On Tue, Oct 06, 2020 at 09:19:32AM -0400, Jonathan Marek wrote: > One example why drm/msm can't use DMA API is multiple page table support > (that is landing in 5.10), which is something that definitely couldn't work > with DMA API. > > Another one is being able to choose the address for mappings, which AFAIK > DMA API can't do (somewhat related to this: qcom hardware often has ranges > of allowed addresses, which the dma_mask mechanism fails to represent, what > I see is drivers using dma_mask as a "maximum address", and since addresses > are allocated from the top it generally works) That sounds like a good enough rason to use the IOMMU API. I just wanted to make sure this really makes sense.
