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Commit 1871ee13 authored by Kevin Hao's avatar Kevin Hao Committed by Tejun Heo
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libata: support the ata host which implements a queue depth less than 32 



The sata on fsl mpc8315e is broken after the commit 8a4aeec8
("libata/ahci: accommodate tag ordered controllers"). The reason is
that the ata controller on this SoC only implement a queue depth of
16. When issuing the commands in tag order, all the commands in tag
16 ~ 31 are mapped to tag 0 unconditionally and then causes the sata
malfunction. It makes no senses to use a 32 queue in software while
the hardware has less queue depth. So consider the queue depth
implemented by the hardware when requesting a command tag.

Fixes: 8a4aeec8 ("libata/ahci: accommodate tag ordered controllers")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarKevin Hao <haokexin@gmail.com>
Acked-by: default avatarDan Williams <dan.j.williams@intel.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 7188b067

drivers/ata/libata-core.c

+19 −3
Original line number Diff line number Diff line
@@ -4787,6 +4787,10 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words) 
 *	ata_qc_new - Request an available ATA command, for queueing

 *	@ap: target port

 *

 *	Some ATA host controllers may implement a queue depth which is less

 *	than ATA_MAX_QUEUE. So we shouldn't allocate a tag which is beyond

 *	the hardware limitation.

 *

 *	LOCKING:

 *	None.

 */
@@ -4794,14 +4798,16 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words) 
static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)

{

	struct ata_queued_cmd *qc = NULL;

	unsigned int i, tag;

	unsigned int i, tag, max_queue;



	max_queue = ap->scsi_host->can_queue;



	/* no command while frozen */

	if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))

		return NULL;



	for (i = 0; i < ATA_MAX_QUEUE; i++) {

		tag = (i + ap->last_tag + 1) % ATA_MAX_QUEUE;

	for (i = 0, tag = ap->last_tag + 1; i < max_queue; i++, tag++) {

		tag = tag < max_queue ? tag : 0;



		/* the last tag is reserved for internal command. */

		if (tag == ATA_TAG_INTERNAL)
@@ -6169,6 +6175,16 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht) 
{

	int i, rc;



	/*

	 * The max queue supported by hardware must not be greater than

	 * ATA_MAX_QUEUE.

	 */

	if (sht->can_queue > ATA_MAX_QUEUE) {

		dev_err(host->dev, "BUG: the hardware max queue is too large\n");

		WARN_ON(1);

		return -EINVAL;

	}



	/* host must have been started */

	if (!(host->flags & ATA_HOST_STARTED)) {

		dev_err(host->dev, "BUG: trying to register unstarted host\n");