bcdcbbc711
The fair share governor has the concept of weights, which is the influence of each cooling device in a thermal zone. The current implementation forces the weights of all cooling devices in a thermal zone to add up to a 100. This complicates setups, as you need to know in advance how many cooling devices you are going to have. If you bind a new cooling device, you have to modify all the other cooling devices weights, which is error prone. Furthermore, you can't specify a "default" weight for platforms since that default value depends on the number of cooling devices in the platform. This patch generalizes the concept of weight by allowing any number to be a "weight". Weights are now relative to each other. Platforms that don't specify weights get the same default value for all their cooling devices, so all their cdevs are considered to be equally influential. It's important to note that previous users of the weights don't need to alter the code: percentages continue to work as they used to. This patch just removes the constraint of all the weights in a thermal zone having to add up to a 100. If they do, you get the same behavior as before. If they don't, fair share now works for that platform. Cc: Zhang Rui <rui.zhang@intel.com> Cc: Eduardo Valentin <edubezval@gmail.com> Cc: Durgadoss R <durgadoss.r@intel.com> Acked-by: Durgadoss R <durgadoss.r@intel.com> Signed-off-by: Javi Merino <javi.merino@arm.com> Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
423 lines
17 KiB
Plaintext
423 lines
17 KiB
Plaintext
Generic Thermal Sysfs driver How To
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===================================
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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
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The generic thermal sysfs provides a set of interfaces for thermal zone
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devices (sensors) and thermal cooling devices (fan, processor...) to register
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with the thermal management solution and to be a part of it.
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This how-to focuses on enabling new thermal zone and cooling devices to
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participate in thermal management.
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This solution is platform independent and any type of thermal zone devices
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and cooling devices should be able to make use of the infrastructure.
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The main task of the thermal sysfs driver is to expose thermal zone attributes
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as well as cooling device attributes to the user space.
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An intelligent thermal management application can make decisions based on
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inputs from thermal zone attributes (the current temperature and trip point
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temperature) and throttle appropriate devices.
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[0-*] denotes any positive number starting from 0
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[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
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1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *type,
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int trips, int mask, void *devdata,
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struct thermal_zone_device_ops *ops,
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const struct thermal_zone_params *tzp,
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int passive_delay, int polling_delay))
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This interface function adds a new thermal zone device (sensor) to
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/sys/class/thermal folder as thermal_zone[0-*]. It tries to bind all the
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thermal cooling devices registered at the same time.
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type: the thermal zone type.
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trips: the total number of trip points this thermal zone supports.
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mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable.
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devdata: device private data
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ops: thermal zone device call-backs.
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.bind: bind the thermal zone device with a thermal cooling device.
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.unbind: unbind the thermal zone device with a thermal cooling device.
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.get_temp: get the current temperature of the thermal zone.
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.get_mode: get the current mode (enabled/disabled) of the thermal zone.
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- "enabled" means the kernel thermal management is enabled.
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- "disabled" will prevent kernel thermal driver action upon trip points
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so that user applications can take charge of thermal management.
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.set_mode: set the mode (enabled/disabled) of the thermal zone.
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.get_trip_type: get the type of certain trip point.
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.get_trip_temp: get the temperature above which the certain trip point
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will be fired.
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.set_emul_temp: set the emulation temperature which helps in debugging
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different threshold temperature points.
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tzp: thermal zone platform parameters.
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passive_delay: number of milliseconds to wait between polls when
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performing passive cooling.
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polling_delay: number of milliseconds to wait between polls when checking
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whether trip points have been crossed (0 for interrupt driven systems).
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1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz)
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This interface function removes the thermal zone device.
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It deletes the corresponding entry form /sys/class/thermal folder and
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unbind all the thermal cooling devices it uses.
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1.2 thermal cooling device interface
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1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name,
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void *devdata, struct thermal_cooling_device_ops *)
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This interface function adds a new thermal cooling device (fan/processor/...)
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to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself
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to all the thermal zone devices register at the same time.
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name: the cooling device name.
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devdata: device private data.
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ops: thermal cooling devices call-backs.
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.get_max_state: get the Maximum throttle state of the cooling device.
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.get_cur_state: get the Current throttle state of the cooling device.
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.set_cur_state: set the Current throttle state of the cooling device.
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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.
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It deletes the corresponding entry form /sys/class/thermal folder and
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unbind itself from all the thermal zone devices using it.
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1.3 interface for binding a thermal zone device with a thermal cooling device
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1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
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int trip, struct thermal_cooling_device *cdev,
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unsigned long upper, unsigned long lower, unsigned int weight);
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This interface function bind a thermal cooling device to the certain trip
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point of a thermal zone device.
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This function is usually called in the thermal zone device .bind callback.
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tz: the thermal zone device
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cdev: thermal cooling device
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trip: indicates which trip point the cooling devices is associated with
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in this thermal zone.
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upper:the Maximum cooling state for this trip point.
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THERMAL_NO_LIMIT means no upper limit,
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and the cooling device can be in max_state.
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lower:the Minimum cooling state can be used for this trip point.
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THERMAL_NO_LIMIT means no lower limit,
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and the cooling device can be in cooling state 0.
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weight: the influence of this cooling device in this thermal
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zone. See 1.4.1 below for more information.
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1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
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int trip, struct thermal_cooling_device *cdev);
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This interface function unbind a thermal cooling device from the certain
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trip point of a thermal zone device. This function is usually called in
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the thermal zone device .unbind callback.
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tz: the thermal zone device
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cdev: thermal cooling device
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trip: indicates which trip point the cooling devices is associated with
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in this thermal zone.
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1.4 Thermal Zone Parameters
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1.4.1 struct thermal_bind_params
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This structure defines the following parameters that are used to bind
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a zone with a cooling device for a particular trip point.
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.cdev: The cooling device pointer
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.weight: The 'influence' of a particular cooling device on this
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zone. This is relative to the rest of the cooling
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devices. For example, if all cooling devices have a
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weight of 1, then they all contribute the same. You can
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use percentages if you want, but it's not mandatory. A
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weight of 0 means that this cooling device doesn't
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contribute to the cooling of this zone unless all cooling
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devices have a weight of 0. If all weights are 0, then
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they all contribute the same.
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.trip_mask:This is a bit mask that gives the binding relation between
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this thermal zone and cdev, for a particular trip point.
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If nth bit is set, then the cdev and thermal zone are bound
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for trip point n.
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.limits: This is an array of cooling state limits. Must have exactly
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2 * thermal_zone.number_of_trip_points. It is an array consisting
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of tuples <lower-state upper-state> of state limits. Each trip
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will be associated with one state limit tuple when binding.
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A NULL pointer means <THERMAL_NO_LIMITS THERMAL_NO_LIMITS>
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on all trips. These limits are used when binding a cdev to a
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trip point.
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.match: This call back returns success(0) if the 'tz and cdev' need to
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be bound, as per platform data.
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1.4.2 struct thermal_zone_params
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This structure defines the platform level parameters for a thermal zone.
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This data, for each thermal zone should come from the platform layer.
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This is an optional feature where some platforms can choose not to
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provide this data.
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.governor_name: Name of the thermal governor used for this zone
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.no_hwmon: a boolean to indicate if the thermal to hwmon sysfs interface
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is required. when no_hwmon == false, a hwmon sysfs interface
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will be created. when no_hwmon == true, nothing will be done.
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In case the thermal_zone_params is NULL, the hwmon interface
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will be created (for backward compatibility).
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.num_tbps: Number of thermal_bind_params entries for this zone
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.tbp: thermal_bind_params entries
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2. sysfs attributes structure
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RO read only value
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RW read/write value
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Thermal sysfs attributes will be represented under /sys/class/thermal.
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Hwmon sysfs I/F extension is also available under /sys/class/hwmon
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if hwmon is compiled in or built as a module.
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Thermal zone device sys I/F, created once it's registered:
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/sys/class/thermal/thermal_zone[0-*]:
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|---type: Type of the thermal zone
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|---temp: Current temperature
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|---mode: Working mode of the thermal zone
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|---policy: Thermal governor used for this zone
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|---trip_point_[0-*]_temp: Trip point temperature
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|---trip_point_[0-*]_type: Trip point type
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|---trip_point_[0-*]_hyst: Hysteresis value for this trip point
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|---emul_temp: Emulated temperature set node
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Thermal cooling device sys I/F, created once it's registered:
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/sys/class/thermal/cooling_device[0-*]:
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|---type: Type of the cooling device(processor/fan/...)
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|---max_state: Maximum cooling state of the cooling device
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|---cur_state: Current cooling state of the cooling device
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Then next two dynamic attributes are created/removed in pairs. They represent
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the relationship between a thermal zone and its associated cooling device.
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They are created/removed for each successful execution of
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thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device.
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/sys/class/thermal/thermal_zone[0-*]:
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|---cdev[0-*]: [0-*]th cooling device in current thermal zone
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|---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with
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|---cdev[0-*]_weight: Influence of the cooling device in
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this thermal zone
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Besides the thermal zone device sysfs I/F and cooling device sysfs I/F,
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the generic thermal driver also creates a hwmon sysfs I/F for each _type_
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of thermal zone device. E.g. the generic thermal driver registers one hwmon
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class device and build the associated hwmon sysfs I/F for all the registered
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ACPI thermal zones.
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/sys/class/hwmon/hwmon[0-*]:
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|---name: The type of the thermal zone devices
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|---temp[1-*]_input: The current temperature of thermal zone [1-*]
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|---temp[1-*]_critical: The critical trip point of thermal zone [1-*]
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Please read Documentation/hwmon/sysfs-interface for additional information.
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***************************
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* Thermal zone attributes *
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***************************
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type
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Strings which represent the thermal zone type.
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This is given by thermal zone driver as part of registration.
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E.g: "acpitz" indicates it's an ACPI thermal device.
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In order to keep it consistent with hwmon sys attribute; this should
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be a short, lowercase string, not containing spaces nor dashes.
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RO, Required
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temp
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Current temperature as reported by thermal zone (sensor).
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Unit: millidegree Celsius
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RO, Required
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mode
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One of the predefined values in [enabled, disabled].
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This file gives information about the algorithm that is currently
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managing the thermal zone. It can be either default kernel based
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algorithm or user space application.
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enabled = enable Kernel Thermal management.
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disabled = Preventing kernel thermal zone driver actions upon
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trip points so that user application can take full
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charge of the thermal management.
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RW, Optional
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policy
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One of the various thermal governors used for a particular zone.
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RW, Required
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trip_point_[0-*]_temp
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The temperature above which trip point will be fired.
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Unit: millidegree Celsius
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RO, Optional
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trip_point_[0-*]_type
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Strings which indicate the type of the trip point.
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E.g. it can be one of critical, hot, passive, active[0-*] for ACPI
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thermal zone.
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RO, Optional
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trip_point_[0-*]_hyst
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The hysteresis value for a trip point, represented as an integer
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Unit: Celsius
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RW, Optional
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cdev[0-*]
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Sysfs link to the thermal cooling device node where the sys I/F
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for cooling device throttling control represents.
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RO, Optional
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cdev[0-*]_trip_point
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The trip point with which cdev[0-*] is associated in this thermal
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zone; -1 means the cooling device is not associated with any trip
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point.
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RO, Optional
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cdev[0-*]_weight
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The influence of cdev[0-*] in this thermal zone. This value
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is relative to the rest of cooling devices in the thermal
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zone. For example, if a cooling device has a weight double
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than that of other, it's twice as effective in cooling the
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thermal zone.
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RW, Optional
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passive
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Attribute is only present for zones in which the passive cooling
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policy is not supported by native thermal driver. Default is zero
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and can be set to a temperature (in millidegrees) to enable a
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passive trip point for the zone. Activation is done by polling with
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an interval of 1 second.
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Unit: millidegrees Celsius
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Valid values: 0 (disabled) or greater than 1000
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RW, Optional
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emul_temp
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Interface to set the emulated temperature method in thermal zone
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(sensor). After setting this temperature, the thermal zone may pass
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this temperature to platform emulation function if registered or
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cache it locally. This is useful in debugging different temperature
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threshold and its associated cooling action. This is write only node
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and writing 0 on this node should disable emulation.
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Unit: millidegree Celsius
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WO, Optional
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WARNING: Be careful while enabling this option on production systems,
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because userland can easily disable the thermal policy by simply
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flooding this sysfs node with low temperature values.
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*****************************
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* Cooling device attributes *
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*****************************
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type
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String which represents the type of device, e.g:
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- for generic ACPI: should be "Fan", "Processor" or "LCD"
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- for memory controller device on intel_menlow platform:
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should be "Memory controller".
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RO, Required
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max_state
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The maximum permissible cooling state of this cooling device.
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RO, Required
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cur_state
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The current cooling state of this cooling device.
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The value can any integer numbers between 0 and max_state:
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- cur_state == 0 means no cooling
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- cur_state == max_state means the maximum cooling.
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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,
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passive, active. If an ACPI thermal zone supports critical, passive,
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active[0] and active[1] at the same time, it may register itself as a
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thermal_zone_device (thermal_zone1) with 4 trip points in all.
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It has one processor and one fan, which are both registered as
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thermal_cooling_device. Both are considered to have the same
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effectiveness in cooling the thermal zone.
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If the processor is listed in _PSL method, and the fan is listed in _AL0
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method, the sys I/F structure will be built like this:
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/sys/class/thermal:
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|thermal_zone1:
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|---type: acpitz
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|---temp: 37000
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|---mode: enabled
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|---policy: step_wise
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|---trip_point_0_temp: 100000
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|---trip_point_0_type: critical
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|---trip_point_1_temp: 80000
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|---trip_point_1_type: passive
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|---trip_point_2_temp: 70000
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|---trip_point_2_type: active0
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|---trip_point_3_temp: 60000
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|---trip_point_3_type: active1
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|---cdev0: --->/sys/class/thermal/cooling_device0
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|---cdev0_trip_point: 1 /* cdev0 can be used for passive */
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|---cdev0_weight: 1024
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|---cdev1: --->/sys/class/thermal/cooling_device3
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|---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
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|---cdev1_weight: 1024
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|cooling_device0:
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|---type: Processor
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|---max_state: 8
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|---cur_state: 0
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|cooling_device3:
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|---type: Fan
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|---max_state: 2
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|---cur_state: 0
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/sys/class/hwmon:
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|hwmon0:
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|---name: acpitz
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|---temp1_input: 37000
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|---temp1_crit: 100000
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4. Event Notification
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The framework includes a simple notification mechanism, in the form of a
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netlink event. Netlink socket initialization is done during the _init_
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of the framework. Drivers which intend to use the notification mechanism
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just need to call thermal_generate_netlink_event() with two arguments viz
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(originator, event). The originator is a pointer to struct thermal_zone_device
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from where the event has been originated. An integer which represents the
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thermal zone device will be used in the message to identify the zone. The
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event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL,
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THERMAL_DEV_FAULT}. Notification can be sent when the current temperature
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crosses any of the configured thresholds.
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5. Export Symbol APIs:
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5.1: get_tz_trend:
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This function returns the trend of a thermal zone, i.e the rate of change
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of temperature of the thermal zone. Ideally, the thermal sensor drivers
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are supposed to implement the callback. If they don't, the thermal
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framework calculated the trend by comparing the previous and the current
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temperature values.
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5.2:get_thermal_instance:
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This function returns the thermal_instance corresponding to a given
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{thermal_zone, cooling_device, trip_point} combination. Returns NULL
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if such an instance does not exist.
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5.3:thermal_notify_framework:
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This function handles the trip events from sensor drivers. It starts
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throttling the cooling devices according to the policy configured.
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For CRITICAL and HOT trip points, this notifies the respective drivers,
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and does actual throttling for other trip points i.e ACTIVE and PASSIVE.
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The throttling policy is based on the configured platform data; if no
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platform data is provided, this uses the step_wise throttling policy.
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5.4:thermal_cdev_update:
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This function serves as an arbitrator to set the state of a cooling
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device. It sets the cooling device to the deepest cooling state if
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possible.
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