Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 1 | Generic Thermal Sysfs driver How To |
| 2 | ========================= |
| 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 | |
| 13 | The generic thermal sysfs provides a set of interfaces for thermal zone devices (sensors) |
| 14 | and thermal cooling devices (fan, processor...) to register with the thermal management |
| 15 | solution and to be a part of it. |
| 16 | |
Len Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 17 | This how-to focuses on enabling new thermal zone and cooling devices to participate |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 18 | in thermal management. |
| 19 | This solution is platform independent and any type of thermal zone devices and |
| 20 | cooling devices should be able to make use of the infrastructure. |
| 21 | |
| 22 | The main task of the thermal sysfs driver is to expose thermal zone attributes as well |
| 23 | as cooling device attributes to the user space. |
| 24 | An intelligent thermal management application can make decisions based on inputs |
| 25 | from thermal zone attributes (the current temperature and trip point temperature) |
| 26 | and throttle appropriate devices. |
| 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 |
| 34 | 1.1.1 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 Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 44 | ops: thermal zone device call-backs. |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 45 | .bind: bind the thermal zone device with a thermal cooling device. |
Len Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 46 | .unbind: unbind the thermal zone device with a thermal cooling device. |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 47 | .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 | |
| 57 | 1.1.2 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 | |
| 63 | 1.2 thermal cooling device interface |
| 64 | 1.2.1 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 Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 72 | ops: thermal cooling devices call-backs. |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 73 | .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 | |
| 77 | 1.2.2 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 | |
| 83 | 1.3 interface for binding a thermal zone device with a thermal cooling device |
| 84 | 1.3.1 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 | |
| 95 | 1.3.2 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 | |
| 106 | 2. sysfs attributes structure |
| 107 | |
| 108 | RO read only value |
| 109 | RW read/write value |
| 110 | |
| 111 | All thermal sysfs attributes will be represented under /sys/class/thermal |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 112 | |
| 113 | Thermal 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 | |
| 121 | Thermal 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 | |
| 128 | These two dynamic attributes are created/removed in pairs. |
| 129 | They represent the relationship between a thermal zone and its associated cooling device. |
| 130 | They are created/removed for each |
Len Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 131 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution. |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 132 | |
| 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 | |
| 142 | type 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, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 146 | Required |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 147 | |
| 148 | temp Current temperature as reported by thermal zone (sensor) |
Zhang, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 149 | Unit: millidegree Celsius |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 150 | RO |
| 151 | Required |
| 152 | |
Len Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 153 | mode One of the predefined values in [kernel, user] |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 154 | 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 | |
| 165 | trip_point_[0-*]_temp The temperature above which trip point will be fired |
Zhang, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 166 | Unit: millidegree Celsius |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 167 | RO |
| 168 | Optional |
| 169 | |
| 170 | trip_point_[0-*]_type Strings which indicate the type of the trip point |
Len Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 171 | E.g. it can be one of critical, hot, passive, |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 172 | active[0-*] for ACPI thermal zone. |
| 173 | RO |
| 174 | Optional |
| 175 | |
| 176 | cdev[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 Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 181 | cdev[0-*]_trip_point The trip point with which cdev[0-*] is associated in this thermal zone |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 182 | -1 means the cooling device is not associated with any trip point. |
| 183 | RO |
| 184 | Optional |
| 185 | |
| 186 | ****************************** |
| 187 | * Cooling device attributes * |
| 188 | ****************************** |
| 189 | |
| 190 | type 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, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 196 | Required |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 197 | |
| 198 | max_state The maximum permissible cooling state of this cooling device. |
| 199 | RO |
| 200 | Required |
| 201 | |
| 202 | cur_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 | |
| 209 | 3. A simple implementation |
| 210 | |
| 211 | ACPI thermal zone may support multiple trip points like critical/hot/passive/active. |
| 212 | If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time, |
Len Brown | 543a956 | 2008-02-07 16:55:08 -0500 | [diff] [blame] | 213 | it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all. |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 214 | It has one processor and one fan, which are both registered as thermal_cooling_device. |
| 215 | If the processor is listed in _PSL method, and the fan is listed in _AL0 method, |
| 216 | the sys I/F structure will be built like this: |
| 217 | |
| 218 | /sys/class/thermal: |
| 219 | |
| 220 | |thermal_zone1: |
| 221 | |-----type: ACPI thermal zone |
Zhang, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 222 | |-----temp: 37000 |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 223 | |-----mode: kernel |
Zhang, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 224 | |-----trip_point_0_temp: 100000 |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 225 | |-----trip_point_0_type: critical |
Zhang, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 226 | |-----trip_point_1_temp: 80000 |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 227 | |-----trip_point_1_type: passive |
Zhang, Rui | 3152fb9 | 2008-02-27 08:37:50 +0800 | [diff] [blame] | 228 | |-----trip_point_2_temp: 70000 |
| 229 | |-----trip_point_2_type: active0 |
| 230 | |-----trip_point_3_temp: 60000 |
| 231 | |-----trip_point_3_type: active1 |
Zhang Rui | 203d3d4 | 2008-01-17 15:51:08 +0800 | [diff] [blame] | 232 | |-----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 |