On 01/07/2020 19:28, Krishna Reddy wrote: >>> + - description: NVIDIA SoCs that use more than one "arm,mmu-500" >> Hmm, there must be a better way to word that to express that it only applies >> to the sets of SMMUs that must be programmed identically, and not any other >> independent MMU-500s that might also happen to be in the same SoC. > > Let me reword it to "NVIDIA SoCs that must program multiple MMU-500s > identically". > >>> + items: >>> + - enum: >>> + - nvdia,tegra194-smmu >>> + - const: arm,mmu-500 > >> Is the fallback compatible appropriate here? If software treats this as a >> standard MMU-500 it will only program the first instance (because the second >> isn't presented as a separate MMU-500) - is there any way that isn't going >> to blow up? > > When compatible is set to both nvidia,tegra194-smmu and arm,mmu-500, > implementation override ensure that both instances are programmed. Isn't it? > I am not sure I follow your comment fully.
The problem is, if for some reason someone had a Tegra194, but only set the compatible string to 'arm,mmu-500' it would assume that it was a normal arm,mmu-500 and only one instance would be programmed. We always want at least 2 of the 3 instances programmed and so we should only match 'nvidia,tegra194-smmu'. In fact, I think that we also need to update the arm_smmu_of_match table to add 'nvidia,tegra194-smmu' with the data set to &arm_mmu500. Jon -- nvpublic _______________________________________________ iommu mailing list firstname.lastname@example.org https://lists.linuxfoundation.org/mailman/listinfo/iommu