linux-kernel - Re: [PATCH 2/3] dt-bindings: dma: snps,dw-axi-dmac: Add iommu property

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Message-ID: <66c1ebf0-1f91-4d9f-985f-71535f1e3d01@kernel.org>
Date: Mon, 20 Oct 2025 13:09:11 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Khairul Anuar Romli <khairul.anuar.romli@...era.com>,
 Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>, Vinod Koul
 <vkoul@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>,
 "open list:DMA GENERIC OFFLOAD ENGINE SUBSYSTEM"
 <dmaengine@...r.kernel.org>,
 "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
 <devicetree@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>,
 Miquel Raynal <miquel.raynal@...tlin.com>,
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
 Niravkumar L Rabara <niravkumar.l.rabara@...el.com>,
 "open list:CADENCE NAND DRIVER" <linux-mtd@...ts.infradead.org>,
 Dinh Nguyen <dinguyen@...nel.org>,
 Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
Subject: Re: [PATCH 2/3] dt-bindings: dma: snps,dw-axi-dmac: Add iommu
 property

On 15/10/2025 02:13, Khairul Anuar Romli wrote:
> Agilex5 integrates an ARM SMMU v3 (System Memory Management Unit) with
> dedicated Translation Buffer Units (TBUs) assigned to various peripherals,
> including the Synopsys DesignWare AXI DMA controller.
> 
> Each TBU handles address translation for its associated device by mapping
> stream IDs to memory access permissions and virtual-to-physical address
> mappings via the SMMU core.
> 
> The DesignWare AXI DMAC instances on Agilex5 are connected to their
> respective TBUs. These TBUs forward DMA transactions from the controller
> through the SMMU, enabling IOMMU-based features such as:
> - Address translation for DMA operations
> - Isolation and protection of memory regions accessed by the DMA controller
> - Support for secure and virtualized environments through enforced access
>   control
> 
> To support this configuration, the `iommus` property must be added to the
> binding schema for `snps,dw-axi-dmac`. This allows the device tree to
> associate each DMA controller with the correct SMMU stream ID, enabling
> the Linux IOMMU framework to configure translation contexts at runtime.
> 
> This change documents the IOMMU support for the DMA controller on Agilex5
> and allows proper integration with the SMMUv3 hardware.
> 
> Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
> Signed-off-by: Khairul Anuar Romli <khairul.anuar.romli@...era.com>
> ---
> Changes in v3:
> 	- Refined commit messages with detailed hardware descriptions.
> 	- Remove redundant commit message and add hardware use for iommu.
> Changes in v2:
>         - Updated the commit message to clarify the need for the changes
> 	  and the hardware used of this changes.
> ---
>  Documentation/devicetree/bindings/dma/snps,dw-axi-dmac.yaml | 3 +++
>  1 file changed, 3 insertions(+)

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof