What happen if there is a SATA port multiplier behing the marvell
controller and NCQ is disabled?
I have the impression that with this patch we are able to only send
one DMA command at a time to all the drives behind the PM, which has
an impact on performance.
Gwendal.
On Wed, Aug 13, 2008 at 4:24 AM, Tejun Heo <htejun@xxxxxxxxx> wrote:
> sata_mv allowed issuing two DMA commands concurrently which the
> hardware allows. Unfortunately, libata core layer isn't ready for
> this yet and spews ugly warning message and malfunctions on this.
> Don't allow concurrent DMA commands for now.
>
> Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
> ---
> No problem, Artem.
>
> Mark, does this look good to you?
>
> drivers/ata/sata_mv.c | 34 ++++++++++------------------------
> 1 file changed, 10 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
> index ad169ff..80c655f 100644
> --- a/drivers/ata/sata_mv.c
> +++ b/drivers/ata/sata_mv.c
> @@ -1134,30 +1134,16 @@ static int mv_qc_defer(struct ata_queued_cmd *qc)
> if (ap->nr_active_links == 0)
> return 0;
>
> - if (pp->pp_flags & MV_PP_FLAG_EDMA_EN) {
> - /*
> - * The port is operating in host queuing mode (EDMA).
> - * It can accomodate a new qc if the qc protocol
> - * is compatible with the current host queue mode.
> - */
> - if (pp->pp_flags & MV_PP_FLAG_NCQ_EN) {
> - /*
> - * The host queue (EDMA) is in NCQ mode.
> - * If the new qc is also an NCQ command,
> - * then allow the new qc.
> - */
> - if (qc->tf.protocol == ATA_PROT_NCQ)
> - return 0;
> - } else {
> - /*
> - * The host queue (EDMA) is in non-NCQ, DMA mode.
> - * If the new qc is also a non-NCQ, DMA command,
> - * then allow the new qc.
> - */
> - if (qc->tf.protocol == ATA_PROT_DMA)
> - return 0;
> - }
> - }
> + /*
> + * The port is operating in host queuing mode (EDMA) with NCQ
> + * enabled, allow multiple NCQ commands. EDMA also allows
> + * queueing multiple DMA commands but libata core currently
> + * doesn't allow it.
> + */
> + if ((pp->pp_flags & MV_PP_FLAG_EDMA_EN) &&
> + (pp->pp_flags & MV_PP_FLAG_NCQ_EN) && ata_is_ncq(qc->tf.protocol))
> + return 0;
> +
> return ATA_DEFER_PORT;
> }
>
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