From fa2387124b1ac8177f7af33668ec98135fdd147f Mon Sep 17 00:00:00 2001 From: Yijing Wang Date: Wed, 30 Jan 2013 09:40:52 +0800 Subject: [PATCH] PCI: Document MPS parameters pci=pcie_bus_safe, pci=pcie_bus_perf, etc Document PCIe bus MPS parameters pcie_bus_tune_off, pcie_bus_safe, pcie_bus_peer2peer, pcie_bus_perf. These parameters were introduced by Jon Mason at commit 5f39e6705 and commit b03e7495a8. [bhelgaas: mention hot-add for pcie_bus_peer2peer] Signed-off-by: Yijing Wang Signed-off-by: Bjorn Helgaas --- Documentation/kernel-parameters.txt | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 69f97a836600..dd80599559a5 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2227,6 +2227,21 @@ bytes respectively. Such letter suffixes can also be entirely omitted. This sorting is done to get a device order compatible with older (<= 2.4) kernels. nobfsort Don't sort PCI devices into breadth-first order. + pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) + tuning and use the BIOS-configured MPS defaults. + pcie_bus_safe Set every device's MPS to the largest value + supported by all devices below the root complex. + pcie_bus_perf Set device MPS to the largest allowable MPS + based on its parent bus. Also set MRRS (Max + Read Request Size) to the largest supported + value (no larger than the MPS that the device + or bus can support) for best performance. + pcie_bus_peer2peer Set every device's MPS to 128B, which + every device is guaranteed to support. This + configuration allows peer-to-peer DMA between + any pair of devices, possibly at the cost of + reduced performance. This also guarantees + that hot-added devices will work. cbiosize=nn[KMG] The fixed amount of bus space which is reserved for the CardBus bridge's IO window. The default value is 256 bytes. -- 2.39.5