[PATCH 0/5] PM / sleep: Support power button wakeup from S2I on recent Dell laptops

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

Hi All,

The underlying issue is that on some relatively new Dell laltops, including
Dell XPS13 9360 and 9365, pressing the power button is not sufficient to
wake up the system from suspend-to-idle (it has to be pressed and held
down for around 5 sec for the wakeup to happen) which is not expected
and does not match the Windows' behavior.

This turns out to be a consequence of the way power button events are signaled
on those systems, which is through the Embedded Controller (EC).  Namely,
button events go to the EC which then signals the event through its ACPI GPE
(General Purpose Event), which triggers an ACPI SCI (System Control Interrupt),
whose handler executes a specicif AML control method and triggers a Notify()
targetting a devie object associated with the power button.  The problem with
suspend-to-idle is that the EC GPE is disabled during suspend, because
otherwise all EC events would wake up the system from suspend-to-idle (and
there can be many of them).

The only way to address this is to allow the EC GPE to stay enabled while
suspended to idle, but that cannot be done unconditionally, because of the
possible spurious wakeup events from the EC.  Fortunately, on the Dell systems
in question it is possible to reduce the number of events coming from the EC
while suspended (see the changelog of patch [3/5] for details), but still some
spurious events may happen.  For this reason, when there is an SCI while
suspended, it is not practical to resume all the way up to user space.
Instead, it is better to resume partially up to the point at which the SCI can
be processed by its handler, which is after calling dpm_resume_noirq(), let
the SCI be processed and if no real wakeup events come out of that,
suspend again.  Actually, that can be done in general, because spurious
SCIs do happen while suspended to idle on other systems too, and that's
which it goes as patch [2/5] before the Dell-related changes.

Patch [1/5] is more of a cleanup, but makes the rest look slightly more
straightforward, and patches [4-5/5] update the drivers used for button
events processing on the affected systems so that they signal wakeup
as expected and avoid propagating the wakeup events as button events
to user space.

The series is available from a git branch at

 git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git s2idle-dell-test

and has been included into the testing branch thereof.

Please let me know if there are any concerns.

Thanks,
Rafael