linux-kernel - RE: [Uclinux-dist-devel] [PATCH v2] mfd: ADP5520 MultifunctionLCDBacklight and Keypad Input Device Driver

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Date:	Fri, 2 Oct 2009 15:37:15 +0100
From:	"Hennerich, Michael" <Michael.Hennerich@...log.com>
To:	"Mark Brown" <broonie@...nsource.wolfsonmicro.com>
CC:	"Samuel Ortiz" <sameo@...ux.intel.com>,
	"Mike Frysinger" <vapier@...too.org>, <tglx@...utronix.de>,
	<uclinux-dist-devel@...ckfin.uclinux.org>,
	<linux-kernel@...r.kernel.org>
Subject: RE: [Uclinux-dist-devel] [PATCH v2] mfd: ADP5520 MultifunctionLCDBacklight and Keypad Input Device Driver



>-----Original Message-----
>From: Mark Brown [mailto:broonie@...nsource.wolfsonmicro.com]
>Sent: Friday, October 02, 2009 4:27 PM
>To: Hennerich, Michael
>Cc: Samuel Ortiz; Mike Frysinger; tglx@...utronix.de;
uclinux-dist-devel@...ckfin.uclinux.org; linux-
>kernel@...r.kernel.org
>Subject: Re: [Uclinux-dist-devel] [PATCH v2] mfd: ADP5520
MultifunctionLCDBacklight and Keypad Input
>Device Driver
>
>On Fri, Oct 02, 2009 at 02:48:27PM +0100, Hennerich, Michael wrote:
>
>> Well the threaded irq handlers are no option here, since we use a
Level
>> Sensitive Interrupt.
>> The work queue here is to schedule the main irq handler outside
hardirq
>> context.
>> I2C can't we invoked form none sleepy context, so we can't clear the
>> interrupt.
>> This will cause that we execute the hardirq over and over again,
>> preventing the irq thread to be run.
>
>> The threaded irqs with its current implementation also doesn't allow
me
>> to disable the irq in the hardirq handler.
>
>This should all work perfectly fine.  If you don't supply a hard IRQ
>handler then the genirq infrastructure will disable the IRQ and
schedule
>the threaded handler, reenabling the IRQ when the threaded handler
>finishes.  The threaded handler runs in a non-atomic context so it can
>happily access I2C devices.

Hi Mark,

I saw your patch: mfd: Convert WM8350 to use request_threaded_irq()

And was wondering how this ever worked.
I'm using: Linux release 2.6.31.1-ADI-2010R1-pre-svn7535, build #10835
Fri Oct 2 14:48:19 CEST 2009

int request_threaded_irq(unsigned int irq, irq_handler_t handler,
			 irq_handler_t thread_fn, unsigned long
irqflags,
			 const char *devname, void *dev_id)
{
--- snip ---

	if (!handler)
		return -EINVAL;

}

So I guess your patch won't work on 2.6.31

>
>> There have been some discussions about this on lkml recently.
>> Until there is a way to workaround this issue
(handle_level_oneshot_irq,
>> etc.),
>> I like to stick with:
>
>> >>> +	disable_irq_nosync(irq);
>> >>> +	schedule_work(&chip->irq_work);
>
>This is essentially what a threaded IRQ handler does with current
>mainline.  There were issues in 2.6.31 but I believe all Thomas' fixes
>have been merged now.

Do you know when they merged?
They are not in latest staple 2.6.31.1.

Best regards,
Michael


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