On Thursday 12 November 2015 09:26:33 Phil Edworthy wrote: > On 11 November 2015 18:25, LIviu wrote: > > On Mon, Nov 09, 2015 at 12:32:13PM +0000, Phil Edworthy wrote: > > I think you're mixing things a bit or not explaining them very well. Having the > > PCIe controller limited to 32-bit AXI does not mean that the PCIe bus cannot > > carry 64-bit addresses. It depends on how they get translated by the host bridge > > or its associated ATS block. I can't see why you can't have a setup where > > the CPU addresses are 32-bit but the PCIe bus addresses are all 64-bit. > > You just have to be careful on how you setup your mem64 ranges so that they > > don't > > overlap with the 32-bit ranges when translated. > From a HW point of view I agree that we can setup the PCI host bridge such that > it uses 64-bit PCI address, with 32-bit cpu addresses. Though in practice doesn't > this mean that the dma ops used by card drivers has to be provided by our PCI > host bridge driver so we can apply the translation to those PCI addresses? > This comes back to my point below about how to do this. Adding a bus notifier > to do this may be too late, and arm64 doesn't implement set_dma_ops(). > > > And no, you should not limit at the card driver the DMA_BIT_MASK() unless the > > card is not capable of supporting more than 32-bit addresses. > If there was infrastructure that checked all parents dma-ranges when the > dma_set_mask() function is called as Arnd pointed out, this would nicely solve > the problem. of_dma_configure calls of_dma_get_range to do all this for the PCIe host, and then calls arch_setup_dma_ops() so the architecture specific code can enforce the limits in dma_set_mask and pick an appropriate set of dma operations. The missing part is in the implementation of arch_setup_dma_ops, which currently happily ignores the base and limit. Arnd -- 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
