linux-kernel - Re: [PATCH v1 2/8] dt-bindings: display: panel: mipi-dbi-spi: add spi-3wire property

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Message-ID: <69fdb6a2-12b6-547d-019b-c77dd2bd98cf@tronnes.org>
Date:   Wed, 7 Jun 2023 21:59:47 +0200
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Leonard Göhrs <l.goehrs@...gutronix.de>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     kernel@...gutronix.de, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, noralf@...nnes.org
Subject: Re: [PATCH v1 2/8] dt-bindings: display: panel: mipi-dbi-spi: add
 spi-3wire property



On 6/7/23 13:55, Leonard Göhrs wrote:
> Some MIPI DBI panels support a three wire mode (clock, chip select,
> bidirectional data) that can be used to ask the panel if it is already set
> up by e.g. the bootloader and can thus skip the initialization.
> This enables a flicker-free boot.
> 
> Signed-off-by: Leonard Göhrs <l.goehrs@...gutronix.de>
> ---
>  .../devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml   | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml b/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
> index c07da1a9e6288..2f0238b770eba 100644
> --- a/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
> +++ b/Documentation/devicetree/bindings/display/panel/panel-mipi-dbi-spi.yaml
> @@ -87,6 +87,8 @@ properties:
>        Logic level supply for interface signals (Vddi).
>        No need to set if this is the same as power-supply.
>  
> +  spi-3wire: true
> +

I don't think this should be added here. spi-cpha and spi-cpol are also
supported but they are not mentioned. Instead those are documented in
bindings/spi/spi-controller.yaml. Why they're not documented in
bindings/spi/spi-peripheral-props.yaml instead which this binding has a
ref to, I have no idea.

Noralf.

>  required:
>    - compatible
>    - reg