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diff --git a/kernel/Documentation/thermal/sysfs-api.txt b/kernel/Documentation/thermal/sysfs-api.txt new file mode 100644 index 000000000..87519cb37 --- /dev/null +++ b/kernel/Documentation/thermal/sysfs-api.txt @@ -0,0 +1,401 @@ +Generic Thermal Sysfs driver How To +=================================== + +Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com> + +Updated: 2 January 2008 + +Copyright (c) 2008 Intel Corporation + + +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 + +1. thermal sysfs driver interface functions + +1.1 thermal zone device interface +1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *type, + int trips, int mask, void *devdata, + struct thermal_zone_device_ops *ops, + const struct thermal_zone_params *tzp, + int passive_delay, int polling_delay)) + + 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. + + type: the thermal zone type. + trips: the total number of trip points this thermal zone supports. + mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable. + 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 (enabled/disabled) of the thermal zone. + - "enabled" means the kernel thermal management is enabled. + - "disabled" will prevent kernel thermal driver action upon trip points + so that user applications can take charge of thermal management. + .set_mode: set the mode (enabled/disabled) 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. + .set_emul_temp: set the emulation temperature which helps in debugging + different threshold temperature points. + tzp: thermal zone platform parameters. + passive_delay: number of milliseconds to wait between polls when + performing passive cooling. + polling_delay: number of milliseconds to wait between polls when checking + whether trip points have been crossed (0 for interrupt driven systems). + + +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) + + 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, + unsigned long upper, unsigned long lower); + + 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. + upper:the Maximum cooling state for this trip point. + THERMAL_NO_LIMIT means no upper limit, + and the cooling device can be in max_state. + lower:the Minimum cooling state can be used for this trip point. + THERMAL_NO_LIMIT means no lower limit, + and the cooling device can be in cooling state 0. + +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. + +1.4 Thermal Zone Parameters +1.4.1 struct thermal_bind_params + This structure defines the following parameters that are used to bind + a zone with a cooling device for a particular trip point. + .cdev: The cooling device pointer + .weight: The 'influence' of a particular cooling device on this zone. + This is on a percentage scale. The sum of all these weights + (for a particular zone) cannot exceed 100. + .trip_mask:This is a bit mask that gives the binding relation between + this thermal zone and cdev, for a particular trip point. + If nth bit is set, then the cdev and thermal zone are bound + for trip point n. + .limits: This is an array of cooling state limits. Must have exactly + 2 * thermal_zone.number_of_trip_points. It is an array consisting + of tuples <lower-state upper-state> of state limits. Each trip + will be associated with one state limit tuple when binding. + A NULL pointer means <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> + on all trips. These limits are used when binding a cdev to a + trip point. + .match: This call back returns success(0) if the 'tz and cdev' need to + be bound, as per platform data. +1.4.2 struct thermal_zone_params + This structure defines the platform level parameters for a thermal zone. + This data, for each thermal zone should come from the platform layer. + This is an optional feature where some platforms can choose not to + provide this data. + .governor_name: Name of the thermal governor used for this zone + .no_hwmon: a boolean to indicate if the thermal to hwmon sysfs interface + is required. when no_hwmon == false, a hwmon sysfs interface + will be created. when no_hwmon == true, nothing will be done. + In case the thermal_zone_params is NULL, the hwmon interface + will be created (for backward compatibility). + .num_tbps: Number of thermal_bind_params entries for this zone + .tbp: thermal_bind_params entries + +2. sysfs attributes structure + +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 + |---policy: Thermal governor used for this zone + |---trip_point_[0-*]_temp: Trip point temperature + |---trip_point_[0-*]_type: Trip point type + |---trip_point_[0-*]_hyst: Hysteresis value for this trip point + |---emul_temp: Emulated temperature set node + +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 + + +Then next 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 successful execution of +thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. + +/sys/class/thermal/thermal_zone[0-*]: + |---cdev[0-*]: [0-*]th cooling device in 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. + E.g: "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 [enabled, disabled]. + 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. + enabled = enable Kernel Thermal management. + disabled = Preventing kernel thermal zone driver actions upon + trip points so that user application can take full + charge of the thermal management. + RW, Optional + +policy + One of the various thermal governors used for a particular zone. + RW, Required + +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 + +trip_point_[0-*]_hyst + The hysteresis value for a trip point, represented as an integer + Unit: Celsius + RW, 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 + +passive + Attribute is only present for zones in which the passive cooling + policy is not supported by native thermal driver. Default is zero + and can be set to a temperature (in millidegrees) to enable a + passive trip point for the zone. Activation is done by polling with + an interval of 1 second. + Unit: millidegrees Celsius + Valid values: 0 (disabled) or greater than 1000 + RW, Optional + +emul_temp + Interface to set the emulated temperature method in thermal zone + (sensor). After setting this temperature, the thermal zone may pass + this temperature to platform emulation function if registered or + cache it locally. This is useful in debugging different temperature + threshold and its associated cooling action. This is write only node + and writing 0 on this node should disable emulation. + Unit: millidegree Celsius + WO, Optional + + WARNING: Be careful while enabling this option on production systems, + because userland can easily disable the thermal policy by simply + flooding this sysfs node with low temperature values. + +***************************** +* Cooling device attributes * +***************************** + +type + String which represents the type of device, e.g: + - for generic ACPI: should be "Fan", "Processor" or "LCD" + - for memory controller device on intel_menlow platform: + 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 + +3. A simple implementation + +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: enabled + |---policy: step_wise + |---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 + +/sys/class/hwmon: + +|hwmon0: + |---name: acpitz + |---temp1_input: 37000 + |---temp1_crit: 100000 + +4. Event Notification + +The framework includes a simple notification mechanism, in the form of a +netlink event. Netlink socket initialization is done during the _init_ +of the framework. Drivers which intend to use the notification mechanism +just need to call thermal_generate_netlink_event() with two arguments viz +(originator, event). The originator is a pointer to struct thermal_zone_device +from where the event has been originated. An integer which represents the +thermal zone device will be used in the message to identify the zone. The +event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, +THERMAL_DEV_FAULT}. Notification can be sent when the current temperature +crosses any of the configured thresholds. + +5. Export Symbol APIs: + +5.1: get_tz_trend: +This function returns the trend of a thermal zone, i.e the rate of change +of temperature of the thermal zone. Ideally, the thermal sensor drivers +are supposed to implement the callback. If they don't, the thermal +framework calculated the trend by comparing the previous and the current +temperature values. + +5.2:get_thermal_instance: +This function returns the thermal_instance corresponding to a given +{thermal_zone, cooling_device, trip_point} combination. Returns NULL +if such an instance does not exist. + +5.3:thermal_notify_framework: +This function handles the trip events from sensor drivers. It starts +throttling the cooling devices according to the policy configured. +For CRITICAL and HOT trip points, this notifies the respective drivers, +and does actual throttling for other trip points i.e ACTIVE and PASSIVE. +The throttling policy is based on the configured platform data; if no +platform data is provided, this uses the step_wise throttling policy. + +5.4:thermal_cdev_update: +This function serves as an arbitrator to set the state of a cooling +device. It sets the cooling device to the deepest cooling state if +possible. |