Re: [PATCH v15 08/10] dt-bindings: display: bridge: it6505: Add mode-switch support - Pin-yen Lin

From: Pin-yen Lin <treapking@chromium.org>
To: Rob Herring <robh@kernel.org>
Cc: "Andrzej Hajda" <andrzej.hajda@intel.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Robert Foss" <rfoss@kernel.org>,
	"Laurent Pinchart" <Laurent.pinchart@ideasonboard.com>,
	"Jonas Karlman" <jonas@kwiboo.se>,
	"Jernej Skrabec" <jernej.skrabec@gmail.com>,
	"David Airlie" <airlied@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Daniel Scally" <djrscally@gmail.com>,
	"Heikki Krogerus" <heikki.krogerus@linux.intel.com>,
	"Sakari Ailus" <sakari.ailus@linux.intel.com>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	"Prashant Malani" <pmalani@chromium.org>,
	"Benson Leung" <bleung@chromium.org>,
	"Guenter Roeck" <groeck@chromium.org>,
	"Xin Ji" <xji@analogixsemi.com>, "Marek Vasut" <marex@denx.de>,
	"Hsin-Yi Wang" <hsinyi@chromium.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"AngeloGioacchino Del Regno"
	<angelogioacchino.delregno@collabora.com>,
	"Lyude Paul" <lyude@redhat.com>,
	devicetree@vger.kernel.org, "Stephen Boyd" <swboyd@chromium.org>,
	dri-devel@lists.freedesktop.org, linux-acpi@vger.kernel.org,
	chrome-platform@lists.linux.dev,
	"Nícolas F . R . A . Prado" <nfraprado@collabora.com>,
	"Javier Martinez Canillas" <javierm@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v15 08/10] dt-bindings: display: bridge: it6505: Add mode-switch support
Date: Fri, 7 Apr 2023 00:50:16 +0900	[thread overview]
Message-ID: <CAEXTbpfwMBOTSe3Vp8arTGK1hanrS7qZTFeaN+qN148XcZ4-Fg@mail.gmail.com> (raw)
In-Reply-To: <20230406151543.GA3098002-robh@kernel.org>

Hi Rob,

Thanks for the review.

On Fri, Apr 7, 2023 at 12:15 AM Rob Herring <robh@kernel.org> wrote:
>
> On Fri, Mar 31, 2023 at 05:11:43PM +0800, Pin-yen Lin wrote:
> > ITE IT6505 can be used in systems to switch the DP traffic between
> > two downstreams, which can be USB Type-C DisplayPort alternate mode
> > lane or regular DisplayPort output ports.
> >
> > Update the binding to accommodate this usage by introducing a
> > data-lanes and a mode-switch property on endpoints.
> >
> > Signed-off-by: Pin-yen Lin <treapking@chromium.org>
> >
> > ---
> >
> > (no changes since v12)
> >
> > Changes in v12:
> > - Fixed the schema of "data-lanes" property for it6505
> > - Reworded the description of the mode-switch property
> >
> > Changes in v11:
> > - Updated the description of the endpoints in the bindings
> > - Referenced video-interfaces.yaml instead for the endpoints binding
> > - Removed duplicated definitions from inherited schema
> >
> > Changes in v9:
> > - Fixed subject prefix again
> > - Changed the naming of the example node for it6505
> >
> > Changes in v8:
> > - Updated bindings for data-lanes property
> > - Fixed subject prefix
> >
> > Changes in v7:
> > - Fixed issues reported by dt_binding_check.
> > - Updated the schema and the example dts for data-lanes.
> > - Changed to generic naming for the example dts node.
> >
> > Changes in v6:
> > - Remove switches node and use endpoints and data-lanes property to
> >   describe the connections.
> >
> >  .../bindings/display/bridge/ite,it6505.yaml   | 101 +++++++++++++++---
> >  1 file changed, 88 insertions(+), 13 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/ite,it6505.yaml b/Documentation/devicetree/bindings/display/bridge/ite,it6505.yaml
> > index c9a882ee6d98..348b02f26041 100644
> > --- a/Documentation/devicetree/bindings/display/bridge/ite,it6505.yaml
> > +++ b/Documentation/devicetree/bindings/display/bridge/ite,it6505.yaml
> > @@ -75,22 +75,49 @@ properties:
> >        port@1:
> >          $ref: /schemas/graph.yaml#/$defs/port-base
> >          unevaluatedProperties: false
> > -        description: Video port for DP output
> > +        description:
> > +          Video port for DP output. Each endpoint connects to a video output
> > +          downstream, and the "data-lanes" property is used to describe the pin
> > +          connections. 0, 1, 2, 3 in "data-lanes" maps to TX0, TX1, TX2, TX3,
> > +          respectively.
> >
> > -        properties:
> > -          endpoint:
> > -            $ref: /schemas/graph.yaml#/$defs/endpoint-base
> > +
> > +        patternProperties:
> > +          "^endpoint@[01]$":
> > +            $ref: /schemas/media/video-interfaces.yaml#
> >              unevaluatedProperties: false
> >
> >              properties:
> > +              reg: true
> > +
> > +              remote-endpoint: true
>
> You don't need to list these 2.
>
> > +
> >                data-lanes:
> > -                minItems: 1
> > -                uniqueItems: true
> > -                items:
> > -                  - enum: [ 0, 1 ]
> > -                  - const: 1
> > -                  - const: 2
> > -                  - const: 3
> > +                oneOf:
> > +                  - items:
> > +                      - enum: [0, 3]
>
> Only lane 1 wasn't valid? If so, mention that in the commit message.

Tha IT6505 bridge only supports "lane swapping" that reverses the
output pins, so only lane 1 or lane 2 is not valid. I'll update this
in the commit message as well.
>
> > +
> > +                  - items:
> > +                      - const: 0
> > +                      - const: 1
> > +
> > +                  - items:
> > +                      - const: 3
> > +                      - const: 2
> > +
> > +                  - items:
> > +                      - const: 0
> > +                      - const: 1
> > +                      - const: 2
> > +                      - const: 3
>
> Isn't this the default if 'data-lanes' is omitted.

I don't think we have a "default" in the IT6505 driver because it
currently doesn't have any use case that has all 4 pins described in
an output node. The old use case uses an extcon node to describe the
output, and a 4-pin connection makes no sense for mode switches.

However, we can drop this binding and make it the default when
'data-lanes' is omitted. This will be useful when we migrate the
extcon description to the an output port node.
>
> > +
> > +              mode-switch:
> > +                type: boolean
> > +                description: Serves as Type-C mode switch if present.
> > +
> > +            required:
> > +              - reg
> > +              - remote-endpoint
>
> required can be dropped.
>
> >
> >      required:
> >        - port@0
> > @@ -102,7 +129,6 @@ required:
> >    - pwr18-supply
> >    - interrupts
> >    - reset-gpios
> > -  - extcon
> >    - ports
> >
> >  additionalProperties: false
> > @@ -139,8 +165,11 @@ examples:
> >                  };
> >
> >                  port@1 {
> > +                    #address-cells = <1>;
> > +                    #size-cells = <0>;
> >                      reg = <1>;
> > -                    it6505_out: endpoint {
> > +                    it6505_out: endpoint@0 {
> > +                        reg = <0>;
> >                          remote-endpoint = <&dp_in>;
> >                          data-lanes = <0 1>;
> >                      };
> > @@ -148,3 +177,49 @@ examples:
> >              };
> >          };
> >      };
> > +  - |
> > +    #include <dt-bindings/interrupt-controller/irq.h>
> > +
> > +    i2c {
>
> Why do we need a whole new example? Just extend the existing example
> with new properties/nodes.

I added a new example because I don't think extcon and mode switches
can co-exist. Should I merge the examples to one anyway?
>
> Rob

I'll address other comments in the next version.

Best regards,
Pin-yen