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Date: Tue, 3 Mar 2026 07:39:58 +0100
From: Krzysztof Kozlowski <krzk@kernel.org>
To: Akhil R <akhilrajeev@nvidia.com>
Cc: Vinod Koul <vkoul@kernel.org>, Frank Li <Frank.Li@kernel.org>, 
	Rob Herring <robh@kernel.org>, Krzysztof Kozlowski <krzk+dt@kernel.org>, 
	Conor Dooley <conor+dt@kernel.org>, Thierry Reding <thierry.reding@kernel.org>, 
	Jonathan Hunter <jonathanh@nvidia.com>, Laxman Dewangan <ldewangan@nvidia.com>, 
	Philipp Zabel <p.zabel@pengutronix.de>, dmaengine@vger.kernel.org, devicetree@vger.kernel.org, 
	linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/9] dt-bindings: dma: nvidia,tegra186-gpc-dma: Add
 iommu-map property
Message-ID: <20260303-famous-fearless-asp-1240cb@quoll>
References: <20260302123239.68441-1-akhilrajeev@nvidia.com>
 <20260302123239.68441-2-akhilrajeev@nvidia.com>
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In-Reply-To: <20260302123239.68441-2-akhilrajeev@nvidia.com>

On Mon, Mar 02, 2026 at 06:02:31PM +0530, Akhil R wrote:
> Add iommu-map property to specify separate stream IDs for each DMA
> channel. This enables each channel to be in its own IOMMU domain,
> keeping memory isolated from other devices sharing the same DMA
> controller.
> 
> Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
> ---
>  .../devicetree/bindings/dma/nvidia,tegra186-gpc-dma.yaml     | 5 +++++
>  1 file changed, 5 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..1e7b5ddd4658 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@nvidia.com>
>    - Rajesh Gumasta <rgumasta@nvidia.com>
> +  - Akhil R <akhilrajeev@nvidia.com>
>  
>  allOf:
>    - $ref: dma-controller.yaml#
> @@ -51,6 +52,10 @@ properties:
>    iommus:
>      maxItems: 1
>  
> +  iommu-map:
> +    minItems: 1
> +    maxItems: 32

Why is this flexible? If it is, means usually items are distinctive, so
I would expect defining/listing them. If they are not distinctive,
commit msg is incorrect. If the list is as simple as 1-to-1 channel
mapping, just add it in the description how they are ordered.

> +
>    dma-coherent: true
>  
>    dma-channel-mask:
> -- 
> 2.50.1
>