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SubjectRe: [PATCH v3] PCI: Document PCIE BUS MPS parameters
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On Fri, Jan 25, 2013 at 2:36 AM, Yijing Wang <wangyijing@huawei.com> wrote:
> 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@myri.com> at
> commit 5f39e6705 and commit b03e7495a8.
>
> Signed-off-by: Yijing Wang <wangyijing@huawei.com>
> ---
> 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.

This isn't correct. It should be something like "The largest MPS
common to all devices below the 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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