linux-kernel - Re: [PATCH 2/7] dt-bindings: usb: dwc3: Add a gpio-usb-connector example

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Message-ID: <158463604559.152100.9219030962819234620@swboyd.mtv.corp.google.com>
Date:   Thu, 19 Mar 2020 09:40:45 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>, balbi@...nel.org,
        gregkh@...uxfoundation.org, linux-usb@...r.kernel.org
Cc:     linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        bjorn.andersson@...aro.org, jackp@...eaurora.org, robh@...nel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/7] dt-bindings: usb: dwc3: Add a gpio-usb-connector example

Quoting Bryan O'Donoghue (2020-03-19 08:22:14)
> On 19/03/2020 01:08, Stephen Boyd wrote:
> > 
> > Maybe it should be a virtual node at the root of the DT if it's GPIO
> > controlled? And then the phy can be connected to the usb connector
> > through the graph binding.
> 
> Graph binding can probably work.
> 
> Re: the PHY.
> 
> For myself the hardware model is
> 
> Connector -> PHY -> Host controller -> Host controller wrapper
> 
> Only
> 
> Connector -> Host controller -> Host controller wrapper
> 
> care about the USB role though.
> 
> If your PHY did care about the role, you'd really need to write a 
> connector/phy type-c type driver, to detect the state and toggle your 
> PHY bits before doing usb_role_switch_set_role() back to DWC3.
> 

Yes some PHYs do care about the role. Sometimes they have to toggle some
bit to switch between host and gadget mode for example. I haven't fully
read this patch series but maybe the PHY can be the one that controls
the gpio for the connector?

We (ChromeOS) need to integrate the type-c connector class, etc. on
sc7180 with the dwc3 driver and the current thinking has the type-c
connectors underneath the cros_ec node because the EC is the type-c
manager. The EC will have a type-c driver associated with it.