linux-kernel - Re: [Uclinux-dist-devel] [PATCH v2] mfd: ADP5520 Multifunction LCDBacklight and Keypad Input Device Driver

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Message-ID: <20091002140517.GA1520@sortiz.org>
Date:	Fri, 2 Oct 2009 16:05:18 +0200
From:	Samuel Ortiz <sameo@...ux.intel.com>
To:	"Hennerich, Michael" <Michael.Hennerich@...log.com>
Cc:	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 Multifunction
 LCDBacklight and Keypad Input Device Driver

Hi Michael,

On Fri, Oct 02, 2009 at 02:48:27PM +0100, Hennerich, Michael wrote:
> >From: uclinux-dist-devel-bounces@...ckfin.uclinux.org
> [mailto:uclinux-dist-devel-
> >bounces@...ckfin.uclinux.org] On Behalf Of Hennerich, Michael
> >Device Driver
> >
> >Hi Samuel,
> >
> >>From: Samuel Ortiz [mailto:sameo@...ux.intel.com]
> >>Hi Mike,
> >>
> >>Some comments on this patch:
> >>
> >>On Wed, Sep 23, 2009 at 01:11:04AM -0400, Mike Frysinger wrote:
> >>> +static irqreturn_t adp5520_irq_handler(int irq, void *data)
> >>> +{
> >>> +	struct adp5520_chip *chip = data;
> >>> +
> >>> +	disable_irq_nosync(irq);
> >>> +	schedule_work(&chip->irq_work);
> >>Have you considered using a threaded irq handler here ?
> >
> >The Linux version I developed this driver on didn't feature threaded
> irq
> >handlers.
> >But thanks I'm going to take a look here.
> 
> Hi Samuel,
> 
> 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.
Ok, that's the piece I missed. Thanks for the clarification.


> 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: 
Fine with me, yes.

Cheers,
Samuel.


> >>> +	disable_irq_nosync(irq);
> >>> +	schedule_work(&chip->irq_work);
> 
> Best regards,
> Michael
> 

-- 
Intel Open Source Technology Centre
http://oss.intel.com/
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