[+cc Jon, can you make sure this documentation is accurate?] On Wed, Jan 23, 2013 at 7:58 PM, Yijing Wang <wangyijing@xxxxxxxxxx> 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. > > 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 | 16 ++++++++++++++++ > 1 files changed, 16 insertions(+), 0 deletions(-) > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index 363e348..0bb279f 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -2227,6 +2227,22 @@ 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) > + turning and using the BIOS-configured MPS defaults. s/turning/tuning/ s/using/use/ > + pcie_bus_safe Use the smallest common denominator MPS > + of the entire tree below a root complex for every > + device on that fabric. Can avoid inconsistent MPS > + problem caused by hotplug. I'm not sure about this. "smallest common denominator" is colloquial and not exact. I think you probably mean "the smallest supported MPS of any device below a root complex." I'm also not sure how this will avoid MPS problems caused by hotplug. I think you have to assume that a hot-added device may support only a 128B MPS, which means the only way to guarantee that you can use that device is to set MPS=128 for any device that will send packets to the hot-added device. Or we could reconfigure things at the time of the hot-add, but I don't think we do that today (except for the hot-added device itself). > + pcie_bus_perf Configure pcie device MPS to the largest Capitalize "PCIe" consistently. Better yet, drop it completely since it's obvious that we're only talking about PCIe here. > + 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 Max performance. s/Max/best/ > + pcie_bus_peer2peer Make the system-wide MPS the smallest > + possible value (128B). This configuration could prevent > + peer to peer DMA transmission from working by having > + the MPS on one root port different than the MPS on > + another. I think the idea is that pcie_bus_peer2peer would *allow* peer-to-peer DMA to work, which is the opposite of what you wrote. Maybe something like this would be better: 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 > > -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
