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 14devices (sensors) and thermal cooling devices (fan, processor...) to register 15with the thermal management solution and to be a part of it. 16 17This 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. 21 22The 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. 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, 35 int trips, 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-*]. It tries to bind all the 39 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 61 unbind all 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/...) 68 to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself 69 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 81 unbind 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 88 point 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 99 trip point of a thermal zone device. This function is usually called in 100 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 130Then next two dynamic attributes are created/removed in pairs. They represent 131the relationship between a thermal zone and its associated cooling device. 132They are created/removed for each successful execution of 133thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. 134 135/sys/class/thermal/thermal_zone[0-*]: 136 |---cdev[0-*]: [0-*]th cooling device in 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_ 141of thermal zone device. E.g. the generic thermal driver registers one hwmon 142class device and build the associated hwmon sysfs I/F for all the registered 143ACPI thermal zones. 144 145/sys/class/hwmon/hwmon[0-*]: 146 |---name: The type of the thermal zone devices 147 |---temp[1-*]_input: The current temperature of thermal zone [1-*] 148 |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] 149 150Please read Documentation/hwmon/sysfs-interface for additional information. 151 152*************************** 153* Thermal zone attributes * 154*************************** 155 156type 157 Strings which represent the thermal zone type. 158 This is given by thermal zone driver as part of registration. 159 E.g: "acpitz" indicates it's an ACPI thermal device. 160 In order to keep it consistent with hwmon sys attribute; this should 161 be a short, lowercase string, not containing spaces nor dashes. 162 RO, Required 163 164temp 165 Current temperature as reported by thermal zone (sensor). 166 Unit: millidegree Celsius 167 RO, Required 168 169mode 170 One of the predefined values in [kernel, user]. 171 This file gives information about the algorithm that is currently 172 managing the thermal zone. It can be either default kernel based 173 algorithm or user space application. 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 RW, Optional 179 180trip_point_[0-*]_temp 181 The temperature above which trip point will be fired. 182 Unit: millidegree Celsius 183 RO, Optional 184 185trip_point_[0-*]_type 186 Strings which indicate the type of the trip point. 187 E.g. it can be one of critical, hot, passive, active[0-*] for ACPI 188 thermal zone. 189 RO, Optional 190 191cdev[0-*] 192 Sysfs link to the thermal cooling device node where the sys I/F 193 for cooling device throttling control represents. 194 RO, Optional 195 196cdev[0-*]_trip_point 197 The trip point with which cdev[0-*] is associated in this thermal 198 zone; -1 means the cooling device is not associated with any trip 199 point. 200 RO, Optional 201 202passive 203 Attribute is only present for zones in which the passive cooling 204 policy is not supported by native thermal driver. Default is zero 205 and can be set to a temperature (in millidegrees) to enable a 206 passive trip point for the zone. Activation is done by polling with 207 an interval of 1 second. 208 Unit: millidegrees Celsius 209 Valid values: 0 (disabled) or greater than 1000 210 RW, Optional 211 212***************************** 213* Cooling device attributes * 214***************************** 215 216type 217 String which represents the type of device, e.g: 218 - for generic ACPI: should be "Fan", "Processor" or "LCD" 219 - for memory controller device on intel_menlow platform: 220 should be "Memory controller". 221 RO, Required 222 223max_state 224 The maximum permissible cooling state of this cooling device. 225 RO, Required 226 227cur_state 228 The current cooling state of this cooling device. 229 The value can any integer numbers between 0 and max_state: 230 - cur_state == 0 means no cooling 231 - cur_state == max_state means the maximum cooling. 232 RW, Required 233 2343. A simple implementation 235 236ACPI thermal zone may support multiple trip points like critical, hot, 237passive, active. If an ACPI thermal zone supports critical, passive, 238active[0] and active[1] at the same time, it may register itself as a 239thermal_zone_device (thermal_zone1) with 4 trip points in all. 240It has one processor and one fan, which are both registered as 241thermal_cooling_device. 242 243If the processor is listed in _PSL method, and the fan is listed in _AL0 244method, the sys I/F structure will be built like this: 245 246/sys/class/thermal: 247 248|thermal_zone1: 249 |---type: acpitz 250 |---temp: 37000 251 |---mode: kernel 252 |---trip_point_0_temp: 100000 253 |---trip_point_0_type: critical 254 |---trip_point_1_temp: 80000 255 |---trip_point_1_type: passive 256 |---trip_point_2_temp: 70000 257 |---trip_point_2_type: active0 258 |---trip_point_3_temp: 60000 259 |---trip_point_3_type: active1 260 |---cdev0: --->/sys/class/thermal/cooling_device0 261 |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ 262 |---cdev1: --->/sys/class/thermal/cooling_device3 263 |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ 264 265|cooling_device0: 266 |---type: Processor 267 |---max_state: 8 268 |---cur_state: 0 269 270|cooling_device3: 271 |---type: Fan 272 |---max_state: 2 273 |---cur_state: 0 274 275/sys/class/hwmon: 276 277|hwmon0: 278 |---name: acpitz 279 |---temp1_input: 37000 280 |---temp1_crit: 100000 281 2824. Event Notification 283 284The framework includes a simple notification mechanism, in the form of a 285netlink event. Netlink socket initialization is done during the _init_ 286of the framework. Drivers which intend to use the notification mechanism 287just need to call thermal_generate_netlink_event() with two arguments viz 288(originator, event). Typically the originator will be an integer assigned 289to a thermal_zone_device when it registers itself with the framework. The 290event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, 291THERMAL_DEV_FAULT}. Notification can be sent when the current temperature 292crosses any of the configured thresholds. 293