linux-kernel - [PATCH 0/3] irq / PM: wakeup interrupt interface for drivers (was: Re: [RFC][PATCH] irq: Rework IRQF_NO

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Message-ID: <8151374.tpuvaHv3nd@vostro.rjw.lan>
Date:	Wed, 30 Jul 2014 23:46:59 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org,
	Linux PM list <linux-pm@...r.kernel.org>,
	Dmitry Torokhov <dtor@...gle.com>
Subject: [PATCH 0/3] irq / PM: wakeup interrupt interface for drivers (was: Re: [RFC][PATCH] irq: Rework IRQF_NO_SUSPENDED)

On Tuesday, July 29, 2014 03:33:23 PM Rafael J. Wysocki wrote:
> On Tuesday, July 29, 2014 02:46:41 PM Thomas Gleixner wrote:
> > On Tue, 29 Jul 2014, Rafael J. Wysocki wrote:
> > 
> > > On Monday, July 28, 2014 11:53:15 PM Rafael J. Wysocki wrote:
> > > > On Monday, July 28, 2014 02:33:41 PM Thomas Gleixner wrote:
> > > > > On Mon, 28 Jul 2014, Peter Zijlstra wrote:
> > > > > > On Sat, Jul 26, 2014 at 01:49:17PM +0200, Rafael J. Wysocki wrote:
> > > 
> > > [cut]
> > > 
> > > > > So we are not going to make everything a single stupid flag and limit
> > > > > the usability of existing code. We rather go and try to remove the
> > > > > stupid flag before it becomes more wide spread.
> > > > > 
> > > > > And we cannot treat the wakeup thing the same way as the
> > > > > IRQF_NO_SUSPEND flag, because there is hardware where the irq line
> > > > > must be disabled at the normal (non suspend) interrupt controller, and
> > > > > the wake mechanism tells the PM microcontroller to monitor the
> > > > > interrupt line and kick the machine back to life.
> > > > > 
> > > > > So we need to very carefully look at all the existing cases instead of
> > > > > yelling crap and inflicting x86 specific horror on everyone. I said on
> > > > > friday, that I need to look at ALL use cases first and I meant it.
> > > > 
> > > > Regardless of the use case, I don't think it is necessary to manipulate
> > > > the interrupt controller settings before the syscore_suspend stage, because
> > > > if an interrupt happens earlier, we need to handle it pretty much in a normal
> > > > way, unless it has been suspended.
> > > > 
> > > > So I'd argue for not using anything like enable_irq_wake() that goes all
> > > > the way to the hardware in drivers.  Instead, we could allow drivers to
> > > > mark interrupts as "set this up for system wakeup" and really do the setup
> > > > right before putting the platform into the final "suspended" state.  And that
> > > > is totally independend of the IRQF_NO_SUSPEND thing.
> > > 
> > > In addition to that we need the interrupt handler of the driver that requested
> > > the irq to be set up for system wakeup to be invoked after suspend_device_irqs()
> > > in case there are interrupts that should abort the suspend transition or we
> > > can lose a wakeup event.  So whatever interface we decide to use it has to
> > > affect suspend/resume_device_irqs() pretty much in the same way as the
> > > IRQF_NO_SUSPEND flag.
> > 
> > Right, that's a different issue. We probably want that even for the
> > existing irq_wake() users.
> 
> I agree.
> 
> There's one more thing to consider here.  Going forward we'll want to avoid
> touching runtime-suspended devices during system suspend.  Then, system wakeup
> devices will need to mark their IRQs for system wakeup at the runtime suspend
> time and I'm not sure if that's the right time for calling enable_irq_wake().

Taking all of the above into consideration I prepared a prototype that will
follow.  Patch [1/3] is the actual prototype of the core changes, patch [2/3]
uses that to implement suspend-to-idle wakeup for PME and patch [3/3] illustrates
how an existing user of enable_irq_wake() can be modified to use the new stuff.

All is on top of https://patchwork.kernel.org/patch/4643871/ which should apply
on top of -tip (if I'm not mistaken).

I've tested patches [1-2/3] with PME on my MSI Wind.

Comments welcome.

Rafael

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