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Zhang Rui203d3d42008-01-17 15:51:08 +08001Generic Thermal Sysfs driver How To
2=========================
3
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
13The generic thermal sysfs provides a set of interfaces for thermal zone devices (sensors)
14and thermal cooling devices (fan, processor...) to register with the thermal management
15solution and to be a part of it.
16
Len Brown543a9562008-02-07 16:55:08 -050017This how-to focuses on enabling new thermal zone and cooling devices to participate
Zhang Rui203d3d42008-01-17 15:51:08 +080018in thermal management.
19This solution is platform independent and any type of thermal zone devices and
20cooling devices should be able to make use of the infrastructure.
21
22The main task of the thermal sysfs driver is to expose thermal zone attributes as well
23as cooling device attributes to the user space.
24An intelligent thermal management application can make decisions based on inputs
25from thermal zone attributes (the current temperature and trip point temperature)
26and throttle appropriate devices.
27
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
341.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, int trips,
35 void *devdata, struct thermal_zone_device_ops *ops)
36
37 This interface function adds a new thermal zone device (sensor) to
38 /sys/class/thermal folder as thermal_zone[0-*].
39 It tries to bind all the thermal cooling devices registered at the same time.
40
41 name: the thermal zone name.
42 trips: the total number of trip points this thermal zone supports.
43 devdata: device private data
Len Brown543a9562008-02-07 16:55:08 -050044 ops: thermal zone device call-backs.
Zhang Rui203d3d42008-01-17 15:51:08 +080045 .bind: bind the thermal zone device with a thermal cooling device.
Len Brown543a9562008-02-07 16:55:08 -050046 .unbind: unbind the thermal zone device with a thermal cooling device.
Zhang Rui203d3d42008-01-17 15:51:08 +080047 .get_temp: get the current temperature of the thermal zone.
48 .get_mode: get the current mode (user/kernel) of the thermal zone.
49 "kernel" means thermal management is done in kernel.
50 "user" will prevent kernel thermal driver actions upon trip points
51 so that user applications can take charge of thermal management.
52 .set_mode: set the mode (user/kernel) of the thermal zone.
53 .get_trip_type: get the type of certain trip point.
54 .get_trip_temp: get the temperature above which the certain trip point
55 will be fired.
56
571.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz)
58
59 This interface function removes the thermal zone device.
60 It deletes the corresponding entry form /sys/class/thermal folder and unbind all
61 the thermal cooling devices it uses.
62
631.2 thermal cooling device interface
641.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name,
65 void *devdata, struct thermal_cooling_device_ops *)
66
67 This interface function adds a new thermal cooling device (fan/processor/...) to
68 /sys/class/thermal/ folder as cooling_device[0-*].
69 It tries to bind itself to all the thermal zone devices register at the same time.
70 name: the cooling device name.
71 devdata: device private data.
Len Brown543a9562008-02-07 16:55:08 -050072 ops: thermal cooling devices call-backs.
Zhang Rui203d3d42008-01-17 15:51:08 +080073 .get_max_state: get the Maximum throttle state of the cooling device.
74 .get_cur_state: get the Current throttle state of the cooling device.
75 .set_cur_state: set the Current throttle state of the cooling device.
76
771.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
78
79 This interface function remove the thermal cooling device.
80 It deletes the corresponding entry form /sys/class/thermal folder and unbind
81 itself from all the thermal zone devices using it.
82
831.3 interface for binding a thermal zone device with a thermal cooling device
841.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
85 int trip, struct thermal_cooling_device *cdev);
86
87 This interface function bind a thermal cooling device to the certain trip point
88 of a thermal zone device.
89 This function is usually called in the thermal zone device .bind callback.
90 tz: the thermal zone device
91 cdev: thermal cooling device
92 trip: indicates which trip point the cooling devices is associated with
93 in this thermal zone.
94
951.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
96 int trip, struct thermal_cooling_device *cdev);
97
98 This interface function unbind a thermal cooling device from the certain trip point
99 of a thermal zone device.
100 This function is usually called in the thermal zone device .unbind callback.
101 tz: the thermal zone device
102 cdev: thermal cooling device
103 trip: indicates which trip point the cooling devices is associated with
104 in this thermal zone.
105
1062. sysfs attributes structure
107
108RO read only value
109RW read/write value
110
111All thermal sysfs attributes will be represented under /sys/class/thermal
Zhang Rui203d3d42008-01-17 15:51:08 +0800112
113Thermal zone device sys I/F, created once it's registered:
114|thermal_zone[0-*]:
115 |-----type: Type of the thermal zone
116 |-----temp: Current temperature
117 |-----mode: Working mode of the thermal zone
118 |-----trip_point_[0-*]_temp: Trip point temperature
119 |-----trip_point_[0-*]_type: Trip point type
120
121Thermal cooling device sys I/F, created once it's registered:
122|cooling_device[0-*]:
123 |-----type : Type of the cooling device(processor/fan/...)
124 |-----max_state: Maximum cooling state of the cooling device
125 |-----cur_state: Current cooling state of the cooling device
126
127
128These two dynamic attributes are created/removed in pairs.
129They represent the relationship between a thermal zone and its associated cooling device.
130They are created/removed for each
Len Brown543a9562008-02-07 16:55:08 -0500131thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution.
Zhang Rui203d3d42008-01-17 15:51:08 +0800132
133|thermal_zone[0-*]
134 |-----cdev[0-*]: The [0-*]th cooling device in the current thermal zone
135 |-----cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with
136
137
138***************************
139* Thermal zone attributes *
140***************************
141
142type Strings which represent the thermal zone type.
143 This is given by thermal zone driver as part of registration.
144 Eg: "ACPI thermal zone" indicates it's a ACPI thermal device
145 RO
Zhang, Rui3152fb92008-02-27 08:37:50 +0800146 Required
Zhang Rui203d3d42008-01-17 15:51:08 +0800147
148temp Current temperature as reported by thermal zone (sensor)
Zhang, Rui3152fb92008-02-27 08:37:50 +0800149 Unit: millidegree Celsius
Zhang Rui203d3d42008-01-17 15:51:08 +0800150 RO
151 Required
152
Len Brown543a9562008-02-07 16:55:08 -0500153mode One of the predefined values in [kernel, user]
Zhang Rui203d3d42008-01-17 15:51:08 +0800154 This file gives information about the algorithm
155 that is currently managing the thermal zone.
156 It can be either default kernel based algorithm
157 or user space application.
158 RW
159 Optional
160 kernel = Thermal management in kernel thermal zone driver.
161 user = Preventing kernel thermal zone driver actions upon
162 trip points so that user application can take full
163 charge of the thermal management.
164
165trip_point_[0-*]_temp The temperature above which trip point will be fired
Zhang, Rui3152fb92008-02-27 08:37:50 +0800166 Unit: millidegree Celsius
Zhang Rui203d3d42008-01-17 15:51:08 +0800167 RO
168 Optional
169
170trip_point_[0-*]_type Strings which indicate the type of the trip point
Len Brown543a9562008-02-07 16:55:08 -0500171 E.g. it can be one of critical, hot, passive,
Zhang Rui203d3d42008-01-17 15:51:08 +0800172 active[0-*] for ACPI thermal zone.
173 RO
174 Optional
175
176cdev[0-*] Sysfs link to the thermal cooling device node where the sys I/F
177 for cooling device throttling control represents.
178 RO
179 Optional
180
Len Brown543a9562008-02-07 16:55:08 -0500181cdev[0-*]_trip_point The trip point with which cdev[0-*] is associated in this thermal zone
Zhang Rui203d3d42008-01-17 15:51:08 +0800182 -1 means the cooling device is not associated with any trip point.
183 RO
184 Optional
185
186******************************
187* Cooling device attributes *
188******************************
189
190type String which represents the type of device
191 eg: For generic ACPI: this should be "Fan",
192 "Processor" or "LCD"
193 eg. For memory controller device on intel_menlow platform:
194 this should be "Memory controller"
195 RO
Zhang, Rui3152fb92008-02-27 08:37:50 +0800196 Required
Zhang Rui203d3d42008-01-17 15:51:08 +0800197
198max_state The maximum permissible cooling state of this cooling device.
199 RO
200 Required
201
202cur_state The current cooling state of this cooling device.
203 the value can any integer numbers between 0 and max_state,
204 cur_state == 0 means no cooling
205 cur_state == max_state means the maximum cooling.
206 RW
207 Required
208
2093. A simple implementation
210
211ACPI thermal zone may support multiple trip points like critical/hot/passive/active.
212If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time,
Len Brown543a9562008-02-07 16:55:08 -0500213it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all.
Zhang Rui203d3d42008-01-17 15:51:08 +0800214It has one processor and one fan, which are both registered as thermal_cooling_device.
215If the processor is listed in _PSL method, and the fan is listed in _AL0 method,
216the sys I/F structure will be built like this:
217
218/sys/class/thermal:
219
220|thermal_zone1:
221 |-----type: ACPI thermal zone
Zhang, Rui3152fb92008-02-27 08:37:50 +0800222 |-----temp: 37000
Zhang Rui203d3d42008-01-17 15:51:08 +0800223 |-----mode: kernel
Zhang, Rui3152fb92008-02-27 08:37:50 +0800224 |-----trip_point_0_temp: 100000
Zhang Rui203d3d42008-01-17 15:51:08 +0800225 |-----trip_point_0_type: critical
Zhang, Rui3152fb92008-02-27 08:37:50 +0800226 |-----trip_point_1_temp: 80000
Zhang Rui203d3d42008-01-17 15:51:08 +0800227 |-----trip_point_1_type: passive
Zhang, Rui3152fb92008-02-27 08:37:50 +0800228 |-----trip_point_2_temp: 70000
229 |-----trip_point_2_type: active0
230 |-----trip_point_3_temp: 60000
231 |-----trip_point_3_type: active1
Zhang Rui203d3d42008-01-17 15:51:08 +0800232 |-----cdev0: --->/sys/class/thermal/cooling_device0
233 |-----cdev0_trip_point: 1 /* cdev0 can be used for passive */
234 |-----cdev1: --->/sys/class/thermal/cooling_device3
235 |-----cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
236
237|cooling_device0:
238 |-----type: Processor
239 |-----max_state: 8
240 |-----cur_state: 0
241
242|cooling_device3:
243 |-----type: Fan
244 |-----max_state: 2
245 |-----cur_state: 0