Re: [PATCH 1/8] dt-bindings: dma: nvidia,tegra186-gpc-dma: Add iommu-map property

[Krzysztof Kozlowski]

On 17/02/2026 18:34, Akhil R wrote:
> Add iommu-map property which helps when each channel requires its own
> stream ID for the transfer. Use iommu-map to specify separate stream
> ID for each channel. This enables each channel to be in its own iommu
> domain and keeps the memory isolated from other devices sharing the
> same DMA controller.
> 
> Signed-off-by: Akhil R <akhilrajeev@xxxxxxxxxx>
> ---
>  .../devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml  | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml b/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml
> index 0dabe9bbb219..542e9cb9f641 100644
> --- a/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml
> +++ b/Documentation/devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml
> @@ -14,6 +14,7 @@ description: |
>  maintainers:
>    - Jon Hunter <jonathanh@xxxxxxxxxx>
>    - Rajesh Gumasta <rgumasta@xxxxxxxxxx>
> +  - Akhil R <akhilrajeev@xxxxxxxxxx>

With 4.5 trillion USD capitalization of Nvidia one could assume they can
spare few resources to test the patch before sending it... instead of
relying on Rob's and my machines to do that for them.

Expect grumpy review because you do not care about our time.

>  
>  allOf:
>    - $ref: dma-controller.yaml#
> @@ -51,6 +52,13 @@ properties:
>    iommus:
>      maxItems: 1
>  
> +  iommu-map:
> +    description: |
> +      The mapping of DMA controller channels to IOMMU stream IDs. Each entry in the map specifies the

Please read Linux coding style.

> +      relationship between a DMA channel and its corresponding IOMMU stream ID. The format is:
> +      "<ch_no &smmu stream_id length>". Example: "<1 &smmu 0x801 1>"

Missing constraints.

Anyway, do not redefine or explain standard properties. See dtschema.

> +    $ref: /schemas/types.yaml#/definitions/phandle-array
> +
>    dma-coherent: true
>  
>    dma-channel-mask:


Best regards,
Krzysztof