linux-kernel - Re: [PATCH v14 0/9] Add multiport support for DWC3 controllers

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Date: Tue, 6 Feb 2024 10:47:30 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Krishna Kurapati PSSNV <quic_kriskura@...cinc.com>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Rob Herring <robh+dt@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Wesley Cheng <quic_wcheng@...cinc.com>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Conor Dooley <conor+dt@...nel.org>, Thinh Nguyen <Thinh.Nguyen@...opsys.com>, 
	Felipe Balbi <balbi@...nel.org>, devicetree@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org, quic_ppratap@...cinc.com, 
	quic_jackp@...cinc.com
Subject: Re: [PATCH v14 0/9] Add multiport support for DWC3 controllers

On Tue, 6 Feb 2024 at 10:45, Krishna Kurapati PSSNV
<quic_kriskura@...cinc.com> wrote:
>
>
>
> On 2/6/2024 2:13 PM, Dmitry Baryshkov wrote:
> > On Tue, 6 Feb 2024 at 10:15, Krishna Kurapati PSSNV
> > <quic_kriskura@...cinc.com> wrote:
> >>
> >>
> >>
> >> On 2/6/2024 1:30 PM, Dmitry Baryshkov wrote:
> >>> Hi Krishna,
> >>>
> >>> On Tue, 6 Feb 2024 at 07:18, Krishna Kurapati <quic_kriskura@...cinc.com> wrote:
> >>>>
> >>>> Currently the DWC3 driver supports only single port controller which
> >>>> requires at most two PHYs ie HS and SS PHYs. There are SoCs that has
> >>>> DWC3 controller with multiple ports that can operate in host mode.
> >>>> Some of the port supports both SS+HS and other port supports only HS
> >>>> mode.
> >>>>
> >>>> This change primarily refactors the Phy logic in core driver to allow
> >>>> multiport support with Generic Phy's.
> >>>>
> >>>> Changes have been tested on  QCOM SoC SA8295P which has 4 ports (2
> >>>> are HS+SS capable and 2 are HS only capable).
> >>>
> >>> Thank you for your patches! Have you tested how this patchset
> >>> interacts with the USB role-switching?
> >>>
> >>> I'm asking because it might be easier to define DT nodes for each of
> >>> USB ports, which can carry the PHY properties (and also other DT
> >>> properties if that's required, e.g. the ports / endpoints and
> >>> usb-role-switch) rather than pushing all USB PHY links to the root DT
> >>> node.
> >>>
> >>
> >> Hi Dmitry,
> >>
> >>    Role switching doesn't work for Multiport controller as it is host
> >> only capable. I don't think it will cause any issues for OTG capable
> >> controllers because they only have one HS and SS phy present. So there
> >> is no possibility or requirement for having endpoints per port in this case.
> >
> > Is it going to remain host-only in future?
> >
> >
> Yes. I believe these are designed that way. I don't know of any
> controllers that have multiple ports and device mode works. Device mode
> can work only on one port AFAIK.

Ack, thanks for the explanation.

-- 
With best wishes
Dmitry