linux-kernel - Re: [PATCH 2/5] ide: ->ide_dma_clear_irq() -> ->clear

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Date:	Mon, 15 Sep 2008 15:29:50 -0700
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] ide: ->ide_dma_clear_irq() -> ->clear_irq()

On Monday 15 September 2008 15:11:21 Sergei Shtylyov wrote:
> Hello, I wrote:
> 
> >> * Rename ->ide_dma_clear_irq method to ->clear_irq
> >>   and move it from ide_hwif_t to struct ide_port_ops.
> >>
> >> * Move ->waiting_for_dma check inside ->clear_irq method.
> >>
> >> * Move ->dma_base check inside ->clear_irq method.
> >>
> >> piix.c:
> >> * Add ich_port_ops and remove init_hwif_ich() wrapper.
> >>
> >> There should be no functional changes caused by this patch.
> >>   
> >
> >   Good. I think it's worth implementing this method in at least 
> > cmd64x.c which actually reads the IDE interrupt latch bits 
> > (independent from the DMA interrupt status) in the dma_test_irq() 
> > methods but never clears them, so the latches may reflect a 
> > non-current state of the IDE interrupt...
> 
>    I forgot that it does clear them in its dma_end() methods (which I 
> myself have reworked :-).
>    It seems however that at least for SFF-8038 compatibles, it makes 
> sense to leave it that way since INTRQ might be asserted while BMIDE 
> interrupt bit is not, so the interrupt latch would need clearing even on 
> DMA timeout...
> 
> >   It may also be worth considering turning this method into 
> > test-and-clear, so that we can get the actual IDE interrupt state on 
> > the chips that implement this...
> 
>    Probably might add the test_irq() method to be called on 
> !hwif->waiting_for_dma. Cleraing the status at once seems impractical...

Or we can test for ->waiting_for_dma inside ->test_irq.
 
> >> Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> >
> > Acked-by: Sergei Shtylyov <sshtylyov@...mvista.com>
> 
>    Not feeling sure about this patch -- ->waiting_for_dma probably 
> should've been left where it was...

Well, it doesn't change behavior and I think having ->clear_irq method
independent from the transfer mode is a preffered approach.

Thanks,
Bart
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