Re: [PATCH] libata drain fifo on stuck DRQ HSM violation (try#2)

[Jeff Garzik <jgarzik@pobox.com>]

Mark Lord wrote:
> I think this original patch still applies cleanly on at least 2.6.23-rc7.
> 
> Drain up to 512 words from host/bridge FIFO on stuck DRQ HSM violation,
> rather than just getting stuck there forever.
> 
> Signed-off-by: Mark Lord <mlord@pobox.com>
> ---
> 
> --- old/drivers/ata/libata-sff.c    2007-09-28 09:29:22.000000000 -0400
> +++ linux/drivers/ata/libata-sff.c    2007-09-28 09:39:44.000000000 -0400
> @@ -420,6 +420,28 @@
>     ap->ops->irq_on(ap);
> }
> 
> +static void ata_drain_fifo(struct ata_port *ap, struct ata_queued_cmd *qc)
> +{
> +    u8 stat = ata_chk_status(ap);
> +    /*
> +     * Try to clear stuck DRQ if necessary,
> +     * by reading/discarding up to two sectors worth of data.
> +     */
> +    if ((stat & ATA_DRQ) && (!qc || qc->dma_dir != DMA_TO_DEVICE)) {
> +        unsigned int i;
> +        unsigned int limit = qc ? qc->sect_size : ATA_SECT_SIZE;
> +
> +        printk(KERN_WARNING "Draining up to %u words from data FIFO.\n",
> +                                    limit);
> +        for (i = 0; i < limit ; ++i) {
> +            ioread16(ap->ioaddr.data_addr);
> +            if (!(ata_chk_status(ap) & ATA_DRQ))
> +                break;
> +        }
> +        printk(KERN_WARNING "Drained %u/%u words.\n", i, limit);
> +    }
> +}
> +
> /**
>  *    ata_bmdma_drive_eh - Perform EH with given methods for BMDMA 
> controller
>  *    @ap: port to handle error for
> @@ -476,7 +498,7 @@
>     }
> 
>     ata_altstatus(ap);
> -    ata_chk_status(ap);
> +    ata_drain_fifo(ap, qc);
>     ap->ops->irq_clear(ap);
> 
>     spin_unlock_irqrestore(ap->lock, flags);

applied, after hand-editing out the top of the message, so that it would 
not be copied into the kernel changelog