linux-kernel - Re: [PATCH v8 10/10] arm64: dts: rockchip: rk3399-evb-ind: Add support for DisplayPort

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Message-ID: <CAL411-rFK0o_cxBO_yJFHWurGFKxZGxw6=kpqxRipMetJskTaQ@mail.gmail.com>
Date: Thu, 30 Oct 2025 14:13:21 +0800
From: Peter Chen <hzpeterchen@...il.com>
To: Chaoyi Chen <chaoyi.chen@...k-chips.com>
Cc: Chaoyi Chen <kernel@...kyi.com>, Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Heiko Stuebner <heiko@...ech.de>, Sandy Huang <hjc@...k-chips.com>, 
	Andy Yan <andy.yan@...k-chips.com>, Yubing Zhang <yubing.zhang@...k-chips.com>, 
	Frank Wang <frank.wang@...k-chips.com>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Amit Sunil Dhamne <amitsd@...gle.com>, Dragan Simic <dsimic@...jaro.org>, Johan Jonker <jbx6244@...il.com>, 
	Diederik de Haas <didi.debian@...ow.org>, Peter Robinson <pbrobinson@...il.com>, linux-usb@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-phy@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
	linux-rockchip@...ts.infradead.org, dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v8 10/10] arm64: dts: rockchip: rk3399-evb-ind: Add
 support for DisplayPort

On Thu, Oct 30, 2025 at 11:14 AM Chaoyi Chen <chaoyi.chen@...k-chips.com> wrote:
>
> On 10/30/2025 10:50 AM, Peter Chen wrote:
>
> >>> Okay.  My question is basic: USB2 PHY supplies DP/DM, and the DP/DM is
> >>> short for Type-C connector,
> >>> and no control is needed for Type-C application.
> >>> Why is there a remote-endpoint connection between USB2 PHY and Type-C connector?
> >>   From the perspective of Type-C, this should not be added.  Is the approach in v2 correct [0] ?
> >>
> > Have you tried debugging based on upstream code?
>
> Yes, I have tried both the v2 and v8 approaches, and both can work.
>
>
> > v2 is correct, but the dts needs to improve.
> > - There is a remote-endpoint connection for USB role switch between
> > Type-C connector
> > device and USB controller device
> > - There is a remote-endpoint connection for orientation and lane configuration
> > between Type-C connector device and USB/DP PHY device.
>
> In v8 patch5, we implemented typec_mux and typec_switch in the USB/DP PHY.
>
> I think the current remote-endpoint connections are all child node of the USB/DP PHY. That is:
>
>
> &tcphy0_dp {
>      mode-switch;
>      ...
> };
>
>
> &tcphy0_usb3 {
>      orientation-switch;
>      ...
> };
>
>
> Does this still need to be improved? Thank you.
>

Hi Chaoyi,

There are two questions I have still not seen the answer to:
- Why USB2 PHY is related to your Type-C patch?
- How does the USB role switch event notify the USB controller driver, eg dwc3?

Peter
>
> >
> > Peter
> >
> >> [0]: https://lore.kernel.org/all/20250715112456.101-6-kernel@airkyi.com/
> >>
> >> Or is the following approach correct?
> >>
> >>
> >> port@0 {
> >>       reg = <0>;
> >>
> >>       usbc_hs: endpoint {
> >>           remote-endpoint = <&tcphy0>;
> >>       };
> >> };
> >>
> >> port@1 {
> >>       reg = <1>;
> >>
> >>       usbc_ss: endpoint {
> >>           remote-endpoint = <&tcphy0>;
> >>       };
> >> };
> >>
> >> port@2 {
> >>       reg = <2>;
> >>
> >>       usbc_dp: endpoint {
> >>           remote-endpoint = <&tcphy0_typec_dp>;
> >>       };
> >> };
> >>
> >>
> >>>>>>> +                               port@1 {
> >>>>>>> +                                       reg = <1>;
> >>>>>>> +
> >>>>>>> +                                       usbc_ss: endpoint {
> >>>>>>> + remote-endpoint = <&tcphy0_typec_ss>;
> >>>>>>> +                                       };
> >>>>>>> +                               };
> >>>>>>> +
> >>>>>>> +                               port@2 {
> >>>>>>> +                                       reg = <2>;
> >>>>>>> +
> >>>>>>> +                                       usbc_dp: endpoint {
> >>>>>>> + remote-endpoint = <&tcphy0_typec_dp>;
> >>>>>>> +                                       };
> >>>>>>> +                               };
> >>>>>>> +                       };
> >>>>>>> +               };
> >>>>>>> +       };
> >>>>>>> +};
> >>>>>>> +
> >>>>>> .....
> >>>>>>>     &u2phy0 {
> >>>>>>>            status = "okay";
> >>>>>>> +
> >>>>>>> +       port {
> >>>>>>> +               u2phy0_typec_hs: endpoint {
> >>>>>>> +                       remote-endpoint = <&usbc_hs>;
> >>>>>>> +               };
> >>>>>>> +       };
> >>>>>>>     };
> >>>>>>>
> >>>>>> There is no switch and mux, how to co-work with Type-C?
> >>>>> I checked the phy-rockchip-inno-usb2.c but did not find any switch or mux. Does this mean that we need to implement them? Thank you.
> >>>> Wait a minute, actually we have multiple hardware interfaces, one of which is Type-C, eventually connected to USBDPPHY, and the other is micro-usb connected to U2PHY.
> >>> I assume the Micro-USB connector does not use Type-C/PD IC, is it
> >>> right? Does it relate to this patch?
> >>>
> >>> Best regards,
> >>> Peter
> >>>
> >
> --
> Best,
> Chaoyi
>