1What:		/sys/power/
2Date:		August 2006
3Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
4Description:
5		The /sys/power directory will contain files that will
6		provide a unified interface to the power management
7		subsystem.
8
9What:		/sys/power/state
10Date:		November 2016
11Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
12Description:
13		The /sys/power/state file controls system sleep states.
14		Reading from this file returns the available sleep state
15		labels, which may be "mem" (suspend), "standby" (power-on
16		suspend), "freeze" (suspend-to-idle) and "disk" (hibernation).
17
18		Writing one of the above strings to this file causes the system
19		to transition into the corresponding state, if available.
20
21		See Documentation/admin-guide/pm/sleep-states.rst for more
22		information.
23
24What:		/sys/power/mem_sleep
25Date:		November 2016
26Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
27Description:
28		The /sys/power/mem_sleep file controls the operating mode of
29		system suspend.  Reading from it returns the available modes
30		as "s2idle" (always present), "shallow" and "deep" (present if
31		supported).  The mode that will be used on subsequent attempts
32		to suspend the system (by writing "mem" to the /sys/power/state
33		file described above) is enclosed in square brackets.
34
35		Writing one of the above strings to this file causes the mode
36		represented by it to be used on subsequent attempts to suspend
37		the system.
38
39		See Documentation/admin-guide/pm/sleep-states.rst for more
40		information.
41
42What:		/sys/power/disk
43Date:		September 2006
44Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
45Description:
46		The /sys/power/disk file controls the operating mode of the
47		suspend-to-disk mechanism.  Reading from this file returns
48		the name of the method by which the system will be put to
49		sleep on the next suspend.  There are four methods supported:
50
51		'firmware' - means that the memory image will be saved to disk
52		by some firmware, in which case we also assume that the
53		firmware will handle the system suspend.
54
55		'platform' - the memory image will be saved by the kernel and
56		the system will be put to sleep by the platform driver (e.g.
57		ACPI or other PM registers).
58
59		'shutdown' - the memory image will be saved by the kernel and
60		the system will be powered off.
61
62		'reboot' - the memory image will be saved by the kernel and
63		the system will be rebooted.
64
65		Additionally, /sys/power/disk can be used to turn on one of the
66		two testing modes of the suspend-to-disk mechanism: 'testproc'
67		or 'test'.  If the suspend-to-disk mechanism is in the
68		'testproc' mode, writing 'disk' to /sys/power/state will cause
69		the kernel to disable nonboot CPUs and freeze tasks, wait for 5
70		seconds, unfreeze tasks and enable nonboot CPUs.  If it is in
71		the 'test' mode, writing 'disk' to /sys/power/state will cause
72		the kernel to disable nonboot CPUs and freeze tasks, shrink
73		memory, suspend devices, wait for 5 seconds, resume devices,
74		unfreeze tasks and enable nonboot CPUs.  Then, we are able to
75		look in the log messages and work out, for example, which code
76		is being slow and which device drivers are misbehaving.
77
78		The suspend-to-disk method may be chosen by writing to this
79		file one of the accepted strings:
80
81		- 'firmware'
82		- 'platform'
83		- 'shutdown'
84		- 'reboot'
85		- 'testproc'
86		- 'test'
87
88		It will only change to 'firmware' or 'platform' if the system
89		supports that.
90
91What:		/sys/power/image_size
92Date:		August 2006
93Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
94Description:
95		The /sys/power/image_size file controls the size of the image
96		created by the suspend-to-disk mechanism.  It can be written a
97		string representing a non-negative integer that will be used
98		as an upper limit of the image size, in bytes.  The kernel's
99		suspend-to-disk code will do its best to ensure the image size
100		will not exceed this number.  However, if it turns out to be
101		impossible, the kernel will try to suspend anyway using the
102		smallest image possible.  In particular, if "0" is written to
103		this file, the suspend image will be as small as possible.
104
105		Reading from this file will display the current image size
106		limit, which is set to around 2/5 of available RAM by default.
107
108What:		/sys/power/pm_trace
109Date:		August 2006
110Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
111Description:
112		The /sys/power/pm_trace file controls the code which saves the
113		last PM event point in the RTC across reboots, so that you can
114		debug a machine that just hangs during suspend (or more
115		commonly, during resume).  Namely, the RTC is only used to save
116		the last PM event point if this file contains '1'.  Initially
117		it contains '0' which may be changed to '1' by writing a
118		string representing a nonzero integer into it.
119
120		To use this debugging feature you should attempt to suspend
121		the machine, then reboot it and run::
122
123		  dmesg -s 1000000 | grep 'hash matches'
124
125		If you do not get any matches (or they appear to be false
126		positives), it is possible that the last PM event point
127		referred to a device created by a loadable kernel module.  In
128		this case cat /sys/power/pm_trace_dev_match (see below) after
129		your system is started up and the kernel modules are loaded.
130
131		CAUTION: Using it will cause your machine's real-time (CMOS)
132		clock to be set to a random invalid time after a resume.
133
134What;		/sys/power/pm_trace_dev_match
135Date:		October 2010
136Contact:	James Hogan <jhogan@kernel.org>
137Description:
138		The /sys/power/pm_trace_dev_match file contains the name of the
139		device associated with the last PM event point saved in the RTC
140		across reboots when pm_trace has been used.  More precisely it
141		contains the list of current devices (including those
142		registered by loadable kernel modules since boot) which match
143		the device hash in the RTC at boot, with a newline after each
144		one.
145
146		The advantage of this file over the hash matches printed to the
147		kernel log (see /sys/power/pm_trace), is that it includes
148		devices created after boot by loadable kernel modules.
149
150		Due to the small hash size necessary to fit in the RTC, it is
151		possible that more than one device matches the hash, in which
152		case further investigation is required to determine which
153		device is causing the problem.  Note that genuine RTC clock
154		values (such as when pm_trace has not been used), can still
155		match a device and output its name here.
156
157What:		/sys/power/pm_async
158Date:		January 2009
159Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
160Description:
161		The /sys/power/pm_async file controls the switch allowing the
162		user space to enable or disable asynchronous suspend and resume
163		of devices.  If enabled, this feature will cause some device
164		drivers' suspend and resume callbacks to be executed in parallel
165		with each other and with the main suspend thread.  It is enabled
166		if this file contains "1", which is the default.  It may be
167		disabled by writing "0" to this file, in which case all devices
168		will be suspended and resumed synchronously.
169
170What:		/sys/power/wakeup_count
171Date:		July 2010
172Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
173Description:
174		The /sys/power/wakeup_count file allows user space to put the
175		system into a sleep state while taking into account the
176		concurrent arrival of wakeup events.  Reading from it returns
177		the current number of registered wakeup events and it blocks if
178		some wakeup events are being processed at the time the file is
179		read from.  Writing to it will only succeed if the current
180		number of wakeup events is equal to the written value and, if
181		successful, will make the kernel abort a subsequent transition
182		to a sleep state if any wakeup events are reported after the
183		write has returned.
184
185What:		/sys/power/reserved_size
186Date:		May 2011
187Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
188Description:
189		The /sys/power/reserved_size file allows user space to control
190		the amount of memory reserved for allocations made by device
191		drivers during the "device freeze" stage of hibernation.  It can
192		be written a string representing a non-negative integer that
193		will be used as the amount of memory to reserve for allocations
194		made by device drivers' "freeze" callbacks, in bytes.
195
196		Reading from this file will display the current value, which is
197		set to 1 MB by default.
198
199What:		/sys/power/autosleep
200Date:		April 2012
201Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
202Description:
203		The /sys/power/autosleep file can be written one of the strings
204		returned by reads from /sys/power/state.  If that happens, a
205		work item attempting to trigger a transition of the system to
206		the sleep state represented by that string is queued up.  This
207		attempt will only succeed if there are no active wakeup sources
208		in the system at that time.  After every execution, regardless
209		of whether or not the attempt to put the system to sleep has
210		succeeded, the work item requeues itself until user space
211		writes "off" to /sys/power/autosleep.
212
213		Reading from this file causes the last string successfully
214		written to it to be returned.
215
216What:		/sys/power/wake_lock
217Date:		February 2012
218Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
219Description:
220		The /sys/power/wake_lock file allows user space to create
221		wakeup source objects and activate them on demand (if one of
222		those wakeup sources is active, reads from the
223		/sys/power/wakeup_count file block or return false).  When a
224		string without white space is written to /sys/power/wake_lock,
225		it will be assumed to represent a wakeup source name.  If there
226		is a wakeup source object with that name, it will be activated
227		(unless active already).  Otherwise, a new wakeup source object
228		will be registered, assigned the given name and activated.
229		If a string written to /sys/power/wake_lock contains white
230		space, the part of the string preceding the white space will be
231		regarded as a wakeup source name and handled as descrived above.
232		The other part of the string will be regarded as a timeout (in
233		nanoseconds) such that the wakeup source will be automatically
234		deactivated after it has expired.  The timeout, if present, is
235		set regardless of the current state of the wakeup source object
236		in question.
237
238		Reads from this file return a string consisting of the names of
239		wakeup sources created with the help of it that are active at
240		the moment, separated with spaces.
241
242
243What:		/sys/power/wake_unlock
244Date:		February 2012
245Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
246Description:
247		The /sys/power/wake_unlock file allows user space to deactivate
248		wakeup sources created with the help of /sys/power/wake_lock.
249		When a string is written to /sys/power/wake_unlock, it will be
250		assumed to represent the name of a wakeup source to deactivate.
251
252		If a wakeup source object of that name exists and is active at
253		the moment, it will be deactivated.
254
255		Reads from this file return a string consisting of the names of
256		wakeup sources created with the help of /sys/power/wake_lock
257		that are inactive at the moment, separated with spaces.
258
259What:		/sys/power/pm_print_times
260Date:		May 2012
261Contact:	Sameer Nanda <snanda@chromium.org>
262Description:
263		The /sys/power/pm_print_times file allows user space to
264		control whether the time taken by devices to suspend and
265		resume is printed.  These prints are useful for hunting down
266		devices that take too long to suspend or resume.
267
268		Writing a "1" enables this printing while writing a "0"
269		disables it.  The default value is "0".  Reading from this file
270		will display the current value.
271
272What:		/sys/power/pm_wakeup_irq
273Date:		April 2015
274Contact:	Alexandra Yates <alexandra.yates@linux.intel.org>
275Description:
276		The /sys/power/pm_wakeup_irq file reports to user space the IRQ
277		number of the first wakeup interrupt (that is, the first
278		interrupt from an IRQ line armed for system wakeup) seen by the
279		kernel during the most recent system suspend/resume cycle.
280
281		This output is useful for system wakeup diagnostics of spurious
282		wakeup interrupts.
283
284What:		/sys/power/pm_debug_messages
285Date:		July 2017
286Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
287Description:
288		The /sys/power/pm_debug_messages file controls the printing
289		of debug messages from the system suspend/hiberbation
290		infrastructure to the kernel log.
291
292		Writing a "1" to this file enables the debug messages and
293		writing a "0" (default) to it disables them.  Reads from
294		this file return the current value.
295
296What:		/sys/power/resume_offset
297Date:		April 2018
298Contact:	Mario Limonciello <mario.limonciello@outlook.com>
299Description:
300		This file is used for telling the kernel an offset into a disk
301		to use when hibernating the system such as with a swap file.
302
303		Reads from this file will display the current offset
304		the kernel will be using on the next hibernation
305		attempt.
306
307		Using this sysfs file will override any values that were
308		set using the kernel command line for disk offset.
309
310What:		/sys/power/suspend_stats
311Date:		July 2019
312Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
313Description:
314		The /sys/power/suspend_stats directory contains suspend related
315		statistics.
316
317What:		/sys/power/suspend_stats/success
318Date:		July 2019
319Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
320Description:
321		The /sys/power/suspend_stats/success file contains the number
322		of times entering system sleep state succeeded.
323
324What:		/sys/power/suspend_stats/fail
325Date:		July 2019
326Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
327Description:
328		The /sys/power/suspend_stats/fail file contains the number
329		of times entering system sleep state failed.
330
331What:		/sys/power/suspend_stats/failed_freeze
332Date:		July 2019
333Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
334Description:
335		The /sys/power/suspend_stats/failed_freeze file contains the
336		number of times freezing processes failed.
337
338What:		/sys/power/suspend_stats/failed_prepare
339Date:		July 2019
340Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
341Description:
342		The /sys/power/suspend_stats/failed_prepare file contains the
343		number of times preparing all non-sysdev devices for
344		a system PM transition failed.
345
346What:		/sys/power/suspend_stats/failed_resume
347Date:		July 2019
348Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
349Description:
350		The /sys/power/suspend_stats/failed_resume file contains the
351		number of times executing "resume" callbacks of
352		non-sysdev devices failed.
353
354What:		/sys/power/suspend_stats/failed_resume_early
355Date:		July 2019
356Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
357Description:
358		The /sys/power/suspend_stats/failed_resume_early file contains
359		the number of times executing "early resume" callbacks
360		of devices failed.
361
362What:		/sys/power/suspend_stats/failed_resume_noirq
363Date:		July 2019
364Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
365Description:
366		The /sys/power/suspend_stats/failed_resume_noirq file contains
367		the number of times executing "noirq resume" callbacks
368		of devices failed.
369
370What:		/sys/power/suspend_stats/failed_suspend
371Date:		July 2019
372Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
373Description:
374		The /sys/power/suspend_stats/failed_suspend file contains
375		the number of times executing "suspend" callbacks
376		of all non-sysdev devices failed.
377
378What:		/sys/power/suspend_stats/failed_suspend_late
379Date:		July 2019
380Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
381Description:
382		The /sys/power/suspend_stats/failed_suspend_late file contains
383		the number of times executing "late suspend" callbacks
384		of all devices failed.
385
386What:		/sys/power/suspend_stats/failed_suspend_noirq
387Date:		July 2019
388Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
389Description:
390		The /sys/power/suspend_stats/failed_suspend_noirq file contains
391		the number of times executing "noirq suspend" callbacks
392		of all devices failed.
393
394What:		/sys/power/suspend_stats/last_failed_dev
395Date:		July 2019
396Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
397Description:
398		The /sys/power/suspend_stats/last_failed_dev file contains
399		the last device for which a suspend/resume callback failed.
400
401What:		/sys/power/suspend_stats/last_failed_errno
402Date:		July 2019
403Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
404Description:
405		The /sys/power/suspend_stats/last_failed_errno file contains
406		the errno of the last failed attempt at entering
407		system sleep state.
408
409What:		/sys/power/suspend_stats/last_failed_step
410Date:		July 2019
411Contact:	Kalesh Singh <kaleshsingh96@gmail.com>
412Description:
413		The /sys/power/suspend_stats/last_failed_step file contains
414		the last failed step in the suspend/resume path.
415
416What:		/sys/power/sync_on_suspend
417Date:		October 2019
418Contact:	Jonas Meurer <jonas@freesources.org>
419Description:
420		This file controls whether or not the kernel will sync()
421		filesystems during system suspend (after freezing user space
422		and before suspending devices).
423
424		Writing a "1" to this file enables the sync() and writing a "0"
425		disables it.  Reads from the file return the current value.
426		The default is "1" if the build-time "SUSPEND_SKIP_SYNC" config
427		flag is unset, or "0" otherwise.
428