linux-kernel - Re: [PATCH 22/40] ide-floppy: start DMA engine in idefloppy_transfer

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Message-Id: <200805272058.48223.bzolnier@gmail.com>
Date:	Tue, 27 May 2008 20:58:48 +0200
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
Cc:	linux-ide@...r.kernel.org, Borislav Petkov <petkovbb@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 22/40] ide-floppy: start DMA engine in idefloppy_transfer_pc1()

On Tuesday 20 May 2008, Sergei Shtylyov wrote:
> Hello.
> 
> Bartlomiej Zolnierkiewicz wrote:
> 
> > Start DMA engine and set PC_FLAG_DMA_IN_PROGRESS flag in
> > idefloppy_transfer_pc1() instead of idefloppy_issue_pc()
> 
>     Good. I have long ago noticed that DMA is started too early in ide-floppy 
> which is known to cobfuse some chips (like PDC20246) and was going to do a 
> patch at first but the lack of hardware (and time) stopped me...
> 
> > so the Status Register and the Interrupt Reason Register
> > are checked first.
> 
> > Cc: Borislav Petkov <petkovbb@...il.com>
> > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> 
> > Index: b/drivers/ide/ide-floppy.c
> > ===================================================================
> > --- a/drivers/ide/ide-floppy.c
> > +++ b/drivers/ide/ide-floppy.c
> [...]
> > @@ -568,6 +569,12 @@ static ide_startstop_t idefloppy_transfe
> >  
> >  	ide_set_handler(drive, &idefloppy_pc_intr, timeout, expiry);
> >  
> > +	/* Begin DMA, if necessary */
> > +	if (pc->flags & PC_FLAG_DMA_OK) {
> > +		pc->flags |= PC_FLAG_DMA_IN_PROGRESS;
> > +		hwif->dma_ops->dma_start(drive);
> > +	}
> > +
> 
>     May be too early still... ide-cd does this after writing the command packet.

I would rather say that ide-cd is doing things too late.

Now that's your patch opportunity!  No excuses this time... ;)

Thanks,
Bart
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