1 =================================== 1 ===================================
2 Generic Thermal Sysfs driver How To 2 Generic Thermal Sysfs driver How To
3 =================================== 3 ===================================
4 4
5 Written by Sujith Thomas <sujith.thomas@intel.c 5 Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com>
6 6
>> 7 Updated: 2 January 2008
>> 8
7 Copyright (c) 2008 Intel Corporation 9 Copyright (c) 2008 Intel Corporation
8 10
9 11
10 0. Introduction 12 0. Introduction
11 =============== 13 ===============
12 14
13 The generic thermal sysfs provides a set of in 15 The generic thermal sysfs provides a set of interfaces for thermal zone
14 devices (sensors) and thermal cooling devices 16 devices (sensors) and thermal cooling devices (fan, processor...) to register
15 with the thermal management solution and to be 17 with the thermal management solution and to be a part of it.
16 18
17 This how-to focuses on enabling new thermal zo 19 This how-to focuses on enabling new thermal zone and cooling devices to
18 participate in thermal management. 20 participate in thermal management.
19 This solution is platform independent and any 21 This solution is platform independent and any type of thermal zone devices
20 and cooling devices should be able to make use 22 and cooling devices should be able to make use of the infrastructure.
21 23
22 The main task of the thermal sysfs driver is t 24 The main task of the thermal sysfs driver is to expose thermal zone attributes
23 as well as cooling device attributes to the us 25 as well as cooling device attributes to the user space.
24 An intelligent thermal management application 26 An intelligent thermal management application can make decisions based on
25 inputs from thermal zone attributes (the curre 27 inputs from thermal zone attributes (the current temperature and trip point
26 temperature) and throttle appropriate devices. 28 temperature) and throttle appropriate devices.
27 29
28 - `[0-*]` denotes any positive number st 30 - `[0-*]` denotes any positive number starting from 0
29 - `[1-*]` denotes any positive number st 31 - `[1-*]` denotes any positive number starting from 1
30 32
31 1. thermal sysfs driver interface functions 33 1. thermal sysfs driver interface functions
32 =========================================== 34 ===========================================
33 35
34 1.1 thermal zone device interface 36 1.1 thermal zone device interface
35 --------------------------------- 37 ---------------------------------
36 38
37 :: 39 ::
38 40
39 struct thermal_zone_device * !! 41 struct thermal_zone_device
40 thermal_zone_device_register_with_trip !! 42 *thermal_zone_device_register(char *type,
41 const !! 43 int trips, int mask, void *devdata,
42 int nu !! 44 struct thermal_zone_device_ops *ops,
43 const !! 45 const struct thermal_zone_params *tzp,
44 const !! 46 int passive_delay, int polling_delay))
45 unsign <<
46 unsign <<
47 47
48 This interface function adds a new thermal !! 48 This interface function adds a new thermal zone device (sensor) to
49 /sys/class/thermal folder as `thermal_zone 49 /sys/class/thermal folder as `thermal_zone[0-*]`. It tries to bind all the
50 thermal cooling devices registered to it a !! 50 thermal cooling devices registered at the same time.
51 51
52 type: 52 type:
53 the thermal zone type. 53 the thermal zone type.
54 trips: 54 trips:
55 the table of trip points for this ther !! 55 the total number of trip points this thermal zone supports.
>> 56 mask:
>> 57 Bit string: If 'n'th bit is set, then trip point 'n' is writable.
56 devdata: 58 devdata:
57 device private data 59 device private data
58 ops: 60 ops:
59 thermal zone device call-backs. 61 thermal zone device call-backs.
60 62
61 .should_bind: !! 63 .bind:
62 check whether or not a given c !! 64 bind the thermal zone device with a thermal cooling device.
63 a given trip point in this the !! 65 .unbind:
>> 66 unbind the thermal zone device with a thermal cooling device.
64 .get_temp: 67 .get_temp:
65 get the current temperature of 68 get the current temperature of the thermal zone.
66 .set_trips: 69 .set_trips:
67 set the trip points window. Wh !! 70 set the trip points window. Whenever the current temperature
68 is updated, the trip points im !! 71 is updated, the trip points immediately below and above the
69 current temperature are found. !! 72 current temperature are found.
70 .change_mode: !! 73 .get_mode:
71 change the mode (enabled/disab !! 74 get the current mode (enabled/disabled) of the thermal zone.
72 .set_trip_temp: !! 75
73 set the temperature of a given !! 76 - "enabled" means the kernel thermal management is
74 .get_crit_temp: !! 77 enabled.
75 get the critical temperature f !! 78 - "disabled" will prevent kernel thermal driver action
>> 79 upon trip points so that user applications can take
>> 80 charge of thermal management.
>> 81 .set_mode:
>> 82 set the mode (enabled/disabled) of the thermal zone.
>> 83 .get_trip_type:
>> 84 get the type of certain trip point.
>> 85 .get_trip_temp:
>> 86 get the temperature above which the certain trip point
>> 87 will be fired.
76 .set_emul_temp: 88 .set_emul_temp:
77 set the emulation temperature !! 89 set the emulation temperature which helps in debugging
78 different threshold temperatur !! 90 different threshold temperature points.
79 .get_trend: <<
80 get the trend of most recent z <<
81 .hot: <<
82 hot trip point crossing handle <<
83 .critical: <<
84 critical trip point crossing h <<
85 tzp: 91 tzp:
86 thermal zone platform parameters. 92 thermal zone platform parameters.
87 passive_delay: 93 passive_delay:
88 number of milliseconds to wait between !! 94 number of milliseconds to wait between polls when
89 cooling. !! 95 performing passive cooling.
90 polling_delay: 96 polling_delay:
91 number of milliseconds to wait between 97 number of milliseconds to wait between polls when checking
92 whether trip points have been crossed 98 whether trip points have been crossed (0 for interrupt driven systems).
93 99
94 :: 100 ::
95 101
96 void thermal_zone_device_unregister(st 102 void thermal_zone_device_unregister(struct thermal_zone_device *tz)
97 103
98 This interface function removes the therma 104 This interface function removes the thermal zone device.
99 It deletes the corresponding entry from /s 105 It deletes the corresponding entry from /sys/class/thermal folder and
100 unbinds all the thermal cooling devices it 106 unbinds all the thermal cooling devices it uses.
101 107
102 :: 108 ::
103 109
104 struct thermal_zone_device 110 struct thermal_zone_device
105 *thermal_zone_of_sensor_register(st 111 *thermal_zone_of_sensor_register(struct device *dev, int sensor_id,
106 void *data, 112 void *data,
107 const struct t 113 const struct thermal_zone_of_device_ops *ops)
108 114
109 This interface adds a new sensor to a 115 This interface adds a new sensor to a DT thermal zone.
110 This function will search the list of 116 This function will search the list of thermal zones described in
111 device tree and look for the zone that 117 device tree and look for the zone that refer to the sensor device
112 pointed by dev->of_node as temperature 118 pointed by dev->of_node as temperature providers. For the zone
113 pointing to the sensor node, the senso 119 pointing to the sensor node, the sensor will be added to the DT
114 thermal zone device. 120 thermal zone device.
115 121
116 The parameters for this interface are: 122 The parameters for this interface are:
117 123
118 dev: 124 dev:
119 Device node of sensor 125 Device node of sensor containing valid node pointer in
120 dev->of_node. 126 dev->of_node.
121 sensor_id: 127 sensor_id:
122 a sensor identifier, i 128 a sensor identifier, in case the sensor IP has more
123 than one sensors 129 than one sensors
124 data: 130 data:
125 a private pointer (own 131 a private pointer (owned by the caller) that will be
126 passed back, when a te 132 passed back, when a temperature reading is needed.
127 ops: 133 ops:
128 `struct thermal_zone_o 134 `struct thermal_zone_of_device_ops *`.
129 135
130 ============== ====== 136 ============== =======================================
131 get_temp a poin 137 get_temp a pointer to a function that reads the
132 sensor 138 sensor temperature. This is mandatory
133 callba 139 callback provided by sensor driver.
134 set_trips a poin 140 set_trips a pointer to a function that sets a
135 temper 141 temperature window. When this window is
136 left t 142 left the driver must inform the thermal
137 core v 143 core via thermal_zone_device_update.
138 get_trend a poin 144 get_trend a pointer to a function that reads the
139 sensor 145 sensor temperature trend.
140 set_emul_temp a poin 146 set_emul_temp a pointer to a function that sets
141 sensor 147 sensor emulated temperature.
142 ============== ====== 148 ============== =======================================
143 149
144 The thermal zone temperature is provid 150 The thermal zone temperature is provided by the get_temp() function
145 pointer of thermal_zone_of_device_ops. 151 pointer of thermal_zone_of_device_ops. When called, it will
146 have the private pointer @data back. 152 have the private pointer @data back.
147 153
148 It returns error pointer if fails othe 154 It returns error pointer if fails otherwise valid thermal zone device
149 handle. Caller should check the return 155 handle. Caller should check the return handle with IS_ERR() for finding
150 whether success or not. 156 whether success or not.
151 157
152 :: 158 ::
153 159
154 void thermal_zone_of_sensor_unregi 160 void thermal_zone_of_sensor_unregister(struct device *dev,
155 161 struct thermal_zone_device *tzd)
156 162
157 This interface unregisters a sensor fr 163 This interface unregisters a sensor from a DT thermal zone which was
158 successfully added by interface therma 164 successfully added by interface thermal_zone_of_sensor_register().
159 This function removes the sensor callb 165 This function removes the sensor callbacks and private data from the
160 thermal zone device registered with th 166 thermal zone device registered with thermal_zone_of_sensor_register()
161 interface. It will also silent the zon 167 interface. It will also silent the zone by remove the .get_temp() and
162 get_trend() thermal zone device callba 168 get_trend() thermal zone device callbacks.
163 169
164 :: 170 ::
165 171
166 struct thermal_zone_device 172 struct thermal_zone_device
167 *devm_thermal_zone_of_sensor_registe 173 *devm_thermal_zone_of_sensor_register(struct device *dev,
168 int sensor_id, 174 int sensor_id,
169 void *data, 175 void *data,
170 const struct t 176 const struct thermal_zone_of_device_ops *ops)
171 177
172 This interface is resource managed ver 178 This interface is resource managed version of
173 thermal_zone_of_sensor_register(). 179 thermal_zone_of_sensor_register().
174 180
175 All details of thermal_zone_of_sensor_ 181 All details of thermal_zone_of_sensor_register() described in
176 section 1.1.3 is applicable here. 182 section 1.1.3 is applicable here.
177 183
178 The benefit of using this interface to 184 The benefit of using this interface to register sensor is that it
179 is not require to explicitly call ther 185 is not require to explicitly call thermal_zone_of_sensor_unregister()
180 in error path or during driver unbindi 186 in error path or during driver unbinding as this is done by driver
181 resource manager. 187 resource manager.
182 188
183 :: 189 ::
184 190
185 void devm_thermal_zone_of_sens 191 void devm_thermal_zone_of_sensor_unregister(struct device *dev,
186 192 struct thermal_zone_device *tzd)
187 193
188 This interface is resource managed ver 194 This interface is resource managed version of
189 thermal_zone_of_sensor_unregister(). 195 thermal_zone_of_sensor_unregister().
190 All details of thermal_zone_of_sensor_ 196 All details of thermal_zone_of_sensor_unregister() described in
191 section 1.1.4 is applicable here. 197 section 1.1.4 is applicable here.
192 Normally this function will not need t 198 Normally this function will not need to be called and the resource
193 management code will ensure that the r 199 management code will ensure that the resource is freed.
194 200
195 :: 201 ::
196 202
197 int thermal_zone_get_slope(str 203 int thermal_zone_get_slope(struct thermal_zone_device *tz)
198 204
199 This interface is used to read the slo 205 This interface is used to read the slope attribute value
200 for the thermal zone device, which mig 206 for the thermal zone device, which might be useful for platform
201 drivers for temperature calculations. 207 drivers for temperature calculations.
202 208
203 :: 209 ::
204 210
205 int thermal_zone_get_offset(st 211 int thermal_zone_get_offset(struct thermal_zone_device *tz)
206 212
207 This interface is used to read the off 213 This interface is used to read the offset attribute value
208 for the thermal zone device, which mig 214 for the thermal zone device, which might be useful for platform
209 drivers for temperature calculations. 215 drivers for temperature calculations.
210 216
211 1.2 thermal cooling device interface 217 1.2 thermal cooling device interface
212 ------------------------------------ 218 ------------------------------------
213 219
214 220
215 :: 221 ::
216 222
217 struct thermal_cooling_device 223 struct thermal_cooling_device
218 *thermal_cooling_device_register(char 224 *thermal_cooling_device_register(char *name,
219 void *devdata, struct 225 void *devdata, struct thermal_cooling_device_ops *)
220 226
221 This interface function adds a new thermal 227 This interface function adds a new thermal cooling device (fan/processor/...)
222 to /sys/class/thermal/ folder as `cooling_ 228 to /sys/class/thermal/ folder as `cooling_device[0-*]`. It tries to bind itself
223 to all the thermal zone devices registered 229 to all the thermal zone devices registered at the same time.
224 230
225 name: 231 name:
226 the cooling device name. 232 the cooling device name.
227 devdata: 233 devdata:
228 device private data. 234 device private data.
229 ops: 235 ops:
230 thermal cooling devices call-backs. 236 thermal cooling devices call-backs.
231 237
232 .get_max_state: 238 .get_max_state:
233 get the Maximum throttle state 239 get the Maximum throttle state of the cooling device.
234 .get_cur_state: 240 .get_cur_state:
235 get the Currently requested th 241 get the Currently requested throttle state of the
236 cooling device. 242 cooling device.
237 .set_cur_state: 243 .set_cur_state:
238 set the Current throttle state 244 set the Current throttle state of the cooling device.
239 245
240 :: 246 ::
241 247
242 void thermal_cooling_device_unregister 248 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
243 249
244 This interface function removes the therma 250 This interface function removes the thermal cooling device.
245 It deletes the corresponding entry from /s 251 It deletes the corresponding entry from /sys/class/thermal folder and
246 unbinds itself from all the thermal zone d 252 unbinds itself from all the thermal zone devices using it.
247 253
>> 254 1.3 interface for binding a thermal zone device with a thermal cooling device
>> 255 -----------------------------------------------------------------------------
>> 256
>> 257 ::
>> 258
>> 259 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
>> 260 int trip, struct thermal_cooling_device *cdev,
>> 261 unsigned long upper, unsigned long lower, unsigned int weight);
>> 262
>> 263 This interface function binds a thermal cooling device to a particular trip
>> 264 point of a thermal zone device.
>> 265
>> 266 This function is usually called in the thermal zone device .bind callback.
>> 267
>> 268 tz:
>> 269 the thermal zone device
>> 270 cdev:
>> 271 thermal cooling device
>> 272 trip:
>> 273 indicates which trip point in this thermal zone the cooling device
>> 274 is associated with.
>> 275 upper:
>> 276 the Maximum cooling state for this trip point.
>> 277 THERMAL_NO_LIMIT means no upper limit,
>> 278 and the cooling device can be in max_state.
>> 279 lower:
>> 280 the Minimum cooling state can be used for this trip point.
>> 281 THERMAL_NO_LIMIT means no lower limit,
>> 282 and the cooling device can be in cooling state 0.
>> 283 weight:
>> 284 the influence of this cooling device in this thermal
>> 285 zone. See 1.4.1 below for more information.
>> 286
>> 287 ::
>> 288
>> 289 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
>> 290 int trip, struct thermal_cooling_device *cdev);
>> 291
>> 292 This interface function unbinds a thermal cooling device from a particular
>> 293 trip point of a thermal zone device. This function is usually called in
>> 294 the thermal zone device .unbind callback.
>> 295
>> 296 tz:
>> 297 the thermal zone device
>> 298 cdev:
>> 299 thermal cooling device
>> 300 trip:
>> 301 indicates which trip point in this thermal zone the cooling device
>> 302 is associated with.
>> 303
248 1.4 Thermal Zone Parameters 304 1.4 Thermal Zone Parameters
249 --------------------------- 305 ---------------------------
250 306
251 :: 307 ::
252 308
>> 309 struct thermal_bind_params
>> 310
>> 311 This structure defines the following parameters that are used to bind
>> 312 a zone with a cooling device for a particular trip point.
>> 313
>> 314 .cdev:
>> 315 The cooling device pointer
>> 316 .weight:
>> 317 The 'influence' of a particular cooling device on this
>> 318 zone. This is relative to the rest of the cooling
>> 319 devices. For example, if all cooling devices have a
>> 320 weight of 1, then they all contribute the same. You can
>> 321 use percentages if you want, but it's not mandatory. A
>> 322 weight of 0 means that this cooling device doesn't
>> 323 contribute to the cooling of this zone unless all cooling
>> 324 devices have a weight of 0. If all weights are 0, then
>> 325 they all contribute the same.
>> 326 .trip_mask:
>> 327 This is a bit mask that gives the binding relation between
>> 328 this thermal zone and cdev, for a particular trip point.
>> 329 If nth bit is set, then the cdev and thermal zone are bound
>> 330 for trip point n.
>> 331 .binding_limits:
>> 332 This is an array of cooling state limits. Must have
>> 333 exactly 2 * thermal_zone.number_of_trip_points. It is an
>> 334 array consisting of tuples <lower-state upper-state> of
>> 335 state limits. Each trip will be associated with one state
>> 336 limit tuple when binding. A NULL pointer means
>> 337 <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> on all trips.
>> 338 These limits are used when binding a cdev to a trip point.
>> 339 .match:
>> 340 This call back returns success(0) if the 'tz and cdev' need to
>> 341 be bound, as per platform data.
>> 342
>> 343 ::
>> 344
253 struct thermal_zone_params 345 struct thermal_zone_params
254 346
255 This structure defines the platform level 347 This structure defines the platform level parameters for a thermal zone.
256 This data, for each thermal zone should co 348 This data, for each thermal zone should come from the platform layer.
257 This is an optional feature where some pla 349 This is an optional feature where some platforms can choose not to
258 provide this data. 350 provide this data.
259 351
260 .governor_name: 352 .governor_name:
261 Name of the thermal governor us 353 Name of the thermal governor used for this zone
262 .no_hwmon: 354 .no_hwmon:
263 a boolean to indicate if the th 355 a boolean to indicate if the thermal to hwmon sysfs interface
264 is required. when no_hwmon == f 356 is required. when no_hwmon == false, a hwmon sysfs interface
265 will be created. when no_hwmon 357 will be created. when no_hwmon == true, nothing will be done.
266 In case the thermal_zone_params 358 In case the thermal_zone_params is NULL, the hwmon interface
267 will be created (for backward c 359 will be created (for backward compatibility).
>> 360 .num_tbps:
>> 361 Number of thermal_bind_params entries for this zone
>> 362 .tbp:
>> 363 thermal_bind_params entries
268 364
269 2. sysfs attributes structure 365 2. sysfs attributes structure
270 ============================= 366 =============================
271 367
272 == ================ 368 == ================
273 RO read only value 369 RO read only value
274 WO write only value 370 WO write only value
275 RW read/write value 371 RW read/write value
276 == ================ 372 == ================
277 373
278 Thermal sysfs attributes will be represented u 374 Thermal sysfs attributes will be represented under /sys/class/thermal.
279 Hwmon sysfs I/F extension is also available un 375 Hwmon sysfs I/F extension is also available under /sys/class/hwmon
280 if hwmon is compiled in or built as a module. 376 if hwmon is compiled in or built as a module.
281 377
282 Thermal zone device sys I/F, created once it's 378 Thermal zone device sys I/F, created once it's registered::
283 379
284 /sys/class/thermal/thermal_zone[0-*]: 380 /sys/class/thermal/thermal_zone[0-*]:
285 |---type: Type of the th 381 |---type: Type of the thermal zone
286 |---temp: Current temper 382 |---temp: Current temperature
287 |---mode: Working mode o 383 |---mode: Working mode of the thermal zone
288 |---policy: Thermal govern 384 |---policy: Thermal governor used for this zone
289 |---available_policies: Available ther 385 |---available_policies: Available thermal governors for this zone
290 |---trip_point_[0-*]_temp: Trip point tem 386 |---trip_point_[0-*]_temp: Trip point temperature
291 |---trip_point_[0-*]_type: Trip point typ 387 |---trip_point_[0-*]_type: Trip point type
292 |---trip_point_[0-*]_hyst: Hysteresis val 388 |---trip_point_[0-*]_hyst: Hysteresis value for this trip point
293 |---emul_temp: Emulated tempe 389 |---emul_temp: Emulated temperature set node
294 |---sustainable_power: Sustainable di 390 |---sustainable_power: Sustainable dissipatable power
295 |---k_po: Proportional t 391 |---k_po: Proportional term during temperature overshoot
296 |---k_pu: Proportional t 392 |---k_pu: Proportional term during temperature undershoot
297 |---k_i: PID's integral 393 |---k_i: PID's integral term in the power allocator gov
298 |---k_d: PID's derivati 394 |---k_d: PID's derivative term in the power allocator
299 |---integral_cutoff: Offset above w 395 |---integral_cutoff: Offset above which errors are accumulated
300 |---slope: Slope constant 396 |---slope: Slope constant applied as linear extrapolation
301 |---offset: Offset constan 397 |---offset: Offset constant applied as linear extrapolation
302 398
303 Thermal cooling device sys I/F, created once i 399 Thermal cooling device sys I/F, created once it's registered::
304 400
305 /sys/class/thermal/cooling_device[0-*]: 401 /sys/class/thermal/cooling_device[0-*]:
306 |---type: Type of the co 402 |---type: Type of the cooling device(processor/fan/...)
307 |---max_state: Maximum coolin 403 |---max_state: Maximum cooling state of the cooling device
308 |---cur_state: Current coolin 404 |---cur_state: Current cooling state of the cooling device
309 |---stats: Directory cont 405 |---stats: Directory containing cooling device's statistics
310 |---stats/reset: Writing any va 406 |---stats/reset: Writing any value resets the statistics
311 |---stats/time_in_state_ms: Time (msec) sp 407 |---stats/time_in_state_ms: Time (msec) spent in various cooling states
312 |---stats/total_trans: Total number o 408 |---stats/total_trans: Total number of times cooling state is changed
313 |---stats/trans_table: Cooling state 409 |---stats/trans_table: Cooling state transition table
314 410
315 411
316 Then next two dynamic attributes are created/r 412 Then next two dynamic attributes are created/removed in pairs. They represent
317 the relationship between a thermal zone and it 413 the relationship between a thermal zone and its associated cooling device.
>> 414 They are created/removed for each successful execution of
>> 415 thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device.
318 416
319 :: 417 ::
320 418
321 /sys/class/thermal/thermal_zone[0-*]: 419 /sys/class/thermal/thermal_zone[0-*]:
322 |---cdev[0-*]: [0-*]th coolin 420 |---cdev[0-*]: [0-*]th cooling device in current thermal zone
323 |---cdev[0-*]_trip_point: Trip point tha 421 |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with
324 |---cdev[0-*]_weight: Influence of t 422 |---cdev[0-*]_weight: Influence of the cooling device in
325 this thermal z 423 this thermal zone
326 424
327 Besides the thermal zone device sysfs I/F and 425 Besides the thermal zone device sysfs I/F and cooling device sysfs I/F,
328 the generic thermal driver also creates a hwmo 426 the generic thermal driver also creates a hwmon sysfs I/F for each _type_
329 of thermal zone device. E.g. the generic therm 427 of thermal zone device. E.g. the generic thermal driver registers one hwmon
330 class device and build the associated hwmon sy 428 class device and build the associated hwmon sysfs I/F for all the registered
331 ACPI thermal zones. 429 ACPI thermal zones.
332 430
333 Please read Documentation/ABI/testing/sysfs-cl 431 Please read Documentation/ABI/testing/sysfs-class-thermal for thermal
334 zone and cooling device attribute details. 432 zone and cooling device attribute details.
335 433
336 :: 434 ::
337 435
338 /sys/class/hwmon/hwmon[0-*]: 436 /sys/class/hwmon/hwmon[0-*]:
339 |---name: The type of th 437 |---name: The type of the thermal zone devices
340 |---temp[1-*]_input: The current te 438 |---temp[1-*]_input: The current temperature of thermal zone [1-*]
341 |---temp[1-*]_critical: The critical t 439 |---temp[1-*]_critical: The critical trip point of thermal zone [1-*]
342 440
343 Please read Documentation/hwmon/sysfs-interfac 441 Please read Documentation/hwmon/sysfs-interface.rst for additional information.
344 442
345 3. A simple implementation 443 3. A simple implementation
346 ========================== 444 ==========================
347 445
348 ACPI thermal zone may support multiple trip po 446 ACPI thermal zone may support multiple trip points like critical, hot,
349 passive, active. If an ACPI thermal zone suppo 447 passive, active. If an ACPI thermal zone supports critical, passive,
350 active[0] and active[1] at the same time, it m 448 active[0] and active[1] at the same time, it may register itself as a
351 thermal_zone_device (thermal_zone1) with 4 tri 449 thermal_zone_device (thermal_zone1) with 4 trip points in all.
352 It has one processor and one fan, which are bo 450 It has one processor and one fan, which are both registered as
353 thermal_cooling_device. Both are considered to 451 thermal_cooling_device. Both are considered to have the same
354 effectiveness in cooling the thermal zone. 452 effectiveness in cooling the thermal zone.
355 453
356 If the processor is listed in _PSL method, and 454 If the processor is listed in _PSL method, and the fan is listed in _AL0
357 method, the sys I/F structure will be built li 455 method, the sys I/F structure will be built like this::
358 456
359 /sys/class/thermal: 457 /sys/class/thermal:
360 |thermal_zone1: 458 |thermal_zone1:
361 |---type: acpitz 459 |---type: acpitz
362 |---temp: 37000 460 |---temp: 37000
363 |---mode: enabled 461 |---mode: enabled
364 |---policy: step_wise 462 |---policy: step_wise
365 |---available_policies: step_wise fair 463 |---available_policies: step_wise fair_share
366 |---trip_point_0_temp: 100000 464 |---trip_point_0_temp: 100000
367 |---trip_point_0_type: critical 465 |---trip_point_0_type: critical
368 |---trip_point_1_temp: 80000 466 |---trip_point_1_temp: 80000
369 |---trip_point_1_type: passive 467 |---trip_point_1_type: passive
370 |---trip_point_2_temp: 70000 468 |---trip_point_2_temp: 70000
371 |---trip_point_2_type: active0 469 |---trip_point_2_type: active0
372 |---trip_point_3_temp: 60000 470 |---trip_point_3_temp: 60000
373 |---trip_point_3_type: active1 471 |---trip_point_3_type: active1
374 |---cdev0: --->/sys/class 472 |---cdev0: --->/sys/class/thermal/cooling_device0
375 |---cdev0_trip_point: 1 /* cde 473 |---cdev0_trip_point: 1 /* cdev0 can be used for passive */
376 |---cdev0_weight: 1024 474 |---cdev0_weight: 1024
377 |---cdev1: --->/sys/class 475 |---cdev1: --->/sys/class/thermal/cooling_device3
378 |---cdev1_trip_point: 2 /* cde 476 |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
379 |---cdev1_weight: 1024 477 |---cdev1_weight: 1024
380 478
381 |cooling_device0: 479 |cooling_device0:
382 |---type: Processor 480 |---type: Processor
383 |---max_state: 8 481 |---max_state: 8
384 |---cur_state: 0 482 |---cur_state: 0
385 483
386 |cooling_device3: 484 |cooling_device3:
387 |---type: Fan 485 |---type: Fan
388 |---max_state: 2 486 |---max_state: 2
389 |---cur_state: 0 487 |---cur_state: 0
390 488
391 /sys/class/hwmon: 489 /sys/class/hwmon:
392 |hwmon0: 490 |hwmon0:
393 |---name: acpitz 491 |---name: acpitz
394 |---temp1_input: 37000 492 |---temp1_input: 37000
395 |---temp1_crit: 100000 493 |---temp1_crit: 100000
396 494
397 4. Export Symbol APIs 495 4. Export Symbol APIs
398 ===================== 496 =====================
399 497
400 4.1. get_tz_trend 498 4.1. get_tz_trend
401 ----------------- 499 -----------------
402 500
403 This function returns the trend of a thermal z 501 This function returns the trend of a thermal zone, i.e the rate of change
404 of temperature of the thermal zone. Ideally, t 502 of temperature of the thermal zone. Ideally, the thermal sensor drivers
405 are supposed to implement the callback. If the 503 are supposed to implement the callback. If they don't, the thermal
406 framework calculated the trend by comparing th 504 framework calculated the trend by comparing the previous and the current
407 temperature values. 505 temperature values.
408 506
409 4.2. thermal_cdev_update !! 507 4.2. get_thermal_instance
>> 508 -------------------------
>> 509
>> 510 This function returns the thermal_instance corresponding to a given
>> 511 {thermal_zone, cooling_device, trip_point} combination. Returns NULL
>> 512 if such an instance does not exist.
>> 513
>> 514 4.3. thermal_cdev_update
410 ------------------------ 515 ------------------------
411 516
412 This function serves as an arbitrator to set t 517 This function serves as an arbitrator to set the state of a cooling
413 device. It sets the cooling device to the deep 518 device. It sets the cooling device to the deepest cooling state if
414 possible. 519 possible.
415 520
416 5. thermal_emergency_poweroff 521 5. thermal_emergency_poweroff
417 ============================= 522 =============================
418 523
419 On an event of critical trip temperature cross 524 On an event of critical trip temperature crossing the thermal framework
420 shuts down the system by calling hw_protection 525 shuts down the system by calling hw_protection_shutdown(). The
421 hw_protection_shutdown() first attempts to per 526 hw_protection_shutdown() first attempts to perform an orderly shutdown
422 but accepts a delay after which it proceeds do 527 but accepts a delay after which it proceeds doing a forced power-off
423 or as last resort an emergency_restart. 528 or as last resort an emergency_restart.
424 529
425 The delay should be carefully profiled so as t 530 The delay should be carefully profiled so as to give adequate time for
426 orderly poweroff. 531 orderly poweroff.
427 532
428 If the delay is set to 0 emergency poweroff wi 533 If the delay is set to 0 emergency poweroff will not be supported. So a
429 carefully profiled non-zero positive value is 534 carefully profiled non-zero positive value is a must for emergency
430 poweroff to be triggered. 535 poweroff to be triggered.
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