Re: [PATCH v1 1/2] dt-bindings: drm/bridge: anx7625: MIPI to DP transmitter binding

[Xin Ji <xji@analogixsemi.com>]

Hi Laurent Pinchart, thanks for your comment.

On Fri, Sep 20, 2019 at 12:46:21PM +0300, Laurent Pinchart wrote:
> Hello Xin Ji,
> 
> Thank you for the patch.
> 
> On Fri, Sep 20, 2019 at 06:05:03AM +0000, 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.
> 
> I assume you meant MIPI DSI ? MIPI has released more standards than DSI,
> so it doesn't hurt to specify this explicitly.
It support DSI and DPI, I will to point out.
> 
> According to
> https://www.analogix.com/en/system/files/AA-002291-PB-6-ANX7625_ProductBrief_0.pdf,
> the ANX7625 supports for MIPI DSI and DPI on the input side.
> Furthermore, it seems to output DisplayPort on USB Type-C. Should this
> be documented ?
It can support both eDP output or USB Type-C output.
> 
> > You can add support to your board with binding.
> > 
> > Example:
> > 	anx_bridge: anx7625@58 {
> > 		compatible = "analogix,anx7625";
> > 		reg = <0x58>;
> > 		low-power-mode = <1>;
> > 		dsi-supported = <1>;
> > 		dsi-channel-id = <1>;
> > 		dsi-lanes-num = <4>;
> > 		internal-pannel-supported = <1>;
> > 		pon-gpios = <&gpio0 45 GPIO_ACTIVE_LOW>;
> > 		reset-gpios = <&gpio0 73 GPIO_ACTIVE_LOW>;
> > 		status = "okay";
> > 		port {
> > 			anx7625_1_in: endpoint {
> > 				remote-endpoint = <&mipi_dsi_bridge_1>;
> > 			};
> > 		};
> > 	};
> > 
> > Signed-off-by: Xin Ji <xji@analogixsemi.com>
> > ---
> >  .../bindings/display/bridge/anx7625.yaml           | 84 ++++++++++++++++++++++
> >  1 file changed, 84 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..95fe18b
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/display/bridge/anx7625.yaml
> > @@ -0,0 +1,84 @@
> > +# 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:
> > +  compatible:
> > +    items:
> > +      - const: analogix,anx7625
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  low-power-gpios:
> > +    description: Low power mode support feature
> > +    maxItems: 1
> > +
> > +  hpd-gpios:
> > +    description: used for HPD interrupt
> > +    maxItems: 1
> > +
> > +  pon-gpios:
> > +    description: used for power on chip control
> > +    maxItems: 1
> > +
> > +  reset-gpios:
> > +    description: used for reset chip control
> > +    maxItems: 1
> 
> How about mentioning which pin of the ANX7625 each GPIO refers to ? For
> the low-power, pon and reset GPIOs I assume they directly control the
> chip. We have standard names for some GPIOs, such as reset or enable. Is
> there one of the low-power and pon GPIOs that would qualify as an enable
> signal ?
OK, I think pon-gpios can qualify as an enable.
> 
> What is the HPD GPIO for ? Does the chip output and HPD signal ?
Once the anx7625 received eDP HPD signal, the firmware will report HPD
interrupt to AP through defined gpio interrupt pin "hpd-gpios". It used
for interrupt between anx7625 and AP, not used for output.
> 
> > +
> > +  extcon-supported:
> > +    description: external connector interface support flag
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +  internal-pannel-supported:
> > +    description: indicate does internal pannel exist or not
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> 
> s/pannel/panel/
OK, will fix it.
> 
> Are those two properties mutually exclusive ? If so you should combine
> them in a single required property with two values. My feeling is that
> they should be dropped though, please see below.
Yes, they are mutually exclusive.
There are 3 case, one is support google "external connector" framework,
one support internal panel, the other is support normal eDP output, so I
defined two flags to distinguish them here. Based on your comment below,
I'll define output port to distinguish them.
> 
> > +
> > +  dsi-supported:
> > +    description: support MIPI DSI or DPI
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +  dsi-channel-id:
> > +    description: dsi channel index
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> 
> This does not belong to DT, the virtual channel used by the DSI source
> should be queried at runtime by communicating between drivers.
I didn't know where can quiry this value. Can you give me more detail?
> 
> > +
> > +  dsi-lanes-num:
> > +    description: dsi lanes used num
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> 
> Please use the standard data-lanes property as defined in
> video-interface.txt. It should be specified in the DSI endpoints.
OK, I'll fetch the dsi lanes from DSI endpoints.
> 
> > +
> > +  port@0:
> > +    type: object
> > +    description:
> > +      A port node pointing to MIPI DSI host port node.
> 
> You need at least 3 ports:
> 
> - a DPI input port
I'll add DPI input port.
> - a DSI input port
> - an output port
> 
> The dsi-supported property should be dropped, detecting the type of
> input should be done based on which of the DPI or DSI input port is
> connected.
OK.
> 
> Assuming the ANX7625 can also output DisplayPort directly without going
> through USB Type-C (I can't verify that without the datasheet), I think
> you should use two output ports, one for USB Type-C and one for
> DisplayPort. The extcon-supported and internal-pannel-supported
> properties should be removed, and deduced from the connect output port.
I think there should exist 3 output port, one is for extern connector,
one is for normal eDP, other is for internal panel eDP.
> 
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - dsi-channel-id
> > +  - dsi-lanes-num
> > +  - port@0
> > +
> > +example:
> > +  - |
> > +    anx_bridge: anx7625@58 {
> > +        compatible = "analogix,anx7625";
> > +        reg = <0x58>;
> > +        low-power-gpios = <0>;
> > +        dsi-supported = <1>;
> > +        dsi-channel-id = <1>;
> > +        dsi-lanes-num = <4>;
> > +        hpd-gpios = <&gpio1 19 IRQ_TYPE_LEVEL_LOW>;
> > +        status = "okay";
> > +    };
> 
> You mention the port@0 node as being required, but it's missing from the
> example.
OK, I'll change it in the next series.
> 
> -- 
> Regards,
> 
> Laurent Pinchart