Re: [PATCH] sata_mv: fix broken DSM/TRIM support (v2)

[Mark Lord <kernel@teksavvy.com>]

On 10-08-19 09:40 PM, Mark Lord wrote:
> Fix DSM/TRIM commands in sata_mv (v2).
> These need to be issued using old-school "BM DMA",
> rather than via the EDMA host queue.
>
> Since the chips don't have proper BM DMA status,
> we need to be more careful with setting the ATA_DMA_INTR bit,
> since DSM/TRIM often has a long delay between "DMA complete"
> and "command complete".
..

Speaking of which.. it appears that BM DMA support for sata_mv
is intentionally broken by 2.6.35 kernels, with the addition of
this code in libata-sff.c:

unsigned int ata_bmdma_qc_issue(struct ata_queued_cmd *qc)
{
         struct ata_port *ap = qc->ap;

         /* see ata_dma_blacklisted() */
         BUG_ON((ap->flags & ATA_FLAG_PIO_POLLING) &&
                qc->tf.protocol == ATAPI_PROT_DMA);


Is that BUG_ON even necessary??
It really should be looking only at tf.flags, not qp->flags there,
as it actually does redundantly further on:

    WARN_ON_ONCE(qc->tf.flags & ATA_TFLAG_POLLING);

sata_mv has ATA_FLAG_PIO_POLLING set for all ports,
but doesn't set ATA_TFLAG_POLLING when doing BM DMA.

???