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[ Upstream commit 03f1444016b71feffa1dfb8a51f15ba592f94b13 ]
When dpm_suspend() fails, some devices with power.direct_complete set
may not have been handled by device_suspend() yet, so runtime PM has
not been disabled for them yet even though power.direct_complete is set.
Since device_resume() expects that runtime PM has been disabled for all
devices with power.direct_complete set, it will attempt to reenable
runtime PM for the devices that have not been processed by device_suspend()
which does not make sense. Had those devices had runtime PM disabled
before device_suspend() had run, device_resume() would have inadvertently
enable runtime PM for them, but this is not expected to happen because
it would require ->prepare() callbacks to return positive values for
devices with runtime PM disabled, which would be invalid.
In practice, this issue is most likely benign because pm_runtime_enable()
will not allow the "disable depth" counter to underflow, but it causes a
warning message to be printed for each affected device.
To allow device_resume() to distinguish the "direct complete" devices
that have been processed by device_suspend() from those which have not
been handled by it, make device_suspend() set power.is_suspended for
"direct complete" devices.
Next, move the power.is_suspended check in device_resume() before the
power.direct_complete check in it to make it skip the "direct complete"
devices that have not been handled by device_suspend().
This change is based on a preliminary patch from Saravana Kannan.
Fixes: aae4518b31 ("PM / sleep: Mechanism to avoid resuming runtime-suspended devices unnecessarily")
Link: https://lore.kernel.org/linux-pm/20241114220921.2529905-2-saravanak@google.com/
Reported-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Saravana Kannan <saravanak@google.com>
Link: https://patch.msgid.link/12627587.O9o76ZdvQC@rjwysocki.net
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.