Re: [PATCH] SATA NCQ support

[Jeff Garzik <jgarzik@pobox.com>]

Jens Axboe wrote:
> Update the patch, it's against bleeding edge git (applies to 2.6.12-rc5
> as well). Changes:

I'll throw this into libata-dev branch "ncq" right now.


> +static void ahci_host_ncq_intr_err(struct ata_port *ap)
> +{
> +	void *mmio = ap->host_set->mmio_base;
> +	void *port_mmio = ahci_port_base(mmio, ap->port_no);
> +	char *buffer;
> +
> +	printk(KERN_ERR "ata%u: ncq interrupt error\n", ap->id);
> +
> +	ahci_intr_error(ap, readl(port_mmio + PORT_IRQ_STAT));
> +
> +	buffer = kmalloc(512, GFP_KERNEL);

cannot use GFP_KERNEL in interrupt context


> @@ -2868,6 +2995,21 @@
>  int ata_qc_issue(struct ata_queued_cmd *qc)
>  {
>  	struct ata_port *ap = qc->ap;
> +	int rc = ATA_QC_ISSUE_FATAL;
> +
> +	/*
> +	 * see if we can queue one more command at this point in time, see
> +	 * comment at ata_qc_issue_ok(). NCQ commands typically originate from
> +	 * the SCSI layer, we can ask the mid layer to defer those commands
> +	 * similar to a QUEUE_FULL condition on a 'real' SCSI device
> +	 */
> +	if (!ata_qc_issue_ok(ap, qc, 0)) {
> +		if (qc->flags & ATA_QCFLAG_DEFER)
> +			return ATA_QC_ISSUE_DEFER;
> +
> +		ata_qc_issue_wait(ap, qc);
> +		assert(ata_qc_issue_ok(ap, qc, 0));
> +	}
>  

This is too late.  We shouldn't get to this point and find out, "uh oh, 
queue full."

ata_qc_new() should fail to obtain a qc if the queue is full, at which 
point you may directly return queue-full.

If ata_qc_new() succeeds, but wish to wait for the queue to drain, add 
that logic -much- earlier than the ata_qc_issue() call.  I would rather 
have that logic at a higher level.


> @@ -353,6 +354,13 @@
>  			 */
>  			blk_queue_max_sectors(sdev->request_queue, 2048);
>  		}
> +
> +		if (dev->flags & ATA_DFLAG_NCQ) {
> +			int ddepth = ata_id_queue_depth(dev->id);
> +
> +			depth = min(sdev->host->can_queue, ddepth);
> +			scsi_adjust_queue_depth(sdev, MSG_SIMPLE_TAG, depth);
> +		}
>  	}
>  
>  	return 0;	/* scsi layer doesn't check return value, sigh */
> @@ -1594,3 +1641,22 @@
>  	}
>  }
>  
> +int ata_scsi_change_queue_depth(struct scsi_device *sdev, int queue_depth)
> +{
> +	struct ata_port *ap;
> +	struct ata_device *dev;
> +	int max_depth;
> +
> +	if (sdev->id >= ATA_MAX_DEVICES)
> +		return sdev->queue_depth;
> +
> +	ap = (struct ata_port *) &sdev->host->hostdata[0];
> +	dev = &ap->device[sdev->id];
> +
> +	max_depth = min(sdev->host->can_queue, ata_id_queue_depth(dev->id));
> +	if (queue_depth > max_depth)
> +		queue_depth = max_depth;
> +
> +	scsi_adjust_queue_depth(sdev, MSG_SIMPLE_TAG, queue_depth);
> +	return queue_depth;
> +}

Please add this function immediately above, or below, 
ata_scsi_slave_config().  That will make backporting to 2.4.x easier.


> ===================================================================
> --- 3ac9a34948049bff79a2b2ce49c0a3c84e35a748/include/linux/ata.h  (mode:100644)
> +++ uncommitted/include/linux/ata.h  (mode:100644)
> @@ -79,7 +79,8 @@
>  	ATA_NIEN		= (1 << 1),	/* disable-irq flag */
>  	ATA_LBA			= (1 << 6),	/* LBA28 selector */
>  	ATA_DEV1		= (1 << 4),	/* Select Device 1 (slave) */
> -	ATA_DEVICE_OBS		= (1 << 7) | (1 << 5), /* obs bits in dev reg */
> +	ATA_DEVICE_OBS		= (1 << 5), 	/* obs bits in dev reg */
> +	ATA_FPDMA_FUA		= (1 << 7),	/* FUA cache bypass bit */
>  	ATA_DEVCTL_OBS		= (1 << 3),	/* obsolete bit in devctl reg */
>  	ATA_BUSY		= (1 << 7),	/* BSY status bit */
>  	ATA_DRDY		= (1 << 6),	/* device ready */

Don't do this.  You can add ATA_FPDMA_FUA, but don't arbitrarily change 
ATA_DEVICE_OBS.

This is something that may have to be done on a per-device basis.

	Jeff