Re: [RFC PATCH 3/4] dt-bindings: panel: Introduce dual-link LVDS panel

[AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>]

Il 03/01/23 07:46, Aradhya Bhatia ha scritto:
> Dual-link LVDS interfaces have 2 links, with even pixels traveling on
> one link, and odd pixels on the other. These panels are also generic in
> nature, with no documented constraints, much like their single-link
> counterparts, "panel-lvds".
> 
> Add a new compatible, "panel-dual-lvds", and a dt-binding document for
> these panels.
> 
> Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
> ---
>   .../display/panel/panel-dual-lvds.yaml        | 157 ++++++++++++++++++
>   MAINTAINERS                                   |   1 +
>   2 files changed, 158 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/display/panel/panel-dual-lvds.yaml
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-dual-lvds.yaml b/Documentation/devicetree/bindings/display/panel/panel-dual-lvds.yaml
> new file mode 100644
> index 000000000000..88a7aa2410be
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/panel-dual-lvds.yaml
> @@ -0,0 +1,157 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/panel/panel-dual-lvds.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Generic Dual-Link LVDS Display Panel
> +
> +maintainers:
> +  - Aradhya Bhatia <a-bhatia1@ti.com>
> +  - Thierry Reding <thierry.reding@gmail.com>
> +
> +description: |
> +  A dual-LVDS interface is a dual-link connection with the even pixels
> +  traveling on one link, and the odd pixels traveling on the other.
> +
> +allOf:
> +  - $ref: panel-common.yaml#
> +  - $ref: /schemas/display/lvds.yaml/#
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - enum:
> +              - lincolntech,lcd185-101ct
> +              - microtips,13-101hieb0hf0-s
> +          - const: panel-dual-lvds
> +      - const: panel-dual-lvds
> +
> +  ports:
> +    $ref: /schemas/graph.yaml#/properties/ports
> +
> +    properties:
> +      port@0:
> +        $ref: /schemas/graph.yaml#/$defs/port-base
> +        unevaluatedProperties: false
> +        description: The sink for first set of LVDS pixels.
> +
> +        properties:
> +          dual-lvds-odd-pixels:
> +            type: boolean
> +
> +          dual-lvds-even-pixels:
> +            type: boolean
> +
> +        oneOf:
> +          - required: [dual-lvds-odd-pixels]

One question: why do we need a "panel-dual-lvds" compatible?
A Dual-LVDS panel is a LVDS panel using two ports, hence still a panel-lvds.

If you're doing this to clearly distinguish, for human readability purposes,
single-link vs dual-link panels, I think that this would still be clear even
if we use panel-lvds alone because dual-link panels, as you wrote in this
binding, does *require* two ports, with "dual-lvds-{odd,even}-pixels" properties.

So... the devicetree node would look like this:

panel {
	compatible = "vendor,panel", "panel-lvds";
	....
	ports {
		port@0 {
			.....
			-> dual-lvds-odd-pixels <-
		}

		port@1 {
			.....
			-> dual-lvds-even-pixels <-
		};
	};
};

> +          - required: [dual-lvds-even-pixels]

...Though, if you expect dual-lvds panels to get other quirks in the future,
that's a whole different story and you may actually need the panel-dual-lvds
compatible.

Regards,
Angelo