linux-kernel - Re: [PATCH RFC 3/3] arm64: dts: qcom: x1e78100-lenovo-thinkpad-t14s: add HDMI nodes

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Message-ID: <26j2trl7lypmqzjnw6kwgqz32eqcags34qpgaua7zbwxd4lbgx@n54gemj42xbd>
Date: Fri, 22 Aug 2025 14:57:24 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 3/3] arm64: dts: qcom: x1e78100-lenovo-thinkpad-t14s:
 add HDMI nodes

On Fri, Aug 22, 2025 at 01:45:38PM +0200, Stephan Gerhold wrote:
> On Fri, Aug 22, 2025 at 02:01:30PM +0300, Dmitry Baryshkov wrote:
> > On Thu, Aug 21, 2025 at 03:53:28PM +0200, Neil Armstrong wrote:
> > > The Thinkpad T14s embeds a transparent 4lanes DP->HDMI transceiver
> > > connected to the third QMP Combo PHY 4 lanes.
> > > 
> > > Add all the data routing, disable mode switching and specify the
> > > QMP Combo PHY should be in DP-Only mode to route the 4 lanes to
> > > the underlying DP phy.
> > > 
> > > Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> > > ---
> > >  .../dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi    | 44 ++++++++++++++++++++++
> > >  1 file changed, 44 insertions(+)
> > > 
> > > diff --git a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
> > > index 4cf61c2a34e31233b1adc93332bcabef22de3f86..5b62b8c3123633360f249e3ecdc8ea23f44e8e09 100644
> > > --- a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
> > > +++ b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi
> > > @@ -62,6 +62,20 @@ switch-lid {
> > >  		};
> > >  	};
> > >  
> > > +
> > > +	hdmi-connector {
> > > +		compatible = "hdmi-connector";
> > > +		type = "a";
> > > +		pinctrl-0 = <&hdmi_hpd_default>;
> > > +		pinctrl-names = "default";
> > [...]
> > > +
> > > +		port {
> > > +			hdmi_con: endpoint {
> > > +				remote-endpoint = <&usb_1_ss2_qmpphy_out>;
> > 
> > Please describe the transparent bridge too. It can be covered by the
> > simple-bridge.yaml / simple-bridge.c
> > 
> 
> I think this isn't the case here(?), but how are we going to handle
> devices where we don't know which bridge chip is used? I've seen at
> least 3 or 4 different chips already across all X1E laptops and we don't
> have schematics for most of them.

Open the case, inspect the board, identify the chip. Everything is as
usual.

-- 
With best wishes
Dmitry