Re: [PATCH 2/5] ide: ->ide_dma_clear_irq() -> ->clear_irq()

[Sergei Shtylyov]

Hello.

Bartlomiej Zolnierkiewicz 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.
>   

  That also will do...

> > > > Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@xxxxxxxxx>
> > > >         
> > > Acked-by: Sergei Shtylyov <sshtylyov@xxxxxxxxxxxxx>
> > >       
> >    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.
>   

  But its implementations will have to depend on it anyway. And 
clearing the IDE interrupt in general already depends on the transfer 
mode -- the BMIDE interrupt which is a (delayed) reflection of INTRQ is 
cleared implicitly by the dma_end() method -- except in at least sgiioc4 
driver.
  BTW, sgiioc4 seems another candidate for clear_irq() implementation 
-- currently clearing is done implicitly by the read_status() method (I 
don't quite understand why it clears DMA error interrupt there). 
However, since there's no documentation, I'm not sure how the IDE 
interrupt is latched by IOC4.

> Thanks,
> Bart
>   

MBR, Sergei


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