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

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Message-ID: <03a8c0e4-bc5c-1447-e3b6-a26f2f221862@linaro.org>
Date:   Tue, 15 Nov 2022 16:04:34 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Robin Murphy <robin.murphy@....com>,
        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>,
        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 14:43, Robin Murphy wrote:
> On 2022-11-15 13:06, Konrad Dybcio wrote:
>>
>>
>> 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 :/
> 
> Right, so it's not a required property. However if it *is* present, then 
> it needs to reference at least one power domain, because having an empty 
> property, i.e.:
> 
>      power-domains = <>;
> 
> or
>      power-domains;
> 
> makes no sense whatsoever.
> 
> Thanks,
> Robin.
OHHHH!

That was the missing piece that made it click for me!
Thanks Krzysztof, Robin for guiding me through this.

Konrad
> 
>>
>>>
>>> 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
>>>