PCI MSI: Don't disable MSIs if the mask bit isn't supported

David Vrabel has a device which generates an interrupt storm on the INTx
pin if we disable MSI interrupts altogether.  Masking interrupts is only
a performance optimisation, so we can ignore the request to mask the
interrupt.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 12 insertions, 3 deletions

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 15af618d36e..18354817173 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -126,7 +126,16 @@ static void msix_flush_writes(unsigned int irq)
         }
 }
 
-static void msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)
+/*
+ * PCI 2.3 does not specify mask bits for each MSI interrupt.  Attempting to
+ * mask all MSI interrupts by clearing the MSI enable bit does not work
+ * reliably as devices without an INTx disable bit will then generate a
+ * level IRQ which will never be cleared.
+ *
+ * Returns 1 if it succeeded in masking the interrupt and 0 if the device
+ * doesn't support MSI masking.
+ */
+static int msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)
 {
         struct msi_desc *entry;
 
@@ -144,8 +153,7 @@ static void msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)
                         mask_bits |= flag & mask;
                         pci_write_config_dword(entry->dev, pos, mask_bits);
                 } else {
-                        __msi_set_enable(entry->dev, entry->msi_attrib.pos,
-                                         !flag);
+                        return 0;
                 }
                 break;
         case PCI_CAP_ID_MSIX:
@@ -161,6 +169,7 @@ static void msi_set_mask_bits(unsigned int irq, u32 mask, u32 flag)
                 break;
         }
         entry->msi_attrib.masked = !!flag;
+        return 1;
 }
 
 void read_msi_msg(unsigned int irq, struct msi_msg *msg)