Re: [PATCH 1/4] dt-bindings: display: renesas,rzg2l-du: Add RZ/T2H and RZ/N2H support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Thu, May 07, 2026 at 09:24:48AM +0000, Biju Das wrote:
> On 06 May 2026 20:58, Lad, Prabhakar wrote:
> > On Wed, May 6, 2026 at 8:50 PM Laurent Pinchart wrote:
> > > On Wed, Apr 29, 2026 at 06:00:09PM +0100, Prabhakar wrote:
> > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> > > >
> > > > Document the Display Unit (DU) support for the RZ/T2H and RZ/N2H SoCs.
> > > >
> > > > The DU block on RZ/T2H is functionally equivalent to the RZ/G2UL DU
> > > > and supports the DPI interface, but includes SoC-specific register differences.
> > > > Add a dedicated compatible string to represent this variant.
> > > >
> > > > As the DU implementation on RZ/N2H matches RZ/T2H, describe it using
> > > > an RZ/N2H specific compatible string with the RZ/T2H compatible as fallback.
> > > >
> > > > Unlike other DU variants which use a multi-port model, the RZ/T2H
> > > > and RZ/N2H DU has a single output and is modelled using a single
> > > > port node with one endpoint. Add a port property to support this and
> > > > update the allOf constraints accordingly.
> > >
> > > Wouldn't it be simpler to always have a "ports" node, even for
> > > variants with a single port ?
> > >
> > I agree that, from a binding perspective, always having a "ports" node keeps things simpler and
> > consistent. Biju suggested this change based on earlier feedback for the RZ/G3E series.
> 
> From G3E feedback, I got the impression that going forward all future SoCs needs to have
> single port and multiple endpoints. That is the reason for suggesting port for new SoCs.

Right, let's clarify that.

TL;DR: it depends on the hardware architecture (what a surprise :-))

When reviewing the G3E, I noticed that the LCDC has a single output that
is connected to one or multiple encoders, depending on the SoC. I think
this should be modeled in DT with a single port.

Note that this does not preclude using a "ports" node, containing a
single "port@0". If you're confident enough that no future generation
will require multiple ports, then it makes sense to standardize on a
single "port" node and no "ports". If, on the other hand, you think that
some SoCs would have multiple ports, then using a top-level "ports" node
unconditionally would lead to simpler bindings.

I'll let you all decide what you think is the most suitable approach.

-- 
Regards,

Laurent Pinchart