PCI: Set MPS to match upstream bridge

Firmware typically configures the PCIe fabric with a consistent Max Payload
Size setting based on the devices present at boot.  A hot-added device
typically has the power-on default MPS setting (128 bytes), which may not
match the fabric.

The previous Linux default, in the absence of any "pci=pcie_bus_*" options,
was PCIE_BUS_TUNE_OFF, in which we never touch MPS, even for hot-added
devices.

Add a new default setting, PCIE_BUS_DEFAULT, in which we make sure every
device's MPS setting matches the upstream bridge.  This makes it more
likely that a hot-added device will work in a system with optimized MPS
configuration.

Note that if we hot-add a device that only supports 128-byte MPS, it still
likely won't work because we don't reconfigure the rest of the fabric.
Booting with "pci=pcie_bus_peer2peer" is a workaround for this because it
sets MPS to 128 for everything.

[bhelgaas: changelog, new default, rework for pci_configure_device() path]
Tested-by: Keith Busch <keith.busch@intel.com>
Tested-by: Jordan Hargrave <jharg93@gmail.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 0008c950452c31e71f8f591354449980893e58f6..b96b4ccc2819fa04f003c96e228cadf1e12ec5c5 100644 (file)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -81,7 +81,7 @@ 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_TUNE_OFF;
+enum pcie_bus_config_types pcie_bus_config = PCIE_BUS_DEFAULT;
 
 /*
  * The default CLS is used if arch didn't set CLS explicitly and not

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index eb32395d589704315acf31b7852e162c6d81db3c..eebabe3a814ef04f997867baa4cfcd38d871ddd5 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1278,7 +1278,7 @@ int pci_setup_device(struct pci_dev *dev)
 static void pci_configure_mps(struct pci_dev *dev)
 {
        struct pci_dev *bridge = pci_upstream_bridge(dev);
-       int mps, p_mps;
+       int mps, p_mps, rc;
 
        if (!pci_is_pcie(dev) || !bridge || !pci_is_pcie(bridge))
                return;
@@ -1294,6 +1294,23 @@ static void pci_configure_mps(struct pci_dev *dev)
                         mps, pci_name(bridge), p_mps);
                return;
        }
+
+       /*
+        * Fancier MPS configuration is done later by
+        * pcie_bus_configure_settings()
+        */
+       if (pcie_bus_config != PCIE_BUS_DEFAULT)
+               return;
+
+       rc = pcie_set_mps(dev, p_mps);
+       if (rc) {
+               dev_warn(&dev->dev, "can't set Max Payload Size to %d; if necessary, use \"pci=pcie_bus_safe\" and report a bug\n",
+                        p_mps);
+               return;
+       }
+
+       dev_info(&dev->dev, "Max Payload Size set to %d (was %d, max %d)\n",
+                p_mps, mps, 128 << dev->pcie_mpss);
 }
 
 static struct hpp_type0 pci_default_type0 = {
@@ -1821,7 +1838,8 @@ static int pcie_bus_configure_set(struct pci_dev *dev, void *data)
        if (!pci_is_pcie(dev))
                return 0;
 
-       if (pcie_bus_config == PCIE_BUS_TUNE_OFF)
+       if (pcie_bus_config == PCIE_BUS_TUNE_OFF ||
+           pcie_bus_config == PCIE_BUS_DEFAULT)
                return 0;
 
        mps = 128 << *(u8 *)data;

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index e9fd0e90fa3b5c6656f7d8939a522add97c29b06..55f2c208bd0ec4b9cf444f46f509bedfbc3a29db 100644 (file)
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -2862,7 +2862,8 @@ static void quirk_intel_mc_errata(struct pci_dev *dev)
        int err;
        u16 rcc;
 
-       if (pcie_bus_config == PCIE_BUS_TUNE_OFF)
+       if (pcie_bus_config == PCIE_BUS_TUNE_OFF ||
+           pcie_bus_config == PCIE_BUS_DEFAULT)
                return;
 
        /* Intel errata specifies bits to change but does not say what they are.

diff --git a/include/linux/pci.h b/include/linux/pci.h
index 4d4f9d29fcc9a8cc642606c224006c4605711891..0007942923a7b20611afe88e3fa646b70d0788e3 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -738,10 +738,11 @@ struct pci_driver {
 void pcie_bus_configure_settings(struct pci_bus *bus);
 
 enum pcie_bus_config_types {
-       PCIE_BUS_TUNE_OFF,
-       PCIE_BUS_SAFE,
-       PCIE_BUS_PERFORMANCE,
-       PCIE_BUS_PEER2PEER,
+       PCIE_BUS_TUNE_OFF,      /* don't touch MPS at all */
+       PCIE_BUS_DEFAULT,       /* ensure MPS matches upstream bridge */
+       PCIE_BUS_SAFE,          /* use largest MPS boot-time devices support */
+       PCIE_BUS_PERFORMANCE,   /* use MPS and MRRS for best performance */
+       PCIE_BUS_PEER2PEER,     /* set MPS = 128 for all devices */
 };
 
 extern enum pcie_bus_config_types pcie_bus_config;