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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 | ||
38bb0849 FP |
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 | |
38bb0849 FP |
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 | |
38bb0849 FP |
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. | |
203d3d4a ZR |
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 | |
514e6d20 | 34 | 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *type, |
c56f5c03 | 35 | int trips, int mask, void *devdata, |
514e6d20 ZR |
36 | struct thermal_zone_device_ops *ops, |
37 | const struct thermal_zone_params *tzp, | |
38 | int passive_delay, int polling_delay)) | |
38bb0849 FP |
39 | |
40 | This interface function adds a new thermal zone device (sensor) to | |
41 | /sys/class/thermal folder as thermal_zone[0-*]. It tries to bind all the | |
42 | thermal cooling devices registered at the same time. | |
43 | ||
514e6d20 | 44 | type: the thermal zone type. |
38bb0849 | 45 | trips: the total number of trip points this thermal zone supports. |
c56f5c03 | 46 | mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable. |
38bb0849 FP |
47 | devdata: device private data |
48 | ops: thermal zone device call-backs. | |
49 | .bind: bind the thermal zone device with a thermal cooling device. | |
50 | .unbind: unbind the thermal zone device with a thermal cooling device. | |
51 | .get_temp: get the current temperature of the thermal zone. | |
060c034a SH |
52 | .set_trips: set the trip points window. Whenever the current temperature |
53 | is updated, the trip points immediately below and above the | |
54 | current temperature are found. | |
8eaa8d6c ZR |
55 | .get_mode: get the current mode (enabled/disabled) of the thermal zone. |
56 | - "enabled" means the kernel thermal management is enabled. | |
57 | - "disabled" will prevent kernel thermal driver action upon trip points | |
38bb0849 | 58 | so that user applications can take charge of thermal management. |
8eaa8d6c | 59 | .set_mode: set the mode (enabled/disabled) of the thermal zone. |
38bb0849 FP |
60 | .get_trip_type: get the type of certain trip point. |
61 | .get_trip_temp: get the temperature above which the certain trip point | |
62 | will be fired. | |
e6e238c3 ADK |
63 | .set_emul_temp: set the emulation temperature which helps in debugging |
64 | different threshold temperature points. | |
514e6d20 ZR |
65 | tzp: thermal zone platform parameters. |
66 | passive_delay: number of milliseconds to wait between polls when | |
67 | performing passive cooling. | |
68 | polling_delay: number of milliseconds to wait between polls when checking | |
69 | whether trip points have been crossed (0 for interrupt driven systems). | |
70 | ||
203d3d4a ZR |
71 | |
72 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | |
73 | ||
38bb0849 | 74 | This interface function removes the thermal zone device. |
c212ed91 AC |
75 | It deletes the corresponding entry from /sys/class/thermal folder and |
76 | unbinds all the thermal cooling devices it uses. | |
203d3d4a | 77 | |
3a7fd9c7 LD |
78 | 1.1.3 struct thermal_zone_device *thermal_zone_of_sensor_register( |
79 | struct device *dev, int sensor_id, void *data, | |
80 | const struct thermal_zone_of_device_ops *ops) | |
81 | ||
82 | This interface adds a new sensor to a DT thermal zone. | |
83 | This function will search the list of thermal zones described in | |
84 | device tree and look for the zone that refer to the sensor device | |
85 | pointed by dev->of_node as temperature providers. For the zone | |
86 | pointing to the sensor node, the sensor will be added to the DT | |
87 | thermal zone device. | |
88 | ||
89 | The parameters for this interface are: | |
90 | dev: Device node of sensor containing valid node pointer in | |
91 | dev->of_node. | |
92 | sensor_id: a sensor identifier, in case the sensor IP has more | |
93 | than one sensors | |
94 | data: a private pointer (owned by the caller) that will be | |
95 | passed back, when a temperature reading is needed. | |
96 | ops: struct thermal_zone_of_device_ops *. | |
97 | ||
98 | get_temp: a pointer to a function that reads the | |
99 | sensor temperature. This is mandatory | |
100 | callback provided by sensor driver. | |
060c034a SH |
101 | set_trips: a pointer to a function that sets a |
102 | temperature window. When this window is | |
103 | left the driver must inform the thermal | |
104 | core via thermal_zone_device_update. | |
3a7fd9c7 LD |
105 | get_trend: a pointer to a function that reads the |
106 | sensor temperature trend. | |
107 | set_emul_temp: a pointer to a function that sets | |
108 | sensor emulated temperature. | |
109 | The thermal zone temperature is provided by the get_temp() function | |
110 | pointer of thermal_zone_of_device_ops. When called, it will | |
111 | have the private pointer @data back. | |
112 | ||
113 | It returns error pointer if fails otherwise valid thermal zone device | |
114 | handle. Caller should check the return handle with IS_ERR() for finding | |
115 | whether success or not. | |
116 | ||
117 | 1.1.4 void thermal_zone_of_sensor_unregister(struct device *dev, | |
118 | struct thermal_zone_device *tzd) | |
119 | ||
120 | This interface unregisters a sensor from a DT thermal zone which was | |
121 | successfully added by interface thermal_zone_of_sensor_register(). | |
122 | This function removes the sensor callbacks and private data from the | |
123 | thermal zone device registered with thermal_zone_of_sensor_register() | |
124 | interface. It will also silent the zone by remove the .get_temp() and | |
125 | get_trend() thermal zone device callbacks. | |
126 | ||
61f846f3 LD |
127 | 1.1.5 struct thermal_zone_device *devm_thermal_zone_of_sensor_register( |
128 | struct device *dev, int sensor_id, | |
129 | void *data, const struct thermal_zone_of_device_ops *ops) | |
130 | ||
131 | This interface is resource managed version of | |
132 | thermal_zone_of_sensor_register(). | |
133 | All details of thermal_zone_of_sensor_register() described in | |
134 | section 1.1.3 is applicable here. | |
135 | The benefit of using this interface to register sensor is that it | |
136 | is not require to explicitly call thermal_zone_of_sensor_unregister() | |
137 | in error path or during driver unbinding as this is done by driver | |
138 | resource manager. | |
139 | ||
140 | 1.1.6 void devm_thermal_zone_of_sensor_unregister(struct device *dev, | |
141 | struct thermal_zone_device *tzd) | |
142 | ||
143 | This interface is resource managed version of | |
144 | thermal_zone_of_sensor_unregister(). | |
145 | All details of thermal_zone_of_sensor_unregister() described in | |
146 | section 1.1.4 is applicable here. | |
147 | Normally this function will not need to be called and the resource | |
148 | management code will ensure that the resource is freed. | |
149 | ||
4a7069a3 RN |
150 | 1.1.7 int thermal_zone_get_slope(struct thermal_zone_device *tz) |
151 | ||
152 | This interface is used to read the slope attribute value | |
153 | for the thermal zone device, which might be useful for platform | |
154 | drivers for temperature calculations. | |
155 | ||
156 | 1.1.8 int thermal_zone_get_offset(struct thermal_zone_device *tz) | |
157 | ||
158 | This interface is used to read the offset attribute value | |
159 | for the thermal zone device, which might be useful for platform | |
160 | drivers for temperature calculations. | |
161 | ||
203d3d4a ZR |
162 | 1.2 thermal cooling device interface |
163 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | |
38bb0849 FP |
164 | void *devdata, struct thermal_cooling_device_ops *) |
165 | ||
166 | This interface function adds a new thermal cooling device (fan/processor/...) | |
167 | to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself | |
c212ed91 | 168 | to all the thermal zone devices registered at the same time. |
38bb0849 FP |
169 | name: the cooling device name. |
170 | devdata: device private data. | |
171 | ops: thermal cooling devices call-backs. | |
172 | .get_max_state: get the Maximum throttle state of the cooling device. | |
c212ed91 | 173 | .get_cur_state: get the Currently requested throttle state of the cooling device. |
38bb0849 | 174 | .set_cur_state: set the Current throttle state of the cooling device. |
203d3d4a ZR |
175 | |
176 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | |
177 | ||
c212ed91 AC |
178 | This interface function removes the thermal cooling device. |
179 | It deletes the corresponding entry from /sys/class/thermal folder and | |
180 | unbinds itself from all the thermal zone devices using it. | |
203d3d4a ZR |
181 | |
182 | 1.3 interface for binding a thermal zone device with a thermal cooling device | |
183 | 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, | |
9d99842f | 184 | int trip, struct thermal_cooling_device *cdev, |
6cd9e9f6 | 185 | unsigned long upper, unsigned long lower, unsigned int weight); |
203d3d4a | 186 | |
c212ed91 | 187 | This interface function binds a thermal cooling device to a particular trip |
38bb0849 FP |
188 | point of a thermal zone device. |
189 | This function is usually called in the thermal zone device .bind callback. | |
190 | tz: the thermal zone device | |
191 | cdev: thermal cooling device | |
c212ed91 AC |
192 | trip: indicates which trip point in this thermal zone the cooling device |
193 | is associated with. | |
9d99842f ZR |
194 | upper:the Maximum cooling state for this trip point. |
195 | THERMAL_NO_LIMIT means no upper limit, | |
196 | and the cooling device can be in max_state. | |
197 | lower:the Minimum cooling state can be used for this trip point. | |
198 | THERMAL_NO_LIMIT means no lower limit, | |
199 | and the cooling device can be in cooling state 0. | |
6cd9e9f6 KS |
200 | weight: the influence of this cooling device in this thermal |
201 | zone. See 1.4.1 below for more information. | |
203d3d4a ZR |
202 | |
203 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | |
38bb0849 | 204 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 205 | |
c212ed91 | 206 | This interface function unbinds a thermal cooling device from a particular |
38bb0849 FP |
207 | trip point of a thermal zone device. This function is usually called in |
208 | the thermal zone device .unbind callback. | |
209 | tz: the thermal zone device | |
210 | cdev: thermal cooling device | |
c212ed91 AC |
211 | trip: indicates which trip point in this thermal zone the cooling device |
212 | is associated with. | |
203d3d4a | 213 | |
6ea083b1 D |
214 | 1.4 Thermal Zone Parameters |
215 | 1.4.1 struct thermal_bind_params | |
216 | This structure defines the following parameters that are used to bind | |
217 | a zone with a cooling device for a particular trip point. | |
218 | .cdev: The cooling device pointer | |
bcdcbbc7 JM |
219 | .weight: The 'influence' of a particular cooling device on this |
220 | zone. This is relative to the rest of the cooling | |
221 | devices. For example, if all cooling devices have a | |
222 | weight of 1, then they all contribute the same. You can | |
223 | use percentages if you want, but it's not mandatory. A | |
224 | weight of 0 means that this cooling device doesn't | |
225 | contribute to the cooling of this zone unless all cooling | |
226 | devices have a weight of 0. If all weights are 0, then | |
227 | they all contribute the same. | |
6ea083b1 D |
228 | .trip_mask:This is a bit mask that gives the binding relation between |
229 | this thermal zone and cdev, for a particular trip point. | |
230 | If nth bit is set, then the cdev and thermal zone are bound | |
231 | for trip point n. | |
c212ed91 AC |
232 | .binding_limits: This is an array of cooling state limits. Must have |
233 | exactly 2 * thermal_zone.number_of_trip_points. It is an | |
234 | array consisting of tuples <lower-state upper-state> of | |
235 | state limits. Each trip will be associated with one state | |
236 | limit tuple when binding. A NULL pointer means | |
237 | <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> on all trips. | |
238 | These limits are used when binding a cdev to a trip point. | |
6ea083b1 D |
239 | .match: This call back returns success(0) if the 'tz and cdev' need to |
240 | be bound, as per platform data. | |
241 | 1.4.2 struct thermal_zone_params | |
242 | This structure defines the platform level parameters for a thermal zone. | |
243 | This data, for each thermal zone should come from the platform layer. | |
244 | This is an optional feature where some platforms can choose not to | |
245 | provide this data. | |
246 | .governor_name: Name of the thermal governor used for this zone | |
ccba4ffd EV |
247 | .no_hwmon: a boolean to indicate if the thermal to hwmon sysfs interface |
248 | is required. when no_hwmon == false, a hwmon sysfs interface | |
249 | will be created. when no_hwmon == true, nothing will be done. | |
250 | In case the thermal_zone_params is NULL, the hwmon interface | |
251 | will be created (for backward compatibility). | |
6ea083b1 D |
252 | .num_tbps: Number of thermal_bind_params entries for this zone |
253 | .tbp: thermal_bind_params entries | |
254 | ||
203d3d4a ZR |
255 | 2. sysfs attributes structure |
256 | ||
257 | RO read only value | |
8ea22951 | 258 | WO write only value |
203d3d4a ZR |
259 | RW read/write value |
260 | ||
e9ae7107 ZR |
261 | Thermal sysfs attributes will be represented under /sys/class/thermal. |
262 | Hwmon sysfs I/F extension is also available under /sys/class/hwmon | |
263 | if hwmon is compiled in or built as a module. | |
203d3d4a ZR |
264 | |
265 | Thermal zone device sys I/F, created once it's registered: | |
e9ae7107 | 266 | /sys/class/thermal/thermal_zone[0-*]: |
38bb0849 FP |
267 | |---type: Type of the thermal zone |
268 | |---temp: Current temperature | |
269 | |---mode: Working mode of the thermal zone | |
6ea083b1 | 270 | |---policy: Thermal governor used for this zone |
25a0a5ce | 271 | |---available_policies: Available thermal governors for this zone |
38bb0849 FP |
272 | |---trip_point_[0-*]_temp: Trip point temperature |
273 | |---trip_point_[0-*]_type: Trip point type | |
27365a6c | 274 | |---trip_point_[0-*]_hyst: Hysteresis value for this trip point |
e6e238c3 | 275 | |---emul_temp: Emulated temperature set node |
9f38271c JM |
276 | |---sustainable_power: Sustainable dissipatable power |
277 | |---k_po: Proportional term during temperature overshoot | |
278 | |---k_pu: Proportional term during temperature undershoot | |
279 | |---k_i: PID's integral term in the power allocator gov | |
280 | |---k_d: PID's derivative term in the power allocator | |
281 | |---integral_cutoff: Offset above which errors are accumulated | |
9d0be7f4 EV |
282 | |---slope: Slope constant applied as linear extrapolation |
283 | |---offset: Offset constant applied as linear extrapolation | |
203d3d4a ZR |
284 | |
285 | Thermal cooling device sys I/F, created once it's registered: | |
e9ae7107 | 286 | /sys/class/thermal/cooling_device[0-*]: |
38bb0849 FP |
287 | |---type: Type of the cooling device(processor/fan/...) |
288 | |---max_state: Maximum cooling state of the cooling device | |
289 | |---cur_state: Current cooling state of the cooling device | |
8ea22951 VK |
290 | |---stats: Directory containing cooling device's statistics |
291 | |---stats/reset: Writing any value resets the statistics | |
292 | |---stats/time_in_state_ms: Time (msec) spent in various cooling states | |
293 | |---stats/total_trans: Total number of times cooling state is changed | |
294 | |---stats/trans_table: Cooing state transition table | |
203d3d4a ZR |
295 | |
296 | ||
38bb0849 FP |
297 | Then next two dynamic attributes are created/removed in pairs. They represent |
298 | the relationship between a thermal zone and its associated cooling device. | |
299 | They are created/removed for each successful execution of | |
300 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. | |
203d3d4a | 301 | |
38bb0849 FP |
302 | /sys/class/thermal/thermal_zone[0-*]: |
303 | |---cdev[0-*]: [0-*]th cooling device in current thermal zone | |
304 | |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
db916513 JM |
305 | |---cdev[0-*]_weight: Influence of the cooling device in |
306 | this thermal zone | |
203d3d4a | 307 | |
e9ae7107 | 308 | Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
38bb0849 FP |
309 | the generic thermal driver also creates a hwmon sysfs I/F for each _type_ |
310 | of thermal zone device. E.g. the generic thermal driver registers one hwmon | |
311 | class device and build the associated hwmon sysfs I/F for all the registered | |
312 | ACPI thermal zones. | |
313 | ||
e9ae7107 | 314 | /sys/class/hwmon/hwmon[0-*]: |
38bb0849 FP |
315 | |---name: The type of the thermal zone devices |
316 | |---temp[1-*]_input: The current temperature of thermal zone [1-*] | |
317 | |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] | |
318 | ||
e9ae7107 | 319 | Please read Documentation/hwmon/sysfs-interface for additional information. |
203d3d4a ZR |
320 | |
321 | *************************** | |
322 | * Thermal zone attributes * | |
323 | *************************** | |
324 | ||
38bb0849 FP |
325 | type |
326 | Strings which represent the thermal zone type. | |
327 | This is given by thermal zone driver as part of registration. | |
328 | E.g: "acpitz" indicates it's an ACPI thermal device. | |
329 | In order to keep it consistent with hwmon sys attribute; this should | |
330 | be a short, lowercase string, not containing spaces nor dashes. | |
331 | RO, Required | |
332 | ||
333 | temp | |
334 | Current temperature as reported by thermal zone (sensor). | |
335 | Unit: millidegree Celsius | |
336 | RO, Required | |
337 | ||
338 | mode | |
8eaa8d6c | 339 | One of the predefined values in [enabled, disabled]. |
38bb0849 FP |
340 | This file gives information about the algorithm that is currently |
341 | managing the thermal zone. It can be either default kernel based | |
342 | algorithm or user space application. | |
8eaa8d6c ZR |
343 | enabled = enable Kernel Thermal management. |
344 | disabled = Preventing kernel thermal zone driver actions upon | |
345 | trip points so that user application can take full | |
346 | charge of the thermal management. | |
38bb0849 FP |
347 | RW, Optional |
348 | ||
6ea083b1 D |
349 | policy |
350 | One of the various thermal governors used for a particular zone. | |
351 | RW, Required | |
352 | ||
25a0a5ce NW |
353 | available_policies |
354 | Available thermal governors which can be used for a particular zone. | |
355 | RO, Required | |
356 | ||
38bb0849 FP |
357 | trip_point_[0-*]_temp |
358 | The temperature above which trip point will be fired. | |
359 | Unit: millidegree Celsius | |
360 | RO, Optional | |
361 | ||
362 | trip_point_[0-*]_type | |
363 | Strings which indicate the type of the trip point. | |
364 | E.g. it can be one of critical, hot, passive, active[0-*] for ACPI | |
365 | thermal zone. | |
366 | RO, Optional | |
367 | ||
27365a6c D |
368 | trip_point_[0-*]_hyst |
369 | The hysteresis value for a trip point, represented as an integer | |
370 | Unit: Celsius | |
371 | RW, Optional | |
372 | ||
38bb0849 FP |
373 | cdev[0-*] |
374 | Sysfs link to the thermal cooling device node where the sys I/F | |
375 | for cooling device throttling control represents. | |
376 | RO, Optional | |
377 | ||
378 | cdev[0-*]_trip_point | |
c212ed91 AC |
379 | The trip point in this thermal zone which cdev[0-*] is associated |
380 | with; -1 means the cooling device is not associated with any trip | |
38bb0849 FP |
381 | point. |
382 | RO, Optional | |
29226ed3 | 383 | |
db916513 JM |
384 | cdev[0-*]_weight |
385 | The influence of cdev[0-*] in this thermal zone. This value | |
386 | is relative to the rest of cooling devices in the thermal | |
387 | zone. For example, if a cooling device has a weight double | |
388 | than that of other, it's twice as effective in cooling the | |
389 | thermal zone. | |
390 | RW, Optional | |
391 | ||
29226ed3 FP |
392 | passive |
393 | Attribute is only present for zones in which the passive cooling | |
394 | policy is not supported by native thermal driver. Default is zero | |
395 | and can be set to a temperature (in millidegrees) to enable a | |
396 | passive trip point for the zone. Activation is done by polling with | |
397 | an interval of 1 second. | |
398 | Unit: millidegrees Celsius | |
3d8e3ad8 | 399 | Valid values: 0 (disabled) or greater than 1000 |
29226ed3 | 400 | RW, Optional |
38bb0849 | 401 | |
e6e238c3 ADK |
402 | emul_temp |
403 | Interface to set the emulated temperature method in thermal zone | |
404 | (sensor). After setting this temperature, the thermal zone may pass | |
405 | this temperature to platform emulation function if registered or | |
406 | cache it locally. This is useful in debugging different temperature | |
407 | threshold and its associated cooling action. This is write only node | |
408 | and writing 0 on this node should disable emulation. | |
409 | Unit: millidegree Celsius | |
410 | WO, Optional | |
411 | ||
8837295a EV |
412 | WARNING: Be careful while enabling this option on production systems, |
413 | because userland can easily disable the thermal policy by simply | |
414 | flooding this sysfs node with low temperature values. | |
415 | ||
9f38271c JM |
416 | sustainable_power |
417 | An estimate of the sustained power that can be dissipated by | |
418 | the thermal zone. Used by the power allocator governor. For | |
419 | more information see Documentation/thermal/power_allocator.txt | |
420 | Unit: milliwatts | |
421 | RW, Optional | |
422 | ||
423 | k_po | |
424 | The proportional term of the power allocator governor's PID | |
425 | controller during temperature overshoot. Temperature overshoot | |
426 | is when the current temperature is above the "desired | |
427 | temperature" trip point. For more information see | |
428 | Documentation/thermal/power_allocator.txt | |
429 | RW, Optional | |
430 | ||
431 | k_pu | |
432 | The proportional term of the power allocator governor's PID | |
433 | controller during temperature undershoot. Temperature undershoot | |
434 | is when the current temperature is below the "desired | |
435 | temperature" trip point. For more information see | |
436 | Documentation/thermal/power_allocator.txt | |
437 | RW, Optional | |
438 | ||
439 | k_i | |
440 | The integral term of the power allocator governor's PID | |
441 | controller. This term allows the PID controller to compensate | |
442 | for long term drift. For more information see | |
443 | Documentation/thermal/power_allocator.txt | |
444 | RW, Optional | |
445 | ||
446 | k_d | |
447 | The derivative term of the power allocator governor's PID | |
448 | controller. For more information see | |
449 | Documentation/thermal/power_allocator.txt | |
450 | RW, Optional | |
451 | ||
452 | integral_cutoff | |
453 | Temperature offset from the desired temperature trip point | |
454 | above which the integral term of the power allocator | |
455 | governor's PID controller starts accumulating errors. For | |
456 | example, if integral_cutoff is 0, then the integral term only | |
457 | accumulates error when temperature is above the desired | |
458 | temperature trip point. For more information see | |
459 | Documentation/thermal/power_allocator.txt | |
ec3fc58b | 460 | Unit: millidegree Celsius |
9f38271c JM |
461 | RW, Optional |
462 | ||
9d0be7f4 EV |
463 | slope |
464 | The slope constant used in a linear extrapolation model | |
465 | to determine a hotspot temperature based off the sensor's | |
466 | raw readings. It is up to the device driver to determine | |
467 | the usage of these values. | |
468 | RW, Optional | |
469 | ||
470 | offset | |
471 | The offset constant used in a linear extrapolation model | |
472 | to determine a hotspot temperature based off the sensor's | |
473 | raw readings. It is up to the device driver to determine | |
474 | the usage of these values. | |
475 | RW, Optional | |
476 | ||
38bb0849 FP |
477 | ***************************** |
478 | * Cooling device attributes * | |
479 | ***************************** | |
480 | ||
481 | type | |
482 | String which represents the type of device, e.g: | |
483 | - for generic ACPI: should be "Fan", "Processor" or "LCD" | |
484 | - for memory controller device on intel_menlow platform: | |
485 | should be "Memory controller". | |
486 | RO, Required | |
487 | ||
488 | max_state | |
489 | The maximum permissible cooling state of this cooling device. | |
490 | RO, Required | |
491 | ||
492 | cur_state | |
493 | The current cooling state of this cooling device. | |
494 | The value can any integer numbers between 0 and max_state: | |
495 | - cur_state == 0 means no cooling | |
496 | - cur_state == max_state means the maximum cooling. | |
497 | RW, Required | |
203d3d4a | 498 | |
8ea22951 VK |
499 | stats/reset |
500 | Writing any value resets the cooling device's statistics. | |
501 | WO, Required | |
502 | ||
503 | stats/time_in_state_ms: | |
504 | The amount of time spent by the cooling device in various cooling | |
505 | states. The output will have "<state> <time>" pair in each line, which | |
506 | will mean this cooling device spent <time> msec of time at <state>. | |
507 | Output will have one line for each of the supported states. usertime | |
508 | units here is 10mS (similar to other time exported in /proc). | |
509 | RO, Required | |
510 | ||
511 | stats/total_trans: | |
512 | A single positive value showing the total number of times the state of a | |
513 | cooling device is changed. | |
514 | RO, Required | |
515 | ||
516 | stats/trans_table: | |
517 | This gives fine grained information about all the cooling state | |
518 | transitions. The cat output here is a two dimensional matrix, where an | |
519 | entry <i,j> (row i, column j) represents the number of transitions from | |
520 | State_i to State_j. If the transition table is bigger than PAGE_SIZE, | |
521 | reading this will return an -EFBIG error. | |
522 | RO, Required | |
523 | ||
203d3d4a ZR |
524 | 3. A simple implementation |
525 | ||
38bb0849 FP |
526 | ACPI thermal zone may support multiple trip points like critical, hot, |
527 | passive, active. If an ACPI thermal zone supports critical, passive, | |
528 | active[0] and active[1] at the same time, it may register itself as a | |
529 | thermal_zone_device (thermal_zone1) with 4 trip points in all. | |
530 | It has one processor and one fan, which are both registered as | |
db916513 JM |
531 | thermal_cooling_device. Both are considered to have the same |
532 | effectiveness in cooling the thermal zone. | |
38bb0849 FP |
533 | |
534 | If the processor is listed in _PSL method, and the fan is listed in _AL0 | |
535 | method, the sys I/F structure will be built like this: | |
203d3d4a ZR |
536 | |
537 | /sys/class/thermal: | |
538 | ||
539 | |thermal_zone1: | |
38bb0849 FP |
540 | |---type: acpitz |
541 | |---temp: 37000 | |
8eaa8d6c | 542 | |---mode: enabled |
6ea083b1 | 543 | |---policy: step_wise |
25a0a5ce | 544 | |---available_policies: step_wise fair_share |
38bb0849 FP |
545 | |---trip_point_0_temp: 100000 |
546 | |---trip_point_0_type: critical | |
547 | |---trip_point_1_temp: 80000 | |
548 | |---trip_point_1_type: passive | |
549 | |---trip_point_2_temp: 70000 | |
550 | |---trip_point_2_type: active0 | |
551 | |---trip_point_3_temp: 60000 | |
552 | |---trip_point_3_type: active1 | |
553 | |---cdev0: --->/sys/class/thermal/cooling_device0 | |
554 | |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
db916513 | 555 | |---cdev0_weight: 1024 |
38bb0849 FP |
556 | |---cdev1: --->/sys/class/thermal/cooling_device3 |
557 | |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
db916513 | 558 | |---cdev1_weight: 1024 |
203d3d4a ZR |
559 | |
560 | |cooling_device0: | |
38bb0849 FP |
561 | |---type: Processor |
562 | |---max_state: 8 | |
563 | |---cur_state: 0 | |
203d3d4a ZR |
564 | |
565 | |cooling_device3: | |
38bb0849 FP |
566 | |---type: Fan |
567 | |---max_state: 2 | |
568 | |---cur_state: 0 | |
e9ae7107 ZR |
569 | |
570 | /sys/class/hwmon: | |
571 | ||
572 | |hwmon0: | |
38bb0849 FP |
573 | |---name: acpitz |
574 | |---temp1_input: 37000 | |
575 | |---temp1_crit: 100000 | |
4cb18728 D |
576 | |
577 | 4. Event Notification | |
578 | ||
579 | The framework includes a simple notification mechanism, in the form of a | |
580 | netlink event. Netlink socket initialization is done during the _init_ | |
581 | of the framework. Drivers which intend to use the notification mechanism | |
2d58d7ea | 582 | just need to call thermal_generate_netlink_event() with two arguments viz |
8ab3e6a0 EV |
583 | (originator, event). The originator is a pointer to struct thermal_zone_device |
584 | from where the event has been originated. An integer which represents the | |
585 | thermal zone device will be used in the message to identify the zone. The | |
4cb18728 D |
586 | event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, |
587 | THERMAL_DEV_FAULT}. Notification can be sent when the current temperature | |
588 | crosses any of the configured thresholds. | |
6ea083b1 D |
589 | |
590 | 5. Export Symbol APIs: | |
591 | ||
592 | 5.1: get_tz_trend: | |
593 | This function returns the trend of a thermal zone, i.e the rate of change | |
594 | of temperature of the thermal zone. Ideally, the thermal sensor drivers | |
595 | are supposed to implement the callback. If they don't, the thermal | |
596 | framework calculated the trend by comparing the previous and the current | |
597 | temperature values. | |
598 | ||
599 | 5.2:get_thermal_instance: | |
600 | This function returns the thermal_instance corresponding to a given | |
601 | {thermal_zone, cooling_device, trip_point} combination. Returns NULL | |
602 | if such an instance does not exist. | |
603 | ||
7b73c993 | 604 | 5.3:thermal_notify_framework: |
6ea083b1 D |
605 | This function handles the trip events from sensor drivers. It starts |
606 | throttling the cooling devices according to the policy configured. | |
607 | For CRITICAL and HOT trip points, this notifies the respective drivers, | |
608 | and does actual throttling for other trip points i.e ACTIVE and PASSIVE. | |
609 | The throttling policy is based on the configured platform data; if no | |
610 | platform data is provided, this uses the step_wise throttling policy. | |
611 | ||
612 | 5.4:thermal_cdev_update: | |
613 | This function serves as an arbitrator to set the state of a cooling | |
614 | device. It sets the cooling device to the deepest cooling state if | |
615 | possible. | |
ef1d87e0 K |
616 | |
617 | 6. thermal_emergency_poweroff: | |
618 | ||
619 | On an event of critical trip temperature crossing. Thermal framework | |
620 | allows the system to shutdown gracefully by calling orderly_poweroff(). | |
621 | In the event of a failure of orderly_poweroff() to shut down the system | |
622 | we are in danger of keeping the system alive at undesirably high | |
623 | temperatures. To mitigate this high risk scenario we program a work | |
624 | queue to fire after a pre-determined number of seconds to start | |
625 | an emergency shutdown of the device using the kernel_power_off() | |
626 | function. In case kernel_power_off() fails then finally | |
627 | emergency_restart() is called in the worst case. | |
628 | ||
629 | The delay should be carefully profiled so as to give adequate time for | |
630 | orderly_poweroff(). In case of failure of an orderly_poweroff() the | |
631 | emergency poweroff kicks in after the delay has elapsed and shuts down | |
632 | the system. | |
633 | ||
634 | If set to 0 emergency poweroff will not be supported. So a carefully | |
635 | profiled non-zero positive value is a must for emergerncy poweroff to be | |
636 | triggered. |