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

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Date:	Tue, 29 Jul 2014 01:01:59 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Thomas Gleixner <tglx@...utronix.de>
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 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.

Rafael

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