Update the device PM documentation in devices.txt and runtime_pm.txt
to reflect the changes in the system suspend and resume handling
related to the introduction of the new power.direct_complete flag.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Fix double words "the the" in various files
within Documentations.
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
The current device suspend/resume phases during system-wide power
transitions appear to be insufficient for some platforms that want
to use the same callback routines for saving device states and
related operations during runtime suspend/resume as well as during
system suspend/resume. In principle, they could point their
.suspend_noirq() and .resume_noirq() to the same callback routines
as their .runtime_suspend() and .runtime_resume(), respectively,
but at least some of them require device interrupts to be enabled
while the code in those routines is running.
It also makes sense to have device suspend-resume callbacks that will
be executed with runtime PM disabled and with device interrupts
enabled in case someone needs to run some special code in that
context during system-wide power transitions.
Apart from this, .suspend_noirq() and .resume_noirq() were introduced
as a workaround for drivers using shared interrupts and failing to
prevent their interrupt handlers from accessing suspended hardware.
It appears to be better not to use them for other porposes, or we may
have to deal with some serious confusion (which seems to be happening
already).
For the above reasons, introduce new device suspend/resume phases,
"late suspend" and "early resume" (and analogously for hibernation)
whose callback will be executed with runtime PM disabled and with
device interrupts enabled and whose callback pointers generally may
point to runtime suspend/resume routines.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Make the PM core execute driver PM callbacks directly if the
corresponding subsystem callbacks are not present.
There are three reasons for doing that. First, it reflects the
behavior of drivers/base/dd.c:really_probe() that runs the driver's
.probe() callback directly if the bus type's one is not defined, so
this change will remove one arbitrary difference between the PM core
and the remaining parts of the driver core. Second, it will allow
some subsystems, whose PM callbacks don't do anything except for
executing driver callbacks, to be simplified quite a bit by removing
those "forward-only" callbacks. Finally, it will allow us to remove
one level of indirection in the system suspend and resume code paths
where it is not necessary, which is going to lead to less debug noise
with initcall_debug passed in the kernel command line (messages won't
be printed for driverless devices whose subsystems don't provide
PM callbacks among other things).
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The system wakeup section of Documentation/power/devices.txt is
outdated, so make it agree with the current code.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The documentation file Documentation/power/devices.txt contains some
information that isn't correct any more due to code modifications
made after that file had been created (or updated last time). Fix
this.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The current power management documentation in Documentation/power/
either doesn't cover PM domains at all, or gives inaccurate
information about them, so update the relevant files in there to
follow the code.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
There is a problem with the current ordering of hibernate code which
leads to deadlocks in some filesystems' memory shrinkers. Namely,
some filesystems use freezable kernel threads that are inactive when
the hibernate memory preallocation is carried out. Those same
filesystems use memory shrinkers that may be triggered by the
hibernate memory preallocation. If those memory shrinkers wait for
the frozen kernel threads, the hibernate process deadlocks (this
happens with XFS, for one example).
Apparently, it is not technically viable to redesign the filesystems
in question to avoid the situation described above, so the only
possible solution of this issue is to defer the freezing of kernel
threads until the hibernate memory preallocation is done, which is
implemented by this change.
Unfortunately, this requires the memory preallocation to be done
before the "prepare" stage of device freeze, so after this change the
only way drivers can allocate additional memory for their freeze
routines in a clean way is to use PM notifiers.
Reported-by: Christoph <cr2005@u-club.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This patch (as1485) documents a change to the kernel's default wakeup
policy. Devices that forward wakeup requests between buses should be
enabled for wakeup by default.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The documents describing the interactions between runtime PM and
system sleep generally refer to the model in which the system sleep
state is entered through a global firmware or hardware operation.
As a result, some recommendations given in there are not entirely
suitable for systems in which this is not the case. Update the
documentation to take the existence of those systems into account.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Kevin Hilman <khilman@ti.com>
The naming convention used by commit 7538e3db6e015e890825fbd9f86599b
(PM: Add support for device power domains), which introduced the
struct dev_power_domain type for representing device power domains,
evidently confuses some developers who tend to think that objects
of this type must correspond to "power domains" as defined by
hardware, which is not the case. Namely, at the kernel level, a
struct dev_power_domain object can represent arbitrary set of devices
that are mutually dependent power management-wise and need not belong
to one hardware power domain. To avoid that confusion, rename struct
dev_power_domain to struct dev_pm_domain and rename the related
pointers in struct device and struct pm_clk_notifier_block from
pwr_domain to pm_domain.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Kevin Hilman <khilman@ti.com>
Commit 4d27e9dcff (PM: Make power
domain callbacks take precedence over subsystem ones) forgot to
update the device power management documentation to take changes
made by it into account. Correct that mistake.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The part of Documentation/power/devices.txt regarding sysdevs is not
valid any more after commit 2e711c04db
(PM: Remove sysdev suspend, resume and shutdown operations), so
remove it.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
If device drivers allocate substantial amounts of memory (above 1 MB)
in their hibernate .freeze() callbacks (or in their legacy suspend
callbcks during hibernation), the subsequent creation of hibernate
image may fail due to the lack of memory. This is the case, because
the drivers' .freeze() callbacks are executed after the hibernate
memory preallocation has been carried out and the preallocated amount
of memory may be too small to cover the new driver allocations.
Unfortunately, the drivers' .prepare() callbacks also are executed
after the hibernate memory preallocation has completed, so they are
not suitable for allocating additional memory either. Thus the only
way a driver can safely allocate memory during hibernation is to use
a hibernate/suspend notifier. However, the notifiers are called
before the freezing of user space and the drivers wanting to use them
for allocating additional memory may not know how much memory needs
to be allocated at that point.
To let device drivers overcome this difficulty rework the hibernation
sequence so that the memory preallocation is carried out after the
drivers' .prepare() callbacks have been executed, so that the
.prepare() callbacks can be used for allocating additional memory
to be used by the drivers' .freeze() callbacks. Update documentation
to match the new behavior of the code.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The code handling system-wide power transitions (eg. suspend-to-RAM)
can in theory execute callbacks provided by the device's bus type,
device type and class in each phase of the power transition. In
turn, the runtime PM core code only calls one of those callbacks at
a time, preferring bus type callbacks to device type or class
callbacks and device type callbacks to class callbacks.
It seems reasonable to make them both behave in the same way in that
respect. Moreover, even though a device may belong to two subsystems
(eg. bus type and device class) simultaneously, in practice power
management callbacks for system-wide power transitions are always
provided by only one of them (ie. if the bus type callbacks are
defined, the device class ones are not and vice versa). Thus it is
possible to modify the code handling system-wide power transitions
so that it follows the core runtime PM code (ie. treats the
subsystem callbacks as mutually exclusive).
On the other hand, the core runtime PM code will choose to execute,
for example, a runtime suspend callback provided by the device type
even if the bus type's struct dev_pm_ops object exists, but the
runtime_suspend pointer in it happens to be NULL. This is confusing,
because it may lead to the execution of callbacks from different
subsystems during different operations (eg. the bus type suspend
callback may be executed during runtime suspend of the device, while
the device type callback will be executed during system suspend).
Make all of the power management code treat subsystem callbacks in
a consistent way, such that:
(1) If the device's type is defined (eg. dev->type is not NULL)
and its pm pointer is not NULL, the callbacks from dev->type->pm
will be used.
(2) If dev->type is NULL or dev->type->pm is NULL, but the device's
class is defined (eg. dev->class is not NULL) and its pm pointer
is not NULL, the callbacks from dev->class->pm will be used.
(3) If dev->type is NULL or dev->type->pm is NULL and dev->class is
NULL or dev->class->pm is NULL, the callbacks from dev->bus->pm
will be used provided that both dev->bus and dev->bus->pm are
not NULL.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Kevin Hilman <khilman@ti.com>
Reasoning-sounds-sane-to: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
The platform bus type is often used to handle Systems-on-a-Chip (SoC)
where all devices are represented by objects of type struct
platform_device. In those cases the same "platform" device driver
may be used with multiple different system configurations, but the
actions needed to put the devices it handles into a low-power state
and back into the full-power state may depend on the design of the
given SoC. The driver, however, cannot possibly include all the
information necessary for the power management of its device on all
the systems it is used with. Moreover, the device hierarchy in its
current form also is not suitable for representing this kind of
information.
The patch below attempts to address this problem by introducing
objects of type struct dev_power_domain that can be used for
representing power domains within a SoC. Every struct
dev_power_domain object provides a sets of device power
management callbacks that can be used to perform what's needed for
device power management in addition to the operations carried out by
the device's driver and subsystem.
Namely, if a struct dev_power_domain object is pointed to by the
pwr_domain field in a struct device, the callbacks provided by its
ops member will be executed in addition to the corresponding
callbacks provided by the device's subsystem and driver during all
power transitions.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Tested-and-acked-by: Kevin Hilman <khilman@ti.com>
Currently, wakeup sysfs attributes are created for all devices,
regardless of whether or not they are wakeup-capable. This is
excessive and complicates wakeup device identification from user
space (i.e. to identify wakeup-capable devices user space has to read
/sys/devices/.../power/wakeup for all devices and see if they are not
empty).
Fix this issue by avoiding to create wakeup sysfs files for devices
that cannot wake up the system from sleep states (i.e. whose
power.can_wakeup flags are unset during registration) and modify
device_set_wakeup_capable() so that it adds (or removes) the relevant
sysfs attributes if a device's wakeup capability status is changed.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Improve the device power management document after it's been
updated by the previous patch.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The device PM document, Documentation/power/devices.txt, is badly
outdated and requires total rework to fit the current design of the
PM framework. Make it more up to date.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Reviewed-by: Randy Dunlap <randy.dunlap@oracle.com>
Remove the ->suspend_late() and ->resume_early() callbacks
from struct bus_type V2. These callbacks are legacy stuff
at this point and since there seem to be no in-tree users
we may as well remove them. New users should use dev_pm_ops.
Signed-off-by: Magnus Damm <damm@igel.co.jp>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Modify the PM core to protect its data structures, specifically the
dpm_active list, from being corrupted if a child of the currently
suspending device is registered concurrently with its ->suspend()
callback. In that case, since the new device (the child) is added
to dpm_active after its parent, the PM core will attempt to
suspend it after the parent, which is wrong.
Introduce a new member of struct dev_pm_info, called 'sleeping',
and use it to check if the parent of the device being added to
dpm_active has been suspended, in which case the device registration
fails. Also, use 'sleeping' for checking if the ordering of devices
on dpm_active is correct.
Introduce variable 'all_sleeping' that will be set to 'true' once all
devices have been suspended and make new device registrations fail
until 'all_sleeping' is reset to 'false', in order to avoid having
unsuspended devices around while the system is going into a sleep state.
Remove pm_sleep_rwsem which is not necessary any more.
Special thanks to Alan Stern for discussions and suggestions that
lead to the creation of this patch.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
During the last step of hibernation in the "platform" mode (with the
help of ACPI) we use the suspend code, including the devices'
->suspend() methods, to prepare the system for entering the ACPI S4
system sleep state.
But at least for some devices the operations performed by the
->suspend() callback in that case must be different from its operations
during regular suspend.
For this reason, introduce the new PM event type PM_EVENT_HIBERNATE and
pass it to the device drivers' ->suspend() methods during the last phase
of hibernation, so that they can distinguish this case and handle it as
appropriate. Modify the drivers that handle PM_EVENT_SUSPEND in a
special way and need to handle PM_EVENT_HIBERNATE in the same way.
These changes are necessary to fix a hibernation regression related
to the i915 driver (ref. http://lkml.org/lkml/2008/2/22/488).
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Tested-by: Jeff Chua <jeff.chua.linux@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The /sys/devices/.../power/state files have been gone for a while
now, but I just noticed some documentation that still refers to
them. (Fortunately described as DEPRECATED and WILL REMOVE).
Time to remove that obsolete documentation too ...
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Len Brown <len.brown@intel.com>
This turned into a rewrite of Documentation/power/devices.txt:
- Provide more of the "big picture"
- Fixup some of the horribly ancient/obsolete description of device suspend()
semantics; lots of text just got deleted.
- Add a decent description of PM_EVENT_* codes, including the new PRETHAW code
needed in some swsusp scenarios.
- Describe the new PM factorization from Linus:
* class suspend, current suspend, then suspend_late
* NOT suspend_prepare, it wasn't really usable
* resume_early, current resume, class resume.
- Updates power/state docs to be correct, and deprecate its usage except for
driver testing.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
The driver model has a "detach_state" mechanism that:
- Has never been used by any in-kernel drive;
- Is superfluous, since driver remove() methods can do the same thing;
- Became buggy when the suspend() parameter changed semantics and type;
- Could self-deadlock when called from certain suspend contexts;
- Is effectively wasted documentation, object code, and headspace.
This removes that "detach_state" mechanism; net code shrink, as well
as a per-device saving in the driver model and sysfs.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
