3 files changed, 20 insertions, 3 deletions

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 4e84fd4a4312..e9651f0a8817 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -77,7 +77,7 @@ unsigned long pci_cardbus_mem_size = DEFAULT_CARDBUS_MEM_SIZE;
 unsigned long pci_hotplug_io_size  = DEFAULT_HOTPLUG_IO_SIZE;
 unsigned long pci_hotplug_mem_size = DEFAULT_HOTPLUG_MEM_SIZE;
 
-enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_SAFE;
+enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_TUNE_OFF;
 
 /*
  * The default CLS is used if arch didn't set CLS explicitly and not
@@ -3568,10 +3568,14 @@ static int __init pci_setup(char *str)
                                 pci_hotplug_io_size = memparse(str + 9, &str);
                         } else if (!strncmp(str, "hpmemsize=", 10)) {
                                 pci_hotplug_mem_size = memparse(str + 10, &str);
+                        } else if (!strncmp(str, "pcie_bus_tune_off", 17)) {
+                                pcie_bus_config = PCIE_BUS_TUNE_OFF;
                         } else if (!strncmp(str, "pcie_bus_safe", 13)) {
                                 pcie_bus_config = PCIE_BUS_SAFE;
                         } else if (!strncmp(str, "pcie_bus_perf", 13)) {
                                 pcie_bus_config = PCIE_BUS_PERFORMANCE;
+                        } else if (!strncmp(str, "pcie_bus_peer2peer", 18)) {
+                                pcie_bus_config = PCIE_BUS_PEER2PEER;
                         } else {
                                 printk(KERN_ERR "PCI: Unknown option `%s'\n",
                                                 str);
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index f3f94a5c068f..6ab6bd3df4b2 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1458,12 +1458,24 @@ static int pcie_bus_configure_set(struct pci_dev *dev, void *data)
  */
 void pcie_bus_configure_settings(struct pci_bus *bus, u8 mpss)
 {
-        u8 smpss = mpss;
+        u8 smpss;
 
         if (!pci_is_pcie(bus->self))
                 return;
 
+        if (pcie_bus_config == PCIE_BUS_TUNE_OFF)
+                return;
+
+        /* FIXME - Peer to peer DMA is possible, though the endpoint would need
+         * to be aware to the MPS of the destination.  To work around this,
+         * simply force the MPS of the entire system to the smallest possible.
+         */
+        if (pcie_bus_config == PCIE_BUS_PEER2PEER)
+                smpss = 0;
+
         if (pcie_bus_config == PCIE_BUS_SAFE) {
+                smpss = mpss;
+
                 pcie_find_smpss(bus->self, &smpss);
                 pci_walk_bus(bus, pcie_find_smpss, &smpss);
         }
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 8c230cbcbb48..9fc01226055b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -621,8 +621,9 @@ struct pci_driver {
 extern void pcie_bus_configure_settings(struct pci_bus *bus, u8 smpss);
 
 enum pcie_bus_config_types {
-        PCIE_BUS_PERFORMANCE,
+        PCIE_BUS_TUNE_OFF,
         PCIE_BUS_SAFE,
+        PCIE_BUS_PERFORMANCE,
         PCIE_BUS_PEER2PEER,
 };