From: AMEET M. PARANJAPE <aparanja@redhat.com>
Date: Tue, 31 Mar 2009 11:04:58 -0400
Subject: [ppc] msi: return the number of MSI-X available
Message-id: 20090331150245.14954.871.sendpatchset@squad5-lp1.lab.bos.redhat.com
O-Subject: [PATCH RHEL5.4 BZ492580 1/8]
Bugzilla: 492580
RH-Acked-by: David Howells <dhowells@redhat.com>

RHBZ#:
======
https://bugzilla.redhat.com/show_bug.cgi?id=492580

Description:
===========
These 8 patches are required inorder to support any MSI-X interrupt capable
devices running MSI-X effectively on Power systems.  Description of patch1 is
below:

There is code in msix_capability_init() which, when the requested number
of MSI-X couldn't be allocated, calculates how many MSI-X /could/ be
allocated and returns that to the driver. That allows the driver to then
make a second request, with a number of MSIs that should succeed.

The current code requires the arch code to setup as many msi_descs as it
can, and then return to the generic code. On some platforms the arch
code may already know how many MSI-X it can allocate, before it sets up
any of the msi_descs.

So change the logic such that if the arch code returns a positive error
code, that is taken to be the number of MSI-X that could be allocated.
If the error code is negative we still calculate the number available
using the old method.

RHEL Version Found:
================
RHEL 5.3

kABI Status:
============
No symbols were harmed.

Brew:
=====
Built on all platforms.
http://brewweb.devel.redhat.com/brew/taskinfo?taskID=1744271

Upstream Status:
================
http://git.kernel.org/?p=linux/kernel/git/jbarnes/pci-2.6.git;a=commit;h=08a2938e40f013ef06d0bc425167294db361fc52

Test Status:
============
There is a testcase provided in the Bugzilla.  A 'cat /proc/interrupts' should
show the device drivers has two interrupt entries for each port.  Run I/O
tests.  Then 'lspci -vv' should display the correct pci capabilities for the
installed adapter and show the adapter is using MSI-X interrupts opposed to MSO
or LSI interrupts.
===============================================================
Ameet Paranjape 978-392-3903 ext 23903
IBM on-site partner

Proposed Patch:
===============

diff --git a/arch/powerpc/kernel/msi.c b/arch/powerpc/kernel/msi.c
index e543d3b..d4d96a0 100644
--- a/arch/powerpc/kernel/msi.c
+++ b/arch/powerpc/kernel/msi.c
@@ -455,7 +455,9 @@ static int msix_capability_init(struct pci_dev *dev,
 	}
 
 	ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
-	if (ret) {
+	if (ret < 0) {
+		/* If we had some success report the number of irqs
+		 * we succeeded in setting up. */
 		int avail = 0;
 		list_for_each_entry(entry, &pdn->msi_list, list) {
 			if (entry->irq != 0) {
@@ -463,14 +465,13 @@ static int msix_capability_init(struct pci_dev *dev,
 			}
 		}
 
-		msi_free_irqs(dev);
+		if (avail != 0)
+			ret = avail;
+	}
 
-		/* If we had some success report the number of irqs
-		 * we succeeded in setting up.
-		 */
-		if (avail == 0)
-			avail = ret;
-		return avail;
+	if (ret) {
+		msi_free_irqs(dev);
+		return ret;
 	}
 
 	i = 0;