Re: [PATCH v8 1/9] dt-bindings: display: fsl,ldb: Add i.MX94 LDB

[Marek Vasut]

On 3/19/26 9:57 AM, Laurentiu Palcu wrote:
> On Fri, Mar 06, 2026 at 09:46:57AM +0100, Marco Felsch wrote:
> > On 26-03-06, Liu Ying wrote:
> > > On Wed, Mar 04, 2026 at 11:34:10AM +0000, Laurentiu Palcu wrote:
> > > > i.MX94 has a single LVDS port and share similar LDB and LVDS control
> > > > registers as i.MX8MP and i.MX93.
> > > >
> > > > Signed-off-by: Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx>
> > > > Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
> > > > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> > > > ---
> > > >   Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml | 2 ++
> > > >   1 file changed, 2 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> > > > index 7f380879fffdf..fb70409161fc0 100644
> > > > --- a/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> > > > +++ b/Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml
> > > > @@ -20,6 +20,7 @@ properties:
> > > >         - fsl,imx6sx-ldb
> > > >         - fsl,imx8mp-ldb
> > > >         - fsl,imx93-ldb
> > > > +      - fsl,imx94-ldb
> > >
> > > Cc'ing Marco.
> > >
> > > Recently, Marco said that LDB node should not have a reg property...
> > >
> > > https://lore.kernel.org/all/4sofljffovrorpxe2os3jl745qfjoglvl54oqf3v7r5bk5f6aq@6y3jwn4abiqy/
> >
> > Yes, this has to be dropped. All variants of this specific "IP" use the
> > same approach. This "IP" is part of a general purpose register layout
> > with very loose reg-field definitions: e.g. resets and clk-gatting share
> > the same register. Or a mux reg-field shares the same register as a
> > MIPI-{C,D}SI configuration reg-field. Therefore this "IP" is part of a
> > syscon and should be abstracted as such within the DT.
>
> Even though I understand the logic behind why 'reg' should be dropped,
> I'm not exactly sure how to proceed with this. It appears Marek made the
> 'reg' required in this commit (merely 2 months ago):
>
> 8aa2f0ac08d3b - dt-bindings: display: bridge: ldb: Add check for reg and reg-names
>
> Should the above patch simply be reverted and have 'reg' as optional again?
> Or should the 'reg' and 'reg-names' be removed completely from the
> binding.
>
> @Marek, any comments?
The LDB driver was always written with parsing 'reg' out of the DT, so 
encoding the register offsets into the driver was a mistake. The LDB 
controls two registers, which can be comfortably described in DT.