Re: [PATCH v2 1/8] dt-bindings: arm-smmu: Add Adreno GPU variant

[Robin Murphy]

On 22/11/2019 11:31 pm, Jordan Crouse wrote:
> Add a compatible string to identify SMMUs that are attached
> to Adreno GPU devices that wish to support split pagetables.

A software policy decision is not, in itself, a good justification for a 
DT property. Is the GPU SMMU fundamentally different in hardware* from 
the other SMMU(s) in any given SoC?

(* where "hardware" may encompass hypervisor shenanigans)

> Signed-off-by: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
> ---
>
>   Documentation/devicetree/bindings/iommu/arm,smmu.yaml | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> index 6515dbe..db9f826 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> @@ -31,6 +31,12 @@ properties:
>                 - qcom,sdm845-smmu-v2
>             - const: qcom,smmu-v2
>   
> +      - description: Qcom Adreno GPU SMMU iplementing split pagetables
> +        items:
> +          - enum:
> +              - qcom,adreno-smmu-v2
> +          - const: qcom,smmu-v2

Given that we already have per-SoC compatibles for Qcom SMMUs in 
general, this seems suspiciously vague.

Robin.

> +
>         - description: Qcom SoCs implementing "arm,mmu-500"
>           items:
>             - enum: