Re: [PATCH v2 1/6] dt-bindings: iommu: arm,smmu: Document interconnects property

[Bibek Kumar Patro <bibek.patro@oss.qualcomm.com>]

On 6/8/2026 7:19 PM, Dmitry Baryshkov wrote:
> On Mon, Jun 08, 2026 at 07:14:43PM +0530, Bibek Kumar Patro wrote:
>>
>>
>> On 6/8/2026 3:22 PM, Konrad Dybcio wrote:
>>> On 5/26/26 4:42 PM, Bibek Kumar Patro wrote:
>>>> Some SoC implementations require a bandwidth vote on an interconnect
>>>> path before the SMMU register space is accessible. Add the optional
>>>> 'interconnects' property to the binding to allow platform DT nodes
>>>> to describe this path.
>>>>
>>>> Signed-off-by: Bibek Kumar Patro <bibek.patro@oss.qualcomm.com>
>>>> ---
>>>>    .../devicetree/bindings/iommu/arm,smmu.yaml        | 27 ++++++++++++++++++++++
>>>>    1 file changed, 27 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>>>> index 06fb5c8e7547cb7a92823adc2772b94f747376a6..3a677ff1a18fcdf5c0ca9ec8a017d41f9eb5ff09 100644
>>>> --- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>>>> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
>>>> @@ -243,6 +243,13 @@ properties:
>>>>        minItems: 1
>>>>        maxItems: 3
>>>> +  interconnects:
>>>> +    maxItems: 1
>>>> +    description:
>>>> +      Interconnect path to the SMMU register space. Required on SoCs
>>>> +      where the SMMU registers are only accessible after a bandwidth
>>>> +      vote has been placed on the interconnect fabric.
>>>> +
>>>>      nvidia,memory-controller:
>>>>        description: |
>>>>          A phandle to the memory controller on NVIDIA Tegra186 and later SoCs.
>>>> @@ -602,6 +609,26 @@ allOf:
>>>>            clock-names: false
>>>>            clocks: false
>>>> +  - if:
>>>> +      properties:
>>>> +        compatible:
>>>> +          items:
>>>> +            - enum:
>>>> +                - qcom,qcs615-smmu-500
>>>> +                - qcom,qcs8300-smmu-500
>>>> +                - qcom,sa8775p-smmu-500
>>>> +                - qcom,sc7280-smmu-500
>>>
>>> This is a list of targets that happen to be supported by QLI.. but should
>>> this list not contain _all_ Qualcomm SoCs, or at least a much broader range?
>>>
>>> Perhaps
>>>
>>> if: properties: compatible: contains: qcom,adreno-smmu
>>>
>>> ?
>>>
>>
>> As of now platforms where the issues [1] getting reported are added, the
>> list will grow.
>> <We still have to evaluate and test on other non-QLI platforms hosted in
>> upstream [2]>
> 
> Do you really need to test, which platforms have an interconnect, or can
> you predict it by checking the SoC documentation? I strongly belive, the
> latter is the case.
> 

Agree, for interconnect path we can surely predict from the SoC 
documentation,
But for the corresponding FLAGS/values (MASTER_GPU_TCU, SLAVE_EBI1), it 
would need some testing before finalizing the change on corresponding 
platforms.

Thanks,
Bibek

>>
>> [1]: https://github.com/qualcomm-linux/kernel/issues/297
>> [2]: https://lore.kernel.org/all/a437f9f9-3560-40f8-85ea-35433e33c428@oss.qualcomm.com/
>>
>>> Konrad
>>
>