Re: [PATCH #upstream-fixes] sata_mv: don't issue two DMA commands concurrently

[Mark Lord <liml@rtr.ca>]

Tejun Heo 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@kernel.org>
Signed-off-by: Mark Lord <mlord@pobox.com>
> ---
> No problem, Artem.
> 
> Mark, does this look good to you?

Yeah, looks fine.  For some odd reason, I must have been thinking
that libata-{scsi,core} would not even attempt multiple simultaneous non-NCQ.
Silly me!

> 
>  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;
>  }
>