Re: [PATCH v2 01/12] dt-bindings: media: qcom,venus: Add context bank subnodes to common schema

[Krzysztof Kozlowski <krzk@kernel.org>]

On Fri, Jul 31, 2026 at 11:52:16PM +0530, Vikash Garodia wrote:
> The VPU issues DMA through several SMMU streams, and the hardware does
> not give every stream the same addressable range. The non-pixel stream
> is restricted to use 0-600MB of IOVA space, while the pixel stream can
> address the full range:
>     +-----------------------------------------------------------+
>     | non-pixel stream addressable range (600 MB - 3.5 GB)      |
>     | 0x25800000 - 0xe0000000                                   |
>     +-----------------------------------------------------------+
>     | pixel stream addressable range (0 - 3.5 GB)               |
>     | 0x00000000 - 0xe0000000                                   |
>     +-----------------------------------------------------------+
> A single "iommus" property on the video-codec node puts every stream in
> one IOMMU domain sharing one IOVA allocator, so nothing keeps a
> non-pixel buffer inside the low 600 MB. Once an allocation lands below
> that boundary the hardware faults, which shows up as unhandled SMMU page
> faults and spontaneous reboots:
> https://gitlab.freedesktop.org/drm/msm/-/work_items/100
> 
> Describe each stream as its own context bank subnode instead, so that
> each can be associated with the IOVA range its stream can actually
> reach. This limitation applies to every VPU generation, so add the
> subnodes to the common schema rather than to each SoC schema
> individually. "video-firmware" moves here from qcom,sc7180-venus.yaml
> for the same reason; it is the same kind of node and was already
> duplicated per-SoC.
> Adding the subnodes requires two supporting properties on the parent
> video-codec node:
> - '#address-cells' and '#size-cells', both fixed at 2. These do not
>    describe registers on the codec node. They set the cell widths
>    used when a reserved-memory node names one of these subnodes in an
>    "iommu-addresses" entry: of_translate_dma_region() reads the
>    address/size cell counts from the parent of the phandle target, not
>    from the reserved-memory node. Pinning both to 2 lets a subnode be
>    referenced with a full 64-bit IOVA base and length, and keeps the
>    encoding identical across SoCs, whose buses vary between 1 and 2
>    cells.
> - "dma-ranges", empty "dma-ranges" states the intended translation:
>    the subnode DMA address space maps 1:1 into the parent's, so an IOVA
>    reservation written against a subnode needs no offset applied.
>    of_translate_one() treats an empty "dma-ranges" as exactly that
>    identity mapping.
> 
> The parent's "iommus" is kept as an alternative via "oneOf", so
> platforms that have not been converted to subnodes still validate. New
> platforms should use the subnode form.
> 
> Fixes: 41661853ae8e ("arm64: dts: qcom: sm8550: add iris DT node")
> Cc: stable@vger.kernel.org
> Tested-by: Daniel J Blueman <daniel@quora.org>

Not a valid tag.




> Signed-off-by: Vikash Garodia <vikash.garodia@oss.qualcomm.com>
> ---
>  .../bindings/media/qcom,sc7180-venus.yaml          | 15 -------
>  .../bindings/media/qcom,venus-common.yaml          | 51 ++++++++++++++++++++++
>  2 files changed, 51 insertions(+), 15 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml b/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml
> index b21bed314848480b82153e49602f0b19e08e7335..bfd8b1ad473128c974bce84639cb0aff59d8c2cc 100644
> --- a/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml
> +++ b/Documentation/devicetree/bindings/media/qcom,sc7180-venus.yaml
> @@ -91,21 +91,6 @@ properties:
>      deprecated: true
>      additionalProperties: false
>  
> -  video-firmware:
> -    type: object
> -    additionalProperties: false
> -
> -    description: |
> -      Firmware subnode is needed when the platform does not
> -      have TrustZone.
> -
> -    properties:
> -      iommus:
> -        maxItems: 1
> -
> -    required:
> -      - iommus
> -
>  required:
>    - compatible
>    - power-domain-names
> diff --git a/Documentation/devicetree/bindings/media/qcom,venus-common.yaml b/Documentation/devicetree/bindings/media/qcom,venus-common.yaml
> index 59a3fde846d2196ab1e4588eb396012ba6860712..ccae41bed757bf3d9518cd4afe4565f043b45166 100644
> --- a/Documentation/devicetree/bindings/media/qcom,venus-common.yaml
> +++ b/Documentation/devicetree/bindings/media/qcom,venus-common.yaml
> @@ -47,6 +47,50 @@ properties:
>      minItems: 1
>      maxItems: 4
>  
> +  dma-ranges: true
> +
> +  '#address-cells':
> +    const: 2
> +
> +  '#size-cells':
> +    const: 2

Above do not look valid. You do not describe the addressing of some
other device node (not a child) here. You describe that addressing in
that other device node's parent.

> +
> +  non-pixel:
> +    type: object
> +    description:
> +      Context bank for VPU non-pixel buffers, including compressed and internal buffers.
> +    properties:
> +      iommus:
> +        maxItems: 1
> +      memory-region:
> +        maxItems: 1
> +    required:
> +      - iommus
> +      - memory-region
> +    additionalProperties: false
> +
> +  pixel:
> +    type: object
> +    description:
> +      Context bank for VPU pixel buffers containing uncompressed video data.
> +    properties:
> +      iommus:
> +        maxItems: 1
> +    required:
> +      - iommus
> +    additionalProperties: false
> +
> +  video-firmware:
> +    type: object
> +    description:
> +      Context bank for the VPU firmware processing domain.

Missing blank line

> +    properties:
> +      iommus:
> +        maxItems: 1
> +    required:
> +      - iommus
> +    additionalProperties: false

For children this follows type or description for readability

foo:
  ...
  description:
  additionalprops:...

  properties:
    ...
  required:
    ...


Best regards,
Krzysztof