247 lines
10 KiB
Plaintext
247 lines
10 KiB
Plaintext
What: /sys/power/
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Date: August 2006
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power directory will contain files that will
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provide a unified interface to the power management
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subsystem.
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What: /sys/power/state
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Date: August 2006
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/state file controls the system power state.
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Reading from this file returns what states are supported,
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which is hard-coded to 'standby' (Power-On Suspend), 'mem'
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(Suspend-to-RAM), and 'disk' (Suspend-to-Disk).
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Writing to this file one of these strings causes the system to
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transition into that state. Please see the file
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Documentation/power/states.txt for a description of each of
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these states.
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What: /sys/power/disk
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Date: September 2006
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/disk file controls the operating mode of the
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suspend-to-disk mechanism. Reading from this file returns
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the name of the method by which the system will be put to
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sleep on the next suspend. There are four methods supported:
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'firmware' - means that the memory image will be saved to disk
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by some firmware, in which case we also assume that the
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firmware will handle the system suspend.
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'platform' - the memory image will be saved by the kernel and
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the system will be put to sleep by the platform driver (e.g.
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ACPI or other PM registers).
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'shutdown' - the memory image will be saved by the kernel and
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the system will be powered off.
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'reboot' - the memory image will be saved by the kernel and
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the system will be rebooted.
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Additionally, /sys/power/disk can be used to turn on one of the
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two testing modes of the suspend-to-disk mechanism: 'testproc'
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or 'test'. If the suspend-to-disk mechanism is in the
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'testproc' mode, writing 'disk' to /sys/power/state will cause
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the kernel to disable nonboot CPUs and freeze tasks, wait for 5
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seconds, unfreeze tasks and enable nonboot CPUs. If it is in
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the 'test' mode, writing 'disk' to /sys/power/state will cause
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the kernel to disable nonboot CPUs and freeze tasks, shrink
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memory, suspend devices, wait for 5 seconds, resume devices,
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unfreeze tasks and enable nonboot CPUs. Then, we are able to
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look in the log messages and work out, for example, which code
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is being slow and which device drivers are misbehaving.
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The suspend-to-disk method may be chosen by writing to this
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file one of the accepted strings:
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'firmware'
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'platform'
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'shutdown'
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'reboot'
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'testproc'
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'test'
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It will only change to 'firmware' or 'platform' if the system
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supports that.
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What: /sys/power/image_size
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Date: August 2006
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/image_size file controls the size of the image
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created by the suspend-to-disk mechanism. It can be written a
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string representing a non-negative integer that will be used
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as an upper limit of the image size, in bytes. The kernel's
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suspend-to-disk code will do its best to ensure the image size
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will not exceed this number. However, if it turns out to be
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impossible, the kernel will try to suspend anyway using the
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smallest image possible. In particular, if "0" is written to
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this file, the suspend image will be as small as possible.
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Reading from this file will display the current image size
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limit, which is set to 500 MB by default.
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What: /sys/power/pm_trace
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Date: August 2006
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/pm_trace file controls the code which saves the
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last PM event point in the RTC across reboots, so that you can
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debug a machine that just hangs during suspend (or more
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commonly, during resume). Namely, the RTC is only used to save
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the last PM event point if this file contains '1'. Initially
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it contains '0' which may be changed to '1' by writing a
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string representing a nonzero integer into it.
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To use this debugging feature you should attempt to suspend
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the machine, then reboot it and run
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dmesg -s 1000000 | grep 'hash matches'
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If you do not get any matches (or they appear to be false
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positives), it is possible that the last PM event point
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referred to a device created by a loadable kernel module. In
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this case cat /sys/power/pm_trace_dev_match (see below) after
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your system is started up and the kernel modules are loaded.
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CAUTION: Using it will cause your machine's real-time (CMOS)
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clock to be set to a random invalid time after a resume.
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What; /sys/power/pm_trace_dev_match
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Date: October 2010
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Contact: James Hogan <james@albanarts.com>
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Description:
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The /sys/power/pm_trace_dev_match file contains the name of the
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device associated with the last PM event point saved in the RTC
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across reboots when pm_trace has been used. More precisely it
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contains the list of current devices (including those
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registered by loadable kernel modules since boot) which match
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the device hash in the RTC at boot, with a newline after each
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one.
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The advantage of this file over the hash matches printed to the
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kernel log (see /sys/power/pm_trace), is that it includes
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devices created after boot by loadable kernel modules.
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Due to the small hash size necessary to fit in the RTC, it is
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possible that more than one device matches the hash, in which
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case further investigation is required to determine which
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device is causing the problem. Note that genuine RTC clock
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values (such as when pm_trace has not been used), can still
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match a device and output it's name here.
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What: /sys/power/pm_async
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Date: January 2009
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/pm_async file controls the switch allowing the
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user space to enable or disable asynchronous suspend and resume
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of devices. If enabled, this feature will cause some device
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drivers' suspend and resume callbacks to be executed in parallel
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with each other and with the main suspend thread. It is enabled
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if this file contains "1", which is the default. It may be
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disabled by writing "0" to this file, in which case all devices
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will be suspended and resumed synchronously.
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What: /sys/power/wakeup_count
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Date: July 2010
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/wakeup_count file allows user space to put the
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system into a sleep state while taking into account the
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concurrent arrival of wakeup events. Reading from it returns
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the current number of registered wakeup events and it blocks if
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some wakeup events are being processed at the time the file is
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read from. Writing to it will only succeed if the current
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number of wakeup events is equal to the written value and, if
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successful, will make the kernel abort a subsequent transition
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to a sleep state if any wakeup events are reported after the
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write has returned.
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What: /sys/power/reserved_size
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Date: May 2011
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/reserved_size file allows user space to control
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the amount of memory reserved for allocations made by device
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drivers during the "device freeze" stage of hibernation. It can
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be written a string representing a non-negative integer that
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will be used as the amount of memory to reserve for allocations
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made by device drivers' "freeze" callbacks, in bytes.
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Reading from this file will display the current value, which is
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set to 1 MB by default.
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What: /sys/power/autosleep
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Date: April 2012
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/autosleep file can be written one of the strings
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returned by reads from /sys/power/state. If that happens, a
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work item attempting to trigger a transition of the system to
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the sleep state represented by that string is queued up. This
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attempt will only succeed if there are no active wakeup sources
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in the system at that time. After every execution, regardless
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of whether or not the attempt to put the system to sleep has
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succeeded, the work item requeues itself until user space
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writes "off" to /sys/power/autosleep.
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Reading from this file causes the last string successfully
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written to it to be returned.
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What: /sys/power/wake_lock
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Date: February 2012
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/wake_lock file allows user space to create
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wakeup source objects and activate them on demand (if one of
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those wakeup sources is active, reads from the
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/sys/power/wakeup_count file block or return false). When a
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string without white space is written to /sys/power/wake_lock,
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it will be assumed to represent a wakeup source name. If there
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is a wakeup source object with that name, it will be activated
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(unless active already). Otherwise, a new wakeup source object
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will be registered, assigned the given name and activated.
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If a string written to /sys/power/wake_lock contains white
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space, the part of the string preceding the white space will be
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regarded as a wakeup source name and handled as descrived above.
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The other part of the string will be regarded as a timeout (in
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nanoseconds) such that the wakeup source will be automatically
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deactivated after it has expired. The timeout, if present, is
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set regardless of the current state of the wakeup source object
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in question.
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Reads from this file return a string consisting of the names of
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wakeup sources created with the help of it that are active at
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the moment, separated with spaces.
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What: /sys/power/wake_unlock
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Date: February 2012
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Contact: Rafael J. Wysocki <rjw@sisk.pl>
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Description:
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The /sys/power/wake_unlock file allows user space to deactivate
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wakeup sources created with the help of /sys/power/wake_lock.
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When a string is written to /sys/power/wake_unlock, it will be
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assumed to represent the name of a wakeup source to deactivate.
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If a wakeup source object of that name exists and is active at
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the moment, it will be deactivated.
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Reads from this file return a string consisting of the names of
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wakeup sources created with the help of /sys/power/wake_lock
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that are inactive at the moment, separated with spaces.
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What: /sys/power/pm_print_times
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Date: May 2012
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Contact: Sameer Nanda <snanda@chromium.org>
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Description:
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The /sys/power/pm_print_times file allows user space to
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control whether the time taken by devices to suspend and
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resume is printed. These prints are useful for hunting down
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devices that take too long to suspend or resume.
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Writing a "1" enables this printing while writing a "0"
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disables it. The default value is "0". Reading from this file
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will display the current value.
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