linux-kernel - Re: [PATCH] ACPI: do not fail suspend if unable to configure wakeup

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Date:	Wed, 19 Nov 2014 00:43:51 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Dmitry Torokhov <dtor@...omium.org>
Cc:	"Rafael J. Wysocki" <rafael@...nel.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Benson Leung <bleung@...omium.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI: do not fail suspend if unable to configure wakeup

On Tuesday, November 18, 2014 10:00:53 AM Dmitry Torokhov wrote:
> Hi Rafael,
> 
> On Thu, Oct 16, 2014 at 9:05 AM, Dmitry Torokhov <dtor@...omium.org> wrote:
> > Hi Rafael,
> >
> > On Thu, Oct 16, 2014 at 10:10:20AM +0200, Rafael J. Wysocki wrote:
> >> Hi,
> >>
> >> On Thu, Oct 16, 2014 at 12:56 AM, Dmitry Torokhov <dtor@...omium.org> wrote:
> >> > Newer kernels put i2c devices with ACPI companion in ACPI power domain and
> >> > then ACPI will try to configure them for wakeup (if requested).
> >> > Unfortunately on some Chromebooks firmware separates wakeup GPIO into a
> >> > completely separate device (which is handled by the kernel as a sleep
> >> > button), leaving the touchpads themselves not wakeup capable (as far as
> >> > ACPI is concerned). This causes ACPI late suspend code to fail to configure
> >> > them as wakeup sources and aborts entire suspend.
> >> >
> >> > To work around this issues let's not abort entire suspend process if
> >> > driver asked to be a wakeup source but ACPI can not satisfy that
> >> > request.
> >> >
> >> > Note that originally I tried to simply change the driver to not mark
> >> > device as wakeup source, unfortunately then we do not know that we
> >> > should not be powering down the device completely, otherwise we can't
> >> > wake up.
> >> >
> >> > Verified by making sure that "echo mem > /sys/power/state" works on
> >> > Squawks.
> >> >
> >> > Reviewed-by: Benson Leung <bleung@...omium.org>
> >> > Signed-off-by: Dmitry Torokhov <dtor@...omium.org>
> >> > ---
> >> >  drivers/acpi/device_pm.c | 16 ++++++++++++----
> >> >  1 file changed, 12 insertions(+), 4 deletions(-)
> >> >
> >> > diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
> >> > index 67075f8..440bc3d 100644
> >> > --- a/drivers/acpi/device_pm.c
> >> > +++ b/drivers/acpi/device_pm.c
> >> > @@ -871,6 +871,7 @@ int acpi_dev_suspend_late(struct device *dev)
> >> >         struct acpi_device *adev = ACPI_COMPANION(dev);
> >> >         u32 target_state;
> >> >         bool wakeup;
> >> > +       bool can_wakeup;
> >> >         int error;
> >> >
> >> >         if (!adev)
> >> > @@ -878,12 +879,19 @@ int acpi_dev_suspend_late(struct device *dev)
> >> >
> >> >         target_state = acpi_target_system_state();
> >> >         wakeup = device_may_wakeup(dev);
> >> > -       error = acpi_device_wakeup(adev, target_state, wakeup);
> >> > -       if (wakeup && error)
> >> > -               return error;
> >> > +       can_wakeup = acpi_device_can_wakeup(adev);
> >> > +
> >> > +       if (can_wakeup) {
> >> > +               error = acpi_device_wakeup(adev, target_state, wakeup);
> >> > +               if (wakeup && error)
> >> > +                       return error;
> >> > +       } else if (wakeup) {
> >>
> >> I think we just need to return an error code in that case, because otherwise
> >
> > We used to return error and that error aborted the suspend altogether,
> > which prompted creating this patch.
> >
> >> this is potentially dangerous (worst case, it may be impossible to wake up
> >> the machine at all after that).
> >
> > Yes, there is such potential, but that kind of error (no working wakeup
> > sources) will be discovered before a box is shipped. Right now we have
> > boxes in the wild that suspend fine with 3.10 and refuse to suspend with
> > 3.14 because between 3.10 and 3.14 we started placing i2c devices with
> > ACPI companions into ACPI power domain and ACPI power domain is now
> > trying to configure them as wakeup sources and fails.
> 
> A gentle ping on the patch - without it (or something else) we basically
> have a regression on shipped hardware: Chromebooks that were
> suspending fine with 3.10 refuse to suspend with 3.14.

It fell of my radar, sorry about that.

So the error here is that device_may_wakeup(dev) returns true, because the
device is technically wakeup-capable, but the wakeup is not via ACPI?

I'd say this is rather not in accordance with the spec, but that means we
need to simply ignore 'wakeup' if acpi_device_can_wakeup(adev) returns false.

So what about the appended patch?

Rafael


---
 drivers/acpi/device_pm.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-pm/drivers/acpi/device_pm.c
===================================================================
--- linux-pm.orig/drivers/acpi/device_pm.c
+++ linux-pm/drivers/acpi/device_pm.c
@@ -878,7 +878,7 @@ int acpi_dev_suspend_late(struct device
 		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_wakeup(adev, target_state, wakeup);
 	if (wakeup && error)
 		return error;

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