Re: [PATCH/RFC 02/12] dt-bindings: display: renesas: lvds: Document renesas,swap-data

[Laurent Pinchart]

Hi Fabrizio,

Thank you for the patch.

On Fri, Aug 02, 2019 at 08:33:59AM +0100, Fabrizio Castro wrote:
> R-Car D3, R-Car E3, and RZ/G2E support dual-link mode.
> In such a mode, the first LVDS encoder emits even data, and the
> second LVDS encoder emits odd data. This patch documents property
> renesas,swap-data, used to swap even and odd data around.
> 
> Signed-off-by: Fabrizio Castro <fabrizio.castro@xxxxxxxxxxxxxx>
> ---
>  Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> index dece79e..8980179 100644
> --- a/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> +++ b/Documentation/devicetree/bindings/display/bridge/renesas,lvds.txt
> @@ -52,6 +52,11 @@ Optional properties:
>    mandatory for the first LVDS encoder on R-Car D3, R-Car E3, and RZ/G2E SoCs,
>    and shall point to the second encoder to be used as a companion in dual-link
>    mode. It shall not be set for any other LVDS encoder.
> +- renesas,swap-data : when in dual-link mode, the first LVDS encoder normally
> +  emits even data, and the second LVDS encoder emits odd data. When property
> +  renesas,swap-data is specified, the data emitted by the two encoders will be
> +  swapped around. This property can only be used in conjunction with property
> +  renesas,companion.

>From an LVDS encoder point of view this is more a configuration option
than a description of the hardware. Wouldn't it be better for the LVDS
sink to report which of the odd or even pixels it expects on each of its
endpoints ? The LVDS encoder driver could then query that at runtime and
configure itself accordingly. Ideally this should be queried through the
drm_bridge_timings structure (or through a similar mean), not through
DT. An LVDS sink that has a fixed mapping of odd/even pixels to
endpoints wouldn't need the information to be specified in DT at all.

>  
>  
>  Example:

-- 
Regards,

Laurent Pinchart