linux-kernel - Re: [PATCH v2 1/9] dt-bindings: arm-smmu: Allow up to 3 power-domains

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Message-ID: <cff269c8-f944-9277-9df8-653522efbba0@linaro.org>
Date:   Tue, 15 Nov 2022 14:06:51 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        linux-arm-msm@...r.kernel.org, andersson@...nel.org,
        agross@...nel.org
Cc:     patches@...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>,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/9] dt-bindings: arm-smmu: Allow up to 3 power-domains



On 15/11/2022 14:00, Krzysztof Kozlowski wrote:
> On 15/11/2022 13:54, Konrad Dybcio wrote:
>>
>>
>> On 14/11/2022 17:58, Krzysztof Kozlowski wrote:
>>> On 14/11/2022 16:53, Konrad Dybcio wrote:
>>>>
>>>> On 14/11/2022 14:00, Krzysztof Kozlowski wrote:
>>>>> On 14/11/2022 12:17, Konrad Dybcio wrote:
>>>>>> On 14/11/2022 12:01, Krzysztof Kozlowski wrote:
>>>>>>> On 14/11/2022 11:42, Konrad Dybcio wrote:
>>>>>>>> Some SMMUs require that a vote is held on as much as 3 separate PDs
>>>>>>>> (hello Qualcomm). Allow it in bindings.
>>>>>>>>
>>>>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>>>>>> ---
>>>>>>>> Changes since v1:
>>>>>>>> - Add minItems
>>>>>>>>
>>>>>>>>      Documentation/devicetree/bindings/iommu/arm,smmu.yaml | 3 ++-
>>>>>>>>      1 file changed, 2 insertions(+), 1 deletion(-)
>>>>>>>>
>>>>>>>> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>>>>>>>> index 9066e6df1ba1..82bc696de662 100644
>>>>>>>> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>>>>>>>> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>>>>>>>> @@ -159,7 +159,8 @@ properties:
>>>>>>>>                through the TCU's programming interface.
>>>>>>>>      
>>>>>>>>        power-domains:
>>>>>>>> -    maxItems: 1
>>>>>>>> +    minItems: 0
>>>>>>> It cannot be 0.
>>>>>>>
>>>>>>> minItems: 1
>>>>>>>
>>>>>>> Anyway you still need to restrict it per variant, as I said in previous
>>>>>>> version.
>>>>>> Hm.. I'm not entirely sure what you mean.. Should I add a list of
>>>>>> compatibles
>>>>> Yes and limit it to maxItems: 1 for "else".
>>>>
>>>> I tried adding:
>>>>
>>>>
>>>>
>>>>      - if:
>>>>          properties:
>>>>            compatible:
>>>>              contains:
>>>>                enum:
>>>>                  - qcom,sm6375-smmu-500
>>>>        then:
>>>>          properties:
>>>>            power-domains:
>>>>              minItems: 3
>>>>              maxItems: 3
>>>>        else:
>>>>          properties:
>>>>            power-domains:
>>>>              maxItems: 1
>>>>
>>>>
>>>> Right under the nvidia reg if-else in the allOf, but dtbs_check throws
>>>> errors like:
>>>>
>>>>
>>>> /home/konrad/linux/arch/arm64/boot/dts/qcom/msm8998-sony-xperia-yoshino-poplar.dtb:
>>>> iommu@...0000: 'power-domains' does not match any of the regexes:
>>>> 'pinctrl-[0-9]+'
>>>>
>>>>
>>>> Any clues as to why?
>>>
>>> I don't know what code do you have there, but generic pattern is:
>>>
>>> https://elixir.bootlin.com/linux/v5.19-rc6/source/Documentation/devicetree/bindings/clock/samsung,exynos7-clock.yaml#L38
>>>
>> I tried many things, but I still don't seem to get a hang of it.. Here's
>> my current diff rebased on top of Dmitry's recent cleanups (available at
>> [1])
>>
>>
>> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>> b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>> index 28f5720824cd..55759aebc4a0 100644
>> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>> @@ -200,7 +200,7 @@ properties:
>>        maxItems: 7
>>
>>      power-domains:
> 
> As I mentioned before - minItems: 1.
But not all SMMUs require a power domain :/

> 
> Just like the link I gave you.
> 
>> -    maxItems: 1
>> +    maxItems: 3
>>
>>      nvidia,memory-controller:
>>        description: |
>> @@ -364,6 +364,26 @@ allOf:
>>                - description: interface clock required to access smmu's
>> registers
>>                    through the TCU's programming interface.
>>
>> +  - if:
>> +      properties:
>> +        compatible:
>> +          contains:
>> +            const: qcom,sm6375-smmu-500
>> +    then:
>> +      properties:
>> +        power-domains:
>> +          items:
>> +            - description: SNoC MMU TBU RT GDSC
>> +            - description: SNoC MMU TBU NRT GDSC
>> +            - description: SNoC TURING MMU TBU0 GDSC
>> +
>> +      required:
>> +        - power-domains
>> +    else:
>> +      properties:
>> +        power-domains:
>> +          maxItems: 1
>> +
>>    examples:
>>      - |+
>>        /* SMMU with stream matching or stream indexing */
>>
>>
>> In my eyes, this should work, but I still get errors like:
>>
>> /home/konrad/linux/arch/arm64/boot/dts/qcom/sm8250-hdk.dtb:
>> iommu@...0000: power-domains: [[108, 0]] is too short
>>
>> as if the else: path was never taken..
> 
> It was, but the top-level property said that minItems=3 (implicitly), so
> it is too short.
So the top-level properties take precedence over the ones that come from 
the if-then-else?? Ugh.

Konrad
> 
> Best regards,
> Krzysztof
>