Re: [PATCH v2 1/2] dt-bindings: drm/bridge: anx7625: MIPI to DP transmitter binding

[Laurent Pinchart]

Hi Andrzej,

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 = "analogix,anx7625";
> > 		reg = <0x58>;
> > 		status = "okay";
> > 		panel-flags = <1>;
> > 		enable-gpios = <&pio 45 GPIO_ACTIVE_HIGH>;
> > 		reset-gpios = <&pio 73 GPIO_ACTIVE_HIGH>;
> > 		#address-cells = <1>;
> > 		#size-cells = <0>;
> >
> > 		port@0 {
> > 		  reg = <0>;
> > 		  anx_1_in: endpoint {
> > 		    remote-endpoint = <&mipi_dsi>;
> > 		  };
> > 		};
> >
> > 		port@3 {
> > 		  reg = <3>;
> > 		  anx_1_out: endpoint {
> > 		    remote-endpoint = <&panel_in>;
> > 		  };
> > 		};
> > 	};
> >
> > Signed-off-by: Xin Ji <xji@xxxxxxxxxxxxxxxx>
> > ---
> >  .../bindings/display/bridge/anx7625.yaml           | 96 ++++++++++++++++++++++
> >  1 file changed, 96 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/display/bridge/anx7625.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/display/bridge/anx7625.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@xxxxxxxxxxxxxxxx>
> > +
> > +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.
> 
> 
> Decrypting available product brief[1], there are following physical lines:
> 
> Input:
> 
> - MIPI DSI/DPI - video data, are DSI and DPI lines shared?

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.

> 
> - I2S - audio data,
> 
> - I2C - control line,
> 
> - ALERT/INTP - interrupt,
> 
> - USB 3.1 SSRc/Tx - for USB forwarding,
> 
> Output:
> 
> - SS1, SS2,
> 
> - SBU/AUX,
> 
> - CC1/2.
> 
> 
> Having this information I try to understand ports defined by you:
> 
> - 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, see
> beginning of [2].
> 
> - 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.

I believe that, when connected to a DP display (either DP or eDP), the
DisplayPort signals are output on SS1 and/or SS2. I this really wonder
if we need two separate ports for this, it seems that port@2 and port@3
should be merged.

> Maybe it would be good to add 2nd example with USB-C port.

That would help with the discussion, yes.

> [1]:
> https://www.analogix.com/system/files/AA-002291-PB-6-ANX7625_ProductBrief.pdf
> 
> [2]: Documentation/devicetree/bindings/connector/usb-connector.txt
> 
> > +
> > +required:
> > +  - "#address-cells"
> > +  - "#size-cells"
> > +  - compatible
> > +  - reg
> > +  - port@0
> > +  - port@3
> > +
> > +example:
> > +  - |
> > +    anx7625_bridge: encoder@58 {
> > +        compatible = "analogix,anx7625";
> > +        reg = <0x58>;
> > +        status = "okay";
> > +        panel-flags = <1>;
> > +        enable-gpios = <&pio 45 GPIO_ACTIVE_HIGH>;
> > +        reset-gpios = <&pio 73 GPIO_ACTIVE_HIGH>;
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        port@0 {
> > +          reg = <0>;
> > +          anx_1_in: endpoint {
> > +            remote-endpoint = <&mipi_dsi>;
> > +          };
> > +        };
> > +
> > +        port@3 {
> > +          reg = <3>;
> > +          anx_1_out: endpoint {
> > +            remote-endpoint = <&panel_in>;
> > +          };
> > +        };
> > +    };

-- 
Regards,

Laurent Pinchart