[PATCH] msi: sanely support hardware level msi disabling

In some cases when we are not using msi we need a way to ensure that the
hardware does not have an msi capability enabled.  Currently the code has been
calling disable_msi_mode to try and achieve that.  However disable_msi_mode
has several other side effects and is only available when msi support is
compiled in so it isn't really appropriate.

Instead this patch implements pci_msi_off which disables all msi and msix
capabilities unconditionally with no additional side effects.

pci_disable_device was redundantly clearing the bus master enable flag and
clearing the msi enable bit.  A device that is not allowed to perform bus
mastering operations cannot generate intx or msi interrupt messages as those
are essentially a special case of dma, and require bus mastering.  So the call
in pci_disable_device to disable msi capabilities was redundant.

quirk_pcie_pxh also called disable_msi_mode and is updated to use pci_msi_off.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 7 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 1e74e1ee8bd8..df495300ce3d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -881,13 +881,6 @@ pci_disable_device(struct pci_dev *dev)
         if (atomic_sub_return(1, &dev->enable_cnt) != 0)
                 return;
 
-        if (dev->msi_enabled)
-                disable_msi_mode(dev, pci_find_capability(dev, PCI_CAP_ID_MSI),
-                        PCI_CAP_ID_MSI);
-        if (dev->msix_enabled)
-                disable_msi_mode(dev, pci_find_capability(dev, PCI_CAP_ID_MSI),
-                        PCI_CAP_ID_MSIX);
-
         pci_read_config_word(dev, PCI_COMMAND, &pci_command);
         if (pci_command & PCI_COMMAND_MASTER) {
                 pci_command &= ~PCI_COMMAND_MASTER;
@@ -1277,6 +1270,33 @@ pci_intx(struct pci_dev *pdev, int enable)
         }
 }
 
+/**
+ * pci_msi_off - disables any msi or msix capabilities
+ * @pdev: the PCI device to operate on
+ *
+ * If you want to use msi see pci_enable_msi and friends.
+ * This is a lower level primitive that allows us to disable
+ * msi operation at the device level.
+ */
+void pci_msi_off(struct pci_dev *dev)
+{
+        int pos;
+        u16 control;
+
+        pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
+        if (pos) {
+                pci_read_config_word(dev, pos + PCI_MSI_FLAGS, &control);
+                control &= ~PCI_MSI_FLAGS_ENABLE;
+                pci_write_config_word(dev, pos + PCI_MSI_FLAGS, control);
+        }
+        pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
+        if (pos) {
+                pci_read_config_word(dev, pos + PCI_MSIX_FLAGS, &control);
+                control &= ~PCI_MSIX_FLAGS_ENABLE;
+                pci_write_config_word(dev, pos + PCI_MSIX_FLAGS, control);
+        }
+}
+
 #ifndef HAVE_ARCH_PCI_SET_DMA_MASK
 /*
  * These can be overridden by arch-specific implementations