linux-kernel - Re: [PATCH 1/2] dt-bindings: arm-smmu: Document SM61[12]5 GPU SMMU

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Date:   Thu, 16 Mar 2023 22:59:49 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>
Cc:     Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: arm-smmu: Document SM61[12]5 GPU SMMU



On 16.03.2023 20:29, Krzysztof Kozlowski wrote:
> On 15/03/2023 11:52, Konrad Dybcio wrote:
>> Both of these SoCs have a Qualcomm MMU500 implementation of SMMU
>> in front of their GPUs that expect 3 clocks. Both of them also have
>> an APPS SMMU that expects no clocks. Remove qcom,sm61[12]5-smmu-500
>> from the "no clocks" list (intentionally 'breaking' the schema checks
>> of APPS SMMU, as now it *can* accept clocks - with the current
>> structure of this file it would have taken a wastefully-long time to
>> sort this out properly..) and add necessary yaml to describe the
>> clocks required by the GPU SMMUs.
> 
> 
>> +      properties:
>> +        compatible:
>> +          items:
>> +            - enum:
>> +                - qcom,sm6115-smmu-500
>> +                - qcom,sm6125-smmu-500
>> +            - const: qcom,adreno-smmu
>> +            - const: qcom,smmu-500
>> +            - const: arm,mmu-500
> 
> If you drop the hunk later (from allOf:if), then what clocks do you
> expect for non-GPU SMMU?
Both 6115 and 6125 require no clocks under the APPS (non-GPU) SMMU.
However, the list below uses a `contains:` which means I'd have
to add a whole another hunk like

	- items:
            - enum:
                - qcom,sm6115-smmu-500
                - qcom,sm6125-smmu-500
            - const: qcom,smmu-500
            - const: arm,mmu-500

and add another level of indentation to the previous one

I figured skipping that was less messy (I think we discussed this
once as well), but if you prefer to keep it strict, I can.

Konrad
	
> 
>> +    then:
>> +      properties:
>> +        clock-names:
>> +          items:
>> +            - const: mem
>> +            - const: hlos
>> +            - const: iface
>> +
>> +        clocks:
>> +          items:
>> +            - description: GPU memory bus clock
>> +            - description: Voter clock required for HLOS SMMU access
>> +            - description: Interface clock required for register access
>> +
>>    # Disallow clocks for all other platforms with specific compatibles
>>    - if:
>>        properties:
>> @@ -394,8 +420,6 @@ allOf:
>>                - qcom,sdm845-smmu-500
>>                - qcom,sdx55-smmu-500
>>                - qcom,sdx65-smmu-500
>> -              - qcom,sm6115-smmu-500
>> -              - qcom,sm6125-smmu-500
>>                - qcom,sm6350-smmu-500
>>                - qcom,sm6375-smmu-500
>>                - qcom,sm8350-smmu-500
>>
> 
> Best regards,
> Krzysztof
>