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

[Xin Ji <xji@analogixsemi.com>]

Hi Laurent Pinchart, please check my comment below.

Thanks,
Xin

On Fri, Oct 11, 2019 at 03:54:18PM +0300, Laurent Pinchart wrote:
> 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@analogixsemi.com>
> > > ---
> > >  .../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@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.
> > 
> > 
> > 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.
Yes DPI pins more 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.
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.
> 
> > Maybe it would be good to add 2nd example with USB-C port.
> 
> That would help with the discussion, yes.
As we disabled USB-C feature in anx7625, we cannot define a USB-C port.
> 
> > [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