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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. | |
203d3d4a | 114 | |
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115 | 1.4 Thermal Zone Parameters |
116 | 1.4.1 struct thermal_bind_params | |
117 | This structure defines the following parameters that are used to bind | |
118 | a zone with a cooling device for a particular trip point. | |
119 | .cdev: The cooling device pointer | |
120 | .weight: The 'influence' of a particular cooling device on this zone. | |
121 | This is on a percentage scale. The sum of all these weights | |
122 | (for a particular zone) cannot exceed 100. | |
123 | .trip_mask:This is a bit mask that gives the binding relation between | |
124 | this thermal zone and cdev, for a particular trip point. | |
125 | If nth bit is set, then the cdev and thermal zone are bound | |
126 | for trip point n. | |
127 | .match: This call back returns success(0) if the 'tz and cdev' need to | |
128 | be bound, as per platform data. | |
129 | 1.4.2 struct thermal_zone_params | |
130 | This structure defines the platform level parameters for a thermal zone. | |
131 | This data, for each thermal zone should come from the platform layer. | |
132 | This is an optional feature where some platforms can choose not to | |
133 | provide this data. | |
134 | .governor_name: Name of the thermal governor used for this zone | |
135 | .num_tbps: Number of thermal_bind_params entries for this zone | |
136 | .tbp: thermal_bind_params entries | |
137 | ||
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138 | 2. sysfs attributes structure |
139 | ||
140 | RO read only value | |
141 | RW read/write value | |
142 | ||
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143 | Thermal sysfs attributes will be represented under /sys/class/thermal. |
144 | Hwmon sysfs I/F extension is also available under /sys/class/hwmon | |
145 | if hwmon is compiled in or built as a module. | |
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146 | |
147 | Thermal zone device sys I/F, created once it's registered: | |
e9ae7107 | 148 | /sys/class/thermal/thermal_zone[0-*]: |
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149 | |---type: Type of the thermal zone |
150 | |---temp: Current temperature | |
151 | |---mode: Working mode of the thermal zone | |
6ea083b1 | 152 | |---policy: Thermal governor used for this zone |
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153 | |---trip_point_[0-*]_temp: Trip point temperature |
154 | |---trip_point_[0-*]_type: Trip point type | |
27365a6c | 155 | |---trip_point_[0-*]_hyst: Hysteresis value for this trip point |
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156 | |
157 | Thermal cooling device sys I/F, created once it's registered: | |
e9ae7107 | 158 | /sys/class/thermal/cooling_device[0-*]: |
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159 | |---type: Type of the cooling device(processor/fan/...) |
160 | |---max_state: Maximum cooling state of the cooling device | |
161 | |---cur_state: Current cooling state of the cooling device | |
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162 | |
163 | ||
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164 | Then next two dynamic attributes are created/removed in pairs. They represent |
165 | the relationship between a thermal zone and its associated cooling device. | |
166 | They are created/removed for each successful execution of | |
167 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. | |
203d3d4a | 168 | |
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169 | /sys/class/thermal/thermal_zone[0-*]: |
170 | |---cdev[0-*]: [0-*]th cooling device in current thermal zone | |
171 | |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
203d3d4a | 172 | |
e9ae7107 | 173 | Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
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174 | the generic thermal driver also creates a hwmon sysfs I/F for each _type_ |
175 | of thermal zone device. E.g. the generic thermal driver registers one hwmon | |
176 | class device and build the associated hwmon sysfs I/F for all the registered | |
177 | ACPI thermal zones. | |
178 | ||
e9ae7107 | 179 | /sys/class/hwmon/hwmon[0-*]: |
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180 | |---name: The type of the thermal zone devices |
181 | |---temp[1-*]_input: The current temperature of thermal zone [1-*] | |
182 | |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] | |
183 | ||
e9ae7107 | 184 | Please read Documentation/hwmon/sysfs-interface for additional information. |
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185 | |
186 | *************************** | |
187 | * Thermal zone attributes * | |
188 | *************************** | |
189 | ||
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190 | type |
191 | Strings which represent the thermal zone type. | |
192 | This is given by thermal zone driver as part of registration. | |
193 | E.g: "acpitz" indicates it's an ACPI thermal device. | |
194 | In order to keep it consistent with hwmon sys attribute; this should | |
195 | be a short, lowercase string, not containing spaces nor dashes. | |
196 | RO, Required | |
197 | ||
198 | temp | |
199 | Current temperature as reported by thermal zone (sensor). | |
200 | Unit: millidegree Celsius | |
201 | RO, Required | |
202 | ||
203 | mode | |
8eaa8d6c | 204 | One of the predefined values in [enabled, disabled]. |
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205 | This file gives information about the algorithm that is currently |
206 | managing the thermal zone. It can be either default kernel based | |
207 | algorithm or user space application. | |
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208 | enabled = enable Kernel Thermal management. |
209 | disabled = Preventing kernel thermal zone driver actions upon | |
210 | trip points so that user application can take full | |
211 | charge of the thermal management. | |
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212 | RW, Optional |
213 | ||
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214 | policy |
215 | One of the various thermal governors used for a particular zone. | |
216 | RW, Required | |
217 | ||
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218 | trip_point_[0-*]_temp |
219 | The temperature above which trip point will be fired. | |
220 | Unit: millidegree Celsius | |
221 | RO, Optional | |
222 | ||
223 | trip_point_[0-*]_type | |
224 | Strings which indicate the type of the trip point. | |
225 | E.g. it can be one of critical, hot, passive, active[0-*] for ACPI | |
226 | thermal zone. | |
227 | RO, Optional | |
228 | ||
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229 | trip_point_[0-*]_hyst |
230 | The hysteresis value for a trip point, represented as an integer | |
231 | Unit: Celsius | |
232 | RW, Optional | |
233 | ||
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234 | cdev[0-*] |
235 | Sysfs link to the thermal cooling device node where the sys I/F | |
236 | for cooling device throttling control represents. | |
237 | RO, Optional | |
238 | ||
239 | cdev[0-*]_trip_point | |
240 | The trip point with which cdev[0-*] is associated in this thermal | |
241 | zone; -1 means the cooling device is not associated with any trip | |
242 | point. | |
243 | RO, Optional | |
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244 | |
245 | passive | |
246 | Attribute is only present for zones in which the passive cooling | |
247 | policy is not supported by native thermal driver. Default is zero | |
248 | and can be set to a temperature (in millidegrees) to enable a | |
249 | passive trip point for the zone. Activation is done by polling with | |
250 | an interval of 1 second. | |
251 | Unit: millidegrees Celsius | |
3d8e3ad8 | 252 | Valid values: 0 (disabled) or greater than 1000 |
29226ed3 | 253 | RW, Optional |
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254 | |
255 | ***************************** | |
256 | * Cooling device attributes * | |
257 | ***************************** | |
258 | ||
259 | type | |
260 | String which represents the type of device, e.g: | |
261 | - for generic ACPI: should be "Fan", "Processor" or "LCD" | |
262 | - for memory controller device on intel_menlow platform: | |
263 | should be "Memory controller". | |
264 | RO, Required | |
265 | ||
266 | max_state | |
267 | The maximum permissible cooling state of this cooling device. | |
268 | RO, Required | |
269 | ||
270 | cur_state | |
271 | The current cooling state of this cooling device. | |
272 | The value can any integer numbers between 0 and max_state: | |
273 | - cur_state == 0 means no cooling | |
274 | - cur_state == max_state means the maximum cooling. | |
275 | RW, Required | |
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276 | |
277 | 3. A simple implementation | |
278 | ||
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279 | ACPI thermal zone may support multiple trip points like critical, hot, |
280 | passive, active. If an ACPI thermal zone supports critical, passive, | |
281 | active[0] and active[1] at the same time, it may register itself as a | |
282 | thermal_zone_device (thermal_zone1) with 4 trip points in all. | |
283 | It has one processor and one fan, which are both registered as | |
284 | thermal_cooling_device. | |
285 | ||
286 | If the processor is listed in _PSL method, and the fan is listed in _AL0 | |
287 | method, the sys I/F structure will be built like this: | |
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288 | |
289 | /sys/class/thermal: | |
290 | ||
291 | |thermal_zone1: | |
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292 | |---type: acpitz |
293 | |---temp: 37000 | |
8eaa8d6c | 294 | |---mode: enabled |
6ea083b1 | 295 | |---policy: step_wise |
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296 | |---trip_point_0_temp: 100000 |
297 | |---trip_point_0_type: critical | |
298 | |---trip_point_1_temp: 80000 | |
299 | |---trip_point_1_type: passive | |
300 | |---trip_point_2_temp: 70000 | |
301 | |---trip_point_2_type: active0 | |
302 | |---trip_point_3_temp: 60000 | |
303 | |---trip_point_3_type: active1 | |
304 | |---cdev0: --->/sys/class/thermal/cooling_device0 | |
305 | |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
306 | |---cdev1: --->/sys/class/thermal/cooling_device3 | |
307 | |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
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308 | |
309 | |cooling_device0: | |
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310 | |---type: Processor |
311 | |---max_state: 8 | |
312 | |---cur_state: 0 | |
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313 | |
314 | |cooling_device3: | |
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315 | |---type: Fan |
316 | |---max_state: 2 | |
317 | |---cur_state: 0 | |
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318 | |
319 | /sys/class/hwmon: | |
320 | ||
321 | |hwmon0: | |
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322 | |---name: acpitz |
323 | |---temp1_input: 37000 | |
324 | |---temp1_crit: 100000 | |
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325 | |
326 | 4. Event Notification | |
327 | ||
328 | The framework includes a simple notification mechanism, in the form of a | |
329 | netlink event. Netlink socket initialization is done during the _init_ | |
330 | of the framework. Drivers which intend to use the notification mechanism | |
2d58d7ea | 331 | just need to call thermal_generate_netlink_event() with two arguments viz |
8ab3e6a0 EV |
332 | (originator, event). The originator is a pointer to struct thermal_zone_device |
333 | from where the event has been originated. An integer which represents the | |
334 | thermal zone device will be used in the message to identify the zone. The | |
4cb18728 D |
335 | event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, |
336 | THERMAL_DEV_FAULT}. Notification can be sent when the current temperature | |
337 | crosses any of the configured thresholds. | |
6ea083b1 D |
338 | |
339 | 5. Export Symbol APIs: | |
340 | ||
341 | 5.1: get_tz_trend: | |
342 | This function returns the trend of a thermal zone, i.e the rate of change | |
343 | of temperature of the thermal zone. Ideally, the thermal sensor drivers | |
344 | are supposed to implement the callback. If they don't, the thermal | |
345 | framework calculated the trend by comparing the previous and the current | |
346 | temperature values. | |
347 | ||
348 | 5.2:get_thermal_instance: | |
349 | This function returns the thermal_instance corresponding to a given | |
350 | {thermal_zone, cooling_device, trip_point} combination. Returns NULL | |
351 | if such an instance does not exist. | |
352 | ||
353 | 5.3:notify_thermal_framework: | |
354 | This function handles the trip events from sensor drivers. It starts | |
355 | throttling the cooling devices according to the policy configured. | |
356 | For CRITICAL and HOT trip points, this notifies the respective drivers, | |
357 | and does actual throttling for other trip points i.e ACTIVE and PASSIVE. | |
358 | The throttling policy is based on the configured platform data; if no | |
359 | platform data is provided, this uses the step_wise throttling policy. | |
360 | ||
361 | 5.4:thermal_cdev_update: | |
362 | This function serves as an arbitrator to set the state of a cooling | |
363 | device. It sets the cooling device to the deepest cooling state if | |
364 | possible. | |
365 | ||
366 | 5.5:thermal_register_governor: | |
367 | This function lets the various thermal governors to register themselves | |
368 | with the Thermal framework. At run time, depending on a zone's platform | |
369 | data, a particular governor is used for throttling. | |
370 | ||
371 | 5.6:thermal_unregister_governor: | |
372 | This function unregisters a governor from the thermal framework. |