[patch 31/37] SCSI: qla1280: Fix queue depth problem

[Greg KH]

2.6.25-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Jeremy Higdon <jeremy@xxxxxxx>

commit af5741c6de4f4a1d8608b0f00867c77cb7123635 upstream

The qla1280 driver was ANDing the output value of mailbox register
0 with (1 << target-number) to determine whether to enable queueing
on the target in question.

But mailbox register 0 has the status code for the mailbox command
(in this case, Set Target Parameters).  Potential values are:
/*
 * ISP mailbox command complete status codes
 */

So clearly that is in error.  I can't think what the author of that
line was looking for in a mailbox register, so I just eliminated the
AND.  flag is used later in the function, and I think that the later
usage was also wrong, though it was used to set values that aren't
used.  Oh well, an overhaul of this driver is not what I want to do
now -- just a bugfix.

After the fix, I found that my disks were getting a queue depth of
255, which is far too many.  Most SCSI disks are limited to 32 or
64.  In any case, there's no point, queueing up a bunch of commands
to the adapter that will just result in queue full or starve other
targets from being issued commands due to running out of internal
memory.  So I dropped default queue depth to 32 (from which 1 is
subtracted elsewhere, giving net of 31).

I tested with a Seagate ST336753LC, and results look good, so
I'm satisfied with this patch.

Signed-off-by: Jeremy Higdon <jeremy@xxxxxxx>
Acked-by: Jes Sorensen <jes@xxxxxxx>
Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 drivers/scsi/qla1280.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/scsi/qla1280.c
+++ b/drivers/scsi/qla1280.c
@@ -2012,7 +2012,7 @@ qla1280_set_defaults(struct scsi_qla_hos
 		nv->bus[bus].config_2.req_ack_active_negation = 1;
 		nv->bus[bus].config_2.data_line_active_negation = 1;
 		nv->bus[bus].selection_timeout = 250;
-		nv->bus[bus].max_queue_depth = 256;
+		nv->bus[bus].max_queue_depth = 32;
 
 		if (IS_ISP1040(ha)) {
 			nv->bus[bus].bus_reset_delay = 3;
@@ -2056,7 +2056,7 @@ qla1280_config_target(struct scsi_qla_ho
 	status = qla1280_mailbox_command(ha, 0x0f, mb);
 
 	/* Save Tag queuing enable flag. */
-	flag = (BIT_0 << target) & mb[0];
+	flag = (BIT_0 << target);
 	if (nv->bus[bus].target[target].parameter.tag_queuing)
 		ha->bus_settings[bus].qtag_enables |= flag;
 

-- 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/