linux-kernel - Re: Seeking clarity on IRQCHIP_MASK_ON

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Date:	Mon, 10 Sep 2012 12:28:35 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	NeilBrown <neilb@...e.de>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	"Shilimkar, Santosh" <santosh.shilimkar@...com>,
	lkml <linux-kernel@...r.kernel.org>, linux-omap@...r.kernel.org,
	Kevin Hilman <khilman@...prootsystems.com>
Subject: Re: Seeking clarity on IRQCHIP_MASK_ON_SUSPEND

On Mon, 10 Sep 2012, NeilBrown wrote:
> 
> The IRQCHIP_MASK_ON_SUSPEND flag seems to be hard to use correctly, so either
> I'm understanding it wrongly, or it could be made easier to use.
> If the first case, I'm hoping that some improvement to documentation might
> result.  If the second, then maybe we can fix the code.
... 
> Is anyone able to give a definitive answer on this?  Should
> IRQCHIP_MASK_ON_SUSPEND be removed?

The whole point of IRQCHIP_MASK_ON_SUSPEND is to deal with hardware
designed by geniuses.

Most SoCs have a way to mark the interrupts which serve as a wake up
source as such. All other interrupts are magically "masked" on entry
to suspend.

Now there is hardware which is missing such a control, so we need to
mask the non wakeup interrupts right before going into suspend.

That's what IRQCHIP_MASK_ON_SUSPEND does. Not more, not less. See
commit d209a699a0b for more ugly details.

You might be looking for a different functionality. Can you explain
what you need?

Thanks,

	tglx
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