linux-kernel - Re: [PATCH 1/1] dt-bindings: display: nwl-dsi: Allow 'data-lanes' property for port@1

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Message-ID: <20241031211421.GG2473@pendragon.ideasonboard.com>
Date: Thu, 31 Oct 2024 23:14:21 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Frank Li <Frank.li@....com>, Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Guido Gúnther <agx@...xcpu.org>,
	Robert Chiras <robert.chiras@....com>,
	"open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>, imx@...ts.linux.dev
Subject: Re: [PATCH 1/1] dt-bindings: display: nwl-dsi: Allow 'data-lanes'
 property for port@1

On Thu, Oct 31, 2024 at 10:55:30PM +0200, Dmitry Baryshkov wrote:
> On Thu, Oct 31, 2024 at 04:20:10PM -0400, Frank Li wrote:
> > On Thu, Oct 31, 2024 at 09:59:26PM +0200, Dmitry Baryshkov wrote:
> > > On Thu, Oct 31, 2024 at 03:47:14PM -0400, Frank Li wrote:
> > > > Change $ref of port@1 from 'port' to 'port-base' and add 'endpoint'
> > > > property referencing video-interfaces.yaml. Allow 'data-lanes' values
> > > > 1, 2, 3, and 4 for port@1.
> > > >
> > > > Fix below CHECK_DTB warnings:
> > > > arch/arm64/boot/dts/freescale/imx8mq-tqma8mq-mba8mx-lvds-tm070jvhg33.dtb:
> > > >  dsi@...00000: ports:port@1:endpoint: Unevaluated properties are not allowed ('data-lanes' was unexpected)
> > > >
> > > > Signed-off-by: Frank Li <Frank.Li@....com>
> > > > ---
> > > >  .../bindings/display/bridge/nwl-dsi.yaml       | 18 +++++++++++++++++-
> > > >  1 file changed, 17 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/display/bridge/nwl-dsi.yaml b/Documentation/devicetree/bindings/display/bridge/nwl-dsi.yaml
> > > > index 350fb8f400f02..5952e6448ed47 100644
> > > > --- a/Documentation/devicetree/bindings/display/bridge/nwl-dsi.yaml
> > > > +++ b/Documentation/devicetree/bindings/display/bridge/nwl-dsi.yaml
> > > > @@ -111,11 +111,27 @@ properties:
> > > >          unevaluatedProperties: false
> > > >
> > > >        port@1:
> > > > -        $ref: /schemas/graph.yaml#/properties/port
> > > > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > > > +        unevaluatedProperties: false
> > > >          description:
> > > >            DSI output port node to the panel or the next bridge
> > > >            in the chain
> > > >
> > > > +        properties:
> > > > +          endpoint:
> > > > +            $ref: /schemas/media/video-interfaces.yaml#
> > > > +            unevaluatedProperties: false
> > > > +
> > > > +            properties:
> > > > +              data-lanes:
> > > > +                description: array of physical DSI data lane indexes.
> > > > +                minItems: 1
> > > > +                items:
> > > > +                  - const: 1
> > > > +                  - const: 2
> > > > +                  - const: 3
> > > > +                  - const: 4
> > >
> > > Why are they indexed starting from 1?
> > 
> > Not sure, git grep -r data-lanes Documentation/devicetree/bindings/
> > Most start from 1. Not sure latest DT team's intention.
> 
> They usually start from 1, because just before the property comes
> 'clock-lanes = <0>'. Otherwise in most of the cases the lanes are
> indexed from 0.

I'm not sure what the rule is for DSI, but for CSI we number data lanes
starting at 1 regardless of whether or not the clock lane is
configurable. Consistency help for driver implementations.

> > > > +
> > > >      required:
> > > >        - port@0
> > > >        - port@1

-- 
Regards,

Laurent Pinchart