linux-kernel - Re: [PATCH 1/2] dt-bindings: usb: Introduce GPIO-based SBU mux

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Message-ID: <CACeCKafDfiZ8o2Ac-QYTcWT0dFtX6gXfrBPsGgwxRG+-FF4aQw@mail.gmail.com>
Date:   Tue, 23 Aug 2022 11:21:33 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Stephen Boyd <swboyd@...omium.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Pin-yen Lin <treapking@...omium.org>
Subject: Re: [PATCH 1/2] dt-bindings: usb: Introduce GPIO-based SBU mux

On Fri, Aug 19, 2022 at 9:04 PM Bjorn Andersson
<bjorn.andersson@...aro.org> wrote:
>
> On Fri 19 Aug 17:18 CDT 2022, Prashant Malani wrote:
>
> > On Fri, Aug 19, 2022 at 2:39 PM Bjorn Andersson
> > <bjorn.andersson@...aro.org> wrote:
>
> Are you saying that two of your SS-lanes in connector A are connected to
> directly to the QMP PHY at the same time as two SS-lanes from connector
> B are connected to the same two pads on the QMP PHY - without any
> mux etc inbetween?
>
> I.e. that there are a set of pins in connector A which is directly
> connected to a set of pins in connector B?
>
>
> I was under the impression that in your hardware there's some component
> muxing the single DP output to one of the connectors. If so there should
> be no graph-link directly connecting the two usb-c-connectors and the
> one QMP PHY.
>
> Is this not the case?

I can't speak to the QMP PHY specifically (since I'm not using that hardware),
but your impression is right.
There is a component (anx7625) muxing the single DP output to the 2
usb-c-connectors
(specifically, 2 lanes each from the 2 usb-c-connectors).
The other 2 lanes (from the 2 USB-C-connectors) go to a USB3 hub; hence the need
for 2 endpoints for each usb-c-connector).

So,  the anx7625 should register the mode switches and it needs the
graph connections
from 2 usb-c-connectors

BR,

-Prashant