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SubjectRe: 2.4.21-pre4: PDC ide driver problems with shared interrupts
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On Wed, 2003-02-05 at 18:19, Ross Biro wrote:
> Benjamin Herrenschmidt wrote:
>
> >While I agree with you here, I don't think it's what's happening.
> > /* clear INTR & ERROR flags */
> > hwif->OUTB(dma_stat|6, hwif->dma_status);
> >
> >
> >
> You have way to much faith in the hardware. Promise is especially known
> for not keeping to the spec. I wouldn't trust the interrupt bit to be
> valid unless a dma is actually active, i.e. that
>
> hwif->OUTB(hwif->INB(dma_base)|1, dma_base);
>
> has actually been written.
>
> I've actually had a manufacturer tell me that they don't worry about the
> spec, just making things work with Windows.

Ok, so that gives us 2 possibilities. The above problem, which would be
fixed by locking all around ide_dma_read/write (or rather in the
_caller_, seems better so we don't have to drop the lock for ATAPI).

And a possible wraparound of waiting_for_dma if 255 IRQs come in from
whatever device we share the IRQ line with.

I beleive both need fixing...

Ben.

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