linux-kernel - Re: [PATCH 15/17] i2c: omap: always return IRQ

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Date:	Thu, 14 Jun 2012 16:55:16 +0530
From:	"Shilimkar, Santosh" <santosh.shilimkar@...com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Felipe Balbi <balbi@...com>, Tony Lindgren <tony@...mide.com>,
	w.sang@...gutronix.de,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-i2c@...r.kernel.org, ben-linux@...ff.org,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel Mailing List 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 15/17] i2c: omap: always return IRQ_HANDLED

On Thu, Jun 14, 2012 at 4:53 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Thu, Jun 14, 2012 at 04:48:56PM +0530, Shilimkar, Santosh wrote:
>> On Thu, Jun 14, 2012 at 3:50 PM, Felipe Balbi <balbi@...com> wrote:
>> > otherwise we could get our IRQ line disabled due
>> > to many spurious IRQs.
>> >
>> > Signed-off-by: Felipe Balbi <balbi@...com>
>> > ---
>> >  drivers/i2c/busses/i2c-omap.c |    2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
>> > index fc5b8bc..5b78a73 100644
>> > --- a/drivers/i2c/busses/i2c-omap.c
>> > +++ b/drivers/i2c/busses/i2c-omap.c
>> > @@ -1015,7 +1015,7 @@ omap_i2c_isr(int this_irq, void *dev_id)
>> >                }
>> >        } while (stat);
>> >
>> > -       return count ? IRQ_HANDLED : IRQ_NONE;
>> > +       return IRQ_HANDLED;
>>
>> no sure if this is correct. if you have IRQ flood and instead of _actually_
>> handling it, if you return handled, you still have interrupt pending, right?
>
> The point of returning IRQ_NONE is to indicate to the interrupt layer that
> the interrupt you received was not processed by any interrupt handler, and
> therefore to provide a way of preventing the system being brought to a halt
> though a stuck interrupt line.
>
> So, if you do process an interrupt, you should always return IRQ_HANDLED
> even if you couldn't complete its processing (eg, because you've serviced
> it 100 times.)
That make sense. Thanks for explanation Russell.

Regards
santosh
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