On Tue, 2012-11-27 at 17:32 +0000, Fujinaka, Todd wrote: > Forgive me if I'm being too repetitious as I think some of this has > been mentioned in the past. > > We (and by we I mean the Ethernet part and driver) can only change the > advertised availability of a larger MaxPayloadSize. The size is > negotiated by both sides of the link when the link is established. The > driver should not change the size of the link as it would be poking at > registers outside of its scope and is controlled by the upstream > bridge (not us). [...]
MaxPayloadSize (MPS) is not negotiated between devices but is programmed by the system firmware (at least for devices present at boot - the kernel may be responsible in case of hotplug). You can use the kernel parameter 'pci=pcie_bus_perf' (or one of several others) to set a policy that overrides this, but no policy will allow setting MPS above the device's MaxPayloadSizeSupported (MPSS). (These parameters are not documented in Documentation/kernel-parameters.txt! Someone ought to fix that.) Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
