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From:   Xin Ji <xji@analogixsemi.com>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
CC:     "devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@siol.net>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        Sheng Pan <span@analogixsemi.com>
Subject: Re: [PATCH v2 1/2] dt-bindings: drm/bridge: anx7625: MIPI to DP
 transmitter binding
Thread-Topic: [PATCH v2 1/2] dt-bindings: drm/bridge: anx7625: MIPI to DP
 transmitter binding
Thread-Index: AQHVf9qi2ZQPn8IAhkqsNtop++SEM6dVTGmAgAAZ3gCABBGvAIABQksAgABQGAA=
Date:   Tue, 15 Oct 2019 03:02:59 +0000
Message-ID: <20191015030250.GA11971@xin-VirtualBox>
References: <cover.1570760115.git.xji@analogixsemi.com>
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Hi Laurent Pinchart,

On Tue, Oct 15, 2019 at 01:16:10AM +0300, Laurent Pinchart wrote:
> Hi Xin Ji,
>=20
> On Mon, Oct 14, 2019 at 03:02:48AM +0000, Xin Ji wrote:
> > On Fri, Oct 11, 2019 at 03:54:18PM +0300, Laurent Pinchart wrote:
> > > On Fri, Oct 11, 2019 at 01:21:43PM +0200, Andrzej Hajda wrote:
> > >> On 11.10.2019 04:21, Xin Ji wrote:
> > >>> The ANX7625 is an ultra-low power 4K Mobile HD Transmitter designed
> > >>> for portable device. It converts MIPI to DisplayPort 1.3 4K.
> > >>>
> > >>> You can add support to your board with binding.
> > >>>
> > >>> Example:
> > >>> 	anx7625_bridge: encoder@58 {
> > >>> 		compatible =3D "analogix,anx7625";
> > >>> 		reg =3D <0x58>;
> > >>> 		status =3D "okay";
> > >>> 		panel-flags =3D <1>;
> > >>> 		enable-gpios =3D <&pio 45 GPIO_ACTIVE_HIGH>;
> > >>> 		reset-gpios =3D <&pio 73 GPIO_ACTIVE_HIGH>;
> > >>> 		#address-cells =3D <1>;
> > >>> 		#size-cells =3D <0>;
> > >>>
> > >>> 		port@0 {
> > >>> 		  reg =3D <0>;
> > >>> 		  anx_1_in: endpoint {
> > >>> 		    remote-endpoint =3D <&mipi_dsi>;
> > >>> 		  };
> > >>> 		};
> > >>>
> > >>> 		port@3 {
> > >>> 		  reg =3D <3>;
> > >>> 		  anx_1_out: endpoint {
> > >>> 		    remote-endpoint =3D <&panel_in>;
> > >>> 		  };
> > >>> 		};
> > >>> 	};
> > >>>
> > >>> Signed-off-by: Xin Ji <xji@analogixsemi.com>
> > >>> ---
> > >>>  .../bindings/display/bridge/anx7625.yaml           | 96 ++++++++++=
++++++++++++
> > >>>  1 file changed, 96 insertions(+)
> > >>>  create mode 100644 Documentation/devicetree/bindings/display/bridg=
e/anx7625.yaml
> > >>>
> > >>> diff --git a/Documentation/devicetree/bindings/display/bridge/anx76=
25.yaml b/Documentation/devicetree/bindings/display/bridge/anx7625.yaml
> > >>> new file mode 100644
> > >>> index 0000000..fc84683
> > >>> --- /dev/null
> > >>> +++ b/Documentation/devicetree/bindings/display/bridge/anx7625.yaml
> > >>> @@ -0,0 +1,96 @@
> > >>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > >>> +# Copyright 2019 Analogix Semiconductor, Inc.
> > >>> +%YAML 1.2
> > >>> +---
> > >>> +$id: "http://devicetree.org/schemas/display/bridge/anx7625.yaml#"
> > >>> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> > >>> +
> > >>> +title: Analogix ANX7625 SlimPort (4K Mobile HD Transmitter)
> > >>> +
> > >>> +maintainers:
> > >>> +  - Xin Ji <xji@analogixsemi.com>
> > >>> +
> > >>> +description: |
> > >>> +  The ANX7625 is an ultra-low power 4K Mobile HD Transmitter
> > >>> +  designed for portable devices.
> > >>> +
> > >>> +properties:
> > >>> +  "#address-cells": true
> > >>> +  "#size-cells": true
> > >>> +
> > >>> +  compatible:
> > >>> +    items:
> > >>> +      - const: analogix,anx7625
> > >>> +
> > >>> +  reg:
> > >>> +    maxItems: 1
> > >>> +
> > >>> +  panel-flags:
> > >>> +    description: indicate the panel is internal or external
> > >>> +    maxItems: 1
> > >>> +
> > >>> +  interrupts:
> > >>> +    maxItems: 1
> > >>> +
> > >>> +  enable-gpios:
> > >>> +    description: used for power on chip control, POWER_EN pin D2.
> > >>> +    maxItems: 1
> > >>> +
> > >>> +  reset-gpios:
> > >>> +    description: used for reset chip control, RESET_N pin B7.
> > >>> +    maxItems: 1
> > >>> +
> > >>> +  port@0:
> > >>> +    type: object
> > >>> +    description:
> > >>> +      A port node pointing to MIPI DSI host port node.
> > >>> +
> > >>> +  port@1:
> > >>> +    type: object
> > >>> +    description:
> > >>> +      A port node pointing to MIPI DPI host port node.
> > >>> +
> > >>> +  port@2:
> > >>> +    type: object
> > >>> +    description:
> > >>> +      A port node pointing to external connector port node.
> > >>> +
> > >>> +  port@3:
> > >>> +    type: object
> > >>> +    description:
> > >>> +      A port node pointing to eDP port node.
> > >>=20
> > >>=20
> > >> Decrypting available product brief[1], there are following physical =
lines:
> > >>=20
> > >> Input:
> > >>=20
> > >> - MIPI DSI/DPI - video data, are DSI and DPI lines shared?
> > >=20
> > > It would be much easier if we could have access to more complete
> > > information. I believe the DSI and DPI pins could be muxed, but there
> > > should be more DPI pins than DSI pins.
> >
> > Yes DPI pins more than DSI pins.
> >=20
> > >>=20
> > >> - I2S - audio data,
> > >>=20
> > >> - I2C - control line,
> > >>=20
> > >> - ALERT/INTP - interrupt,
> > >>=20
> > >> - USB 3.1 SSRc/Tx - for USB forwarding,
> > >>=20
> > >> Output:
> > >>=20
> > >> - SS1, SS2,
> > >>=20
> > >> - SBU/AUX,
> > >>=20
> > >> - CC1/2.
> > >>=20
> > >>=20
> > >> Having this information I try to understand ports defined by you:
> > >>=20
> > >> - port@2 you have defined as pointing to external port, but here the
> > >> port should be rather subnode of ANX7625 - the chip has CC lines, se=
e
> > >> beginning of [2].
> > >>=20
> > >> - port@3 describes SS1, SS2 and SBU/AUX lines together, am I right? =
In
> > >> USB-C binding SBU and SS lines are represented by different ports,
> > >> different approach, but maybe better in this case.
> > >=20
> > > I believe that, when connected to a DP display (either DP or eDP), th=
e
> > > DisplayPort signals are output on SS1 and/or SS2. I this really wonde=
r
> > > if we need two separate ports for this, it seems that port@2 and port=
@3
> > > should be merged.
> >
> > OK, I will merge the port@2 and port@3, and use a flag to indicate
> > whether the control is external connector control or not.
>=20
> Could this be inferred from the connected DT node ? If the node
> connected to the endpoint is a display connector node, then we have an
> external connector. Otherwise we have an eDP panel. Ideally this should
> even be done at runtime, by communicating with the drm_bridge or
> drm_panel corresponding to the connected node.

I think the port@2 should be removed, it could not be inferred from the
connected DT node.

>=20
> > >> Maybe it would be good to add 2nd example with USB-C port.
> > >=20
> > > That would help with the discussion, yes.
> >
> > As we disabled USB-C feature in anx7625, we cannot define a USB-C port.
>=20
> It's fine if the feature isn't implemented in the driver, but we should
> still take it into account to design the DT bindings. Otherwise, when
> someone will want to add support for USB-C to the ANX7625 bindings, they
> may find it impossible to do so in a nice backward-compatible way.
> That's why an example would already be useful.
OK.
>=20
> > >> [1]:
> > >> https://www.analogix.com/system/files/AA-002291-PB-6-ANX7625_Product=
Brief.pdf
> > >>=20
> > >> [2]: Documentation/devicetree/bindings/connector/usb-connector.txt
> > >>=20
> > >>> +
> > >>> +required:
> > >>> +  - "#address-cells"
> > >>> +  - "#size-cells"
> > >>> +  - compatible
> > >>> +  - reg
> > >>> +  - port@0
> > >>> +  - port@3
> > >>> +
> > >>> +example:
> > >>> +  - |
> > >>> +    anx7625_bridge: encoder@58 {
> > >>> +        compatible =3D "analogix,anx7625";
> > >>> +        reg =3D <0x58>;
> > >>> +        status =3D "okay";
> > >>> +        panel-flags =3D <1>;
> > >>> +        enable-gpios =3D <&pio 45 GPIO_ACTIVE_HIGH>;
> > >>> +        reset-gpios =3D <&pio 73 GPIO_ACTIVE_HIGH>;
> > >>> +        #address-cells =3D <1>;
> > >>> +        #size-cells =3D <0>;
> > >>> +
> > >>> +        port@0 {
> > >>> +          reg =3D <0>;
> > >>> +          anx_1_in: endpoint {
> > >>> +            remote-endpoint =3D <&mipi_dsi>;
> > >>> +          };
> > >>> +        };
> > >>> +
> > >>> +        port@3 {
> > >>> +          reg =3D <3>;
> > >>> +          anx_1_out: endpoint {
> > >>> +            remote-endpoint =3D <&panel_in>;
> > >>> +          };
> > >>> +        };
> > >>> +    };
>=20
> --=20
> Regards,
>=20
> Laurent Pinchart