xref: /kernel/linux/linux-5.10/Documentation/ABI/testing/sysfs-class-devfreq (revision 8c2ecf20)

What:		/sys/class/devfreq/.../
Date:		September 2011
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		Provide a place in sysfs for the devfreq objects.
		This allows accessing various devfreq specific variables.
		The name of devfreq object denoted as ... is same as the
		name of device using devfreq.

What:		/sys/class/devfreq/.../name
Date:		November 2019
Contact:	Chanwoo Choi <cw00.choi@samsung.com>
Description:
		The /sys/class/devfreq/.../name shows the name of device
		of the corresponding devfreq object.

What:		/sys/class/devfreq/.../governor
Date:		September 2011
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		The /sys/class/devfreq/.../governor show or set the name of the
		governor used by the corresponding devfreq object.

What:		/sys/class/devfreq/.../cur_freq
Date:		September 2011
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		The /sys/class/devfreq/.../cur_freq shows the current
		frequency of the corresponding devfreq object. Same as
		target_freq when get_cur_freq() is not implemented by
		devfreq driver.

What:		/sys/class/devfreq/.../target_freq
Date:		September 2012
Contact:	Rajagopal Venkat <rajagopal.venkat@linaro.org>
Description:
		The /sys/class/devfreq/.../target_freq shows the next governor
		predicted target frequency of the corresponding devfreq object.

What:		/sys/class/devfreq/.../polling_interval
Date:		September 2011
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		The /sys/class/devfreq/.../polling_interval shows and sets
		the requested polling interval of the corresponding devfreq
		object. The values are represented in ms. If the value is
		less than 1 jiffy, it is considered to be 0, which means
		no polling. This value is meaningless if the governor is
		not polling; thus. If the governor is not using
		devfreq-provided central polling
		(/sys/class/devfreq/.../central_polling is 0), this value
		may be useless.

What:		/sys/class/devfreq/.../trans_stat
Date:		October 2012
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		This ABI shows or clears the statistics of devfreq behavior
		on a specific device. It shows the time spent in each state
		and the number of transitions between states.
		In order to activate this ABI, the devfreq target device
		driver should provide the list of available frequencies
		with its profile. If need to reset the statistics of devfreq
		behavior on a specific device, enter 0(zero) to 'trans_stat'
		as following::

			echo 0 > /sys/class/devfreq/.../trans_stat

		If the transition table is bigger than PAGE_SIZE, reading
		this will return an -EFBIG error.

What:		/sys/class/devfreq/.../userspace/set_freq
Date:		September 2011
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		The /sys/class/devfreq/.../userspace/set_freq shows and
		sets the requested frequency for the devfreq object if
		userspace governor is in effect.

What:		/sys/class/devfreq/.../available_frequencies
Date:		October 2012
Contact:	Nishanth Menon <nm@ti.com>
Description:
		The /sys/class/devfreq/.../available_frequencies shows
		the available frequencies of the corresponding devfreq object.
		This is a snapshot of available frequencies and not limited
		by the min/max frequency restrictions.

What:		/sys/class/devfreq/.../available_governors
Date:		October 2012
Contact:	Nishanth Menon <nm@ti.com>
Description:
		The /sys/class/devfreq/.../available_governors shows
		currently available governors in the system.

What:		/sys/class/devfreq/.../min_freq
Date:		January 2013
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		The /sys/class/devfreq/.../min_freq shows and stores
		the minimum frequency requested by users. It is 0 if
		the user does not care. min_freq overrides the
		frequency requested by governors.

What:		/sys/class/devfreq/.../max_freq
Date:		January 2013
Contact:	MyungJoo Ham <myungjoo.ham@samsung.com>
Description:
		The /sys/class/devfreq/.../max_freq shows and stores
		the maximum frequency requested by users. It is 0 if
		the user does not care. max_freq overrides the
		frequency requested by governors and min_freq.
		The max_freq overrides min_freq because max_freq may be
		used to throttle devices to avoid overheating.

What:		/sys/class/devfreq/.../timer
Date:		July 2020
Contact:	Chanwoo Choi <cw00.choi@samsung.com>
Description:
		This ABI shows and stores the kind of work timer by users.
		This work timer is used by devfreq workqueue in order to
		monitor the device status such as utilization. The user
		can change the work timer on runtime according to their demand
		as following::

			echo deferrable > /sys/class/devfreq/.../timer
			echo delayed > /sys/class/devfreq/.../timer