Re: [PATCH v2 1/2] dt-bindings: iommu: arm,smmu-v3: Add SC8280XP compatible

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On 2024-03-09 1:31 pm, Konrad Dybcio wrote:
The smmu-v3 binding currently doesn't differentiate the SoCs it's
implemented on. This is a poor design choice that may bite in the future,
should any quirks surface.

That doesn't seem entirely fair to say - the vast majority of bindings don't have separate compatibles for every known integration of the same implementation in different SoCs. And in this case we don't have per-implementation compatibles for quirks and errata because the implementation is architecturally discoverable from the SMMU_IIDR register.

We have the whole mess for QCom SMMUv2 because the effective *implementation* is a mix of hardware and hypervisor, whose behaviour does seem to vary on almost a per-SoC basis. I'm not at all keen to start repeating that here without very good reason, and that of "documenting" a device which we typically expect to not even be accessible isn't really convincing me...


Add a compatible for the instance found on Qualcomm SC8280XP.

Signed-off-by: Konrad Dybcio <konrad.dybcio@xxxxxxxxxx>
  Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
index 75fcf4cb52d9..f284f7b0c1d8 100644
--- a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
+++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
@@ -20,7 +20,11 @@ properties:
      pattern: "^iommu@[0-9a-f]*"
-    const: arm,smmu-v3
+    oneOf:
+      - items:
+          - const: qcom,sc8280xp-smmu-v3
+          - const: arm,smmu-v3
+      - const: arm,smmu-v3
      maxItems: 1

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