Re: [PATCH] mvsas: defer non-NCQ cmds when NCQ cmds are active

[James Bottomley <James.Bottomley@suse.de>]

On Tue, 2010-09-21 at 14:17 -0500, David Milburn wrote:
> Non-NCQ commands should run exclusively, ata_qc_issue warns when mixing
> non-NCQ and NCQ commands.
> 
> Signed-off-by: David Milburn <dmilburn@redhat.com>
> Reported-by: Konstantinos Skarlatos <k.skarlatos@gmail.com>
> ---
>  drivers/scsi/libsas/sas_ata.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
> index 042153c..ddbade7 100644
> --- a/drivers/scsi/libsas/sas_ata.c
> +++ b/drivers/scsi/libsas/sas_ata.c
> @@ -347,6 +347,7 @@ static int sas_ata_scr_read(struct ata_link *link, unsigned int sc_reg_in,
>  static struct ata_port_operations sas_sata_ops = {
>  	.phy_reset		= sas_ata_phy_reset,
>  	.post_internal_cmd	= sas_ata_post_internal,
> +	.qc_defer               = ata_std_qc_defer,

What does this do on the card that doesn't need it: the aic94xx?  That
one takes in a pipeline of commands and takes responsibility for getting
the issue right.  Something like this throttles the pipeline higher than
the aic94xx is expecting.  However, as long as it's not too much of a
performance problem, I don't mind applying it.

James