[PATCH 3.15 10/37] libata: support the ata host which implements a queue depth less than 32

Greg Kroah-Hartman
2014-07-30T01:48:46Z

From: Kevin Hao <haokexin@gmail.com>

commit 1871ee134b73fb4cadab75752a7152ed2813c751 upstream.

The sata on fsl mpc8315e is broken after the commit 8a4aeec8d2d6
("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: 8a4aeec8d2d6 ("libata/ahci: accommodate tag ordered controllers")
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/ata/libata-core.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)

--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -4787,6 +4787,10 @@ void swap_buf_le16(u16 *buf, unsigned in
* 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 in
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 *h
{
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");