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SubjectRe: [PATCH] sata_nv: don't use legacy DMA in ADMA mode (v2)
Robert Hancock wrote:
> We need to run any DMA command with result taskfile requested in ADMA mode
> when the port is in ADMA mode, otherwise it may try to use the legacy DMA engine
> in ADMA mode which is not allowed. Enforce this with BUG_ON() since data
> corruption could potentially result if this happened. Also WARN_ON() if we try
> and send result taskfile commands while NCQ commands are still active, since the
> hardware doesn't allow this.
>
> Signed-off-by: Robert Hancock <hancockr@shaw.ca>
>
> @@ -1425,9 +1427,17 @@
> + /* We can't handle result taskfile with NCQ commands active, since
> + retrieving the taskfile switches us out of ADMA mode and would abort
> + existing commands. */
> + WARN_ON((qc->flags & ATA_QCFLAG_RESULT_TF) &&
> + (qc->ap->qc_allocated & ~(1 << qc->tag)));

I owe an apology here. ap->qc_allocated & ~(1 << qc->tag) test isn't
correct. Sorry. qc deferring happens after qc is allocated so the
condition can trigger (although it should be rare) even when nothing is
going wrong, so I guess it should be WARN_ON((qc->flags &
ATA_QCFLAG_RESULT_TF) && link->sactive).

Sorry. :-)

--
tejun
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