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

On 8/19/2026 12:45 PM, Krzysztof Kozlowski wrote:
> 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
> No, the driver does not.
>
> Anyway, explain the hardware.

Ack.

>
>> 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]
> Nothing to be fixed here, I already told you.
>
> NAK

I'll remove the fixes tag in next revision.

>
>> 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
> ABI break.

I'll skip to add in the required field.

>
>>    - 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
>>