[SCSI] lpfc: restore MSI-X/MSI support

A Gentoo bug report [1] showed that as of 2.6.31 lpfc only uses INTx interrupts.
This patch restores lpfc's ability to support MSI-X/MSI interrupts that the
"Addition of SLI4 Interface - Base Support" patch [2] broke.
It reestablishes MSI-X as the default interrupt method and in case MSI-X is not
supported lpfc_sli{4,}_enable_intr fallbacks to MSI and then to INTx.

[1]: http://bugs.gentoo.org/show_bug.cgi?id=296319
[2]: commit da0436e915a5c17ee79e72c1bf978a4ebb1cbf4d

[James Smart:
Background:
Nothing Broke. This was intended.

We had originally enabled MSI-X by default, but in qualification within the
last 12 months, we encountered a major catch-22:

There were at least 4 platforms, from 2 major OEMs, that :
- Say they support MSI-X - platform routines work and act as if they do.
- We enable it, generate a test interrupt to check they really do deliver it,
and it works.
- But shortly after attachment, the system hangs or loses interrupts,
resulting in a bad system behavior.

Given the distro's picking up the 2.6.32 kernel, we had to stick with a
default of MSI-X off, with user-enabled MSI-X as these platforms couldn't get
fixed.

However, we're also now encountering platforms that require MSI-X and never
INTx, so we must change. It's desired also for also for performance reasons.

So - now (2.6.33) is the right time to re-enable MSI-X by default.
]
[jejb: fix up comment on default values]

Signed-off-by:  George Kadianakis <desnacked@gmail.com>
Acked-by: James Smart  <james.smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

diff --git a/drivers/scsi/lpfc/lpfc_attr.c b/drivers/scsi/lpfc/lpfc_attr.c
index 91542f7..a8908e7 100644 (file)
--- a/drivers/scsi/lpfc/lpfc_attr.c
+++ b/drivers/scsi/lpfc/lpfc_attr.c
@@ -3114,12 +3114,12 @@ LPFC_ATTR_RW(poll_tmo, 10, 1, 255,
 /*
 # lpfc_use_msi: Use MSI (Message Signaled Interrupts) in systems that
 #              support this feature
-#       0  = MSI disabled (default)
+#       0  = MSI disabled
 #       1  = MSI enabled
-#       2  = MSI-X enabled
-# Value range is [0,2]. Default value is 0.
+#       2  = MSI-X enabled (default)
+# Value range is [0,2]. Default value is 2.
 */
-LPFC_ATTR_R(use_msi, 0, 0, 2, "Use Message Signaled Interrupts (1) or "
+LPFC_ATTR_R(use_msi, 2, 0, 2, "Use Message Signaled Interrupts (1) or "
            "MSI-X (2), if possible");
 
 /*