0001 What: /sys/power/
0002 Date: August 2006
0003 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0004 Description:
0005 The /sys/power directory will contain files that will
0006 provide a unified interface to the power management
0007 subsystem.
0008
0009 What: /sys/power/state
0010 Date: November 2016
0011 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0012 Description:
0013 The /sys/power/state file controls system sleep states.
0014 Reading from this file returns the available sleep state
0015 labels, which may be "mem" (suspend), "standby" (power-on
0016 suspend), "freeze" (suspend-to-idle) and "disk" (hibernation).
0017
0018 Writing one of the above strings to this file causes the system
0019 to transition into the corresponding state, if available.
0020
0021 See Documentation/admin-guide/pm/sleep-states.rst for more
0022 information.
0023
0024 What: /sys/power/mem_sleep
0025 Date: November 2016
0026 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0027 Description:
0028 The /sys/power/mem_sleep file controls the operating mode of
0029 system suspend. Reading from it returns the available modes
0030 as "s2idle" (always present), "shallow" and "deep" (present if
0031 supported). The mode that will be used on subsequent attempts
0032 to suspend the system (by writing "mem" to the /sys/power/state
0033 file described above) is enclosed in square brackets.
0034
0035 Writing one of the above strings to this file causes the mode
0036 represented by it to be used on subsequent attempts to suspend
0037 the system.
0038
0039 See Documentation/admin-guide/pm/sleep-states.rst for more
0040 information.
0041
0042 What: /sys/power/disk
0043 Date: September 2006
0044 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0045 Description:
0046 The /sys/power/disk file controls the operating mode of the
0047 suspend-to-disk mechanism. Reading from this file returns
0048 the name of the method by which the system will be put to
0049 sleep on the next suspend. There are four methods supported:
0050
0051 'firmware' - means that the memory image will be saved to disk
0052 by some firmware, in which case we also assume that the
0053 firmware will handle the system suspend.
0054
0055 'platform' - the memory image will be saved by the kernel and
0056 the system will be put to sleep by the platform driver (e.g.
0057 ACPI or other PM registers).
0058
0059 'shutdown' - the memory image will be saved by the kernel and
0060 the system will be powered off.
0061
0062 'reboot' - the memory image will be saved by the kernel and
0063 the system will be rebooted.
0064
0065 Additionally, /sys/power/disk can be used to turn on one of the
0066 two testing modes of the suspend-to-disk mechanism: 'testproc'
0067 or 'test'. If the suspend-to-disk mechanism is in the
0068 'testproc' mode, writing 'disk' to /sys/power/state will cause
0069 the kernel to disable nonboot CPUs and freeze tasks, wait for 5
0070 seconds, unfreeze tasks and enable nonboot CPUs. If it is in
0071 the 'test' mode, writing 'disk' to /sys/power/state will cause
0072 the kernel to disable nonboot CPUs and freeze tasks, shrink
0073 memory, suspend devices, wait for 5 seconds, resume devices,
0074 unfreeze tasks and enable nonboot CPUs. Then, we are able to
0075 look in the log messages and work out, for example, which code
0076 is being slow and which device drivers are misbehaving.
0077
0078 The suspend-to-disk method may be chosen by writing to this
0079 file one of the accepted strings:
0080
0081 - 'firmware'
0082 - 'platform'
0083 - 'shutdown'
0084 - 'reboot'
0085 - 'testproc'
0086 - 'test'
0087
0088 It will only change to 'firmware' or 'platform' if the system
0089 supports that.
0090
0091 What: /sys/power/image_size
0092 Date: August 2006
0093 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0094 Description:
0095 The /sys/power/image_size file controls the size of the image
0096 created by the suspend-to-disk mechanism. It can be written a
0097 string representing a non-negative integer that will be used
0098 as an upper limit of the image size, in bytes. The kernel's
0099 suspend-to-disk code will do its best to ensure the image size
0100 will not exceed this number. However, if it turns out to be
0101 impossible, the kernel will try to suspend anyway using the
0102 smallest image possible. In particular, if "0" is written to
0103 this file, the suspend image will be as small as possible.
0104
0105 Reading from this file will display the current image size
0106 limit, which is set to around 2/5 of available RAM by default.
0107
0108 What: /sys/power/pm_trace
0109 Date: August 2006
0110 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0111 Description:
0112 The /sys/power/pm_trace file controls the code which saves the
0113 last PM event point in the RTC across reboots, so that you can
0114 debug a machine that just hangs during suspend (or more
0115 commonly, during resume). Namely, the RTC is only used to save
0116 the last PM event point if this file contains '1'. Initially
0117 it contains '0' which may be changed to '1' by writing a
0118 string representing a nonzero integer into it.
0119
0120 To use this debugging feature you should attempt to suspend
0121 the machine, then reboot it and run::
0122
0123 dmesg -s 1000000 | grep 'hash matches'
0124
0125 If you do not get any matches (or they appear to be false
0126 positives), it is possible that the last PM event point
0127 referred to a device created by a loadable kernel module. In
0128 this case cat /sys/power/pm_trace_dev_match (see below) after
0129 your system is started up and the kernel modules are loaded.
0130
0131 CAUTION: Using it will cause your machine's real-time (CMOS)
0132 clock to be set to a random invalid time after a resume.
0133
0134 What; /sys/power/pm_trace_dev_match
0135 Date: October 2010
0136 Contact: James Hogan <jhogan@kernel.org>
0137 Description:
0138 The /sys/power/pm_trace_dev_match file contains the name of the
0139 device associated with the last PM event point saved in the RTC
0140 across reboots when pm_trace has been used. More precisely it
0141 contains the list of current devices (including those
0142 registered by loadable kernel modules since boot) which match
0143 the device hash in the RTC at boot, with a newline after each
0144 one.
0145
0146 The advantage of this file over the hash matches printed to the
0147 kernel log (see /sys/power/pm_trace), is that it includes
0148 devices created after boot by loadable kernel modules.
0149
0150 Due to the small hash size necessary to fit in the RTC, it is
0151 possible that more than one device matches the hash, in which
0152 case further investigation is required to determine which
0153 device is causing the problem. Note that genuine RTC clock
0154 values (such as when pm_trace has not been used), can still
0155 match a device and output it's name here.
0156
0157 What: /sys/power/pm_async
0158 Date: January 2009
0159 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0160 Description:
0161 The /sys/power/pm_async file controls the switch allowing the
0162 user space to enable or disable asynchronous suspend and resume
0163 of devices. If enabled, this feature will cause some device
0164 drivers' suspend and resume callbacks to be executed in parallel
0165 with each other and with the main suspend thread. It is enabled
0166 if this file contains "1", which is the default. It may be
0167 disabled by writing "0" to this file, in which case all devices
0168 will be suspended and resumed synchronously.
0169
0170 What: /sys/power/wakeup_count
0171 Date: July 2010
0172 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0173 Description:
0174 The /sys/power/wakeup_count file allows user space to put the
0175 system into a sleep state while taking into account the
0176 concurrent arrival of wakeup events. Reading from it returns
0177 the current number of registered wakeup events and it blocks if
0178 some wakeup events are being processed at the time the file is
0179 read from. Writing to it will only succeed if the current
0180 number of wakeup events is equal to the written value and, if
0181 successful, will make the kernel abort a subsequent transition
0182 to a sleep state if any wakeup events are reported after the
0183 write has returned.
0184
0185 What: /sys/power/reserved_size
0186 Date: May 2011
0187 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0188 Description:
0189 The /sys/power/reserved_size file allows user space to control
0190 the amount of memory reserved for allocations made by device
0191 drivers during the "device freeze" stage of hibernation. It can
0192 be written a string representing a non-negative integer that
0193 will be used as the amount of memory to reserve for allocations
0194 made by device drivers' "freeze" callbacks, in bytes.
0195
0196 Reading from this file will display the current value, which is
0197 set to 1 MB by default.
0198
0199 What: /sys/power/autosleep
0200 Date: April 2012
0201 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0202 Description:
0203 The /sys/power/autosleep file can be written one of the strings
0204 returned by reads from /sys/power/state. If that happens, a
0205 work item attempting to trigger a transition of the system to
0206 the sleep state represented by that string is queued up. This
0207 attempt will only succeed if there are no active wakeup sources
0208 in the system at that time. After every execution, regardless
0209 of whether or not the attempt to put the system to sleep has
0210 succeeded, the work item requeues itself until user space
0211 writes "off" to /sys/power/autosleep.
0212
0213 Reading from this file causes the last string successfully
0214 written to it to be returned.
0215
0216 What: /sys/power/wake_lock
0217 Date: February 2012
0218 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0219 Description:
0220 The /sys/power/wake_lock file allows user space to create
0221 wakeup source objects and activate them on demand (if one of
0222 those wakeup sources is active, reads from the
0223 /sys/power/wakeup_count file block or return false). When a
0224 string without white space is written to /sys/power/wake_lock,
0225 it will be assumed to represent a wakeup source name. If there
0226 is a wakeup source object with that name, it will be activated
0227 (unless active already). Otherwise, a new wakeup source object
0228 will be registered, assigned the given name and activated.
0229 If a string written to /sys/power/wake_lock contains white
0230 space, the part of the string preceding the white space will be
0231 regarded as a wakeup source name and handled as descrived above.
0232 The other part of the string will be regarded as a timeout (in
0233 nanoseconds) such that the wakeup source will be automatically
0234 deactivated after it has expired. The timeout, if present, is
0235 set regardless of the current state of the wakeup source object
0236 in question.
0237
0238 Reads from this file return a string consisting of the names of
0239 wakeup sources created with the help of it that are active at
0240 the moment, separated with spaces.
0241
0242
0243 What: /sys/power/wake_unlock
0244 Date: February 2012
0245 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0246 Description:
0247 The /sys/power/wake_unlock file allows user space to deactivate
0248 wakeup sources created with the help of /sys/power/wake_lock.
0249 When a string is written to /sys/power/wake_unlock, it will be
0250 assumed to represent the name of a wakeup source to deactivate.
0251
0252 If a wakeup source object of that name exists and is active at
0253 the moment, it will be deactivated.
0254
0255 Reads from this file return a string consisting of the names of
0256 wakeup sources created with the help of /sys/power/wake_lock
0257 that are inactive at the moment, separated with spaces.
0258
0259 What: /sys/power/pm_print_times
0260 Date: May 2012
0261 Contact: Sameer Nanda <snanda@chromium.org>
0262 Description:
0263 The /sys/power/pm_print_times file allows user space to
0264 control whether the time taken by devices to suspend and
0265 resume is printed. These prints are useful for hunting down
0266 devices that take too long to suspend or resume.
0267
0268 Writing a "1" enables this printing while writing a "0"
0269 disables it. The default value is "0". Reading from this file
0270 will display the current value.
0271
0272 What: /sys/power/pm_wakeup_irq
0273 Date: April 2015
0274 Contact: Alexandra Yates <alexandra.yates@linux.intel.org>
0275 Description:
0276 The /sys/power/pm_wakeup_irq file reports to user space the IRQ
0277 number of the first wakeup interrupt (that is, the first
0278 interrupt from an IRQ line armed for system wakeup) seen by the
0279 kernel during the most recent system suspend/resume cycle.
0280
0281 This output is useful for system wakeup diagnostics of spurious
0282 wakeup interrupts.
0283
0284 What: /sys/power/pm_debug_messages
0285 Date: July 2017
0286 Contact: Rafael J. Wysocki <rjw@rjwysocki.net>
0287 Description:
0288 The /sys/power/pm_debug_messages file controls the printing
0289 of debug messages from the system suspend/hiberbation
0290 infrastructure to the kernel log.
0291
0292 Writing a "1" to this file enables the debug messages and
0293 writing a "0" (default) to it disables them. Reads from
0294 this file return the current value.
0295
0296 What: /sys/power/resume_offset
0297 Date: April 2018
0298 Contact: Mario Limonciello <mario.limonciello@outlook.com>
0299 Description:
0300 This file is used for telling the kernel an offset into a disk
0301 to use when hibernating the system such as with a swap file.
0302
0303 Reads from this file will display the current offset
0304 the kernel will be using on the next hibernation
0305 attempt.
0306
0307 Using this sysfs file will override any values that were
0308 set using the kernel command line for disk offset.
0309
0310 What: /sys/power/suspend_stats
0311 Date: July 2019
0312 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0313 Description:
0314 The /sys/power/suspend_stats directory contains suspend related
0315 statistics.
0316
0317 What: /sys/power/suspend_stats/success
0318 Date: July 2019
0319 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0320 Description:
0321 The /sys/power/suspend_stats/success file contains the number
0322 of times entering system sleep state succeeded.
0323
0324 What: /sys/power/suspend_stats/fail
0325 Date: July 2019
0326 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0327 Description:
0328 The /sys/power/suspend_stats/fail file contains the number
0329 of times entering system sleep state failed.
0330
0331 What: /sys/power/suspend_stats/failed_freeze
0332 Date: July 2019
0333 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0334 Description:
0335 The /sys/power/suspend_stats/failed_freeze file contains the
0336 number of times freezing processes failed.
0337
0338 What: /sys/power/suspend_stats/failed_prepare
0339 Date: July 2019
0340 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0341 Description:
0342 The /sys/power/suspend_stats/failed_prepare file contains the
0343 number of times preparing all non-sysdev devices for
0344 a system PM transition failed.
0345
0346 What: /sys/power/suspend_stats/failed_resume
0347 Date: July 2019
0348 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0349 Description:
0350 The /sys/power/suspend_stats/failed_resume file contains the
0351 number of times executing "resume" callbacks of
0352 non-sysdev devices failed.
0353
0354 What: /sys/power/suspend_stats/failed_resume_early
0355 Date: July 2019
0356 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0357 Description:
0358 The /sys/power/suspend_stats/failed_resume_early file contains
0359 the number of times executing "early resume" callbacks
0360 of devices failed.
0361
0362 What: /sys/power/suspend_stats/failed_resume_noirq
0363 Date: July 2019
0364 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0365 Description:
0366 The /sys/power/suspend_stats/failed_resume_noirq file contains
0367 the number of times executing "noirq resume" callbacks
0368 of devices failed.
0369
0370 What: /sys/power/suspend_stats/failed_suspend
0371 Date: July 2019
0372 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0373 Description:
0374 The /sys/power/suspend_stats/failed_suspend file contains
0375 the number of times executing "suspend" callbacks
0376 of all non-sysdev devices failed.
0377
0378 What: /sys/power/suspend_stats/failed_suspend_late
0379 Date: July 2019
0380 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0381 Description:
0382 The /sys/power/suspend_stats/failed_suspend_late file contains
0383 the number of times executing "late suspend" callbacks
0384 of all devices failed.
0385
0386 What: /sys/power/suspend_stats/failed_suspend_noirq
0387 Date: July 2019
0388 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0389 Description:
0390 The /sys/power/suspend_stats/failed_suspend_noirq file contains
0391 the number of times executing "noirq suspend" callbacks
0392 of all devices failed.
0393
0394 What: /sys/power/suspend_stats/last_failed_dev
0395 Date: July 2019
0396 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0397 Description:
0398 The /sys/power/suspend_stats/last_failed_dev file contains
0399 the last device for which a suspend/resume callback failed.
0400
0401 What: /sys/power/suspend_stats/last_failed_errno
0402 Date: July 2019
0403 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0404 Description:
0405 The /sys/power/suspend_stats/last_failed_errno file contains
0406 the errno of the last failed attempt at entering
0407 system sleep state.
0408
0409 What: /sys/power/suspend_stats/last_failed_step
0410 Date: July 2019
0411 Contact: Kalesh Singh <kaleshsingh96@gmail.com>
0412 Description:
0413 The /sys/power/suspend_stats/last_failed_step file contains
0414 the last failed step in the suspend/resume path.
0415
0416 What: /sys/power/sync_on_suspend
0417 Date: October 2019
0418 Contact: Jonas Meurer <jonas@freesources.org>
0419 Description:
0420 This file controls whether or not the kernel will sync()
0421 filesystems during system suspend (after freezing user space
0422 and before suspending devices).
0423
0424 Writing a "1" to this file enables the sync() and writing a "0"
0425 disables it. Reads from the file return the current value.
0426 The default is "1" if the build-time "SUSPEND_SKIP_SYNC" config
0427 flag is unset, or "0" otherwise.
