
276 | |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
277 | |---cdev1: --->/sys/class/thermal/cooling_device3 | |
278 | |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
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279 | |
280 | |cooling_device0: | |
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281 | |---type: Processor |
282 | |---max_state: 8 | |
283 | |---cur_state: 0 | |
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284 | |
285 | |cooling_device3: | |
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286 | |---type: Fan |
287 | |---max_state: 2 | |
288 | |---cur_state: 0 | |
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289 | |
290 | /sys/class/hwmon: | |
291 | ||
292 | |hwmon0: | |
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293 | |---name: acpitz |
294 | |---temp1_input: 37000 | |
295 | |---temp1_crit: 100000 | |
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296 | |
297 | 4. Event Notification | |
298 | ||
299 | The framework includes a simple notification mechanism, in the form of a | |
300 | netlink event. Netlink socket initialization is done during the _init_ | |
301 | of the framework. Drivers which intend to use the notification mechanism | |
2d58d7ea | 302 | just need to call thermal_generate_netlink_event() with two arguments viz |
4cb18728 D |
303 | (originator, event). Typically the originator will be an integer assigned |
304 | to a thermal_zone_device when it registers itself with the framework. The | |
305 | event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, | |
306 | THERMAL_DEV_FAULT}. Notification can be sent when the current temperature | |
307 | crosses any of the configured thresholds. |