What: /sys/power/ Date: August 2006 Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 500 MB by default. What: /sys/power/pm_trace Date: August 2006 Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 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 <jhogan@kernel.org> 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 it's name here. What: /sys/power/pm_async Date: January 2009 Contact: Rafael J. Wysocki <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <rjw@rjwysocki.net> 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 <snanda@chromium.org> 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 <alexandra.yates@linux.intel.org> 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 <rjw@rjwysocki.net> 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 <mario.limonciello@dell.com> 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.
