RE: [PATCH v8 2/3] dt-bindings: arm-smmu: Add binding for Tegra194 SMMU

[Krishna Reddy]

>>>> +        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.

In that case, new binding "nvidia,smmu-v2" can be added with data set to &arm_mmu500 and enumeration would have nvidia,tegra194-smmu and another variant for next generation SoC in future. 

-KR
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nvpublic