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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 | ||
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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 | |
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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 | |
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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. | |
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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 | |
38bb0849 | 34 | 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, |
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35 | int trips, int mask, void *devdata, |
36 | struct thermal_zone_device_ops *ops) | |
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37 | |
38 | This interface function adds a new thermal zone device (sensor) to | |
39 | /sys/class/thermal folder as thermal_zone[0-*]. It tries to bind all the | |
40 | thermal cooling devices registered at the same time. | |
41 | ||
42 | name: the thermal zone name. | |
43 | trips: the total number of trip points this thermal zone supports. | |
c56f5c03 | 44 | mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable. |
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45 | devdata: device private data |
46 | ops: thermal zone device call-backs. | |
47 | .bind: bind the thermal zone device with a thermal cooling device. | |
48 | .unbind: unbind the thermal zone device with a thermal cooling device. | |
49 | .get_temp: get the current temperature of the thermal zone. | |
50 | .get_mode: get the current mode (user/kernel) of the thermal zone. | |
51 | - "kernel" means thermal management is done in kernel. | |
52 | - "user" will prevent kernel thermal driver actions upon trip points | |
53 | so that user applications can take charge of thermal management. | |
54 | .set_mode: set the mode (user/kernel) of the thermal zone. | |
55 | .get_trip_type: get the type of certain trip point. | |
56 | .get_trip_temp: get the temperature above which the certain trip point | |
57 | will be fired. | |
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58 | |
59 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | |
60 | ||
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61 | This interface function removes the thermal zone device. |
62 | It deletes the corresponding entry form /sys/class/thermal folder and | |
63 | unbind all the thermal cooling devices it uses. | |
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64 | |
65 | 1.2 thermal cooling device interface | |
66 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | |
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67 | void *devdata, struct thermal_cooling_device_ops *) |
68 | ||
69 | This interface function adds a new thermal cooling device (fan/processor/...) | |
70 | to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself | |
71 | to all the thermal zone devices register at the same time. | |
72 | name: the cooling device name. | |
73 | devdata: device private data. | |
74 | ops: thermal cooling devices call-backs. | |
75 | .get_max_state: get the Maximum throttle state of the cooling device. | |
76 | .get_cur_state: get the Current throttle state of the cooling device. | |
77 | .set_cur_state: set the Current throttle state of the cooling device. | |
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78 | |
79 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | |
80 | ||
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81 | This interface function remove the thermal cooling device. |
82 | It deletes the corresponding entry form /sys/class/thermal folder and | |
83 | unbind itself from all the thermal zone devices using it. | |
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84 | |
85 | 1.3 interface for binding a thermal zone device with a thermal cooling device | |
86 | 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, | |
38bb0849 | 87 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 88 | |
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89 | This interface function bind a thermal cooling device to the certain trip |
90 | point of a thermal zone device. | |
91 | This function is usually called in the thermal zone device .bind callback. | |
92 | tz: the thermal zone device | |
93 | cdev: thermal cooling device | |
94 | trip: indicates which trip point the cooling devices is associated with | |
95 | in this thermal zone. | |
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96 | |
97 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | |
38bb0849 | 98 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 99 | |
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100 | This interface function unbind a thermal cooling device from the certain |
101 | trip point of a thermal zone device. This function is usually called in | |
102 | the thermal zone device .unbind 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. | |
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107 | |
108 | 2. sysfs attributes structure | |
109 | ||
110 | RO read only value | |
111 | RW read/write value | |
112 | ||
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113 | Thermal sysfs attributes will be represented under /sys/class/thermal. |
114 | Hwmon sysfs I/F extension is also available under /sys/class/hwmon | |
115 | if hwmon is compiled in or built as a module. | |
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116 | |
117 | Thermal zone device sys I/F, created once it's registered: | |
e9ae7107 | 118 | /sys/class/thermal/thermal_zone[0-*]: |
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119 | |---type: Type of the thermal zone |
120 | |---temp: Current temperature | |
121 | |---mode: Working mode of the thermal zone | |
122 | |---trip_point_[0-*]_temp: Trip point temperature | |
123 | |---trip_point_[0-*]_type: Trip point type | |
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124 | |
125 | Thermal cooling device sys I/F, created once it's registered: | |
e9ae7107 | 126 | /sys/class/thermal/cooling_device[0-*]: |
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127 | |---type: Type of the cooling device(processor/fan/...) |
128 | |---max_state: Maximum cooling state of the cooling device | |
129 | |---cur_state: Current cooling state of the cooling device | |
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130 | |
131 | ||
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132 | Then next two dynamic attributes are created/removed in pairs. They represent |
133 | the relationship between a thermal zone and its associated cooling device. | |
134 | They are created/removed for each successful execution of | |
135 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. | |
203d3d4a | 136 | |
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137 | /sys/class/thermal/thermal_zone[0-*]: |
138 | |---cdev[0-*]: [0-*]th cooling device in current thermal zone | |
139 | |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
203d3d4a | 140 | |
e9ae7107 | 141 | Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
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142 | the generic thermal driver also creates a hwmon sysfs I/F for each _type_ |
143 | of thermal zone device. E.g. the generic thermal driver registers one hwmon | |
144 | class device and build the associated hwmon sysfs I/F for all the registered | |
145 | ACPI thermal zones. | |
146 | ||
e9ae7107 | 147 | /sys/class/hwmon/hwmon[0-*]: |
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148 | |---name: The type of the thermal zone devices |
149 | |---temp[1-*]_input: The current temperature of thermal zone [1-*] | |
150 | |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] | |
151 | ||
e9ae7107 | 152 | Please read Documentation/hwmon/sysfs-interface for additional information. |
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153 | |
154 | *************************** | |
155 | * Thermal zone attributes * | |
156 | *************************** | |
157 | ||
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158 | type |
159 | Strings which represent the thermal zone type. | |
160 | This is given by thermal zone driver as part of registration. | |
161 | E.g: "acpitz" indicates it's an ACPI thermal device. | |
162 | In order to keep it consistent with hwmon sys attribute; this should | |
163 | be a short, lowercase string, not containing spaces nor dashes. | |
164 | RO, Required | |
165 | ||
166 | temp | |
167 | Current temperature as reported by thermal zone (sensor). | |
168 | Unit: millidegree Celsius | |
169 | RO, Required | |
170 | ||
171 | mode | |
172 | One of the predefined values in [kernel, user]. | |
173 | This file gives information about the algorithm that is currently | |
174 | managing the thermal zone. It can be either default kernel based | |
175 | algorithm or user space application. | |
176 | kernel = Thermal management in kernel thermal zone driver. | |
177 | user = Preventing kernel thermal zone driver actions upon | |
178 | trip points so that user application can take full | |
179 | charge of the thermal management. | |
180 | RW, Optional | |
181 | ||
182 | trip_point_[0-*]_temp | |
183 | The temperature above which trip point will be fired. | |
184 | Unit: millidegree Celsius | |
185 | RO, Optional | |
186 | ||
187 | trip_point_[0-*]_type | |
188 | Strings which indicate the type of the trip point. | |
189 | E.g. it can be one of critical, hot, passive, active[0-*] for ACPI | |
190 | thermal zone. | |
191 | RO, Optional | |
192 | ||
193 | cdev[0-*] | |
194 | Sysfs link to the thermal cooling device node where the sys I/F | |
195 | for cooling device throttling control represents. | |
196 | RO, Optional | |
197 | ||
198 | cdev[0-*]_trip_point | |
199 | The trip point with which cdev[0-*] is associated in this thermal | |
200 | zone; -1 means the cooling device is not associated with any trip | |
201 | point. | |
202 | RO, Optional | |
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203 | |
204 | passive | |
205 | Attribute is only present for zones in which the passive cooling | |
206 | policy is not supported by native thermal driver. Default is zero | |
207 | and can be set to a temperature (in millidegrees) to enable a | |
208 | passive trip point for the zone. Activation is done by polling with | |
209 | an interval of 1 second. | |
210 | Unit: millidegrees Celsius | |
3d8e3ad8 | 211 | Valid values: 0 (disabled) or greater than 1000 |
29226ed3 | 212 | RW, Optional |
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213 | |
214 | ***************************** | |
215 | * Cooling device attributes * | |
216 | ***************************** | |
217 | ||
218 | type | |
219 | String which represents the type of device, e.g: | |
220 | - for generic ACPI: should be "Fan", "Processor" or "LCD" | |
221 | - for memory controller device on intel_menlow platform: | |
222 | should be "Memory controller". | |
223 | RO, Required | |
224 | ||
225 | max_state | |
226 | The maximum permissible cooling state of this cooling device. | |
227 | RO, Required | |
228 | ||
229 | cur_state | |
230 | The current cooling state of this cooling device. | |
231 | The value can any integer numbers between 0 and max_state: | |
232 | - cur_state == 0 means no cooling | |
233 | - cur_state == max_state means the maximum cooling. | |
234 | RW, Required | |
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235 | |
236 | 3. A simple implementation | |
237 | ||
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238 | ACPI thermal zone may support multiple trip points like critical, hot, |
239 | passive, active. If an ACPI thermal zone supports critical, passive, | |
240 | active[0] and active[1] at the same time, it may register itself as a | |
241 | thermal_zone_device (thermal_zone1) with 4 trip points in all. | |
242 | It has one processor and one fan, which are both registered as | |
243 | thermal_cooling_device. | |
244 | ||
245 | If the processor is listed in _PSL method, and the fan is listed in _AL0 | |
246 | method, the sys I/F structure will be built like this: | |
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247 | |
248 | /sys/class/thermal: | |
249 | ||
250 | |thermal_zone1: | |
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251 | |---type: acpitz |
252 | |---temp: 37000 | |
253 | |---mode: kernel | |
254 | |---trip_point_0_temp: 100000 | |
255 | |---trip_point_0_type: critical | |
256 | |---trip_point_1_temp: 80000 | |
257 | |---trip_point_1_type: passive | |
258 | |---trip_point_2_temp: 70000 | |
259 | |---trip_point_2_type: active0 | |
260 | |---trip_point_3_temp: 60000 | |
261 | |---trip_point_3_type: active1 | |
262 | |---cdev0: --->/sys/class/thermal/cooling_device0 | |
263 | |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
264 | |---cdev1: --->/sys/class/thermal/cooling_device3 | |
265 | |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
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266 | |
267 | |cooling_device0: | |
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268 | |---type: Processor |
269 | |---max_state: 8 | |
270 | |---cur_state: 0 | |
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271 | |
272 | |cooling_device3: | |
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273 | |---type: Fan |
274 | |---max_state: 2 | |
275 | |---cur_state: 0 | |
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276 | |
277 | /sys/class/hwmon: | |
278 | ||
279 | |hwmon0: | |
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280 | |---name: acpitz |
281 | |---temp1_input: 37000 | |
282 | |---temp1_crit: 100000 | |
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283 | |
284 | 4. Event Notification | |
285 | ||
286 | The framework includes a simple notification mechanism, in the form of a | |
287 | netlink event. Netlink socket initialization is done during the _init_ | |
288 | of the framework. Drivers which intend to use the notification mechanism | |
2d58d7ea | 289 | just need to call thermal_generate_netlink_event() with two arguments viz |
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290 | (originator, event). Typically the originator will be an integer assigned |
291 | to a thermal_zone_device when it registers itself with the framework. The | |
292 | event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, | |
293 | THERMAL_DEV_FAULT}. Notification can be sent when the current temperature | |
294 | crosses any of the configured thresholds. |