linux-kernel - Re: [PATCH v4 13/18] dt-bindings: usb-switch: Extend for DisplayPort altmode

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Message-ID: <yatu2snt2w7lrveftlfbkw6yfvso3jbsma5v6jij4rn7v37hjt@ww42wer6bytj>
Date: Fri, 25 Oct 2024 09:36:51 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Stephen Boyd <swboyd@...omium.org>
Cc: chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	patches@...ts.linux.dev, devicetree@...r.kernel.org, 
	Douglas Anderson <dianders@...omium.org>, Pin-yen Lin <treapking@...omium.org>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Benson Leung <bleung@...omium.org>, 
	Conor Dooley <conor+dt@...nel.org>, Daniel Vetter <daniel@...ll.ch>, 
	David Airlie <airlied@...il.com>, dri-devel@...ts.freedesktop.org, 
	Guenter Roeck <groeck@...omium.org>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Jonas Karlman <jonas@...boo.se>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Lee Jones <lee@...nel.org>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Prashant Malani <pmalani@...omium.org>, 
	Robert Foss <rfoss@...nel.org>, Rob Herring <robh+dt@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Tzung-Bi Shih <tzungbi@...nel.org>, 
	Alexandre Belloni <alexandre.belloni@...tlin.com>, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
	Daniel Scally <djrscally@...il.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>, Ivan Orlov <ivan.orlov0322@...il.com>, 
	linux-acpi@...r.kernel.org, linux-usb@...r.kernel.org, 
	Mika Westerberg <mika.westerberg@...ux.intel.com>, "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, Vinod Koul <vkoul@...nel.org>, Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v4 13/18] dt-bindings: usb-switch: Extend for DisplayPort
 altmode

On Thu, Oct 10, 2024 at 06:43:35PM -0400, Stephen Boyd wrote:
> Quoting Dmitry Baryshkov (2024-09-19 03:40:19)
> > On Sat, Aug 31, 2024 at 09:06:51PM GMT, Stephen Boyd wrote:
> > > diff --git a/Documentation/devicetree/bindings/usb/usb-switch.yaml b/Documentation/devicetree/bindings/usb/usb-switch.yaml
> > > index f5dc7e23b134..816f295f322f 100644
> > > --- a/Documentation/devicetree/bindings/usb/usb-switch.yaml
> > > +++ b/Documentation/devicetree/bindings/usb/usb-switch.yaml
> > > @@ -52,6 +52,14 @@ properties:
> > >            endpoint:
> > >              $ref: '#/$defs/usbc-in-endpoint'
> > >
> > > +      port@2:
> > > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > > +        unevaluatedProperties: false
> > > +
> > > +        properties:
> > > +          endpoint:
> > > +            $ref: '#/$defs/dp-endpoint'
> >
> > Is it a separate port or is it an endpoint of the same upstream-facing
> > (non-connector-facing) SS port?
> 
> I don't quite follow this comment. This is an input DP endpoint/port.

This is the question: is this a separate port or just an endpoint on the
port?

> 
> >
> > > +
> > >  oneOf:
> > >    - required:
> > >        - port
> > > @@ -65,6 +73,19 @@ $defs:
> > >      $ref: /schemas/graph.yaml#/$defs/endpoint-base
> > >      description: Super Speed (SS) output endpoint to a type-c connector
> > >      unevaluatedProperties: false
> > > +    properties:
> > > +      data-lanes:
> > > +        $ref: /schemas/types.yaml#/definitions/uint32-array
> > > +        description: |
> > > +          An array of physical USB Type-C data lane indexes.
> > > +          - 0 is SSRX1 lane
> > > +          - 1 is SSTX1 lane
> > > +          - 2 is SSTX2 lane
> > > +          - 3 is SSRX2 lane
> > > +        minItems: 4
> > > +        maxItems: 4
> > > +        items:
> > > +          maximum: 3
> >
> > What is the usecase to delare less than 4 lanes going to the USB-C
> > connector?
> 
> I'm not aware of any usecase. The 'maximum: 3' is the max value in the
> cell, i.e. 0, 1, 2, or 3.

-- 
With best wishes
Dmitry