What: /sys/power/
Date: August 2006
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power directory will contain files that will
provide a unified interface to the power management
subsystem.
What: /sys/power/state
Date: November 2016
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/state file controls system sleep states.
Reading from this file returns the available sleep state
labels, which may be "mem" (suspend), "standby" (power-on
suspend), "freeze" (suspend-to-idle) and "disk" (hibernation).
Writing one of the above strings to this file causes the system
to transition into the corresponding state, if available.
See Documentation/admin-guide/pm/sleep-states.rst for more
information.
What: /sys/power/mem_sleep
Date: November 2016
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/mem_sleep file controls the operating mode of
system suspend. Reading from it returns the available modes
as "s2idle" (always present), "shallow" and "deep" (present if
supported). The mode that will be used on subsequent attempts
to suspend the system (by writing "mem" to the /sys/power/state
file described above) is enclosed in square brackets.
Writing one of the above strings to this file causes the mode
represented by it to be used on subsequent attempts to suspend
the system.
See Documentation/admin-guide/pm/sleep-states.rst for more
information.
What: /sys/power/disk
Date: September 2006
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/disk file controls the operating mode of the
suspend-to-disk mechanism. Reading from this file returns
the name of the method by which the system will be put to
sleep on the next suspend. There are four methods supported:
'firmware' - means that the memory image will be saved to disk
by some firmware, in which case we also assume that the
firmware will handle the system suspend.
'platform' - the memory image will be saved by the kernel and
the system will be put to sleep by the platform driver (e.g.
ACPI or other PM registers).
'shutdown' - the memory image will be saved by the kernel and
the system will be powered off.
'reboot' - the memory image will be saved by the kernel and
the system will be rebooted.
Additionally, /sys/power/disk can be used to turn on one of the
two testing modes of the suspend-to-disk mechanism: 'testproc'
or 'test'. If the suspend-to-disk mechanism is in the
'testproc' mode, writing 'disk' to /sys/power/state will cause
the kernel to disable nonboot CPUs and freeze tasks, wait for 5
seconds, unfreeze tasks and enable nonboot CPUs. If it is in
the 'test' mode, writing 'disk' to /sys/power/state will cause
the kernel to disable nonboot CPUs and freeze tasks, shrink
memory, suspend devices, wait for 5 seconds, resume devices,
unfreeze tasks and enable nonboot CPUs. Then, we are able to
look in the log messages and work out, for example, which code
is being slow and which device drivers are misbehaving.
The suspend-to-disk method may be chosen by writing to this
file one of the accepted strings:
- 'firmware'
- 'platform'
- 'shutdown'
- 'reboot'
- 'testproc'
- 'test'
It will only change to 'firmware' or 'platform' if the system
supports that.
What: /sys/power/image_size
Date: August 2006
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/image_size file controls the size of the image
created by the suspend-to-disk mechanism. It can be written a
string representing a non-negative integer that will be used
as an upper limit of the image size, in bytes. The kernel's
suspend-to-disk code will do its best to ensure the image size
will not exceed this number. However, if it turns out to be
impossible, the kernel will try to suspend anyway using the
smallest image possible. In particular, if "0" is written to
this file, the suspend image will be as small as possible.
Reading from this file will display the current image size
limit, which is set to around 2/5 of available RAM by default.
What: /sys/power/pm_trace
Date: August 2006
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/pm_trace file controls the code which saves the
last PM event point in the RTC across reboots, so that you can
debug a machine that just hangs during suspend (or more
commonly, during resume). Namely, the RTC is only used to save
the last PM event point if this file contains '1'. Initially
it contains '0' which may be changed to '1' by writing a
string representing a nonzero integer into it.
To use this debugging feature you should attempt to suspend
the machine, then reboot it and run::
dmesg -s 1000000 | grep 'hash matches'
If you do not get any matches (or they appear to be false
positives), it is possible that the last PM event point
referred to a device created by a loadable kernel module. In
this case cat /sys/power/pm_trace_dev_match (see below) after
your system is started up and the kernel modules are loaded.
CAUTION: Using it will cause your machine's real-time (CMOS)
clock to be set to a random invalid time after a resume.
What; /sys/power/pm_trace_dev_match
Date: October 2010
Contact: James Hogan <[email protected]>
Description:
The /sys/power/pm_trace_dev_match file contains the name of the
device associated with the last PM event point saved in the RTC
across reboots when pm_trace has been used. More precisely it
contains the list of current devices (including those
registered by loadable kernel modules since boot) which match
the device hash in the RTC at boot, with a newline after each
one.
The advantage of this file over the hash matches printed to the
kernel log (see /sys/power/pm_trace), is that it includes
devices created after boot by loadable kernel modules.
Due to the small hash size necessary to fit in the RTC, it is
possible that more than one device matches the hash, in which
case further investigation is required to determine which
device is causing the problem. Note that genuine RTC clock
values (such as when pm_trace has not been used), can still
match a device and output its name here.
What: /sys/power/pm_async
Date: January 2009
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/pm_async file controls the switch allowing the
user space to enable or disable asynchronous suspend and resume
of devices. If enabled, this feature will cause some device
drivers' suspend and resume callbacks to be executed in parallel
with each other and with the main suspend thread. It is enabled
if this file contains "1", which is the default. It may be
disabled by writing "0" to this file, in which case all devices
will be suspended and resumed synchronously.
What: /sys/power/wakeup_count
Date: July 2010
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/wakeup_count file allows user space to put the
system into a sleep state while taking into account the
concurrent arrival of wakeup events. Reading from it returns
the current number of registered wakeup events and it blocks if
some wakeup events are being processed at the time the file is
read from. Writing to it will only succeed if the current
number of wakeup events is equal to the written value and, if
successful, will make the kernel abort a subsequent transition
to a sleep state if any wakeup events are reported after the
write has returned.
What: /sys/power/reserved_size
Date: May 2011
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/reserved_size file allows user space to control
the amount of memory reserved for allocations made by device
drivers during the "device freeze" stage of hibernation. It can
be written a string representing a non-negative integer that
will be used as the amount of memory to reserve for allocations
made by device drivers' "freeze" callbacks, in bytes.
Reading from this file will display the current value, which is
set to 1 MB by default.
What: /sys/power/autosleep
Date: April 2012
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/autosleep file can be written one of the strings
returned by reads from /sys/power/state. If that happens, a
work item attempting to trigger a transition of the system to
the sleep state represented by that string is queued up. This
attempt will only succeed if there are no active wakeup sources
in the system at that time. After every execution, regardless
of whether or not the attempt to put the system to sleep has
succeeded, the work item requeues itself until user space
writes "off" to /sys/power/autosleep.
Reading from this file causes the last string successfully
written to it to be returned.
What: /sys/power/wake_lock
Date: February 2012
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/wake_lock file allows user space to create
wakeup source objects and activate them on demand (if one of
those wakeup sources is active, reads from the
/sys/power/wakeup_count file block or return false). When a
string without white space is written to /sys/power/wake_lock,
it will be assumed to represent a wakeup source name. If there
is a wakeup source object with that name, it will be activated
(unless active already). Otherwise, a new wakeup source object
will be registered, assigned the given name and activated.
If a string written to /sys/power/wake_lock contains white
space, the part of the string preceding the white space will be
regarded as a wakeup source name and handled as descrived above.
The other part of the string will be regarded as a timeout (in
nanoseconds) such that the wakeup source will be automatically
deactivated after it has expired. The timeout, if present, is
set regardless of the current state of the wakeup source object
in question.
Reads from this file return a string consisting of the names of
wakeup sources created with the help of it that are active at
the moment, separated with spaces.
What: /sys/power/wake_unlock
Date: February 2012
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/wake_unlock file allows user space to deactivate
wakeup sources created with the help of /sys/power/wake_lock.
When a string is written to /sys/power/wake_unlock, it will be
assumed to represent the name of a wakeup source to deactivate.
If a wakeup source object of that name exists and is active at
the moment, it will be deactivated.
Reads from this file return a string consisting of the names of
wakeup sources created with the help of /sys/power/wake_lock
that are inactive at the moment, separated with spaces.
What: /sys/power/pm_print_times
Date: May 2012
Contact: Sameer Nanda <[email protected]>
Description:
The /sys/power/pm_print_times file allows user space to
control whether the time taken by devices to suspend and
resume is printed. These prints are useful for hunting down
devices that take too long to suspend or resume.
Writing a "1" enables this printing while writing a "0"
disables it. The default value is "0". Reading from this file
will display the current value.
What: /sys/power/pm_wakeup_irq
Date: April 2015
Contact: Alexandra Yates <[email protected]>
Description:
The /sys/power/pm_wakeup_irq file reports to user space the IRQ
number of the first wakeup interrupt (that is, the first
interrupt from an IRQ line armed for system wakeup) seen by the
kernel during the most recent system suspend/resume cycle.
This output is useful for system wakeup diagnostics of spurious
wakeup interrupts.
What: /sys/power/pm_debug_messages
Date: July 2017
Contact: Rafael J. Wysocki <[email protected]>
Description:
The /sys/power/pm_debug_messages file controls the printing
of debug messages from the system suspend/hiberbation
infrastructure to the kernel log.
Writing a "1" to this file enables the debug messages and
writing a "0" (default) to it disables them. Reads from
this file return the current value.
What: /sys/power/resume_offset
Date: April 2018
Contact: Mario Limonciello <[email protected]>
Description:
This file is used for telling the kernel an offset into a disk
to use when hibernating the system such as with a swap file.
Reads from this file will display the current offset
the kernel will be using on the next hibernation
attempt.
Using this sysfs file will override any values that were
set using the kernel command line for disk offset.
What: /sys/power/suspend_stats
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats directory contains suspend related
statistics.
What: /sys/power/suspend_stats/success
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/success file contains the number
of times entering system sleep state succeeded.
What: /sys/power/suspend_stats/fail
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/fail file contains the number
of times entering system sleep state failed.
What: /sys/power/suspend_stats/failed_freeze
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_freeze file contains the
number of times freezing processes failed.
What: /sys/power/suspend_stats/failed_prepare
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_prepare file contains the
number of times preparing all non-sysdev devices for
a system PM transition failed.
What: /sys/power/suspend_stats/failed_resume
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_resume file contains the
number of times executing "resume" callbacks of
non-sysdev devices failed.
What: /sys/power/suspend_stats/failed_resume_early
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_resume_early file contains
the number of times executing "early resume" callbacks
of devices failed.
What: /sys/power/suspend_stats/failed_resume_noirq
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_resume_noirq file contains
the number of times executing "noirq resume" callbacks
of devices failed.
What: /sys/power/suspend_stats/failed_suspend
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_suspend file contains
the number of times executing "suspend" callbacks
of all non-sysdev devices failed.
What: /sys/power/suspend_stats/failed_suspend_late
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_suspend_late file contains
the number of times executing "late suspend" callbacks
of all devices failed.
What: /sys/power/suspend_stats/failed_suspend_noirq
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/failed_suspend_noirq file contains
the number of times executing "noirq suspend" callbacks
of all devices failed.
What: /sys/power/suspend_stats/last_failed_dev
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/last_failed_dev file contains
the last device for which a suspend/resume callback failed.
What: /sys/power/suspend_stats/last_failed_errno
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/last_failed_errno file contains
the errno of the last failed attempt at entering
system sleep state.
What: /sys/power/suspend_stats/last_failed_step
Date: July 2019
Contact: Kalesh Singh <[email protected]>
Description:
The /sys/power/suspend_stats/last_failed_step file contains
the last failed step in the suspend/resume path.
What: /sys/power/suspend_stats/last_hw_sleep
Date: June 2023
Contact: Mario Limonciello <[email protected]>
Description:
The /sys/power/suspend_stats/last_hw_sleep file
contains the duration of time spent in a hardware sleep
state in the most recent system suspend-resume cycle.
This number is measured in microseconds.
What: /sys/power/suspend_stats/total_hw_sleep
Date: June 2023
Contact: Mario Limonciello <[email protected]>
Description:
The /sys/power/suspend_stats/total_hw_sleep file
contains the aggregate of time spent in a hardware sleep
state since the kernel was booted. This number
is measured in microseconds.
What: /sys/power/suspend_stats/max_hw_sleep
Date: June 2023
Contact: Mario Limonciello <[email protected]>
Description:
The /sys/power/suspend_stats/max_hw_sleep file
contains the maximum amount of time that the hardware can
report for time spent in a hardware sleep state. When sleep
cycles are longer than this time, the values for
'total_hw_sleep' and 'last_hw_sleep' may not be accurate.
This number is measured in microseconds.
What: /sys/power/sync_on_suspend
Date: October 2019
Contact: Jonas Meurer <[email protected]>
Description:
This file controls whether or not the kernel will sync()
filesystems during system suspend (after freezing user space
and before suspending devices).
Writing a "1" to this file enables the sync() and writing a "0"
disables it. Reads from the file return the current value.
The default is "1" if the build-time "SUSPEND_SKIP_SYNC" config
flag is unset, or "0" otherwise.
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