linux-kernel - Re: [PATCH] dt-bindings: arm-smmu: disallow clocks when not used

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Message-ID: <20221222101611.nwt5arux2hcvvtvf@SoMainline.org>
Date:   Thu, 22 Dec 2022 11:16:11 +0100
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>
Subject: Re: [PATCH] dt-bindings: arm-smmu: disallow clocks when not used

Is this missing a cc to linux-arm-msm?

On 2022-12-22 10:23:55, Krzysztof Kozlowski wrote:
> Disallow clocks for variants other than:
> 1. SMMUs with platform-specific compatibles which list explicit clocks
>    and clock-names,
> 2. SMMUs using only generic compatibles, e.g. arm,mmu-500, which have a
>    variable clocks on different implementations.
> 
> This requires such variants with platform-specific compatible, to
> explicitly list the clocks or omit them, making the binding more
> constraint.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Reviewed-by: Marijn Suijten <marijn.suijten@...ainline.org>

But...

> ---
> 
> Cc: Marijn Suijten <marijn.suijten@...ainline.org>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Cc: Konrad Dybcio <konrad.dybcio@...aro.org>
> ---
>  .../devicetree/bindings/iommu/arm,smmu.yaml   | 28 +++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> index 895ec8418465..0d88395e43ad 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
> @@ -367,6 +367,34 @@ allOf:
>              - description: interface clock required to access smmu's registers
>                  through the TCU's programming interface.
>  
> +  # Disallow clocks for all other platforms with specific compatibles
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            enum:
> +              - cavium,smmu-v2
> +              - marvell,ap806-smmu-500
> +              - nvidia,smmu-500
> +              - qcom,qcm2290-smmu-500
> +              - qcom,qdu1000-smmu-500
> +              - qcom,sc7180-smmu-500

Hmm, sc7280 has two SMMUs.  The one for Adreno has clocks and a PD, the
one for APPS has neither.  Same story on sm8[12]50.  Aren't those going
to trip up the other `if` that requires clocks in both scenarios?

Note that the Adreno SMMUs have (or will get when we/Konrad submit
support for it) the "qcom,adreno-smmu" compatible to distinguish them.

- Marijn

> +              - qcom,sc8180x-smmu-500
> +              - qcom,sc8280xp-smmu-500
> +              - qcom,sdm670-smmu-500
> +              - qcom,sdm845-smmu-500
> +              - qcom,sdx55-smmu-500
> +              - qcom,sdx65-smmu-500
> +              - qcom,sm6115-smmu-500
> +              - qcom,sm6350-smmu-500
> +              - qcom,sm6375-smmu-500
> +              - qcom,sm8350-smmu-500
> +              - qcom,sm8450-smmu-500
> +    then:
> +      properties:
> +        clock-names: false
> +        clocks: false
> +
>    - if:
>        properties:
>          compatible:
> -- 
> 2.34.1
>