[PATCH] PCI: Provide a boot parameter to disable MSI

Several drivers are starting to grow options to disable MSI.  However,
it's often a host chipset issue, not something which individual drivers
should handle.  So we add the pci=nomsi kernel parameter to allow the user
to disable MSI modes for systems we haven't added to the quirk list yet.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

5 files changed, 26 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7b7382d0f758..44a25f3f51d1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -49,6 +49,7 @@ restrictions referred to are that the relevant option is valid if:
         MCA     MCA bus support is enabled.
         MDA     MDA console support is enabled.
         MOUSE   Appropriate mouse support is enabled.
+        MSI     Message Signaled Interrupts (PCI).
         MTD     MTD support is enabled.
         NET     Appropriate network support is enabled.
         NUMA    NUMA support is enabled.
@@ -1152,6 +1153,9 @@ running once the system is up.
                                 Mechanism 2.
                 nommconf        [IA-32,X86_64] Disable use of MMCONFIG for PCI
                                 Configuration
+                nomsi           [MSI] If the PCI_MSI kernel config parameter is
+                                enabled, this kernel boot option can be used to
+                                disable the use of MSI interrupts system-wide.
                 nosort          [IA-32] Don't sort PCI devices according to
                                 order given by the PCI BIOS. This sorting is
                                 done to get a device order compatible with
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index d3dcce815d15..4d762fc4878c 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -11,6 +11,10 @@ config PCI_MSI
            generate an interrupt using an inbound Memory Write on its
            PCI bus instead of asserting a device IRQ pin.
 
+           Use of PCI MSI interrupts can be disabled at kernel boot time
+           by using the 'pci=nomsi' option.  This disables MSI for the
+           entire system.
+
            If you don't know what to do here, say N.
 
 config PCI_DEBUG
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index aea8b258b9b8..a77e79c8c82e 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -765,8 +765,11 @@ void pci_disable_msi(struct pci_dev* dev)
         u16 control;
         unsigned long flags;
 
+        if (!pci_msi_enable)
+                return;
         if (!dev)
                 return;
+
         pos = pci_find_capability(dev, PCI_CAP_ID_MSI);
         if (!pos)
                 return;
@@ -1026,6 +1029,8 @@ void pci_disable_msix(struct pci_dev* dev)
         int pos, temp;
         u16 control;
 
+        if (!pci_msi_enable)
+                return;
         if (!dev)
                 return;
 
@@ -1152,6 +1157,11 @@ void msi_remove_pci_irq_vectors(struct pci_dev* dev)
         }
 }
 
+void pci_no_msi(void)
+{
+        pci_msi_enable = 0;
+}
+
 EXPORT_SYMBOL(pci_enable_msi);
 EXPORT_SYMBOL(pci_disable_msi);
 EXPORT_SYMBOL(pci_enable_msix);
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 0bf6d254426b..03af23238939 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -900,8 +900,12 @@ static int __devinit pci_setup(char *str)
                 if (k)
                         *k++ = 0;
                 if (*str && (str = pcibios_setup(str)) && *str) {
-                        /* PCI layer options should be handled here */
-                        printk(KERN_ERR "PCI: Unknown option `%s'\n", str);
+                        if (!strcmp(str, "nomsi")) {
+                                pci_no_msi();
+                        } else {
+                                printk(KERN_ERR "PCI: Unknown option `%s'\n",
+                                                str);
+                        }
                 }
                 str = k;
         }
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index a6dfee2f6d2b..8f3fb47ea671 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -50,8 +50,10 @@ extern int pci_msi_quirk;
 
 #ifdef CONFIG_PCI_MSI
 void disable_msi_mode(struct pci_dev *dev, int pos, int type);
+void pci_no_msi(void);
 #else
 static inline void disable_msi_mode(struct pci_dev *dev, int pos, int type) { }
+static inline void pci_no_msi(void) { }
 #endif
 
 extern int pcie_mch_quirk;