Dear Arnd Bergmann, On Tue, 29 Jan 2013 20:15:21 +0000, Arnd Bergmann wrote: > I mean you could make each root port look like a separate host > bridge that is not related to the others, and not have any > emulated PCI-to-PCI bridges at all. Ok. > > Remember that the very reason to use emulated PCI-to-PCI bridges is > > that we want to assign a global range of addresses of I/O regions > > and a global range of addresses of memory regions, and let the > > Linux PCI core allocate from those two ranges to the different > > devices connected downstream of the PCI-to-PCI bridges. This gives > > us for free the rather complex allocation of addresses we need to > > set up our address decoding windows. > > > > If we have have separate domains for each of our hardware PCIe > > interface, can we still benefit from this allocation of resources > > from a globally defined range of I/O addresses and memory addresses? > > My interpretation of what you told me in the previous mail is that > each root port has > > * A separate configuration space > * A separate 64KB I/O window that is not shared with the other ports, > or potentially multiple 64KB windows, which we would not want to use > * A configurable range of the memory space that does not overlap > with the other ports > > Is the above a correct description? > > If so, I think it would be most sensible to not try to put all ports > into the same domain, but give each port the full view of its own > 256 buses, and 64KB I/O space. The memory space can still be directly > mapped, if you only set up the physical address window for that after > the bus scan is complete. Does this still allows me to give the Linux PCI *one* global range of addresses for I/O space, and *one* global range of addresses for memory space, and the the Linux PCI core assign ranges, within those global ranges, to each host bridge? This is absolutely essential for me, as I then read those allocated ranges to configure the address decoding windows. Basically, I have currently two suggestions: * From Jason Gunthorpe, to not use any host bridge, and instead use only PCI-to-PCI bridges, one per PCIe interface. * From you, to not use any PCI-to-PCI bridge, and use only host bridges, one per PCIe interface. Would it be possible to get some consensus on this? In the review of RFCv1, I was already told to use one global host bridge, and then one PCI-to-PCI bridge per PCIe interface, and now we're talking about doing something different. I'd like to avoid having to try gazillions of different possible implementations :-) Best regards, Thomas -- Thomas Petazzoni, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
