xref: /linux/Documentation/ABI/testing/sysfs-power (revision 0399d4db3edf5c58b6ec7f672f089f5085e49ed5)
184ed64eeSRafael J. WysockiWhat:		/sys/power/
284ed64eeSRafael J. WysockiDate:		August 2006
349db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
484ed64eeSRafael J. WysockiDescription:
584ed64eeSRafael J. Wysocki		The /sys/power directory will contain files that will
684ed64eeSRafael J. Wysocki		provide a unified interface to the power management
784ed64eeSRafael J. Wysocki		subsystem.
884ed64eeSRafael J. Wysocki
984ed64eeSRafael J. WysockiWhat:		/sys/power/state
10*0399d4dbSRafael J. WysockiDate:		May 2014
1149db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
1284ed64eeSRafael J. WysockiDescription:
13*0399d4dbSRafael J. Wysocki		The /sys/power/state file controls system sleep states.
14*0399d4dbSRafael J. Wysocki		Reading from this file returns the available sleep state
15*0399d4dbSRafael J. Wysocki		labels, which may be "mem", "standby", "freeze" and "disk"
16*0399d4dbSRafael J. Wysocki		(hibernation).  The meanings of the first three labels depend on
17*0399d4dbSRafael J. Wysocki		the relative_sleep_states command line argument as follows:
18*0399d4dbSRafael J. Wysocki		 1) relative_sleep_states = 1
19*0399d4dbSRafael J. Wysocki		    "mem", "standby", "freeze" represent non-hibernation sleep
20*0399d4dbSRafael J. Wysocki		    states from the deepest ("mem", always present) to the
21*0399d4dbSRafael J. Wysocki		    shallowest ("freeze").  "standby" and "freeze" may or may
22*0399d4dbSRafael J. Wysocki		    not be present depending on the capabilities of the
23*0399d4dbSRafael J. Wysocki		    platform.  "freeze" can only be present if "standby" is
24*0399d4dbSRafael J. Wysocki		    present.
25*0399d4dbSRafael J. Wysocki		 2) relative_sleep_states = 0 (default)
26*0399d4dbSRafael J. Wysocki		    "mem" - "suspend-to-RAM", present if supported.
27*0399d4dbSRafael J. Wysocki		    "standby" - "power-on suspend", present if supported.
28*0399d4dbSRafael J. Wysocki		    "freeze" - "suspend-to-idle", always present.
2984ed64eeSRafael J. Wysocki
3084ed64eeSRafael J. Wysocki		Writing to this file one of these strings causes the system to
31*0399d4dbSRafael J. Wysocki		transition into the corresponding state, if available.  See
32*0399d4dbSRafael J. Wysocki		Documentation/power/states.txt for a description of what
33*0399d4dbSRafael J. Wysocki		"suspend-to-RAM", "power-on suspend" and "suspend-to-idle" mean.
3484ed64eeSRafael J. Wysocki
3584ed64eeSRafael J. WysockiWhat:		/sys/power/disk
36b918f6e6SRafael J. WysockiDate:		September 2006
3749db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
3884ed64eeSRafael J. WysockiDescription:
3984ed64eeSRafael J. Wysocki		The /sys/power/disk file controls the operating mode of the
4084ed64eeSRafael J. Wysocki		suspend-to-disk mechanism.  Reading from this file returns
4184ed64eeSRafael J. Wysocki		the name of the method by which the system will be put to
4284ed64eeSRafael J. Wysocki		sleep on the next suspend.  There are four methods supported:
4384ed64eeSRafael J. Wysocki		'firmware' - means that the memory image will be saved to disk
4484ed64eeSRafael J. Wysocki		by some firmware, in which case we also assume that the
4584ed64eeSRafael J. Wysocki		firmware will handle the system suspend.
4684ed64eeSRafael J. Wysocki		'platform' - the memory image will be saved by the kernel and
4784ed64eeSRafael J. Wysocki		the system will be put to sleep by the platform driver (e.g.
4884ed64eeSRafael J. Wysocki		ACPI or other PM registers).
4984ed64eeSRafael J. Wysocki		'shutdown' - the memory image will be saved by the kernel and
5084ed64eeSRafael J. Wysocki		the system will be powered off.
5184ed64eeSRafael J. Wysocki		'reboot' - the memory image will be saved by the kernel and
5284ed64eeSRafael J. Wysocki		the system will be rebooted.
5384ed64eeSRafael J. Wysocki
54b918f6e6SRafael J. Wysocki		Additionally, /sys/power/disk can be used to turn on one of the
55b918f6e6SRafael J. Wysocki		two testing modes of the suspend-to-disk mechanism: 'testproc'
56b918f6e6SRafael J. Wysocki		or 'test'.  If the suspend-to-disk mechanism is in the
57b918f6e6SRafael J. Wysocki		'testproc' mode, writing 'disk' to /sys/power/state will cause
58b918f6e6SRafael J. Wysocki		the kernel to disable nonboot CPUs and freeze tasks, wait for 5
59b918f6e6SRafael J. Wysocki		seconds, unfreeze tasks and enable nonboot CPUs.  If it is in
60b918f6e6SRafael J. Wysocki		the 'test' mode, writing 'disk' to /sys/power/state will cause
61b918f6e6SRafael J. Wysocki		the kernel to disable nonboot CPUs and freeze tasks, shrink
62b918f6e6SRafael J. Wysocki		memory, suspend devices, wait for 5 seconds, resume devices,
63b918f6e6SRafael J. Wysocki		unfreeze tasks and enable nonboot CPUs.  Then, we are able to
64b918f6e6SRafael J. Wysocki		look in the log messages and work out, for example, which code
65b918f6e6SRafael J. Wysocki		is being slow and which device drivers are misbehaving.
66b918f6e6SRafael J. Wysocki
6784ed64eeSRafael J. Wysocki		The suspend-to-disk method may be chosen by writing to this
6884ed64eeSRafael J. Wysocki		file one of the accepted strings:
6984ed64eeSRafael J. Wysocki
7084ed64eeSRafael J. Wysocki		'firmware'
7184ed64eeSRafael J. Wysocki		'platform'
7284ed64eeSRafael J. Wysocki		'shutdown'
7384ed64eeSRafael J. Wysocki		'reboot'
74b918f6e6SRafael J. Wysocki		'testproc'
75b918f6e6SRafael J. Wysocki		'test'
7684ed64eeSRafael J. Wysocki
7784ed64eeSRafael J. Wysocki		It will only change to 'firmware' or 'platform' if the system
7884ed64eeSRafael J. Wysocki		supports that.
7984ed64eeSRafael J. Wysocki
8084ed64eeSRafael J. WysockiWhat:		/sys/power/image_size
8184ed64eeSRafael J. WysockiDate:		August 2006
8249db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
8384ed64eeSRafael J. WysockiDescription:
8484ed64eeSRafael J. Wysocki		The /sys/power/image_size file controls the size of the image
8584ed64eeSRafael J. Wysocki		created by the suspend-to-disk mechanism.  It can be written a
8684ed64eeSRafael J. Wysocki		string representing a non-negative integer that will be used
8784ed64eeSRafael J. Wysocki		as an upper limit of the image size, in bytes.  The kernel's
8884ed64eeSRafael J. Wysocki		suspend-to-disk code will do its best to ensure the image size
8984ed64eeSRafael J. Wysocki		will not exceed this number.  However, if it turns out to be
9084ed64eeSRafael J. Wysocki		impossible, the kernel will try to suspend anyway using the
9184ed64eeSRafael J. Wysocki		smallest image possible.  In particular, if "0" is written to
9284ed64eeSRafael J. Wysocki		this file, the suspend image will be as small as possible.
9384ed64eeSRafael J. Wysocki
9484ed64eeSRafael J. Wysocki		Reading from this file will display the current image size
9584ed64eeSRafael J. Wysocki		limit, which is set to 500 MB by default.
9684ed64eeSRafael J. Wysocki
9784ed64eeSRafael J. WysockiWhat:		/sys/power/pm_trace
9884ed64eeSRafael J. WysockiDate:		August 2006
9949db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
10084ed64eeSRafael J. WysockiDescription:
10184ed64eeSRafael J. Wysocki		The /sys/power/pm_trace file controls the code which saves the
10284ed64eeSRafael J. Wysocki		last PM event point in the RTC across reboots, so that you can
10384ed64eeSRafael J. Wysocki		debug a machine that just hangs during suspend (or more
10484ed64eeSRafael J. Wysocki		commonly, during resume).  Namely, the RTC is only used to save
10584ed64eeSRafael J. Wysocki		the last PM event point if this file contains '1'.  Initially
10684ed64eeSRafael J. Wysocki		it contains '0' which may be changed to '1' by writing a
10784ed64eeSRafael J. Wysocki		string representing a nonzero integer into it.
10884ed64eeSRafael J. Wysocki
10984ed64eeSRafael J. Wysocki		To use this debugging feature you should attempt to suspend
11084ed64eeSRafael J. Wysocki		the machine, then reboot it and run
11184ed64eeSRafael J. Wysocki
11284ed64eeSRafael J. Wysocki		dmesg -s 1000000 | grep 'hash matches'
11384ed64eeSRafael J. Wysocki
114d33ac60bSJames Hogan		If you do not get any matches (or they appear to be false
115d33ac60bSJames Hogan		positives), it is possible that the last PM event point
116d33ac60bSJames Hogan		referred to a device created by a loadable kernel module.  In
117d33ac60bSJames Hogan		this case cat /sys/power/pm_trace_dev_match (see below) after
118d33ac60bSJames Hogan		your system is started up and the kernel modules are loaded.
119d33ac60bSJames Hogan
12084ed64eeSRafael J. Wysocki		CAUTION: Using it will cause your machine's real-time (CMOS)
12184ed64eeSRafael J. Wysocki		clock to be set to a random invalid time after a resume.
1220e06b4a8SRafael J. Wysocki
123d33ac60bSJames HoganWhat;		/sys/power/pm_trace_dev_match
124d33ac60bSJames HoganDate:		October 2010
125d33ac60bSJames HoganContact:	James Hogan <james@albanarts.com>
126d33ac60bSJames HoganDescription:
127d33ac60bSJames Hogan		The /sys/power/pm_trace_dev_match file contains the name of the
128d33ac60bSJames Hogan		device associated with the last PM event point saved in the RTC
129d33ac60bSJames Hogan		across reboots when pm_trace has been used.  More precisely it
130d33ac60bSJames Hogan		contains the list of current devices (including those
131d33ac60bSJames Hogan		registered by loadable kernel modules since boot) which match
132d33ac60bSJames Hogan		the device hash in the RTC at boot, with a newline after each
133d33ac60bSJames Hogan		one.
134d33ac60bSJames Hogan
135d33ac60bSJames Hogan		The advantage of this file over the hash matches printed to the
136d33ac60bSJames Hogan		kernel log (see /sys/power/pm_trace), is that it includes
137d33ac60bSJames Hogan		devices created after boot by loadable kernel modules.
138d33ac60bSJames Hogan
139d33ac60bSJames Hogan		Due to the small hash size necessary to fit in the RTC, it is
140d33ac60bSJames Hogan		possible that more than one device matches the hash, in which
141d33ac60bSJames Hogan		case further investigation is required to determine which
142d33ac60bSJames Hogan		device is causing the problem.  Note that genuine RTC clock
143d33ac60bSJames Hogan		values (such as when pm_trace has not been used), can still
144d33ac60bSJames Hogan		match a device and output it's name here.
145d33ac60bSJames Hogan
1460e06b4a8SRafael J. WysockiWhat:		/sys/power/pm_async
1470e06b4a8SRafael J. WysockiDate:		January 2009
14849db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
1490e06b4a8SRafael J. WysockiDescription:
1500e06b4a8SRafael J. Wysocki		The /sys/power/pm_async file controls the switch allowing the
1510e06b4a8SRafael J. Wysocki		user space to enable or disable asynchronous suspend and resume
1520e06b4a8SRafael J. Wysocki		of devices.  If enabled, this feature will cause some device
1530e06b4a8SRafael J. Wysocki		drivers' suspend and resume callbacks to be executed in parallel
1540e06b4a8SRafael J. Wysocki		with each other and with the main suspend thread.  It is enabled
1550e06b4a8SRafael J. Wysocki		if this file contains "1", which is the default.  It may be
1560e06b4a8SRafael J. Wysocki		disabled by writing "0" to this file, in which case all devices
1570e06b4a8SRafael J. Wysocki		will be suspended and resumed synchronously.
158c125e96fSRafael J. Wysocki
159c125e96fSRafael J. WysockiWhat:		/sys/power/wakeup_count
160c125e96fSRafael J. WysockiDate:		July 2010
16149db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
162c125e96fSRafael J. WysockiDescription:
163c125e96fSRafael J. Wysocki		The /sys/power/wakeup_count file allows user space to put the
164c125e96fSRafael J. Wysocki		system into a sleep state while taking into account the
165c125e96fSRafael J. Wysocki		concurrent arrival of wakeup events.  Reading from it returns
166c125e96fSRafael J. Wysocki		the current number of registered wakeup events and it blocks if
167c125e96fSRafael J. Wysocki		some wakeup events are being processed at the time the file is
168c125e96fSRafael J. Wysocki		read from.  Writing to it will only succeed if the current
169c125e96fSRafael J. Wysocki		number of wakeup events is equal to the written value and, if
170c125e96fSRafael J. Wysocki		successful, will make the kernel abort a subsequent transition
171c125e96fSRafael J. Wysocki		to a sleep state if any wakeup events are reported after the
172c125e96fSRafael J. Wysocki		write has returned.
173ddeb6487SRafael J. Wysocki
174ddeb6487SRafael J. WysockiWhat:		/sys/power/reserved_size
175ddeb6487SRafael J. WysockiDate:		May 2011
17649db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
177ddeb6487SRafael J. WysockiDescription:
178ddeb6487SRafael J. Wysocki		The /sys/power/reserved_size file allows user space to control
179ddeb6487SRafael J. Wysocki		the amount of memory reserved for allocations made by device
180ddeb6487SRafael J. Wysocki		drivers during the "device freeze" stage of hibernation.  It can
181ddeb6487SRafael J. Wysocki		be written a string representing a non-negative integer that
182ddeb6487SRafael J. Wysocki		will be used as the amount of memory to reserve for allocations
183ddeb6487SRafael J. Wysocki		made by device drivers' "freeze" callbacks, in bytes.
184ddeb6487SRafael J. Wysocki
185ddeb6487SRafael J. Wysocki		Reading from this file will display the current value, which is
186ddeb6487SRafael J. Wysocki		set to 1 MB by default.
1877483b4a4SRafael J. Wysocki
1887483b4a4SRafael J. WysockiWhat:		/sys/power/autosleep
1897483b4a4SRafael J. WysockiDate:		April 2012
19049db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
1917483b4a4SRafael J. WysockiDescription:
1927483b4a4SRafael J. Wysocki		The /sys/power/autosleep file can be written one of the strings
1937483b4a4SRafael J. Wysocki		returned by reads from /sys/power/state.  If that happens, a
1947483b4a4SRafael J. Wysocki		work item attempting to trigger a transition of the system to
1957483b4a4SRafael J. Wysocki		the sleep state represented by that string is queued up.  This
1967483b4a4SRafael J. Wysocki		attempt will only succeed if there are no active wakeup sources
1977483b4a4SRafael J. Wysocki		in the system at that time.  After every execution, regardless
1987483b4a4SRafael J. Wysocki		of whether or not the attempt to put the system to sleep has
1997483b4a4SRafael J. Wysocki		succeeded, the work item requeues itself until user space
2007483b4a4SRafael J. Wysocki		writes "off" to /sys/power/autosleep.
2017483b4a4SRafael J. Wysocki
2027483b4a4SRafael J. Wysocki		Reading from this file causes the last string successfully
2037483b4a4SRafael J. Wysocki		written to it to be returned.
204b86ff982SRafael J. Wysocki
205b86ff982SRafael J. WysockiWhat:		/sys/power/wake_lock
206b86ff982SRafael J. WysockiDate:		February 2012
20749db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
208b86ff982SRafael J. WysockiDescription:
209b86ff982SRafael J. Wysocki		The /sys/power/wake_lock file allows user space to create
210b86ff982SRafael J. Wysocki		wakeup source objects and activate them on demand (if one of
211b86ff982SRafael J. Wysocki		those wakeup sources is active, reads from the
212b86ff982SRafael J. Wysocki		/sys/power/wakeup_count file block or return false).  When a
213b86ff982SRafael J. Wysocki		string without white space is written to /sys/power/wake_lock,
214b86ff982SRafael J. Wysocki		it will be assumed to represent a wakeup source name.  If there
215b86ff982SRafael J. Wysocki		is a wakeup source object with that name, it will be activated
216b86ff982SRafael J. Wysocki		(unless active already).  Otherwise, a new wakeup source object
217b86ff982SRafael J. Wysocki		will be registered, assigned the given name and activated.
218b86ff982SRafael J. Wysocki		If a string written to /sys/power/wake_lock contains white
219b86ff982SRafael J. Wysocki		space, the part of the string preceding the white space will be
220b86ff982SRafael J. Wysocki		regarded as a wakeup source name and handled as descrived above.
221b86ff982SRafael J. Wysocki		The other part of the string will be regarded as a timeout (in
222b86ff982SRafael J. Wysocki		nanoseconds) such that the wakeup source will be automatically
223b86ff982SRafael J. Wysocki		deactivated after it has expired.  The timeout, if present, is
224b86ff982SRafael J. Wysocki		set regardless of the current state of the wakeup source object
225b86ff982SRafael J. Wysocki		in question.
226b86ff982SRafael J. Wysocki
227b86ff982SRafael J. Wysocki		Reads from this file return a string consisting of the names of
228b86ff982SRafael J. Wysocki		wakeup sources created with the help of it that are active at
229b86ff982SRafael J. Wysocki		the moment, separated with spaces.
230b86ff982SRafael J. Wysocki
231b86ff982SRafael J. Wysocki
232b86ff982SRafael J. WysockiWhat:		/sys/power/wake_unlock
233b86ff982SRafael J. WysockiDate:		February 2012
23449db1903SRafael J. WysockiContact:	Rafael J. Wysocki <rjw@rjwysocki.net>
235b86ff982SRafael J. WysockiDescription:
236b86ff982SRafael J. Wysocki		The /sys/power/wake_unlock file allows user space to deactivate
237b86ff982SRafael J. Wysocki		wakeup sources created with the help of /sys/power/wake_lock.
238b86ff982SRafael J. Wysocki		When a string is written to /sys/power/wake_unlock, it will be
239b86ff982SRafael J. Wysocki		assumed to represent the name of a wakeup source to deactivate.
240b86ff982SRafael J. Wysocki		If a wakeup source object of that name exists and is active at
241b86ff982SRafael J. Wysocki		the moment, it will be deactivated.
242b86ff982SRafael J. Wysocki
243b86ff982SRafael J. Wysocki		Reads from this file return a string consisting of the names of
244b86ff982SRafael J. Wysocki		wakeup sources created with the help of /sys/power/wake_lock
245b86ff982SRafael J. Wysocki		that are inactive at the moment, separated with spaces.
2464b7760baSSameer Nanda
2474b7760baSSameer NandaWhat:		/sys/power/pm_print_times
2484b7760baSSameer NandaDate:		May 2012
2494b7760baSSameer NandaContact:	Sameer Nanda <snanda@chromium.org>
2504b7760baSSameer NandaDescription:
2514b7760baSSameer Nanda		The /sys/power/pm_print_times file allows user space to
2524b7760baSSameer Nanda		control whether the time taken by devices to suspend and
2534b7760baSSameer Nanda		resume is printed.  These prints are useful for hunting down
2544b7760baSSameer Nanda		devices that take too long to suspend or resume.
2554b7760baSSameer Nanda
2564b7760baSSameer Nanda		Writing a "1" enables this printing while writing a "0"
2574b7760baSSameer Nanda		disables it.  The default value is "0".  Reading from this file
2584b7760baSSameer Nanda		will display the current value.
259