On Tue, Oct 17, 2017 at 12:11:55PM -0400, Jim Quinlan wrote: > My understanding is that dma_pfn_offset is that it is a single > constant offset from RAM, in our case, to map to PCIe space. Yes. > But in > my commit message I detail how our PCIe controller presents memory > with multiple regions with multiple different offsets. If an EP device > maps to a region on the host memory, yes we can set the dma_pfn_offset > for that device for that location within that range,. But if the > device then unmaps and allocates from another region with a different > offset, it won't work. If I set dma_pfn_offset I have to assume that > the device is using only one region of memory only, not more than one, > and that it is not unmapping that region and mapping another (with a > different offset). Can I make those assumptions? No, we can't make that assumption unfortunately. But how is your code going to work if the mapping spans multiple of your translation regions? Also I really don't think the stacking of dma_ops as in this patch is a good idea. For MIPS you should do the variant suggested in the patch description and hook into dma_to_phys/phys_to_dma helpers, and for ARM/ARM64 you should talk to the maintainers on how they want the translation integrated.
