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1 Generic Thermal Sysfs driver How To
14 devices (sensors) and thermal cooling devices (fan, processor...) to register
15 with the thermal management solution and to be a part of it.
17 This how-to focuses on enabling new thermal zone and cooling devices to
20 and cooling devices should be able to make use of the infrastructure.
22 The main task of the thermal sysfs driver is to expose thermal zone attributes
23 as well as cooling device attributes to the user space.
25 inputs from thermal zone attributes (the current temperature and trip point
28 [0-*] denotes any positive number starting from 0
29 [1-*] denotes any positive number starting from 1
40 This interface function adds a new thermal zone device (sensor) to
41 /sys/class/thermal folder as thermal_zone[0-*]. It tries to bind all the
46 mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable.
48 ops: thermal zone device call-backs.
56 - "enabled" means the kernel thermal management is enabled.
57 - "disabled" will prevent kernel thermal driver action upon trip points
60 .get_trip_type: get the type of certain trip point.
61 .get_trip_temp: get the temperature above which the certain trip point
66 passive_delay: number of milliseconds to wait between polls when
68 polling_delay: number of milliseconds to wait between polls when checking
82 This interface adds a new sensor to a DT thermal zone.
84 device tree and look for the zone that refer to the sensor device
85 pointed by dev->of_node as temperature providers. For the zone
86 pointing to the sensor node, the sensor will be added to the DT
91 dev->of_node.
98 get_temp: a pointer to a function that reads the
101 set_trips: a pointer to a function that sets a
105 get_trend: a pointer to a function that reads the
107 set_emul_temp: a pointer to a function that sets
135 The benefit of using this interface to register sensor is that it
136 is not require to explicitly call thermal_zone_of_sensor_unregister()
147 Normally this function will not need to be called and the resource
152 This interface is used to read the slope attribute value
158 This interface is used to read the offset attribute value
167 to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself
168 to all the thermal zone devices registered at the same time.
171 ops: thermal cooling devices call-backs.
187 This interface function binds a thermal cooling device to a particular trip
188 point of a thermal zone device.
192 trip: indicates which trip point in this thermal zone the cooling device
194 upper:the Maximum cooling state for this trip point.
197 lower:the Minimum cooling state can be used for this trip point.
207 trip point of a thermal zone device. This function is usually called in
211 trip: indicates which trip point in this thermal zone the cooling device
216 This structure defines the following parameters that are used to bind
217 a zone with a cooling device for a particular trip point.
220 zone. This is relative to the rest of the cooling
225 contribute to the cooling of this zone unless all cooling
229 this thermal zone and cdev, for a particular trip point.
231 for trip point n.
234 array consisting of tuples <lower-state upper-state> of
238 These limits are used when binding a cdev to a trip point.
239 .match: This call back returns success(0) if the 'tz and cdev' need to
244 This is an optional feature where some platforms can choose not to
247 .no_hwmon: a boolean to indicate if the thermal to hwmon sysfs interface
266 /sys/class/thermal/thermal_zone[0-*]:
267 |---type: Type of the thermal zone
268 |---temp: Current temperature
269 |---mode: Working mode of the thermal zone
270 |---policy: Thermal governor used for this zone
271 |---available_policies: Available thermal governors for this zone
272 |---trip_point_[0-*]_temp: Trip point temperature
273 |---trip_point_[0-*]_type: Trip point type
274 |---trip_point_[0-*]_hyst: Hysteresis value for this trip point
275 |---emul_temp: Emulated temperature set node
276 |---sustainable_power: Sustainable dissipatable power
277 |---k_po: Proportional term during temperature overshoot
278 |---k_pu: Proportional term during temperature undershoot
279 |---k_i: PID's integral term in the power allocator gov
280 |---k_d: PID's derivative term in the power allocator
281 |---integral_cutoff: Offset above which errors are accumulated
282 |---slope: Slope constant applied as linear extrapolation
283 |---offset: Offset constant applied as linear extrapolation
286 /sys/class/thermal/cooling_device[0-*]:
287 |---type: Type of the cooling device(processor/fan/...)
288 |---max_state: Maximum cooling state of the cooling device
289 |---cur_state: Current cooling state of the cooling device
290 |---stats: Directory containing cooling device's statistics
291 |---stats/reset: Writing any value resets the statistics
292 |---stats/time_in_state_ms: Time (msec) spent in various cooling states
293 |---stats/total_trans: Total number of times cooling state is changed
294 |---stats/trans_table: Cooing state transition table
302 /sys/class/thermal/thermal_zone[0-*]:
303 |---cdev[0-*]: [0-*]th cooling device in current thermal zone
304 |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with
305 |---cdev[0-*]_weight: Influence of the cooling device in
314 /sys/class/hwmon/hwmon[0-*]:
315 |---name: The type of the thermal zone devices
316 |---temp[1-*]_input: The current temperature of thermal zone [1-*]
317 |---temp[1-*]_critical: The critical trip point of thermal zone [1-*]
319 Please read Documentation/hwmon/sysfs-interface for additional information.
329 In order to keep it consistent with hwmon sys attribute; this should
357 trip_point_[0-*]_temp
358 The temperature above which trip point will be fired.
362 trip_point_[0-*]_type
363 Strings which indicate the type of the trip point.
364 E.g. it can be one of critical, hot, passive, active[0-*] for ACPI
368 trip_point_[0-*]_hyst
369 The hysteresis value for a trip point, represented as an integer
373 cdev[0-*]
374 Sysfs link to the thermal cooling device node where the sys I/F
378 cdev[0-*]_trip_point
379 The trip point in this thermal zone which cdev[0-*] is associated
380 with; -1 means the cooling device is not associated with any trip
381 point.
384 cdev[0-*]_weight
385 The influence of cdev[0-*] in this thermal zone. This value
386 is relative to the rest of cooling devices in the thermal
395 and can be set to a temperature (in millidegrees) to enable a
396 passive trip point for the zone. Activation is done by polling with
403 Interface to set the emulated temperature method in thermal zone
405 this temperature to platform emulation function if registered or
427 temperature" trip point. For more information see
435 temperature" trip point. For more information see
441 controller. This term allows the PID controller to compensate
453 Temperature offset from the desired temperature trip point
458 temperature trip point. For more information see
465 to determine a hotspot temperature based off the sensor's
466 raw readings. It is up to the device driver to determine
472 to determine a hotspot temperature based off the sensor's
473 raw readings. It is up to the device driver to determine
483 - for generic ACPI: should be "Fan", "Processor" or "LCD"
484 - for memory controller device on intel_menlow platform:
495 - cur_state == 0 means no cooling
496 - cur_state == max_state means the maximum cooling.
508 units here is 10mS (similar to other time exported in /proc).
520 State_i to State_j. If the transition table is bigger than PAGE_SIZE,
521 reading this will return an -EFBIG error.
531 thermal_cooling_device. Both are considered to have the same
540 |---type: acpitz
541 |---temp: 37000
542 |---mode: enabled
543 |---policy: step_wise
544 |---available_policies: step_wise fair_share
545 |---trip_point_0_temp: 100000
546 |---trip_point_0_type: critical
547 |---trip_point_1_temp: 80000
548 |---trip_point_1_type: passive
549 |---trip_point_2_temp: 70000
550 |---trip_point_2_type: active0
551 |---trip_point_3_temp: 60000
552 |---trip_point_3_type: active1
553 |---cdev0: --->/sys/class/thermal/cooling_device0
554 |---cdev0_trip_point: 1 /* cdev0 can be used for passive */
555 |---cdev0_weight: 1024
556 |---cdev1: --->/sys/class/thermal/cooling_device3
557 |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
558 |---cdev1_weight: 1024
561 |---type: Processor
562 |---max_state: 8
563 |---cur_state: 0
566 |---type: Fan
567 |---max_state: 2
568 |---cur_state: 0
573 |---name: acpitz
574 |---temp1_input: 37000
575 |---temp1_crit: 100000
581 of the framework. Drivers which intend to use the notification mechanism
582 just need to call thermal_generate_netlink_event() with two arguments viz
583 (originator, event). The originator is a pointer to struct thermal_zone_device
585 thermal zone device will be used in the message to identify the zone. The
595 are supposed to implement the callback. If they don't, the thermal
600 This function returns the thermal_instance corresponding to a given
606 throttling the cooling devices according to the policy configured.
613 This function serves as an arbitrator to set the state of a cooling
614 device. It sets the cooling device to the deepest cooling state if
620 allows the system to shutdown gracefully by calling orderly_poweroff().
621 In the event of a failure of orderly_poweroff() to shut down the system
623 temperatures. To mitigate this high risk scenario we program a work
624 queue to fire after a pre-determined number of seconds to start
629 The delay should be carefully profiled so as to give adequate time for
634 If set to 0 emergency poweroff will not be supported. So a carefully
635 profiled non-zero positive value is a must for emergerncy poweroff to be