linux-kernel - Re: [PATCH] GPIO button wth wakeup attribute is supposed to wake the system up

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Message-ID: <1489151.dWxTTZlWzH@vostro.rjw.lan>
Date:	Tue, 08 Jul 2014 23:47:01 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	"Li, Aubrey" <aubrey.li@...ux.intel.com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH] GPIO button wth wakeup attribute is supposed to wake the system up

On Tuesday, July 08, 2014 02:12:59 PM Dmitry Torokhov wrote:
> On Tue, Jul 08, 2014 at 11:06:17PM +0200, Rafael J. Wysocki wrote:
> > On Tuesday, July 08, 2014 01:45:30 PM Dmitry Torokhov wrote:
> > > On Tue, Jul 08, 2014 at 10:52:52PM +0200, Rafael J. Wysocki wrote:
> > > > On Thursday, June 19, 2014 08:51:25 AM Li, Aubrey wrote:
> > > > > When the wakeup attribute is set, the GPIO button is capable of
> > > > > waking up the system from sleep states, including the "freeze"
> > > > > sleep state.  For that to work, its driver needs to pass the
> > > > > IRQF_NO_SUSPEND flag to devm_request_any_context_irq(), or the
> > > > > interrupt will be disabled by suspend_device_irqs() and the
> > > > > system won't be woken up by it from the "freeze" sleep state.
> > > > > 
> > > > > The suspend_device_irqs() routine is a workaround for drivers
> > > > > that mishandle interrupts triggered when the devices handled
> > > > > by them are suspended, so it is safe to use IRQF_NO_SUSPEND in
> > > > > all drivers that don't have that problem.
> > > > > 
> > > > > The affected/tested machines include Dell Venue 11 Pro and Asus T100TA.
> > > > > 
> > > > > Signed-off-by: Aubrey Li <aubrey.li@...ux.intel.com>
> > > > > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > 
> > > > OK
> > > > 
> > > > Due to the lack of response (ie. no objections) and because the issue
> > > > addressed by this patch is real, I'm queuing it up as a PM-related fix
> > > > for 3.17.
> > > 
> > > Please do not. The response is till the same: board code should make sure
> > > that enable_irq_wake() does the right thing and keeps interrupts enabled.
> > 
> > Which board code?  That's nothing like that for the platforms in question.
> 
> Then it needs to be written.

Well, excuse me, but I don't get it.  Why would I need to write any board code
for an ACPI-based system?

> > > It is wrong to patch drivers for this.
> > 
> > Why is it?  Only drivers know if they can handle incoming interrupts after
> > having suspended their devices.
> 
> The driver correctly used enable_irq_wake() to indicate that interrupt should
> be a wakeup source, the now the core/board needs to make sure the interrupt
> gets delivered to the driver properly. We should not be patching every driver
> that uses enable_irq_wake() with IRQF_NO_SUSPEND.

Interrupts that can wake up from the "freeze" sleep state need not be set up
with enable_irq_wake() and the flag doesn't say "this is a wakeup interrupt".
It says "do not suspend this interrupt, I can handle it after the device has
been suspended" (as I said).

And if it is OK for a driver to set IRQF_SHARED, it is equally OK for it to
set IRQF_NO_SUSPEND, because, in fact, those two flags are related.

> If you look at the earlier patch discussion Tegra folks managed to implement
> this behavior just fine.

I'm not sure whose idea it was that IRQF_NO_SUSPEND was not to be set by drivers,
but it is not a correct one.  I know why suspend_device_irqs() was introduced
and I'm telling you this has nothing to do with setting up the IRQ chip to do
system wakeup.

And please grep for IRQF_NO_SUSPEND to see how drivers generally use it.

Rafael

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