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

[Vikash Garodia]

On 8/6/2026 2:19 PM, Dmitry Baryshkov wrote:
> 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
> >
> >   
> > +  dma-ranges: true
> > +
> > +  '#address-cells':
> > +    const: 2
> > +
> > +  '#size-cells':
> > +    const: 2
>
> This would conflict with the 32-bit addressed Venus nodes (and it will
> also break examples). So both should be just 'true'

With "true", i see following comment from sashiko (when ran locally)

Without a const constraint, a device tree could specify #address-cells = 
<1> or a non-empty dma-ranges, and it would silently pass schema 
validation. The DT bindings guidelines also recommend that cell-count 
properties have a const constraint matching the hardware.

> >   
> > +oneOf:
> > +  - required:
> > +      - iommus
> > +  - required:
> > +      - non-pixel
> > +      - pixel
>
> - #address-cells
> - #size-cells
> - dma-ranges
>
> > +
> >   additionalProperties: true
> >
> > --
> > 2.34.1