linux-kernel - Re: [PATCH v2 1/4] dt-bindings: Add cros-ec Type C port driver

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Message-ID: <20200212155309.GG1498@kuha.fi.intel.com>
Date:   Wed, 12 Feb 2020 17:53:09 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Prashant Malani <pmalani@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        heikki.krogerus@...el.com,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Benson Leung <bleung@...omium.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Guenter Roeck <groeck@...omium.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 1/4] dt-bindings: Add cros-ec Type C port driver

Hi Rob,

On Tue, Feb 11, 2020 at 05:25:13PM -0600, Rob Herring wrote:
> > +examples:
> > +  - |+
> > +    typec {
> > +      compatible = "google,cros-ec-typec";
> > +
> > +      port@0 {
> 
> 'port' is reserved for OF graph binding which this is not.
> 
> > +        port-number = <0>;
> > +        power-role = "dual";
> > +        data-role = "dual";
> > +        try-power-role = "source";
> 
> These are usb-connector binding properties, but this is not a
> usb-connector node. However, I think it should be. The main thing to
> work out seems to be have multiple connectors.
> 
> With your binding, how does one associate the USB host controller with
> each port/connector? That's a solved problem with the connector
> binding.

It looks like OF graph is required to be used for that. The plan was
actually to propose that we use device properties "usb2-port" and
"usb3-port" that directly reference the port nodes under the USB host
controller, but I guess that's too late for that.

OF graph creates one problem. We are going to need to identify the
endpoints somehow in the USB Type-C drivers, so how do we know which
endpoint is for example the USB2 port, which is USB3, which is
DisplayPort, etc?

Does the remote-endpoint parent need to have a specific compatible
property, like the USB2 port needs to have compatible = "usb2-port"
and so on?

thanks,

-- 
heikki