Re: [PATCH v2 2/5] dt-bindings: media: qcom,sc7280-venus: Add dma-coherent property

On Tue, Aug 18, 2026 at 09:24:15PM +0530, Vishnu Reddy wrote:
> The venus video hardware on SC7280 is IO-coherent hardware: even though
> the driver does dma_sync*() calls for the input and output buffers, the

Don't mention the driver wrt. DT bindings. Either the hardware is DMA
coherent or it is not.

> venus node still needs to declare dma-coherent so that the DMA mapping
> layer relies on this hardware level snooping to keep the CPU cache and
> the DMA buffers in sync. This avoids the unnecessary cache clean or
> invalidate operations performed by the dma_sync*() calls, which are not
> required once hardware level snooping is enabled via dma-coherent.
> 
> Add the dma-coherent property to the venus node to describe this
> hardware capability.
> 
> Fixes: 37613aee2179 ("arm64: dts: qcom: sc7280: Add venus DT node")
> Cc: [email protected]
> Reviewed-by: Bryan O'Donoghue <[email protected]>
> Signed-off-by: Vishnu Reddy <[email protected]>
> ---
>  Documentation/devicetree/bindings/media/qcom,sc7280-venus.yaml | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/media/qcom,sc7280-venus.yaml b/Documentation/devicetree/bindings/media/qcom,sc7280-venus.yaml
> index 9725fcb761dc..cc31f3ba7e7e 100644
> --- a/Documentation/devicetree/bindings/media/qcom,sc7280-venus.yaml
> +++ b/Documentation/devicetree/bindings/media/qcom,sc7280-venus.yaml
> @@ -42,6 +42,8 @@ properties:
>        - const: vcodec_core
>        - const: vcodec_bus
>  
> +  dma-coherent: true
> +
>    iommus:
>      maxItems: 1
>  
> @@ -85,6 +87,7 @@ properties:
>  
>  required:
>    - compatible
> +  - dma-coherent
>    - power-domain-names
>    - iommus
>  
> @@ -119,6 +122,8 @@ examples:
>                          <&mmss_noc MASTER_VIDEO_P0 0 &mc_virt SLAVE_EBI1 0>;
>          interconnect-names = "cpu-cfg", "video-mem";
>  
> +        dma-coherent;
> +
>          iommus = <&apps_smmu 0x2180 0x20>;
>  
>          memory-region = <&video_mem>;
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry