[PATCH 3.16.y-ckt 047/168] ACPI / PM: Ignore wakeup setting if the ACPI companion can't wake up

[Luis Henriques]

3.16.7-ckt3 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>

commit 78579b7c7eb45f0e7ec5e9437087ed21749f9a9c upstream.

As reported by Dmitry, on some Chromebooks there are devices with
corresponding ACPI objects and with unusual system wakeup
configuration.  Namely, they technically are wakeup-capable, but the
wakeup is handled via a platform-specific out-of-band mechanism and
the ACPI PM layer has no information on the wakeup capability.  As
a result, device_may_wakeup(dev) called from acpi_dev_suspend_late()
returns 'true' for those devices, but the wakeup.flags.valid flag is
unset for the corresponding ACPI device objects, so acpi_device_wakeup()
reproducibly fails for them causing acpi_dev_suspend_late() to return
an error code.  The entire system suspend is then aborted and the
machines in question cannot suspend at all.

Address the problem by ignoring the device_may_wakeup(dev) return
value in acpi_dev_suspend_late() if the ACPI companion of the device
being handled has wakeup.flags.valid unset (in which case it is clear
that the wakeup is supposed to be handled by other means).

This fixes a regression introduced by commit a76e9bd89ae7 (i2c:
attach/detach I2C client device to the ACPI power domain) as the
affected systems could suspend and resume successfully before that
commit.

Fixes: a76e9bd89ae7 (i2c: attach/detach I2C client device to the ACPI power domain)
Reported-by: Dmitry Torokhov <dtor@xxxxxxxxxxxx>
Reviewed-by: Dmitry Torokhov <dtor@xxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 drivers/acpi/device_pm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
index 49a51277f81d..9ea7b99bc9a0 100644
--- a/drivers/acpi/device_pm.c
+++ b/drivers/acpi/device_pm.c
@@ -859,7 +859,7 @@ int acpi_dev_suspend_late(struct device *dev)
 		return 0;
 
 	target_state = acpi_target_system_state();
-	wakeup = device_may_wakeup(dev);
+	wakeup = device_may_wakeup(dev) && acpi_device_can_wakeup(adev);
 	error = __acpi_device_sleep_wake(adev, target_state, wakeup);
 	if (wakeup && error)
 		return error;
-- 
2.1.3

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