Re: [PATCH 09/19] drm: sun4i: Add DT bindings documentation

[Maxime Ripard <maxime.ripard@free-electrons.com>]

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Hi Rob,

On Fri, Oct 30, 2015 at 11:40:03AM -0500, Rob Herring wrote:
> > +Display Engine Backend
> > +----------------------
> > +
> > +The display engine backend exposes layers and sprites to the
> > +system. It's split into two components, the frontend and backend, the
> > +frontend doing formats conversion, scaling, deinterlacing, while the
> > +backend actually manages the layers.
> > +
> > +Required properties:
> > +  - compatible: value must be one of:
> > +    * allwinner,sun5i-a13-display-engine
> > +
> > +  - reg: base address and size of the memory-mapped region. Two are needed:
> > +    * backend0: registers of the display engine backend
> > +    * frontend0: registers of the display engine frontend
> 
> Why the zeros? I think they should be dropped.

We have SoCs that have two backends and two frontends, hence why I
added 0. I guess I can also add several devices for them, but then I'd
need to move to the component framework I guess (which was the plan anyway).

> > +
> > +  - allwinner,tcon: phandle to the TCON in our pipeline
> 
> Use of-graph or just let the relationship live in the driver. If there
> is only 1 instance of the blocks, the latter is fine.

We can also have several TCON instances in the SoC, and even though
you can on a theorical point of view use any TCON with any backend,
usually you're tied because of how the pins are routed on the boards.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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