Re: [PATCH 1/6] media: dt-bindings: Document SC8280XP/SM8350 Venus

[Bryan O'Donoghue]

On 07/08/2023 16:02, Konrad Dybcio wrote:
> On 7.08.2023 16:04, Krzysztof Kozlowski wrote:
> > On 07/08/2023 14:41, Konrad Dybcio wrote:
> > > On 5.08.2023 21:29, Krzysztof Kozlowski wrote:
> > > > On 04/08/2023 22:09, Konrad Dybcio wrote:
> > > > > Both of these SoCs implement an IRIS2 block, with SC8280XP being able
> > > > > to clock it a bit higher.
> > > >
> > > > ...
> > > >
> > > > > +
> > > > > +  iommus:
> > > > > +    maxItems: 1
> > > > > +
> > > > > +  video-decoder:
> > > > > +    type: object
> > > > > +
> > > > > +    properties:
> > > > > +      compatible:
> > > > > +        const: venus-decoder
> > > >
> > > > That's not how compatibles are constructed... missing vendor prefix, SoC
> > > > or IP block name.
> > > >
> > > > > +
> > > > > +    required:
> > > > > +      - compatible
> > > > > +
> > > > > +    additionalProperties: false
> > > >
> > > > Why do you need this child node? Child nodes without properties are
> > > > usually useless.
> > > For both comments: I aligned with what was there..
> > >
> > > The driver abuses these compats to probe enc/dec submodules, even though
> > > every Venus implementation (to my knowledge) is implicitly enc/dec capable..
> >
> > Holy crap, I see...
> >
> > > Perhaps a bigger clean-up is due. I guess I could just create the venc/vdec
> > > devices from the venus core probe and get rid of this fake stuff?
> >
> > Few devices (qcom,msm8996-venus.yaml, sdm660, sdm845) have clocks there,
> > so we actually could stay with these subnodes, just correct the
> > compatibles to a list with correct prefixes:
> >
> > qcom,sc8280xp-venus-decoder + qcom,venus-decoder
> Hm.. looks like pre-845-v2 (with the v2 being "v2 binding" and not
> "v2 chip" or "v2 hardware") these were used to look up clocks but
> then they were moved to the root node.
>
> I am not quite sure if it makes sense to distinguish e.g.
> sc8280xp-venus-decoder within sc8280xp-venus..
>
> Perhaps deprecating the "8916 way" (clocks under subnodes), adding
> some boilerplate to look up clocks/pds in both places and converting
> everybody to the "7180 way" way of doing things (clocks under venus),
> and then getting rid of venus encoder/decoder completely (by calling
> device creation from venus probe) would be better. WDYT?
>
> Konrad

As I understand it though, for some classes of venus hardware - earlier, 
it was possible to have two encoders or two decoders and it really 
didn't - perhaps still doesn't matter which order they are declared in.

That's the logic behind having a compat string that assigns either 
encoder or decoder to one of the logical blocks.

You can have any mixture of
- encoder
- decoder

- encoder
- encoder

- decoder
- decoder

- decoder
- encoder

- encoder

- decoder

I think it should *still* be the case - whether it is a practical 
reality or not, that any of those mapping can be selected and supported.

---
bod