| Generic Thermal Sysfs driver How To |
| ========================= |
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| Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com> |
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| Updated: 2 January 2008 |
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| Copyright (c) 2008 Intel Corporation |
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| 0. Introduction |
| |
| The generic thermal sysfs provides a set of interfaces for thermal zone devices (sensors) |
| and thermal cooling devices (fan, processor...) to register with the thermal management |
| solution and to be a part of it. |
| |
| This how-to focuses on enabling new thermal zone and cooling devices to participate |
| in thermal management. |
| This solution is platform independent and any type of thermal zone devices and |
| cooling devices should be able to make use of the infrastructure. |
| |
| The main task of the thermal sysfs driver is to expose thermal zone attributes as well |
| as cooling device attributes to the user space. |
| An intelligent thermal management application can make decisions based on inputs |
| from thermal zone attributes (the current temperature and trip point temperature) |
| and throttle appropriate devices. |
| |
| [0-*] denotes any positive number starting from 0 |
| [1-*] denotes any positive number starting from 1 |
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| 1. thermal sysfs driver interface functions |
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| 1.1 thermal zone device interface |
| 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, int trips, |
| void *devdata, struct thermal_zone_device_ops *ops) |
| |
| This interface function adds a new thermal zone device (sensor) to |
| /sys/class/thermal folder as thermal_zone[0-*]. |
| It tries to bind all the thermal cooling devices registered at the same time. |
| |
| name: the thermal zone name. |
| trips: the total number of trip points this thermal zone supports. |
| devdata: device private data |
| ops: thermal zone device call-backs. |
| .bind: bind the thermal zone device with a thermal cooling device. |
| .unbind: unbind the thermal zone device with a thermal cooling device. |
| .get_temp: get the current temperature of the thermal zone. |
| .get_mode: get the current mode (user/kernel) of the thermal zone. |
| "kernel" means thermal management is done in kernel. |
| "user" will prevent kernel thermal driver actions upon trip points |
| so that user applications can take charge of thermal management. |
| .set_mode: set the mode (user/kernel) of the thermal zone. |
| .get_trip_type: get the type of certain trip point. |
| .get_trip_temp: get the temperature above which the certain trip point |
| will be fired. |
| |
| 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) |
| |
| This interface function removes the thermal zone device. |
| It deletes the corresponding entry form /sys/class/thermal folder and unbind all |
| the thermal cooling devices it uses. |
| |
| 1.2 thermal cooling device interface |
| 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, |
| void *devdata, struct thermal_cooling_device_ops *) |
| |
| This interface function adds a new thermal cooling device (fan/processor/...) to |
| /sys/class/thermal/ folder as cooling_device[0-*]. |
| It tries to bind itself to all the thermal zone devices register at the same time. |
| name: the cooling device name. |
| devdata: device private data. |
| ops: thermal cooling devices call-backs. |
| .get_max_state: get the Maximum throttle state of the cooling device. |
| .get_cur_state: get the Current throttle state of the cooling device. |
| .set_cur_state: set the Current throttle state of the cooling device. |
| |
| 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) |
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| This interface function remove the thermal cooling device. |
| It deletes the corresponding entry form /sys/class/thermal folder and unbind |
| itself from all the thermal zone devices using it. |
| |
| 1.3 interface for binding a thermal zone device with a thermal cooling device |
| 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, |
| int trip, struct thermal_cooling_device *cdev); |
| |
| This interface function bind a thermal cooling device to the certain trip point |
| of a thermal zone device. |
| This function is usually called in the thermal zone device .bind callback. |
| tz: the thermal zone device |
| cdev: thermal cooling device |
| trip: indicates which trip point the cooling devices is associated with |
| in this thermal zone. |
| |
| 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, |
| int trip, struct thermal_cooling_device *cdev); |
| |
| This interface function unbind a thermal cooling device from the certain trip point |
| of a thermal zone device. |
| This function is usually called in the thermal zone device .unbind callback. |
| tz: the thermal zone device |
| cdev: thermal cooling device |
| trip: indicates which trip point the cooling devices is associated with |
| in this thermal zone. |
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| 2. sysfs attributes structure |
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| RO read only value |
| RW read/write value |
| |
| Thermal sysfs attributes will be represented under /sys/class/thermal. |
| Hwmon sysfs I/F extension is also available under /sys/class/hwmon |
| if hwmon is compiled in or built as a module. |
| |
| Thermal zone device sys I/F, created once it's registered: |
| /sys/class/thermal/thermal_zone[0-*]: |
| |-----type: Type of the thermal zone |
| |-----temp: Current temperature |
| |-----mode: Working mode of the thermal zone |
| |-----trip_point_[0-*]_temp: Trip point temperature |
| |-----trip_point_[0-*]_type: Trip point type |
| |
| Thermal cooling device sys I/F, created once it's registered: |
| /sys/class/thermal/cooling_device[0-*]: |
| |-----type : Type of the cooling device(processor/fan/...) |
| |-----max_state: Maximum cooling state of the cooling device |
| |-----cur_state: Current cooling state of the cooling device |
| |
| |
| These two dynamic attributes are created/removed in pairs. |
| They represent the relationship between a thermal zone and its associated cooling device. |
| They are created/removed for each |
| thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution. |
| |
| /sys/class/thermal/thermal_zone[0-*] |
| |-----cdev[0-*]: The [0-*]th cooling device in the current thermal zone |
| |-----cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with |
| |
| Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
| the generic thermal driver also creates a hwmon sysfs I/F for each _type_ of |
| thermal zone device. E.g. the generic thermal driver registers one hwmon class device |
| and build the associated hwmon sysfs I/F for all the registered ACPI thermal zones. |
| /sys/class/hwmon/hwmon[0-*]: |
| |-----name: The type of the thermal zone devices. |
| |-----temp[1-*]_input: The current temperature of thermal zone [1-*]. |
| |-----temp[1-*]_critical: The critical trip point of thermal zone [1-*]. |
| Please read Documentation/hwmon/sysfs-interface for additional information. |
| |
| *************************** |
| * Thermal zone attributes * |
| *************************** |
| |
| type Strings which represent the thermal zone type. |
| This is given by thermal zone driver as part of registration. |
| Eg: "acpitz" indicates it's an ACPI thermal device. |
| In order to keep it consistent with hwmon sys attribute, |
| this should be a short, lowercase string, |
| not containing spaces nor dashes. |
| RO |
| Required |
| |
| temp Current temperature as reported by thermal zone (sensor) |
| Unit: millidegree Celsius |
| RO |
| Required |
| |
| mode One of the predefined values in [kernel, user] |
| This file gives information about the algorithm |
| that is currently managing the thermal zone. |
| It can be either default kernel based algorithm |
| or user space application. |
| RW |
| Optional |
| kernel = Thermal management in kernel thermal zone driver. |
| user = Preventing kernel thermal zone driver actions upon |
| trip points so that user application can take full |
| charge of the thermal management. |
| |
| trip_point_[0-*]_temp The temperature above which trip point will be fired |
| Unit: millidegree Celsius |
| RO |
| Optional |
| |
| trip_point_[0-*]_type Strings which indicate the type of the trip point |
| E.g. it can be one of critical, hot, passive, |
| active[0-*] for ACPI thermal zone. |
| RO |
| Optional |
| |
| cdev[0-*] Sysfs link to the thermal cooling device node where the sys I/F |
| for cooling device throttling control represents. |
| RO |
| Optional |
| |
| cdev[0-*]_trip_point The trip point with which cdev[0-*] is associated in this thermal zone |
| -1 means the cooling device is not associated with any trip point. |
| RO |
| Optional |
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| ****************************** |
| * Cooling device attributes * |
| ****************************** |
| |
| type String which represents the type of device |
| eg: For generic ACPI: this should be "Fan", |
| "Processor" or "LCD" |
| eg. For memory controller device on intel_menlow platform: |
| this should be "Memory controller" |
| RO |
| Required |
| |
| max_state The maximum permissible cooling state of this cooling device. |
| RO |
| Required |
| |
| cur_state The current cooling state of this cooling device. |
| the value can any integer numbers between 0 and max_state, |
| cur_state == 0 means no cooling |
| cur_state == max_state means the maximum cooling. |
| RW |
| Required |
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| 3. A simple implementation |
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| ACPI thermal zone may support multiple trip points like critical/hot/passive/active. |
| If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time, |
| it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all. |
| It has one processor and one fan, which are both registered as thermal_cooling_device. |
| If the processor is listed in _PSL method, and the fan is listed in _AL0 method, |
| the sys I/F structure will be built like this: |
| |
| /sys/class/thermal: |
| |
| |thermal_zone1: |
| |-----type: acpitz |
| |-----temp: 37000 |
| |-----mode: kernel |
| |-----trip_point_0_temp: 100000 |
| |-----trip_point_0_type: critical |
| |-----trip_point_1_temp: 80000 |
| |-----trip_point_1_type: passive |
| |-----trip_point_2_temp: 70000 |
| |-----trip_point_2_type: active0 |
| |-----trip_point_3_temp: 60000 |
| |-----trip_point_3_type: active1 |
| |-----cdev0: --->/sys/class/thermal/cooling_device0 |
| |-----cdev0_trip_point: 1 /* cdev0 can be used for passive */ |
| |-----cdev1: --->/sys/class/thermal/cooling_device3 |
| |-----cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ |
| |
| |cooling_device0: |
| |-----type: Processor |
| |-----max_state: 8 |
| |-----cur_state: 0 |
| |
| |cooling_device3: |
| |-----type: Fan |
| |-----max_state: 2 |
| |-----cur_state: 0 |
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| /sys/class/hwmon: |
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| |hwmon0: |
| |-----name: acpitz |
| |-----temp1_input: 37000 |
| |-----temp1_crit: 100000 |