RE: [PATCH 10/22] dt-bindings: display: renesas,rzg2l-du: Add support for RZ/G3E SoC

[Biju Das <biju.das.jz@bp.renesas.com>]

Hi Geert,

Thanks for the feedback.

> -----Original Message-----
> From: Geert Uytterhoeven <geert@linux-m68k.org>
> Sent: 14 January 2026 12:38
> Subject: Re: [PATCH 10/22] dt-bindings: display: renesas,rzg2l-du: Add support for RZ/G3E SoC
> 
> Hi Tommaso,
> 
> On Wed, 3 Dec 2025 at 14:42, Tommaso Merciai <tommaso.merciai.xr@bp.renesas.com> wrote:
> > On Wed, Dec 03, 2025 at 09:23:53AM +0100, Krzysztof Kozlowski wrote:
> > > On Wed, Nov 26, 2025 at 03:07:22PM +0100, Tommaso Merciai wrote:
> > > > The RZ/G3E Soc has 2 LCD controller (LCDC), contain a Frame
> > > > Compression Processor (FCPVD), a Video Signal Processor (VSPD),
> > > > Video Signal Processor (VSPD), and Display Unit (DU).
> > > >
> > > >  - LCDC0 supports DSI and LVDS (single or dual-channel) outputs.
> > > >  - LCDC1 supports DSI, LVDS (single-channel), and RGB outputs.
> > > >
> > > > Add then two new SoC-specific compatible strings 'renesas,r9a09g047-du0'
> > > > and 'renesas,r9a09g047-du1'.
> > >
> > > LCDC0/1 but compatibles du0/du1...
> > >
> > > What are the differences between DU0 and DU1? Just different
> > > outputs? Is the programming model the same?
> >
> > The hardware configurations are different: these are two distinct hardware blocks.
> >
> > Based on the block diagrams shown in Figures 9.4-2 (LCDC1) and 9.4-1
> > (LCDC0), the only difference concerns the output, but this variation
> > is internal to the hardware blocks themselves.
> > Therefore, LCDC0 and LCDC1 are not identical blocks, and their
> > programming models differ as a result.
> >
> > In summary, although most of the internal functions are the same, the
> > two blocks have output signals connected to different components within the SoC.
> > This requires different hardware configurations and inevitably leads
> > to different programming models for LCDC0 and LCDC1.
> 
> Isn't that merely an SoC integration issue?
> Are there any differences in programming LCDC0 or LCDC1 for the common output types supported by both
> (single channel LVDS and 4-lane MIPI-DSI)?

Dual LVDS case, dot clock from LCDC0 is used in both LCDC's.
Standalone LVDS and DSI the programming flow is same.

> 
> Of there are no such differences, both instances should use the same compatible value.

Then we need to use a property called display-id, to describe the supported
output types in bindings, right??

Display-id=0 {LVDS, DSI)
Display-id=1 {LVDS, DSI, DPI)

Cheers,
Biju