From 27d868b5e6cfaee4fec66b388e4085ff94050fa7 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Mon, 24 Aug 2015 08:48:16 -0500 Subject: 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 Tested-by: Jordan Hargrave Signed-off-by: Keith Busch Signed-off-by: Bjorn Helgaas Acked-by: Yinghai Lu --- include/linux/pci.h | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/pci.h b/include/linux/pci.h index 4d4f9d29fcc9..0007942923a7 100644 --- 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; -- cgit v1.2.3