powerpc/pseries: Disable MSI using new interface if possible

On upcoming hardware, we have a PCI adapter with two functions, one of
which uses MSI and the other uses MSI-X. This adapter, when MSI is
disabled using the "old" firmware interface (RTAS_CHANGE_FN), still
signals an MSI-X interrupt and triggers an EEH. We are working with the
vendor to ensure that the hardware is not at fault, but if we use the
"new" interface (RTAS_CHANGE_MSI_FN) to disable MSI, we also
automatically disable MSI-X and the adapter does not appear to signal
any stray MSI-X interrupt.

Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Acked-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 12 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/pseries/msi.c b/arch/powerpc/platforms/pseries/msi.c
index 1164c3430f2c..18ac801f8e90 100644
--- a/arch/powerpc/platforms/pseries/msi.c
+++ b/arch/powerpc/platforms/pseries/msi.c
@@ -93,8 +93,18 @@ static void rtas_disable_msi(struct pci_dev *pdev)
         if (!pdn)
                 return;
 
-        if (rtas_change_msi(pdn, RTAS_CHANGE_FN, 0) != 0)
-                pr_debug("rtas_msi: Setting MSIs to 0 failed!\n");
+        /*
+         * disabling MSI with the explicit interface also disables MSI-X
+         */
+        if (rtas_change_msi(pdn, RTAS_CHANGE_MSI_FN, 0) != 0) {
+                /* 
+                 * may have failed because explicit interface is not
+                 * present
+                 */
+                if (rtas_change_msi(pdn, RTAS_CHANGE_FN, 0) != 0) {
+                        pr_debug("rtas_msi: Setting MSIs to 0 failed!\n");
+                }
+        }
 }
 
 static int rtas_query_irq_number(struct pci_dn *pdn, int offset)