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Based on kernel version 4.13.3. Page generated on 2017-09-23 13:54 EST.

1	What:		/sys/power/
2	Date:		August 2006
3	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
4	Description:
5			The /sys/power directory will contain files that will
6			provide a unified interface to the power management
7			subsystem.
8	
9	What:		/sys/power/state
10	Date:		November 2016
11	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
12	Description:
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/power/states.txt for more information.
22	
23	What:		/sys/power/mem_sleep
24	Date:		November 2016
25	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
26	Description:
27			The /sys/power/mem_sleep file controls the operating mode of
28			system suspend.  Reading from it returns the available modes
29			as "s2idle" (always present), "shallow" and "deep" (present if
30			supported).  The mode that will be used on subsequent attempts
31			to suspend the system (by writing "mem" to the /sys/power/state
32			file described above) is enclosed in square brackets.
33	
34			Writing one of the above strings to this file causes the mode
35			represented by it to be used on subsequent attempts to suspend
36			the system.
37	
38			See Documentation/power/states.txt for more information.
39	
40	What:		/sys/power/disk
41	Date:		September 2006
42	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
43	Description:
44			The /sys/power/disk file controls the operating mode of the
45			suspend-to-disk mechanism.  Reading from this file returns
46			the name of the method by which the system will be put to
47			sleep on the next suspend.  There are four methods supported:
48			'firmware' - means that the memory image will be saved to disk
49			by some firmware, in which case we also assume that the
50			firmware will handle the system suspend.
51			'platform' - the memory image will be saved by the kernel and
52			the system will be put to sleep by the platform driver (e.g.
53			ACPI or other PM registers).
54			'shutdown' - the memory image will be saved by the kernel and
55			the system will be powered off.
56			'reboot' - the memory image will be saved by the kernel and
57			the system will be rebooted.
58	
59			Additionally, /sys/power/disk can be used to turn on one of the
60			two testing modes of the suspend-to-disk mechanism: 'testproc'
61			or 'test'.  If the suspend-to-disk mechanism is in the
62			'testproc' mode, writing 'disk' to /sys/power/state will cause
63			the kernel to disable nonboot CPUs and freeze tasks, wait for 5
64			seconds, unfreeze tasks and enable nonboot CPUs.  If it is in
65			the 'test' mode, writing 'disk' to /sys/power/state will cause
66			the kernel to disable nonboot CPUs and freeze tasks, shrink
67			memory, suspend devices, wait for 5 seconds, resume devices,
68			unfreeze tasks and enable nonboot CPUs.  Then, we are able to
69			look in the log messages and work out, for example, which code
70			is being slow and which device drivers are misbehaving.
71	
72			The suspend-to-disk method may be chosen by writing to this
73			file one of the accepted strings:
74	
75			'firmware'
76			'platform'
77			'shutdown'
78			'reboot'
79			'testproc'
80			'test'
81	
82			It will only change to 'firmware' or 'platform' if the system
83			supports that.
84	
85	What:		/sys/power/image_size
86	Date:		August 2006
87	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
88	Description:
89			The /sys/power/image_size file controls the size of the image
90			created by the suspend-to-disk mechanism.  It can be written a
91			string representing a non-negative integer that will be used
92			as an upper limit of the image size, in bytes.  The kernel's
93			suspend-to-disk code will do its best to ensure the image size
94			will not exceed this number.  However, if it turns out to be
95			impossible, the kernel will try to suspend anyway using the
96			smallest image possible.  In particular, if "0" is written to
97			this file, the suspend image will be as small as possible.
98	
99			Reading from this file will display the current image size
100			limit, which is set to 500 MB by default.
101	
102	What:		/sys/power/pm_trace
103	Date:		August 2006
104	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
105	Description:
106			The /sys/power/pm_trace file controls the code which saves the
107			last PM event point in the RTC across reboots, so that you can
108			debug a machine that just hangs during suspend (or more
109			commonly, during resume).  Namely, the RTC is only used to save
110			the last PM event point if this file contains '1'.  Initially
111			it contains '0' which may be changed to '1' by writing a
112			string representing a nonzero integer into it.
113	
114			To use this debugging feature you should attempt to suspend
115			the machine, then reboot it and run
116	
117			dmesg -s 1000000 | grep 'hash matches'
118	
119			If you do not get any matches (or they appear to be false
120			positives), it is possible that the last PM event point
121			referred to a device created by a loadable kernel module.  In
122			this case cat /sys/power/pm_trace_dev_match (see below) after
123			your system is started up and the kernel modules are loaded.
124	
125			CAUTION: Using it will cause your machine's real-time (CMOS)
126			clock to be set to a random invalid time after a resume.
127	
128	What;		/sys/power/pm_trace_dev_match
129	Date:		October 2010
130	Contact:	James Hogan <james@albanarts.com>
131	Description:
132			The /sys/power/pm_trace_dev_match file contains the name of the
133			device associated with the last PM event point saved in the RTC
134			across reboots when pm_trace has been used.  More precisely it
135			contains the list of current devices (including those
136			registered by loadable kernel modules since boot) which match
137			the device hash in the RTC at boot, with a newline after each
138			one.
139	
140			The advantage of this file over the hash matches printed to the
141			kernel log (see /sys/power/pm_trace), is that it includes
142			devices created after boot by loadable kernel modules.
143	
144			Due to the small hash size necessary to fit in the RTC, it is
145			possible that more than one device matches the hash, in which
146			case further investigation is required to determine which
147			device is causing the problem.  Note that genuine RTC clock
148			values (such as when pm_trace has not been used), can still
149			match a device and output it's name here.
150	
151	What:		/sys/power/pm_async
152	Date:		January 2009
153	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
154	Description:
155			The /sys/power/pm_async file controls the switch allowing the
156			user space to enable or disable asynchronous suspend and resume
157			of devices.  If enabled, this feature will cause some device
158			drivers' suspend and resume callbacks to be executed in parallel
159			with each other and with the main suspend thread.  It is enabled
160			if this file contains "1", which is the default.  It may be
161			disabled by writing "0" to this file, in which case all devices
162			will be suspended and resumed synchronously.
163	
164	What:		/sys/power/wakeup_count
165	Date:		July 2010
166	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
167	Description:
168			The /sys/power/wakeup_count file allows user space to put the
169			system into a sleep state while taking into account the
170			concurrent arrival of wakeup events.  Reading from it returns
171			the current number of registered wakeup events and it blocks if
172			some wakeup events are being processed at the time the file is
173			read from.  Writing to it will only succeed if the current
174			number of wakeup events is equal to the written value and, if
175			successful, will make the kernel abort a subsequent transition
176			to a sleep state if any wakeup events are reported after the
177			write has returned.
178	
179	What:		/sys/power/reserved_size
180	Date:		May 2011
181	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
182	Description:
183			The /sys/power/reserved_size file allows user space to control
184			the amount of memory reserved for allocations made by device
185			drivers during the "device freeze" stage of hibernation.  It can
186			be written a string representing a non-negative integer that
187			will be used as the amount of memory to reserve for allocations
188			made by device drivers' "freeze" callbacks, in bytes.
189	
190			Reading from this file will display the current value, which is
191			set to 1 MB by default.
192	
193	What:		/sys/power/autosleep
194	Date:		April 2012
195	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
196	Description:
197			The /sys/power/autosleep file can be written one of the strings
198			returned by reads from /sys/power/state.  If that happens, a
199			work item attempting to trigger a transition of the system to
200			the sleep state represented by that string is queued up.  This
201			attempt will only succeed if there are no active wakeup sources
202			in the system at that time.  After every execution, regardless
203			of whether or not the attempt to put the system to sleep has
204			succeeded, the work item requeues itself until user space
205			writes "off" to /sys/power/autosleep.
206	
207			Reading from this file causes the last string successfully
208			written to it to be returned.
209	
210	What:		/sys/power/wake_lock
211	Date:		February 2012
212	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
213	Description:
214			The /sys/power/wake_lock file allows user space to create
215			wakeup source objects and activate them on demand (if one of
216			those wakeup sources is active, reads from the
217			/sys/power/wakeup_count file block or return false).  When a
218			string without white space is written to /sys/power/wake_lock,
219			it will be assumed to represent a wakeup source name.  If there
220			is a wakeup source object with that name, it will be activated
221			(unless active already).  Otherwise, a new wakeup source object
222			will be registered, assigned the given name and activated.
223			If a string written to /sys/power/wake_lock contains white
224			space, the part of the string preceding the white space will be
225			regarded as a wakeup source name and handled as descrived above.
226			The other part of the string will be regarded as a timeout (in
227			nanoseconds) such that the wakeup source will be automatically
228			deactivated after it has expired.  The timeout, if present, is
229			set regardless of the current state of the wakeup source object
230			in question.
231	
232			Reads from this file return a string consisting of the names of
233			wakeup sources created with the help of it that are active at
234			the moment, separated with spaces.
235	
236	
237	What:		/sys/power/wake_unlock
238	Date:		February 2012
239	Contact:	Rafael J. Wysocki <rjw@rjwysocki.net>
240	Description:
241			The /sys/power/wake_unlock file allows user space to deactivate
242			wakeup sources created with the help of /sys/power/wake_lock.
243			When a string is written to /sys/power/wake_unlock, it will be
244			assumed to represent the name of a wakeup source to deactivate.
245			If a wakeup source object of that name exists and is active at
246			the moment, it will be deactivated.
247	
248			Reads from this file return a string consisting of the names of
249			wakeup sources created with the help of /sys/power/wake_lock
250			that are inactive at the moment, separated with spaces.
251	
252	What:		/sys/power/pm_print_times
253	Date:		May 2012
254	Contact:	Sameer Nanda <snanda@chromium.org>
255	Description:
256			The /sys/power/pm_print_times file allows user space to
257			control whether the time taken by devices to suspend and
258			resume is printed.  These prints are useful for hunting down
259			devices that take too long to suspend or resume.
260	
261			Writing a "1" enables this printing while writing a "0"
262			disables it.  The default value is "0".  Reading from this file
263			will display the current value.
264	
265	What:		/sys/power/pm_wakeup_irq
266	Date:		April 2015
267	Contact:	Alexandra Yates <alexandra.yates@linux.intel.org>
268	Description:
269			The /sys/power/pm_wakeup_irq file reports to user space the IRQ
270			number of the first wakeup interrupt (that is, the first
271			interrupt from an IRQ line armed for system wakeup) seen by the
272			kernel during the most recent system suspend/resume cycle.
273	
274			This output is useful for system wakeup diagnostics of spurious
275			wakeup interrupts.
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