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

[Robin Murphy <robin.murphy@arm.com>]

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@linaro.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@5040000: '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.

> 
>>
>> 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@3da0000: 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
>>