Re: [PATCH 2/4] media: dt-binding: media: Document rk3588’s vepu121

[Nicolas Dufresne]

Le jeudi 21 mars 2024 à 10:32 +0100, Heiko Stübner a écrit :
> Am Donnerstag, 21. März 2024, 10:19:54 CET schrieb Krzysztof Kozlowski:
> > On 21/03/2024 09:47, Heiko Stübner wrote:
> > > > >      enum:
> > > > >        - rockchip,rk3568-vepu
> > > > > +      - rockchip,rk3588-vepu121
> > > > 
> > > > What is 121?
> > > 
> > > That is the strange naming of the ip block inside the soc.
> > > 
> > > I.e. the rk3588 TRM lists a number of different video encoders and decoders:
> > > - VDPU121 is decoding h.263 and mpeg1,2,4
> > > - VDPU381 is decoding h.265, h.264 and some more
> > > - VDPU720 is decoding jpeg
> > > - VDPU981 decodes AV1
> > > - VEPU121 is the jpeg encoder above
> > > - VEPU580 encodes h.264 and h.265
> > > 
> > > Each of those are separate IP blocks with their own io-memory, their own
> > > interrupts and their own iommus, etc.
> > 
> > Thanks for explanation. Short introduction in commit msg would be nice
> > (e.g. VEPU121, one of two VEPU encoders). OTOH, why not documenting all
> > of them? Bindings are supposed to be as complete as possible.
> 
> We have a concurrent series for the vdpu121 running at
>   https://lore.kernel.org/all/20240316071100.2419369-1-liujianfeng1994@xxxxxxxxx
> 
> I think not all of those encoders/decoders are based on the Hantro IP
> or at least at the moment we don't know this yet.
> Hence people adding compatibles for the blocks they have actually
> managed to run on their hardware.

Correct, on top of this legacy core, only VDPU981 (AV1 decode) is a chip from
Hantro / Verisilicon. Everything else looks like their own design and derived
from their original rkvdec codec pack. We didn't name this AV1 decoder after VSI
brand as we didn't have the proper version information available, but we suspect
that is variant of their VSI9000D cores. In short, we tried to avoid documenting
our speculation, even if we believe we are right.

> 
> Bindings are supposed to be as complete as possible, but revising a wrong
> binding later is very hard. And the whole media part is full of binary libraries
> in the vendor kernel and has not the best documentation.

I agree with this, but I must give to RK that despite the lack of documentation,
their CODEC software is fully open-source and blob free on this platform.

> 
> So I guess people are just cautious ;-)
> 

exactly!

Nicolas