1Generic 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 17This how-to focuses on enabling new thermal zone and cooling devices to participate 18in 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 44 ops: thermal zone device call-backs. 45 .bind: bind the thermal zone device with a thermal cooling device. 46 .unbind: unbind the thermal zone device with a thermal cooling device. 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. 56 571.1.2 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. 72 ops: thermal cooling devices call-backs. 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. 76 771.2.2 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 111Thermal sysfs attributes will be represented under /sys/class/thermal. 112Hwmon sysfs I/F extension is also available under /sys/class/hwmon 113if hwmon is compiled in or built as a module. 114 115Thermal zone device sys I/F, created once it's registered: 116/sys/class/thermal/thermal_zone[0-*]: 117 |-----type: Type of the thermal zone 118 |-----temp: Current temperature 119 |-----mode: Working mode of the thermal zone 120 |-----trip_point_[0-*]_temp: Trip point temperature 121 |-----trip_point_[0-*]_type: Trip point type 122 123Thermal cooling device sys I/F, created once it's registered: 124/sys/class/thermal/cooling_device[0-*]: 125 |-----type : Type of the cooling device(processor/fan/...) 126 |-----max_state: Maximum cooling state of the cooling device 127 |-----cur_state: Current cooling state of the cooling device 128 129 130These two dynamic attributes are created/removed in pairs. 131They represent the relationship between a thermal zone and its associated cooling device. 132They are created/removed for each 133thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution. 134 135/sys/class/thermal/thermal_zone[0-*] 136 |-----cdev[0-*]: The [0-*]th cooling device in the current thermal zone 137 |-----cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with 138 139Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, 140the generic thermal driver also creates a hwmon sysfs I/F for each _type_ of 141thermal zone device. E.g. the generic thermal driver registers one hwmon class device 142and build the associated hwmon sysfs I/F for all the registered ACPI thermal zones. 143/sys/class/hwmon/hwmon[0-*]: 144 |-----name: The type of the thermal zone devices. 145 |-----temp[1-*]_input: The current temperature of thermal zone [1-*]. 146 |-----temp[1-*]_critical: The critical trip point of thermal zone [1-*]. 147Please read Documentation/hwmon/sysfs-interface for additional information. 148 149*************************** 150* Thermal zone attributes * 151*************************** 152 153type Strings which represent the thermal zone type. 154 This is given by thermal zone driver as part of registration. 155 Eg: "acpitz" indicates it's an ACPI thermal device. 156 In order to keep it consistent with hwmon sys attribute, 157 this should be a short, lowercase string, 158 not containing spaces nor dashes. 159 RO 160 Required 161 162temp Current temperature as reported by thermal zone (sensor) 163 Unit: millidegree Celsius 164 RO 165 Required 166 167mode One of the predefined values in [kernel, user] 168 This file gives information about the algorithm 169 that is currently managing the thermal zone. 170 It can be either default kernel based algorithm 171 or user space application. 172 RW 173 Optional 174 kernel = Thermal management in kernel thermal zone driver. 175 user = Preventing kernel thermal zone driver actions upon 176 trip points so that user application can take full 177 charge of the thermal management. 178 179trip_point_[0-*]_temp The temperature above which trip point will be fired 180 Unit: millidegree Celsius 181 RO 182 Optional 183 184trip_point_[0-*]_type Strings which indicate the type of the trip point 185 E.g. it can be one of critical, hot, passive, 186 active[0-*] for ACPI thermal zone. 187 RO 188 Optional 189 190cdev[0-*] Sysfs link to the thermal cooling device node where the sys I/F 191 for cooling device throttling control represents. 192 RO 193 Optional 194 195cdev[0-*]_trip_point The trip point with which cdev[0-*] is associated in this thermal zone 196 -1 means the cooling device is not associated with any trip point. 197 RO 198 Optional 199 200****************************** 201* Cooling device attributes * 202****************************** 203 204type String which represents the type of device 205 eg: For generic ACPI: this should be "Fan", 206 "Processor" or "LCD" 207 eg. For memory controller device on intel_menlow platform: 208 this should be "Memory controller" 209 RO 210 Required 211 212max_state The maximum permissible cooling state of this cooling device. 213 RO 214 Required 215 216cur_state The current cooling state of this cooling device. 217 the value can any integer numbers between 0 and max_state, 218 cur_state == 0 means no cooling 219 cur_state == max_state means the maximum cooling. 220 RW 221 Required 222 2233. A simple implementation 224 225ACPI thermal zone may support multiple trip points like critical/hot/passive/active. 226If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time, 227it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all. 228It has one processor and one fan, which are both registered as thermal_cooling_device. 229If the processor is listed in _PSL method, and the fan is listed in _AL0 method, 230the sys I/F structure will be built like this: 231 232/sys/class/thermal: 233 234|thermal_zone1: 235 |-----type: acpitz 236 |-----temp: 37000 237 |-----mode: kernel 238 |-----trip_point_0_temp: 100000 239 |-----trip_point_0_type: critical 240 |-----trip_point_1_temp: 80000 241 |-----trip_point_1_type: passive 242 |-----trip_point_2_temp: 70000 243 |-----trip_point_2_type: active0 244 |-----trip_point_3_temp: 60000 245 |-----trip_point_3_type: active1 246 |-----cdev0: --->/sys/class/thermal/cooling_device0 247 |-----cdev0_trip_point: 1 /* cdev0 can be used for passive */ 248 |-----cdev1: --->/sys/class/thermal/cooling_device3 249 |-----cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ 250 251|cooling_device0: 252 |-----type: Processor 253 |-----max_state: 8 254 |-----cur_state: 0 255 256|cooling_device3: 257 |-----type: Fan 258 |-----max_state: 2 259 |-----cur_state: 0 260 261/sys/class/hwmon: 262 263|hwmon0: 264 |-----name: acpitz 265 |-----temp1_input: 37000 266 |-----temp1_crit: 100000 267