From mboxrd@z Thu Jan  1 00:00:00 1970
From: LW@KARO-electronics.de (=?utf-8?Q?Lothar_Wa=C3=9Fmann?=)
Date: Wed, 30 Mar 2011 11:15:37 +0200
Subject: [PATCH V3 2/6] dmaengine: change the flags of request_irq()
In-Reply-To: <20110330091323.GB20019@S2100-06.ap.freescale.net>
References: <1301474413-28821-1-git-send-email-b32955@freescale.com>
	<1301474413-28821-3-git-send-email-b32955@freescale.com>
	<19858.61894.956256.280158@ipc1.ka-ro>
	<20110330091323.GB20019@S2100-06.ap.freescale.net>
Message-ID: <19858.62649.218523.984252@ipc1.ka-ro>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Shawn Guo writes:
> On Wed, Mar 30, 2011 at 11:03:02AM +0200, Lothar Wa?mann wrote:
> > Hi,
> > 
> > Huang Shijie writes:
> > > The GPMI may have many DMA channels, such as the imx23 has
> > > four DMA channels. All these DMA channels share the same interrupt.
> > > So change the flags from '0' to IRQF_SHARED, else there will be
> > > an EBUSY error returns.
> > > 
> > > Signed-off-by: Huang Shijie <b32955@freescale.com>
> > > ---
> > >  drivers/dma/mxs-dma.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
> > > index 88aad4f..0ee5b52 100644
> > > --- a/drivers/dma/mxs-dma.c
> > > +++ b/drivers/dma/mxs-dma.c
> > > @@ -328,7 +328,7 @@ static int mxs_dma_alloc_chan_resources(struct dma_chan *chan)
> > >  	memset(mxs_chan->ccw, 0, PAGE_SIZE);
> > >  
> > >  	ret = request_irq(mxs_chan->chan_irq, mxs_dma_int_handler,
> > > -				0, "mxs-dma", mxs_dma);
> > > +				IRQF_SHARED, "mxs-dma", mxs_dma);
> > >  	if (ret)
> > >  		goto err_irq;
> > >  
> > IMO this is wrong. The interrupt is requested with all the same
> > parameters for each DMA channel. So, actually it is not a shared IRQ,
> 
> The parameter mxs_chan->chan_irq is different for each channel, except
> gpmi which has 4 channels sharing one irq.
> 
That's what I mean. The other interrupts won't need the IRQF_SHARED
flag anyway.

> > but an IRQ with the same handler registered multiple times, which is
> > just nonsense.
> > 
> > Instead of declaring it as shared, it would be more sensible to only
> > register it for the first channel. Otherwise the handler will be
> > called multiple times in case of an interrupt with only the first
> > invocation doing all the work and the subsequent invocations just
> > returning without doing anything.
> > 
> 
> -- 
> Regards,
> Shawn
> 
Lothar Wa?mann
-- 
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