Re: [PATCH Linux 2.6.12 07/09] NCQ: stop dma before reset

[Jeff Garzik <jgarzik@pobox.com>]

Tejun Heo wrote:
> 07_NCQ_ahci-stop-dma-before-reset.patch
> 
> 	AHCI 1.1 mandates stopping dma before issueing COMMRESET.  The
> 	original code didn't and it resulted in occasional lockup of
> 	the controller during EH recovery.  This patch fixes the
> 	problem.
> 
> Signed-off-by: Tejun Heo <htejun@gmail.com>
> 
>  ahci.c |    2 ++
>  1 files changed, 2 insertions(+)
> 
> Index: work/drivers/scsi/ahci.c
> ===================================================================
> --- work.orig/drivers/scsi/ahci.c	2005-06-27 00:20:31.000000000 +0900
> +++ work/drivers/scsi/ahci.c	2005-06-27 00:20:31.000000000 +0900
> @@ -474,7 +474,9 @@ static void ahci_phy_reset(struct ata_po
>  	struct ata_device *dev = &ap->device[0];
>  	u32 tmp;
>  
> +	ahci_stop_dma(ap);
>  	__sata_phy_reset(ap);
> +	ahci_start_dma(ap);

This is a bit worrisome, because we really shouldn't be calling 
ahci_phy_reset() when DMA is -not- stopped.  That's a violation of the 
state machine.

	Jeff