Re: [PATCH 1/4] dt-bindings: brige: lt9611c: add port-select property for LT9611C

[Laurent Pinchart]

On Mon, Jun 22, 2026 at 05:31:36PM +0530, Mohit Dsor wrote:
> On Thu, Jun 11, 2026 at 12:40:38PM +0200, Krzysztof Kozlowski wrote:
> > On Thu, Jun 11, 2026 at 02:44:56AM +0530, Mohit Dsor wrote:
> > > Add a new optional `lontium,port-select` property to describe the DSI
> > > input port configuration for the LT9611C variant, which supports
> > > single-port (A or B) and dual-port (A+B) operation.
> > > 
> > > This property allows explicitly selecting the active DSI input port(s):
> > >   0 = port A (default)
> > >   1 = port B
> > >   2 = ports A and B (dual-port)
> > > 
> > > Signed-off-by: Mohit Dsor <mohit.dsor@xxxxxxxxxxxxxxxx>
> > > ---
> > >  .../devicetree/bindings/display/bridge/lontium,lt9611.yaml  | 13 +++++++++++++
> > >  1 file changed, 13 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml b/Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml
> > > index e0821a63d9d7..77220f893bf8 100644
> > > --- a/Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml
> > > +++ b/Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml
> > > @@ -41,6 +41,17 @@ properties:
> > >    vcc-supply:
> > >      description: Regulator for 3.3V IO power.
> > >  
> > > +  lontium,port-select:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    enum: [0, 1, 2]
> > > +    default: 0
> > > +    description: |
> > > +      Selects which DSI input port(s) the bridge uses. Only relevant for
> > > +      the lontium,lt9611c compatible.
> > > +        0 = PORT_SELECT_A  - single DSI port A (default)
> > > +        1 = PORT_SELECT_B  - single DSI port B
> > > +        2 = PORT_SELECT_AB - dual DSI ports A and B
> > 
> > Why graph is not enough? Seems exactly duplicating the graph ports.
> > 
> > Best regards,
> > Krzysztof
> >
> Hi Krzysztof,
> 
> Thanks for the review.
> 
> The graph describes the physical connectivity between endpoints,
> however it does not fully capture the internal mode of operation of
> the LT9611C. This variant supports multiple functional configurations
> (single-port A, single-port B, or dual-port A+B), which affect how the
> hardware internally combines or selects DSI inputs.
> 
> In particular:
> - The graph can describe connections to both ports, but it does not
>   indicate whether the device should operate in single-port or dual-port
>   aggregation mode.
> - For single-port use, both ports may be described in DT for board
>   consistency, while the driver still needs to know which port is
>   actively selected.
> - Dual-port mode requires explicit configuration even when both
>   endpoints are present in the graph.

If both modes of operation are possible on a given board, then it sounds
like the mode should be selected at runtime, not hardcoded in the device
tree.

> So, this property is not duplicating connectivity, but rather
> describing the *operational mode* of the device, which cannot be
> reliably inferred from the graph alone.

-- 
Regards,

Laurent Pinchart