[PATCH v3] PCI: Document PCIE BUS MPS parameters

[Yijing Wang]

v0->v1: Update MPS parameters as non-arch and add MRRS
		description into pcie_bus_perf parameter suggested
		by Andrew Murray.
v1->v2: Update some semantic problems and add MPS and MRRS
		explanation suggested by Joe Lawrence and Randy Dunlap.
v2->v3: Update some semantic problems and the description
		of pcie_bus_safe and pcie_bus_peer2peer suggested
		by Bjorn Helgaas.

Document PCIE BUS MPS parameters pcie_bus_tune_off, pcie_bus_safe,
pcie_bus_peer2peer, pcie_bus_perf into Documentation/kernel-parameters.txt.
These parameters were introduced by Jon Mason <mason@xxxxxxxx> at
commit 5f39e6705 and commit b03e7495a8.

Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
---
 Documentation/kernel-parameters.txt |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 363e348..2997df2 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2227,6 +2227,19 @@ 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	Use the smallest supported MPS of any device
+				below a root complex.
+		pcie_bus_perf	Configure 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.
 		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.
-- 
1.7.1


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