mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-02 08:34:20 +08:00
7483b4a4d9
Introduce a mechanism by which the kernel can trigger global transitions to a sleep state chosen by user space if there are no active wakeup sources. It consists of a new sysfs attribute, /sys/power/autosleep, that can be written one of the strings returned by reads from /sys/power/state, an ordered workqueue and a work item carrying out the "suspend" operations. If a string representing the system's sleep state is written to /sys/power/autosleep, the work item triggering transitions to that state is queued up and it requeues itself after every execution until user space writes "off" to /sys/power/autosleep. That work item enables the detection of wakeup events using the functions already defined in drivers/base/power/wakeup.c (with one small modification) and calls either pm_suspend(), or hibernate() to put the system into a sleep state. If a wakeup event is reported while the transition is in progress, it will abort the transition and the "system suspend" work item will be queued up again. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-by: NeilBrown <neilb@suse.de>
192 lines
8.0 KiB
Plaintext
192 lines
8.0 KiB
Plaintext
What: /sys/power/
|
|
Date: August 2006
|
|
Contact: Rafael J. Wysocki <rjw@sisk.pl>
|
|
Description:
|
|
The /sys/power directory will contain files that will
|
|
provide a unified interface to the power management
|
|
subsystem.
|
|
|
|
What: /sys/power/state
|
|
Date: August 2006
|
|
Contact: Rafael J. Wysocki <rjw@sisk.pl>
|
|
Description:
|
|
The /sys/power/state file controls the system power state.
|
|
Reading from this file returns what states are supported,
|
|
which is hard-coded to 'standby' (Power-On Suspend), 'mem'
|
|
(Suspend-to-RAM), and 'disk' (Suspend-to-Disk).
|
|
|
|
Writing to this file one of these strings causes the system to
|
|
transition into that state. Please see the file
|
|
Documentation/power/states.txt for a description of each of
|
|
these states.
|
|
|
|
What: /sys/power/disk
|
|
Date: September 2006
|
|
Contact: Rafael J. Wysocki <rjw@sisk.pl>
|
|
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@sisk.pl>
|
|
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@sisk.pl>
|
|
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 <james@albanarts.com>
|
|
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@sisk.pl>
|
|
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@sisk.pl>
|
|
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@sisk.pl>
|
|
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@sisk.pl>
|
|
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.
|