linux-kernel - Re: [RFC][PATCH] irq: Rework IRQF_NO

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Message-ID: <alpine.DEB.2.10.1407291445570.4129@nanos>
Date:	Tue, 29 Jul 2014 14:46:41 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [RFC][PATCH] irq: Rework IRQF_NO_SUSPENDED

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.

Thanks,

	tglx
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