Re: [PATCH v2 2/5] dt-bindings: iommu: verisilicon: Add binding for VSI IOMMU

From: Conor Dooley <conor@kernel.org>
To: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Cc: joro@8bytes.org, will@kernel.org, robin.murphy@arm.com,
	robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org,
	heiko@sntech.de, nicolas.dufresne@collabora.com, jgg@ziepe.ca,
	iommu@lists.linux.dev, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org, kernel@collabora.com
Subject: Re: [PATCH v2 2/5] dt-bindings: iommu: verisilicon: Add binding for VSI IOMMU
Date: Wed, 18 Jun 2025 16:55:59 +0100	[thread overview]
Message-ID: <20250618-tighten-morphing-47953075b131@spud> (raw)
In-Reply-To: <20250618140923.97693-3-benjamin.gaignard@collabora.com>

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On Wed, Jun 18, 2025 at 04:09:11PM +0200, Benjamin Gaignard wrote:
> Add a device tree binding for the Verisilicon (VSI) IOMMU.
> This IOMMU sits in front of hardware encoder and decoder
> blocks on SoCs using Verisilicon IP, such as the Rockchip RK3588.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> ---
> changes in version 2:
> - Add a compatible "rockchip,rk3588-av1-iommu"
> - Fix clock-names in binding 
> - Remove "vsi_mmu" label in binding example.
> 
>  .../bindings/iommu/verisilicon,iommu.yaml     | 72 +++++++++++++++++++
>  1 file changed, 72 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iommu/verisilicon,iommu.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iommu/verisilicon,iommu.yaml b/Documentation/devicetree/bindings/iommu/verisilicon,iommu.yaml
> new file mode 100644
> index 000000000000..9ae4a45d76f4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/verisilicon,iommu.yaml
> @@ -0,0 +1,72 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iommu/verisilicon,iommu.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Verisilicon IOMMU
> +
> +maintainers:
> +  - Benjamin Gaignard <benjamin.gaignard@collabora.com>
> +
> +description: |+
> +  A Versilicon iommu translates io virtual addresses to physical addresses for
> +  its associated video decoder.
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - enum:
> +          - verisilicon,iommu
> +          - rockchip,rk3588-av1-iommu

This isn't right. Firstly, the "oneOf: - enum" construct doesn't do
anything. oneOf one item is just the item. Secondly this still allows
verisilicon,iommu in isolation which is not okay. What you actually want
here is
items:
  - const: a
  - const: b

Thirdly, Nicolas mentioned that the version of this iommu is 1.2.0,
which I would like to see reflected in the compatible.

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