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Zhang Rui203d3d42008-01-17 15:51:08 +08001Generic Thermal Sysfs driver How To
Frans Pop38bb0842009-10-26 08:38:59 +01002===================================
Zhang Rui203d3d42008-01-17 15:51:08 +08003
4Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com>
5
6Updated: 2 January 2008
7
8Copyright (c) 2008 Intel Corporation
9
10
110. Introduction
12
Frans Pop38bb0842009-10-26 08:38:59 +010013The generic thermal sysfs provides a set of interfaces for thermal zone
14devices (sensors) and thermal cooling devices (fan, processor...) to register
15with the thermal management solution and to be a part of it.
Zhang Rui203d3d42008-01-17 15:51:08 +080016
Frans Pop38bb0842009-10-26 08:38:59 +010017This how-to focuses on enabling new thermal zone and cooling devices to
18participate in thermal management.
19This solution is platform independent and any type of thermal zone devices
20and cooling devices should be able to make use of the infrastructure.
Zhang Rui203d3d42008-01-17 15:51:08 +080021
Frans Pop38bb0842009-10-26 08:38:59 +010022The main task of the thermal sysfs driver is to expose thermal zone attributes
23as well as cooling device attributes to the user space.
24An intelligent thermal management application can make decisions based on
25inputs from thermal zone attributes (the current temperature and trip point
26temperature) and throttle appropriate devices.
Zhang Rui203d3d42008-01-17 15:51:08 +080027
28[0-*] denotes any positive number starting from 0
29[1-*] denotes any positive number starting from 1
30
311. thermal sysfs driver interface functions
32
331.1 thermal zone device interface
Zhang Rui514e6d22013-04-24 16:59:22 +0000341.1.1 struct thermal_zone_device *thermal_zone_device_register(char *type,
Durgadoss Rc56f5c02012-07-25 10:10:58 +080035 int trips, int mask, void *devdata,
Zhang Rui514e6d22013-04-24 16:59:22 +000036 struct thermal_zone_device_ops *ops,
37 const struct thermal_zone_params *tzp,
38 int passive_delay, int polling_delay))
Zhang Rui203d3d42008-01-17 15:51:08 +080039
Frans Pop38bb0842009-10-26 08:38:59 +010040 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.
Zhang Rui203d3d42008-01-17 15:51:08 +080043
Zhang Rui514e6d22013-04-24 16:59:22 +000044 type: the thermal zone type.
Frans Pop38bb0842009-10-26 08:38:59 +010045 trips: the total number of trip points this thermal zone supports.
Durgadoss Rc56f5c02012-07-25 10:10:58 +080046 mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable.
Frans Pop38bb0842009-10-26 08:38:59 +010047 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.
Zhang Rui8eaa8d62012-07-25 10:11:00 +080052 .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
Frans Pop38bb0842009-10-26 08:38:59 +010055 so that user applications can take charge of thermal management.
Zhang Rui8eaa8d62012-07-25 10:11:00 +080056 .set_mode: set the mode (enabled/disabled) of the thermal zone.
Frans Pop38bb0842009-10-26 08:38:59 +010057 .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.
Amit Daniel Kachhape6e238c2013-02-04 00:30:15 +000060 .set_emul_temp: set the emulation temperature which helps in debugging
61 different threshold temperature points.
Zhang Rui514e6d22013-04-24 16:59:22 +000062 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
Zhang Rui203d3d42008-01-17 15:51:08 +080068
691.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz)
70
Frans Pop38bb0842009-10-26 08:38:59 +010071 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.
Zhang Rui203d3d42008-01-17 15:51:08 +080074
751.2 thermal cooling device interface
761.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name,
Frans Pop38bb0842009-10-26 08:38:59 +010077 void *devdata, struct thermal_cooling_device_ops *)
Zhang Rui203d3d42008-01-17 15:51:08 +080078
Frans Pop38bb0842009-10-26 08:38:59 +010079 This interface function adds a new thermal cooling device (fan/processor/...)
80 to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself
81 to all the thermal zone devices register at the same time.
82 name: the cooling device name.
83 devdata: device private data.
84 ops: thermal cooling devices call-backs.
85 .get_max_state: get the Maximum throttle state of the cooling device.
86 .get_cur_state: get the Current throttle state of the cooling device.
87 .set_cur_state: set the Current throttle state of the cooling device.
Zhang Rui203d3d42008-01-17 15:51:08 +080088
891.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
90
Frans Pop38bb0842009-10-26 08:38:59 +010091 This interface function remove the thermal cooling device.
92 It deletes the corresponding entry form /sys/class/thermal folder and
93 unbind itself from all the thermal zone devices using it.
Zhang Rui203d3d42008-01-17 15:51:08 +080094
951.3 interface for binding a thermal zone device with a thermal cooling device
961.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
Zhang Rui9d998422012-06-26 16:35:57 +080097 int trip, struct thermal_cooling_device *cdev,
98 unsigned long upper, unsigned long lower);
Zhang Rui203d3d42008-01-17 15:51:08 +080099
Frans Pop38bb0842009-10-26 08:38:59 +0100100 This interface function bind a thermal cooling device to the certain trip
101 point of a thermal zone device.
102 This function is usually called in the thermal zone device .bind callback.
103 tz: the thermal zone device
104 cdev: thermal cooling device
105 trip: indicates which trip point the cooling devices is associated with
106 in this thermal zone.
Zhang Rui9d998422012-06-26 16:35:57 +0800107 upper:the Maximum cooling state for this trip point.
108 THERMAL_NO_LIMIT means no upper limit,
109 and the cooling device can be in max_state.
110 lower:the Minimum cooling state can be used for this trip point.
111 THERMAL_NO_LIMIT means no lower limit,
112 and the cooling device can be in cooling state 0.
Zhang Rui203d3d42008-01-17 15:51:08 +0800113
1141.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
Frans Pop38bb0842009-10-26 08:38:59 +0100115 int trip, struct thermal_cooling_device *cdev);
Zhang Rui203d3d42008-01-17 15:51:08 +0800116
Frans Pop38bb0842009-10-26 08:38:59 +0100117 This interface function unbind a thermal cooling device from the certain
118 trip point of a thermal zone device. This function is usually called in
119 the thermal zone device .unbind callback.
120 tz: the thermal zone device
121 cdev: thermal cooling device
122 trip: indicates which trip point the cooling devices is associated with
123 in this thermal zone.
Zhang Rui203d3d42008-01-17 15:51:08 +0800124
Durgadoss R6ea083b2012-09-18 11:05:06 +05301251.4 Thermal Zone Parameters
1261.4.1 struct thermal_bind_params
127 This structure defines the following parameters that are used to bind
128 a zone with a cooling device for a particular trip point.
129 .cdev: The cooling device pointer
130 .weight: The 'influence' of a particular cooling device on this zone.
131 This is on a percentage scale. The sum of all these weights
132 (for a particular zone) cannot exceed 100.
133 .trip_mask:This is a bit mask that gives the binding relation between
134 this thermal zone and cdev, for a particular trip point.
135 If nth bit is set, then the cdev and thermal zone are bound
136 for trip point n.
137 .match: This call back returns success(0) if the 'tz and cdev' need to
138 be bound, as per platform data.
1391.4.2 struct thermal_zone_params
140 This structure defines the platform level parameters for a thermal zone.
141 This data, for each thermal zone should come from the platform layer.
142 This is an optional feature where some platforms can choose not to
143 provide this data.
144 .governor_name: Name of the thermal governor used for this zone
145 .num_tbps: Number of thermal_bind_params entries for this zone
146 .tbp: thermal_bind_params entries
147
Zhang Rui203d3d42008-01-17 15:51:08 +08001482. sysfs attributes structure
149
150RO read only value
151RW read/write value
152
Zhang Ruie9ae7102008-04-22 08:50:09 +0800153Thermal sysfs attributes will be represented under /sys/class/thermal.
154Hwmon sysfs I/F extension is also available under /sys/class/hwmon
155if hwmon is compiled in or built as a module.
Zhang Rui203d3d42008-01-17 15:51:08 +0800156
157Thermal zone device sys I/F, created once it's registered:
Zhang Ruie9ae7102008-04-22 08:50:09 +0800158/sys/class/thermal/thermal_zone[0-*]:
Frans Pop38bb0842009-10-26 08:38:59 +0100159 |---type: Type of the thermal zone
160 |---temp: Current temperature
161 |---mode: Working mode of the thermal zone
Durgadoss R6ea083b2012-09-18 11:05:06 +0530162 |---policy: Thermal governor used for this zone
Frans Pop38bb0842009-10-26 08:38:59 +0100163 |---trip_point_[0-*]_temp: Trip point temperature
164 |---trip_point_[0-*]_type: Trip point type
Durgadoss R27365a62012-07-25 10:10:59 +0800165 |---trip_point_[0-*]_hyst: Hysteresis value for this trip point
Amit Daniel Kachhape6e238c2013-02-04 00:30:15 +0000166 |---emul_temp: Emulated temperature set node
Zhang Rui203d3d42008-01-17 15:51:08 +0800167
168Thermal cooling device sys I/F, created once it's registered:
Zhang Ruie9ae7102008-04-22 08:50:09 +0800169/sys/class/thermal/cooling_device[0-*]:
Frans Pop38bb0842009-10-26 08:38:59 +0100170 |---type: Type of the cooling device(processor/fan/...)
171 |---max_state: Maximum cooling state of the cooling device
172 |---cur_state: Current cooling state of the cooling device
Zhang Rui203d3d42008-01-17 15:51:08 +0800173
174
Frans Pop38bb0842009-10-26 08:38:59 +0100175Then next two dynamic attributes are created/removed in pairs. They represent
176the relationship between a thermal zone and its associated cooling device.
177They are created/removed for each successful execution of
178thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device.
Zhang Rui203d3d42008-01-17 15:51:08 +0800179
Frans Pop38bb0842009-10-26 08:38:59 +0100180/sys/class/thermal/thermal_zone[0-*]:
181 |---cdev[0-*]: [0-*]th cooling device in current thermal zone
182 |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with
Zhang Rui203d3d42008-01-17 15:51:08 +0800183
Zhang Ruie9ae7102008-04-22 08:50:09 +0800184Besides the thermal zone device sysfs I/F and cooling device sysfs I/F,
Frans Pop38bb0842009-10-26 08:38:59 +0100185the generic thermal driver also creates a hwmon sysfs I/F for each _type_
186of thermal zone device. E.g. the generic thermal driver registers one hwmon
187class device and build the associated hwmon sysfs I/F for all the registered
188ACPI thermal zones.
189
Zhang Ruie9ae7102008-04-22 08:50:09 +0800190/sys/class/hwmon/hwmon[0-*]:
Frans Pop38bb0842009-10-26 08:38:59 +0100191 |---name: The type of the thermal zone devices
192 |---temp[1-*]_input: The current temperature of thermal zone [1-*]
193 |---temp[1-*]_critical: The critical trip point of thermal zone [1-*]
194
Zhang Ruie9ae7102008-04-22 08:50:09 +0800195Please read Documentation/hwmon/sysfs-interface for additional information.
Zhang Rui203d3d42008-01-17 15:51:08 +0800196
197***************************
198* Thermal zone attributes *
199***************************
200
Frans Pop38bb0842009-10-26 08:38:59 +0100201type
202 Strings which represent the thermal zone type.
203 This is given by thermal zone driver as part of registration.
204 E.g: "acpitz" indicates it's an ACPI thermal device.
205 In order to keep it consistent with hwmon sys attribute; this should
206 be a short, lowercase string, not containing spaces nor dashes.
207 RO, Required
Zhang Rui203d3d42008-01-17 15:51:08 +0800208
Frans Pop38bb0842009-10-26 08:38:59 +0100209temp
210 Current temperature as reported by thermal zone (sensor).
211 Unit: millidegree Celsius
212 RO, Required
Zhang Rui203d3d42008-01-17 15:51:08 +0800213
Frans Pop38bb0842009-10-26 08:38:59 +0100214mode
Zhang Rui8eaa8d62012-07-25 10:11:00 +0800215 One of the predefined values in [enabled, disabled].
Frans Pop38bb0842009-10-26 08:38:59 +0100216 This file gives information about the algorithm that is currently
217 managing the thermal zone. It can be either default kernel based
218 algorithm or user space application.
Zhang Rui8eaa8d62012-07-25 10:11:00 +0800219 enabled = enable Kernel Thermal management.
220 disabled = Preventing kernel thermal zone driver actions upon
221 trip points so that user application can take full
222 charge of the thermal management.
Frans Pop38bb0842009-10-26 08:38:59 +0100223 RW, Optional
Zhang Rui203d3d42008-01-17 15:51:08 +0800224
Durgadoss R6ea083b2012-09-18 11:05:06 +0530225policy
226 One of the various thermal governors used for a particular zone.
227 RW, Required
228
Frans Pop38bb0842009-10-26 08:38:59 +0100229trip_point_[0-*]_temp
230 The temperature above which trip point will be fired.
231 Unit: millidegree Celsius
232 RO, Optional
Zhang Rui203d3d42008-01-17 15:51:08 +0800233
Frans Pop38bb0842009-10-26 08:38:59 +0100234trip_point_[0-*]_type
235 Strings which indicate the type of the trip point.
236 E.g. it can be one of critical, hot, passive, active[0-*] for ACPI
237 thermal zone.
238 RO, Optional
Zhang Rui203d3d42008-01-17 15:51:08 +0800239
Durgadoss R27365a62012-07-25 10:10:59 +0800240trip_point_[0-*]_hyst
241 The hysteresis value for a trip point, represented as an integer
242 Unit: Celsius
243 RW, Optional
244
Frans Pop38bb0842009-10-26 08:38:59 +0100245cdev[0-*]
246 Sysfs link to the thermal cooling device node where the sys I/F
247 for cooling device throttling control represents.
248 RO, Optional
Zhang Rui203d3d42008-01-17 15:51:08 +0800249
Frans Pop38bb0842009-10-26 08:38:59 +0100250cdev[0-*]_trip_point
251 The trip point with which cdev[0-*] is associated in this thermal
252 zone; -1 means the cooling device is not associated with any trip
253 point.
254 RO, Optional
Zhang Rui203d3d42008-01-17 15:51:08 +0800255
Frans Pop29226ed2009-10-26 08:39:00 +0100256passive
257 Attribute is only present for zones in which the passive cooling
258 policy is not supported by native thermal driver. Default is zero
259 and can be set to a temperature (in millidegrees) to enable a
260 passive trip point for the zone. Activation is done by polling with
261 an interval of 1 second.
262 Unit: millidegrees Celsius
Frans Pop3d8e3ad2009-10-26 08:39:02 +0100263 Valid values: 0 (disabled) or greater than 1000
Frans Pop29226ed2009-10-26 08:39:00 +0100264 RW, Optional
265
Amit Daniel Kachhape6e238c2013-02-04 00:30:15 +0000266emul_temp
267 Interface to set the emulated temperature method in thermal zone
268 (sensor). After setting this temperature, the thermal zone may pass
269 this temperature to platform emulation function if registered or
270 cache it locally. This is useful in debugging different temperature
271 threshold and its associated cooling action. This is write only node
272 and writing 0 on this node should disable emulation.
273 Unit: millidegree Celsius
274 WO, Optional
275
Eduardo Valentin88372952013-03-26 21:38:34 +0000276 WARNING: Be careful while enabling this option on production systems,
277 because userland can easily disable the thermal policy by simply
278 flooding this sysfs node with low temperature values.
279
Frans Pop38bb0842009-10-26 08:38:59 +0100280*****************************
281* Cooling device attributes *
282*****************************
Zhang Rui203d3d42008-01-17 15:51:08 +0800283
Frans Pop38bb0842009-10-26 08:38:59 +0100284type
285 String which represents the type of device, e.g:
286 - for generic ACPI: should be "Fan", "Processor" or "LCD"
287 - for memory controller device on intel_menlow platform:
288 should be "Memory controller".
289 RO, Required
Zhang Rui203d3d42008-01-17 15:51:08 +0800290
Frans Pop38bb0842009-10-26 08:38:59 +0100291max_state
292 The maximum permissible cooling state of this cooling device.
293 RO, Required
Zhang Rui203d3d42008-01-17 15:51:08 +0800294
Frans Pop38bb0842009-10-26 08:38:59 +0100295cur_state
296 The current cooling state of this cooling device.
297 The value can any integer numbers between 0 and max_state:
298 - cur_state == 0 means no cooling
299 - cur_state == max_state means the maximum cooling.
300 RW, Required
Zhang Rui203d3d42008-01-17 15:51:08 +0800301
3023. A simple implementation
303
Frans Pop38bb0842009-10-26 08:38:59 +0100304ACPI thermal zone may support multiple trip points like critical, hot,
305passive, active. If an ACPI thermal zone supports critical, passive,
306active[0] and active[1] at the same time, it may register itself as a
307thermal_zone_device (thermal_zone1) with 4 trip points in all.
308It has one processor and one fan, which are both registered as
309thermal_cooling_device.
310
311If the processor is listed in _PSL method, and the fan is listed in _AL0
312method, the sys I/F structure will be built like this:
Zhang Rui203d3d42008-01-17 15:51:08 +0800313
314/sys/class/thermal:
315
316|thermal_zone1:
Frans Pop38bb0842009-10-26 08:38:59 +0100317 |---type: acpitz
318 |---temp: 37000
Zhang Rui8eaa8d62012-07-25 10:11:00 +0800319 |---mode: enabled
Durgadoss R6ea083b2012-09-18 11:05:06 +0530320 |---policy: step_wise
Frans Pop38bb0842009-10-26 08:38:59 +0100321 |---trip_point_0_temp: 100000
322 |---trip_point_0_type: critical
323 |---trip_point_1_temp: 80000
324 |---trip_point_1_type: passive
325 |---trip_point_2_temp: 70000
326 |---trip_point_2_type: active0
327 |---trip_point_3_temp: 60000
328 |---trip_point_3_type: active1
329 |---cdev0: --->/sys/class/thermal/cooling_device0
330 |---cdev0_trip_point: 1 /* cdev0 can be used for passive */
331 |---cdev1: --->/sys/class/thermal/cooling_device3
332 |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
Zhang Rui203d3d42008-01-17 15:51:08 +0800333
334|cooling_device0:
Frans Pop38bb0842009-10-26 08:38:59 +0100335 |---type: Processor
336 |---max_state: 8
337 |---cur_state: 0
Zhang Rui203d3d42008-01-17 15:51:08 +0800338
339|cooling_device3:
Frans Pop38bb0842009-10-26 08:38:59 +0100340 |---type: Fan
341 |---max_state: 2
342 |---cur_state: 0
Zhang Ruie9ae7102008-04-22 08:50:09 +0800343
344/sys/class/hwmon:
345
346|hwmon0:
Frans Pop38bb0842009-10-26 08:38:59 +0100347 |---name: acpitz
348 |---temp1_input: 37000
349 |---temp1_crit: 100000
R.Durgadoss4cb18722010-10-27 03:33:29 +0530350
3514. Event Notification
352
353The framework includes a simple notification mechanism, in the form of a
354netlink event. Netlink socket initialization is done during the _init_
355of the framework. Drivers which intend to use the notification mechanism
Jean Delvare2d58d7e2011-11-04 10:31:04 +0100356just need to call thermal_generate_netlink_event() with two arguments viz
Eduardo Valentin8ab3e6a2013-01-02 15:29:39 +0000357(originator, event). The originator is a pointer to struct thermal_zone_device
358from where the event has been originated. An integer which represents the
359thermal zone device will be used in the message to identify the zone. The
R.Durgadoss4cb18722010-10-27 03:33:29 +0530360event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL,
361THERMAL_DEV_FAULT}. Notification can be sent when the current temperature
362crosses any of the configured thresholds.
Durgadoss R6ea083b2012-09-18 11:05:06 +0530363
3645. Export Symbol APIs:
365
3665.1: get_tz_trend:
367This function returns the trend of a thermal zone, i.e the rate of change
368of temperature of the thermal zone. Ideally, the thermal sensor drivers
369are supposed to implement the callback. If they don't, the thermal
370framework calculated the trend by comparing the previous and the current
371temperature values.
372
3735.2:get_thermal_instance:
374This function returns the thermal_instance corresponding to a given
375{thermal_zone, cooling_device, trip_point} combination. Returns NULL
376if such an instance does not exist.
377
Eduardo Valentin7b73c992013-04-23 21:48:14 +00003785.3:thermal_notify_framework:
Durgadoss R6ea083b2012-09-18 11:05:06 +0530379This function handles the trip events from sensor drivers. It starts
380throttling the cooling devices according to the policy configured.
381For CRITICAL and HOT trip points, this notifies the respective drivers,
382and does actual throttling for other trip points i.e ACTIVE and PASSIVE.
383The throttling policy is based on the configured platform data; if no
384platform data is provided, this uses the step_wise throttling policy.
385
3865.4:thermal_cdev_update:
387This function serves as an arbitrator to set the state of a cooling
388device. It sets the cooling device to the deepest cooling state if
389possible.