linux-kernel - Re: [PATCH v4 1/4] dt-bindings: Add binding for the Analogix ANX7688 chip

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Message-ID: <20200330225842.GA20868@bogus>
Date:   Mon, 30 Mar 2020 16:58:42 -0600
From:   Rob Herring <robh@...nel.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     linux-kernel@...r.kernel.org,
        Collabora Kernel ML <kernel@...labora.com>,
        Andrzej Hajda <a.hajda@...sung.com>, icenowy@...c.io,
        anarsoul@...il.com, Neil Armstrong <narmstrong@...libre.com>,
        matthias.bgg@...il.com, drinkcat@...omium.org, hsinyi@...omium.org,
        megous@...ous.com, Lee Jones <lee.jones@...aro.org>,
        Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org
Subject: Re: [PATCH v4 1/4] dt-bindings: Add binding for the Analogix ANX7688
 chip

On Wed, Mar 18, 2020 at 08:07:27AM +0100, Enric Balletbo i Serra wrote:
> The ANX7688 chip is a Type-C Port Controller, HDMI to DP converter and
> USB-C mux between USB 3.0 lanes and the DP output.
> 
> For our use case a big part of the chip, like power supplies, control
> gpios and the usb-c part is managed by an Embedded Controller, hence,
> this is its simplest form of the binding. We'd prefer introduce these
> properties for someone with a different use case so they can test
> on their hardware.

I'm not sure this is a move in the right direction from the prior 
version. Just because you have multiple functions that doesn't mean 
the DT has multiple child nodes. What's a 'function' exactly may vary 
by OS (or in time). Are the USB-C functions separate h/w? Are there 
separate resources for each sub-function that need to be defined in DT?

We do need to be able to construct a graph with this device, HDMI 
output, USB host, and USB connector. That may dictate what does or 
doesn't work here.

> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
> 
> Changes in v4: None
> Changes in v3:
> - Add binding for ANX7688 multi-function device.
> 
> Changes in v2: None
> 
>  .../bindings/mfd/analogix,anx7688.yaml        | 48 +++++++++++++++++++
>  1 file changed, 48 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/analogix,anx7688.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mfd/analogix,anx7688.yaml b/Documentation/devicetree/bindings/mfd/analogix,anx7688.yaml
> new file mode 100644
> index 000000000000..bb95a4e87188
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/analogix,anx7688.yaml
> @@ -0,0 +1,48 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mfd/analogix,anx7688.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analogix ANX7688 HDMI to USB Type-C Bridge (Port Controller with MUX)
> +
> +maintainers:
> +  - Nicolas Boichat <drinkcat@...omium.org>
> +  - Enric Balletbo i Serra <enric.balletbo@...labora.com>
> +
> +description: |
> +  ANX7688 converts HDMI 2.0 to DisplayPort 1.3 Ultra-HDi (4096x2160p60)
> +  including an intelligent crosspoint switch to support USB Type-C (USB-C).
> +  The integrated crosspoint switch supports USB 3.1 data transfer along with
> +  the DisplayPort Alternate Mode signaling over USB Type-C. Additionally,
> +  an on-chip microcontroller (OCM) is available to manage the signal switching,
> +  Channel Configuration (CC) detection, USB Power Delivery (USB-PD), Vendor
> +  Defined Message (VDM) protocol support and other functions as defined in the
> +  USB TypeC and USB Power Delivery specifications.
> +
> +  As a result, a multi-function device is exposed as parent of the video
> +  bridge, TCPC and MUX blocks.
> +
> +properties:
> +  compatible:
> +    const: analogix,anx7688
> +
> +  reg:
> +    maxItems: 1
> +    description: I2C address of the device
> +
> +required:
> +  - compatible
> +  - reg

If this does stay like this, then you need to define the child node(s) 
here and reference their bindings.

> +
> +examples:
> +  - |
> +    i2c0 {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        anx7688: anx7688@2c {
> +            compatible = "analogix,anx7688";
> +            reg = <0x2c>;
> +        };
> +    };
> -- 
> 2.25.1
>