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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. | |
8eaa8d6c ZR |
52 | .get_mode: get the current mode (enabled/disabled) of the thermal zone. |
53 | - "enabled" means the kernel thermal management is enabled. | |
54 | - "disabled" will prevent kernel thermal driver action upon trip points | |
38bb0849 | 55 | so that user applications can take charge of thermal management. |
8eaa8d6c | 56 | .set_mode: set the mode (enabled/disabled) of the thermal zone. |
38bb0849 FP |
57 | .get_trip_type: get the type of certain trip point. |
58 | .get_trip_temp: get the temperature above which the certain trip point | |
59 | will be fired. | |
e6e238c3 ADK |
60 | .set_emul_temp: set the emulation temperature which helps in debugging |
61 | different threshold temperature points. | |
514e6d20 ZR |
62 | tzp: thermal zone platform parameters. |
63 | passive_delay: number of milliseconds to wait between polls when | |
64 | performing passive cooling. | |
65 | polling_delay: number of milliseconds to wait between polls when checking | |
66 | whether trip points have been crossed (0 for interrupt driven systems). | |
67 | ||
203d3d4a ZR |
68 | |
69 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | |
70 | ||
38bb0849 FP |
71 | This interface function removes the thermal zone device. |
72 | It deletes the corresponding entry form /sys/class/thermal folder and | |
73 | unbind all the thermal cooling devices it uses. | |
203d3d4a | 74 | |
3a7fd9c7 LD |
75 | 1.1.3 struct thermal_zone_device *thermal_zone_of_sensor_register( |
76 | struct device *dev, int sensor_id, void *data, | |
77 | const struct thermal_zone_of_device_ops *ops) | |
78 | ||
79 | This interface adds a new sensor to a DT thermal zone. | |
80 | This function will search the list of thermal zones described in | |
81 | device tree and look for the zone that refer to the sensor device | |
82 | pointed by dev->of_node as temperature providers. For the zone | |
83 | pointing to the sensor node, the sensor will be added to the DT | |
84 | thermal zone device. | |
85 | ||
86 | The parameters for this interface are: | |
87 | dev: Device node of sensor containing valid node pointer in | |
88 | dev->of_node. | |
89 | sensor_id: a sensor identifier, in case the sensor IP has more | |
90 | than one sensors | |
91 | data: a private pointer (owned by the caller) that will be | |
92 | passed back, when a temperature reading is needed. | |
93 | ops: struct thermal_zone_of_device_ops *. | |
94 | ||
95 | get_temp: a pointer to a function that reads the | |
96 | sensor temperature. This is mandatory | |
97 | callback provided by sensor driver. | |
98 | get_trend: a pointer to a function that reads the | |
99 | sensor temperature trend. | |
100 | set_emul_temp: a pointer to a function that sets | |
101 | sensor emulated temperature. | |
102 | The thermal zone temperature is provided by the get_temp() function | |
103 | pointer of thermal_zone_of_device_ops. When called, it will | |
104 | have the private pointer @data back. | |
105 | ||
106 | It returns error pointer if fails otherwise valid thermal zone device | |
107 | handle. Caller should check the return handle with IS_ERR() for finding | |
108 | whether success or not. | |
109 | ||
110 | 1.1.4 void thermal_zone_of_sensor_unregister(struct device *dev, | |
111 | struct thermal_zone_device *tzd) | |
112 | ||
113 | This interface unregisters a sensor from a DT thermal zone which was | |
114 | successfully added by interface thermal_zone_of_sensor_register(). | |
115 | This function removes the sensor callbacks and private data from the | |
116 | thermal zone device registered with thermal_zone_of_sensor_register() | |
117 | interface. It will also silent the zone by remove the .get_temp() and | |
118 | get_trend() thermal zone device callbacks. | |
119 | ||
61f846f3 LD |
120 | 1.1.5 struct thermal_zone_device *devm_thermal_zone_of_sensor_register( |
121 | struct device *dev, int sensor_id, | |
122 | void *data, const struct thermal_zone_of_device_ops *ops) | |
123 | ||
124 | This interface is resource managed version of | |
125 | thermal_zone_of_sensor_register(). | |
126 | All details of thermal_zone_of_sensor_register() described in | |
127 | section 1.1.3 is applicable here. | |
128 | The benefit of using this interface to register sensor is that it | |
129 | is not require to explicitly call thermal_zone_of_sensor_unregister() | |
130 | in error path or during driver unbinding as this is done by driver | |
131 | resource manager. | |
132 | ||
133 | 1.1.6 void devm_thermal_zone_of_sensor_unregister(struct device *dev, | |
134 | struct thermal_zone_device *tzd) | |
135 | ||
136 | This interface is resource managed version of | |
137 | thermal_zone_of_sensor_unregister(). | |
138 | All details of thermal_zone_of_sensor_unregister() described in | |
139 | section 1.1.4 is applicable here. | |
140 | Normally this function will not need to be called and the resource | |
141 | management code will ensure that the resource is freed. | |
142 | ||
203d3d4a ZR |
143 | 1.2 thermal cooling device interface |
144 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | |
38bb0849 FP |
145 | void *devdata, struct thermal_cooling_device_ops *) |
146 | ||
147 | This interface function adds a new thermal cooling device (fan/processor/...) | |
148 | to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself | |
149 | to all the thermal zone devices register at the same time. | |
150 | name: the cooling device name. | |
151 | devdata: device private data. | |
152 | ops: thermal cooling devices call-backs. | |
153 | .get_max_state: get the Maximum throttle state of the cooling device. | |
154 | .get_cur_state: get the Current throttle state of the cooling device. | |
155 | .set_cur_state: set the Current throttle state of the cooling device. | |
203d3d4a ZR |
156 | |
157 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | |
158 | ||
38bb0849 FP |
159 | This interface function remove the thermal cooling device. |
160 | It deletes the corresponding entry form /sys/class/thermal folder and | |
161 | unbind itself from all the thermal zone devices using it. | |
203d3d4a ZR |
162 | |
163 | 1.3 interface for binding a thermal zone device with a thermal cooling device | |
164 | 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, | |
9d99842f | 165 | int trip, struct thermal_cooling_device *cdev, |
6cd9e9f6 | 166 | unsigned long upper, unsigned long lower, unsigned int weight); |
203d3d4a | 167 | |
38bb0849 FP |
168 | This interface function bind a thermal cooling device to the certain trip |
169 | point of a thermal zone device. | |
170 | This function is usually called in the thermal zone device .bind callback. | |
171 | tz: the thermal zone device | |
172 | cdev: thermal cooling device | |
173 | trip: indicates which trip point the cooling devices is associated with | |
174 | in this thermal zone. | |
9d99842f ZR |
175 | upper:the Maximum cooling state for this trip point. |
176 | THERMAL_NO_LIMIT means no upper limit, | |
177 | and the cooling device can be in max_state. | |
178 | lower:the Minimum cooling state can be used for this trip point. | |
179 | THERMAL_NO_LIMIT means no lower limit, | |
180 | and the cooling device can be in cooling state 0. | |
6cd9e9f6 KS |
181 | weight: the influence of this cooling device in this thermal |
182 | zone. See 1.4.1 below for more information. | |
203d3d4a ZR |
183 | |
184 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | |
38bb0849 | 185 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 186 | |
38bb0849 FP |
187 | This interface function unbind a thermal cooling device from the certain |
188 | trip point of a thermal zone device. This function is usually called in | |
189 | the thermal zone device .unbind callback. | |
190 | tz: the thermal zone device | |
191 | cdev: thermal cooling device | |
192 | trip: indicates which trip point the cooling devices is associated with | |
193 | in this thermal zone. | |
203d3d4a | 194 | |
6ea083b1 D |
195 | 1.4 Thermal Zone Parameters |
196 | 1.4.1 struct thermal_bind_params | |
197 | This structure defines the following parameters that are used to bind | |
198 | a zone with a cooling device for a particular trip point. | |
199 | .cdev: The cooling device pointer | |
bcdcbbc7 JM |
200 | .weight: The 'influence' of a particular cooling device on this |
201 | zone. This is relative to the rest of the cooling | |
202 | devices. For example, if all cooling devices have a | |
203 | weight of 1, then they all contribute the same. You can | |
204 | use percentages if you want, but it's not mandatory. A | |
205 | weight of 0 means that this cooling device doesn't | |
206 | contribute to the cooling of this zone unless all cooling | |
207 | devices have a weight of 0. If all weights are 0, then | |
208 | they all contribute the same. | |
6ea083b1 D |
209 | .trip_mask:This is a bit mask that gives the binding relation between |
210 | this thermal zone and cdev, for a particular trip point. | |
211 | If nth bit is set, then the cdev and thermal zone are bound | |
212 | for trip point n. | |
a8892d83 EV |
213 | .limits: This is an array of cooling state limits. Must have exactly |
214 | 2 * thermal_zone.number_of_trip_points. It is an array consisting | |
215 | of tuples <lower-state upper-state> of state limits. Each trip | |
216 | will be associated with one state limit tuple when binding. | |
217 | A NULL pointer means <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> | |
218 | on all trips. These limits are used when binding a cdev to a | |
219 | trip point. | |
6ea083b1 D |
220 | .match: This call back returns success(0) if the 'tz and cdev' need to |
221 | be bound, as per platform data. | |
222 | 1.4.2 struct thermal_zone_params | |
223 | This structure defines the platform level parameters for a thermal zone. | |
224 | This data, for each thermal zone should come from the platform layer. | |
225 | This is an optional feature where some platforms can choose not to | |
226 | provide this data. | |
227 | .governor_name: Name of the thermal governor used for this zone | |
ccba4ffd EV |
228 | .no_hwmon: a boolean to indicate if the thermal to hwmon sysfs interface |
229 | is required. when no_hwmon == false, a hwmon sysfs interface | |
230 | will be created. when no_hwmon == true, nothing will be done. | |
231 | In case the thermal_zone_params is NULL, the hwmon interface | |
232 | will be created (for backward compatibility). | |
6ea083b1 D |
233 | .num_tbps: Number of thermal_bind_params entries for this zone |
234 | .tbp: thermal_bind_params entries | |
235 | ||
203d3d4a ZR |
236 | 2. sysfs attributes structure |
237 | ||
238 | RO read only value | |
239 | RW read/write value | |
240 | ||
e9ae7107 ZR |
241 | Thermal sysfs attributes will be represented under /sys/class/thermal. |
242 | Hwmon sysfs I/F extension is also available under /sys/class/hwmon | |
243 | if hwmon is compiled in or built as a module. | |
203d3d4a ZR |
244 | |
245 | Thermal zone device sys I/F, created once it's registered: | |
e9ae7107 | 246 | /sys/class/thermal/thermal_zone[0-*]: |
38bb0849 FP |
247 | |---type: Type of the thermal zone |
248 | |---temp: Current temperature | |
249 | |---mode: Working mode of the thermal zone | |
6ea083b1 | 250 | |---policy: Thermal governor used for this zone |
25a0a5ce | 251 | |---available_policies: Available thermal governors for this zone |
38bb0849 FP |
252 | |---trip_point_[0-*]_temp: Trip point temperature |
253 | |---trip_point_[0-*]_type: Trip point type | |
27365a6c | 254 | |---trip_point_[0-*]_hyst: Hysteresis value for this trip point |
e6e238c3 | 255 | |---emul_temp: Emulated temperature set node |
9f38271c JM |
256 | |---sustainable_power: Sustainable dissipatable power |
257 | |---k_po: Proportional term during temperature overshoot | |
258 | |---k_pu: Proportional term during temperature undershoot | |
259 | |---k_i: PID's integral term in the power allocator gov | |
260 | |---k_d: PID's derivative term in the power allocator | |
261 | |---integral_cutoff: Offset above which errors are accumulated | |
9d0be7f4 EV |
262 | |---slope: Slope constant applied as linear extrapolation |
263 | |---offset: Offset constant applied as linear extrapolation | |
203d3d4a ZR |
264 | |
265 | Thermal cooling device sys I/F, created once it's registered: | |
e9ae7107 | 266 | /sys/class/thermal/cooling_device[0-*]: |
38bb0849 FP |
267 | |---type: Type of the cooling device(processor/fan/...) |
268 | |---max_state: Maximum cooling state of the cooling device | |
269 | |---cur_state: Current cooling state of the cooling device | |
203d3d4a ZR |
270 | |
271 | ||
38bb0849 FP |
272 | Then next two dynamic attributes are created/removed in pairs. They represent |
273 | the relationship between a thermal zone and its associated cooling device. | |
274 | They are created/removed for each successful execution of | |
275 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. | |
203d3d4a | 276 | |
38bb0849 FP |
277 | /sys/class/thermal/thermal_zone[0-*]: |
278 | |---cdev[0-*]: [0-*]th cooling device in current thermal zone | |
279 | |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
db916513 JM |
280 | |---cdev[0-*]_weight: Influence of the cooling device in |
281 | this thermal zone | |
203d3d4a | 282 | |
e9ae7107 | 283 | Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
38bb0849 FP |
284 | the generic thermal driver also creates a hwmon sysfs I/F for each _type_ |
285 | of thermal zone device. E.g. the generic thermal driver registers one hwmon | |
286 | class device and build the associated hwmon sysfs I/F for all the registered | |
287 | ACPI thermal zones. | |
288 | ||
e9ae7107 | 289 | /sys/class/hwmon/hwmon[0-*]: |
38bb0849 FP |
290 | |---name: The type of the thermal zone devices |
291 | |---temp[1-*]_input: The current temperature of thermal zone [1-*] | |
292 | |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] | |
293 | ||
e9ae7107 | 294 | Please read Documentation/hwmon/sysfs-interface for additional information. |
203d3d4a ZR |
295 | |
296 | *************************** | |
297 | * Thermal zone attributes * | |
298 | *************************** | |
299 | ||
38bb0849 FP |
300 | type |
301 | Strings which represent the thermal zone type. | |
302 | This is given by thermal zone driver as part of registration. | |
303 | E.g: "acpitz" indicates it's an ACPI thermal device. | |
304 | In order to keep it consistent with hwmon sys attribute; this should | |
305 | be a short, lowercase string, not containing spaces nor dashes. | |
306 | RO, Required | |
307 | ||
308 | temp | |
309 | Current temperature as reported by thermal zone (sensor). | |
310 | Unit: millidegree Celsius | |
311 | RO, Required | |
312 | ||
313 | mode | |
8eaa8d6c | 314 | One of the predefined values in [enabled, disabled]. |
38bb0849 FP |
315 | This file gives information about the algorithm that is currently |
316 | managing the thermal zone. It can be either default kernel based | |
317 | algorithm or user space application. | |
8eaa8d6c ZR |
318 | enabled = enable Kernel Thermal management. |
319 | disabled = Preventing kernel thermal zone driver actions upon | |
320 | trip points so that user application can take full | |
321 | charge of the thermal management. | |
38bb0849 FP |
322 | RW, Optional |
323 | ||
6ea083b1 D |
324 | policy |
325 | One of the various thermal governors used for a particular zone. | |
326 | RW, Required | |
327 | ||
25a0a5ce NW |
328 | available_policies |
329 | Available thermal governors which can be used for a particular zone. | |
330 | RO, Required | |
331 | ||
38bb0849 FP |
332 | trip_point_[0-*]_temp |
333 | The temperature above which trip point will be fired. | |
334 | Unit: millidegree Celsius | |
335 | RO, Optional | |
336 | ||
337 | trip_point_[0-*]_type | |
338 | Strings which indicate the type of the trip point. | |
339 | E.g. it can be one of critical, hot, passive, active[0-*] for ACPI | |
340 | thermal zone. | |
341 | RO, Optional | |
342 | ||
27365a6c D |
343 | trip_point_[0-*]_hyst |
344 | The hysteresis value for a trip point, represented as an integer | |
345 | Unit: Celsius | |
346 | RW, Optional | |
347 | ||
38bb0849 FP |
348 | cdev[0-*] |
349 | Sysfs link to the thermal cooling device node where the sys I/F | |
350 | for cooling device throttling control represents. | |
351 | RO, Optional | |
352 | ||
353 | cdev[0-*]_trip_point | |
354 | The trip point with which cdev[0-*] is associated in this thermal | |
355 | zone; -1 means the cooling device is not associated with any trip | |
356 | point. | |
357 | RO, Optional | |
29226ed3 | 358 | |
db916513 JM |
359 | cdev[0-*]_weight |
360 | The influence of cdev[0-*] in this thermal zone. This value | |
361 | is relative to the rest of cooling devices in the thermal | |
362 | zone. For example, if a cooling device has a weight double | |
363 | than that of other, it's twice as effective in cooling the | |
364 | thermal zone. | |
365 | RW, Optional | |
366 | ||
29226ed3 FP |
367 | passive |
368 | Attribute is only present for zones in which the passive cooling | |
369 | policy is not supported by native thermal driver. Default is zero | |
370 | and can be set to a temperature (in millidegrees) to enable a | |
371 | passive trip point for the zone. Activation is done by polling with | |
372 | an interval of 1 second. | |
373 | Unit: millidegrees Celsius | |
3d8e3ad8 | 374 | Valid values: 0 (disabled) or greater than 1000 |
29226ed3 | 375 | RW, Optional |
38bb0849 | 376 | |
e6e238c3 ADK |
377 | emul_temp |
378 | Interface to set the emulated temperature method in thermal zone | |
379 | (sensor). After setting this temperature, the thermal zone may pass | |
380 | this temperature to platform emulation function if registered or | |
381 | cache it locally. This is useful in debugging different temperature | |
382 | threshold and its associated cooling action. This is write only node | |
383 | and writing 0 on this node should disable emulation. | |
384 | Unit: millidegree Celsius | |
385 | WO, Optional | |
386 | ||
8837295a EV |
387 | WARNING: Be careful while enabling this option on production systems, |
388 | because userland can easily disable the thermal policy by simply | |
389 | flooding this sysfs node with low temperature values. | |
390 | ||
9f38271c JM |
391 | sustainable_power |
392 | An estimate of the sustained power that can be dissipated by | |
393 | the thermal zone. Used by the power allocator governor. For | |
394 | more information see Documentation/thermal/power_allocator.txt | |
395 | Unit: milliwatts | |
396 | RW, Optional | |
397 | ||
398 | k_po | |
399 | The proportional term of the power allocator governor's PID | |
400 | controller during temperature overshoot. Temperature overshoot | |
401 | is when the current temperature is above the "desired | |
402 | temperature" trip point. For more information see | |
403 | Documentation/thermal/power_allocator.txt | |
404 | RW, Optional | |
405 | ||
406 | k_pu | |
407 | The proportional term of the power allocator governor's PID | |
408 | controller during temperature undershoot. Temperature undershoot | |
409 | is when the current temperature is below the "desired | |
410 | temperature" trip point. For more information see | |
411 | Documentation/thermal/power_allocator.txt | |
412 | RW, Optional | |
413 | ||
414 | k_i | |
415 | The integral term of the power allocator governor's PID | |
416 | controller. This term allows the PID controller to compensate | |
417 | for long term drift. For more information see | |
418 | Documentation/thermal/power_allocator.txt | |
419 | RW, Optional | |
420 | ||
421 | k_d | |
422 | The derivative term of the power allocator governor's PID | |
423 | controller. For more information see | |
424 | Documentation/thermal/power_allocator.txt | |
425 | RW, Optional | |
426 | ||
427 | integral_cutoff | |
428 | Temperature offset from the desired temperature trip point | |
429 | above which the integral term of the power allocator | |
430 | governor's PID controller starts accumulating errors. For | |
431 | example, if integral_cutoff is 0, then the integral term only | |
432 | accumulates error when temperature is above the desired | |
433 | temperature trip point. For more information see | |
434 | Documentation/thermal/power_allocator.txt | |
ec3fc58b | 435 | Unit: millidegree Celsius |
9f38271c JM |
436 | RW, Optional |
437 | ||
9d0be7f4 EV |
438 | slope |
439 | The slope constant used in a linear extrapolation model | |
440 | to determine a hotspot temperature based off the sensor's | |
441 | raw readings. It is up to the device driver to determine | |
442 | the usage of these values. | |
443 | RW, Optional | |
444 | ||
445 | offset | |
446 | The offset constant used in a linear extrapolation model | |
447 | to determine a hotspot temperature based off the sensor's | |
448 | raw readings. It is up to the device driver to determine | |
449 | the usage of these values. | |
450 | RW, Optional | |
451 | ||
38bb0849 FP |
452 | ***************************** |
453 | * Cooling device attributes * | |
454 | ***************************** | |
455 | ||
456 | type | |
457 | String which represents the type of device, e.g: | |
458 | - for generic ACPI: should be "Fan", "Processor" or "LCD" | |
459 | - for memory controller device on intel_menlow platform: | |
460 | should be "Memory controller". | |
461 | RO, Required | |
462 | ||
463 | max_state | |
464 | The maximum permissible cooling state of this cooling device. | |
465 | RO, Required | |
466 | ||
467 | cur_state | |
468 | The current cooling state of this cooling device. | |
469 | The value can any integer numbers between 0 and max_state: | |
470 | - cur_state == 0 means no cooling | |
471 | - cur_state == max_state means the maximum cooling. | |
472 | RW, Required | |
203d3d4a ZR |
473 | |
474 | 3. A simple implementation | |
475 | ||
38bb0849 FP |
476 | ACPI thermal zone may support multiple trip points like critical, hot, |
477 | passive, active. If an ACPI thermal zone supports critical, passive, | |
478 | active[0] and active[1] at the same time, it may register itself as a | |
479 | thermal_zone_device (thermal_zone1) with 4 trip points in all. | |
480 | It has one processor and one fan, which are both registered as | |
db916513 JM |
481 | thermal_cooling_device. Both are considered to have the same |
482 | effectiveness in cooling the thermal zone. | |
38bb0849 FP |
483 | |
484 | If the processor is listed in _PSL method, and the fan is listed in _AL0 | |
485 | method, the sys I/F structure will be built like this: | |
203d3d4a ZR |
486 | |
487 | /sys/class/thermal: | |
488 | ||
489 | |thermal_zone1: | |
38bb0849 FP |
490 | |---type: acpitz |
491 | |---temp: 37000 | |
8eaa8d6c | 492 | |---mode: enabled |
6ea083b1 | 493 | |---policy: step_wise |
25a0a5ce | 494 | |---available_policies: step_wise fair_share |
38bb0849 FP |
495 | |---trip_point_0_temp: 100000 |
496 | |---trip_point_0_type: critical | |
497 | |---trip_point_1_temp: 80000 | |
498 | |---trip_point_1_type: passive | |
499 | |---trip_point_2_temp: 70000 | |
500 | |---trip_point_2_type: active0 | |
501 | |---trip_point_3_temp: 60000 | |
502 | |---trip_point_3_type: active1 | |
503 | |---cdev0: --->/sys/class/thermal/cooling_device0 | |
504 | |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
db916513 | 505 | |---cdev0_weight: 1024 |
38bb0849 FP |
506 | |---cdev1: --->/sys/class/thermal/cooling_device3 |
507 | |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
db916513 | 508 | |---cdev1_weight: 1024 |
203d3d4a ZR |
509 | |
510 | |cooling_device0: | |
38bb0849 FP |
511 | |---type: Processor |
512 | |---max_state: 8 | |
513 | |---cur_state: 0 | |
203d3d4a ZR |
514 | |
515 | |cooling_device3: | |
38bb0849 FP |
516 | |---type: Fan |
517 | |---max_state: 2 | |
518 | |---cur_state: 0 | |
e9ae7107 ZR |
519 | |
520 | /sys/class/hwmon: | |
521 | ||
522 | |hwmon0: | |
38bb0849 FP |
523 | |---name: acpitz |
524 | |---temp1_input: 37000 | |
525 | |---temp1_crit: 100000 | |
4cb18728 D |
526 | |
527 | 4. Event Notification | |
528 | ||
529 | The framework includes a simple notification mechanism, in the form of a | |
530 | netlink event. Netlink socket initialization is done during the _init_ | |
531 | of the framework. Drivers which intend to use the notification mechanism | |
2d58d7ea | 532 | just need to call thermal_generate_netlink_event() with two arguments viz |
8ab3e6a0 EV |
533 | (originator, event). The originator is a pointer to struct thermal_zone_device |
534 | from where the event has been originated. An integer which represents the | |
535 | thermal zone device will be used in the message to identify the zone. The | |
4cb18728 D |
536 | event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, |
537 | THERMAL_DEV_FAULT}. Notification can be sent when the current temperature | |
538 | crosses any of the configured thresholds. | |
6ea083b1 D |
539 | |
540 | 5. Export Symbol APIs: | |
541 | ||
542 | 5.1: get_tz_trend: | |
543 | This function returns the trend of a thermal zone, i.e the rate of change | |
544 | of temperature of the thermal zone. Ideally, the thermal sensor drivers | |
545 | are supposed to implement the callback. If they don't, the thermal | |
546 | framework calculated the trend by comparing the previous and the current | |
547 | temperature values. | |
548 | ||
549 | 5.2:get_thermal_instance: | |
550 | This function returns the thermal_instance corresponding to a given | |
551 | {thermal_zone, cooling_device, trip_point} combination. Returns NULL | |
552 | if such an instance does not exist. | |
553 | ||
7b73c993 | 554 | 5.3:thermal_notify_framework: |
6ea083b1 D |
555 | This function handles the trip events from sensor drivers. It starts |
556 | throttling the cooling devices according to the policy configured. | |
557 | For CRITICAL and HOT trip points, this notifies the respective drivers, | |
558 | and does actual throttling for other trip points i.e ACTIVE and PASSIVE. | |
559 | The throttling policy is based on the configured platform data; if no | |
560 | platform data is provided, this uses the step_wise throttling policy. | |
561 | ||
562 | 5.4:thermal_cdev_update: | |
563 | This function serves as an arbitrator to set the state of a cooling | |
564 | device. It sets the cooling device to the deepest cooling state if | |
565 | possible. |