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

[Xin Ji <xji@analogixsemi.com>]

Hi Laurent Pinchart,

On Tue, Oct 15, 2019 at 01:16:10AM +0300, Laurent Pinchart wrote:
> Hi Xin Ji,
> 
> 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 = "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.
> 
> 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.

> 
> > >> 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.
> 
> 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.
> 
> > >> [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
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