[PATCH v3 1/3] dt-bindings: arm-smmu: Document nvidia, memory-controller property

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@nvidia.com>

On NVIDIA SoC's the ARM SMMU needs to interact with the memory
controller in order to map memory clients to the corresponding stream
IDs. Document how the nvidia,memory-controller property can be used to
achieve this.

Note that this is a backwards-incompatible change that is, however,
necessary to ensure correctness. Without the new property, most of the
devices would still work but it is not guaranteed that all will.

Reviewed-by: Rob Herring <robh@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v2:
- clarify why the new nvidia,memory-controller property is required

 .../devicetree/bindings/iommu/arm,smmu.yaml     | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
index da5381c8ee11..44606ad5aa39 100644
--- a/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
+++ b/Documentation/devicetree/bindings/iommu/arm,smmu.yaml
@@ -157,6 +157,17 @@ properties:
   power-domains:
     maxItems: 1
 
+  nvidia,memory-controller:
+    description: |
+      A phandle to the memory controller on NVIDIA Tegra186 and later SoCs.
+      The memory controller needs to be programmed with a mapping of memory
+      client IDs to ARM SMMU stream IDs.
+
+      If this property is absent, the mapping programmed by early firmware
+      will be used and it is not guaranteed that IOMMU translations will be
+      enabled for any given device.
+    $ref: /schemas/types.yaml#/definitions/phandle
+
 required:
   - compatible
   - reg
@@ -179,6 +190,12 @@ allOf:
         reg:
           minItems: 1
           maxItems: 2
+
+      # The reference to the memory controller is required to ensure that the
+      # memory client to stream ID mapping can be done synchronously with the
+      # IOMMU attachment.
+      required:
+        - nvidia,memory-controller
     else:
       properties:
         reg:
-- 
2.35.1

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