linux-kernel - Re: [PATCH v3 1/2] arm64: dts: qcom: monaco: add lt8713sx bridge with displayport

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Message-ID: <z3y6wb6irac2ef3f55roy66wzyufel4vannfbynoivzgl2cuob@um5eomgvt5uc>
Date: Sun, 28 Dec 2025 17:49:30 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Vishnu Saini <vishnu.saini@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        prahlad.valluru@....qualcomm.com,
        Prahlad Valluru <vvalluru@....qualcomm.com>
Subject: Re: [PATCH v3 1/2] arm64: dts: qcom: monaco: add lt8713sx bridge
 with displayport

On Sun, Dec 28, 2025 at 07:10:38PM +0530, Vishnu Saini wrote:
> Monaco-evk has LT8713sx which act as DP to 3 DP output
> converter. Edp PHY from monaco soc is connected to lt8713sx
> as input and output of lt8713sx is connected to 3 mini DP ports.
> 
> Two ports are available in mainboard and one port
> is available on Mezz board.
> 
> lt8713sx is connected to soc over i2c0 and with reset gpio
> connected to pin6 of ioexpander5.
> 
> Enable the edp nodes from monaco and enable lontium lt8713sx
> bridge node.
> 
> Co-developed-by: Prahlad Valluru <vvalluru@....qualcomm.com>
> Signed-off-by: Prahlad Valluru <vvalluru@....qualcomm.com>
> Signed-off-by: Vishnu Saini <vishnu.saini@....qualcomm.com>
> ---
>  arch/arm64/boot/dts/qcom/monaco-evk.dts | 89 +++++++++++++++++++++++++++++++++
>  arch/arm64/boot/dts/qcom/monaco.dtsi    |  6 +++
>  2 files changed, 95 insertions(+)
> 

> @@ -396,10 +456,39 @@ expander6: gpio@3e {
>  	};
>  };
>  
> +&mdss {
> +	status = "okay";
> +};
> +
> +&mdss_dp0 {
> +	pinctrl-0 = <&dp_hot_plug_det>;
> +	pinctrl-names = "default";

Is there a single HPD? How does it work? What happens if either of
connected displays sends a HPD pulse signal?

> +
> +	status = "okay";
> +};
> +
> +&mdss_dp0_out {
> +	data-lanes = <0 1 2 3>;
> +	link-frequencies = /bits/ 64 <1620000000 2700000000 5400000000 8100000000>;
> +	remote-endpoint = <&lt8713sx_dp_in>;

Does the bridge use DP signalling or does it use USB-C signalling here?
And even if it is DP signalling, it should be correctly described as
it uses signals coming from the QMP PHY. See how it's done for laptops
with DP-HDMI convertors.

> +};
> +
> +&mdss_dp0_phy {
> +	vdda-phy-supply = <&vreg_l5a>;
> +	vdda-pll-supply = <&vreg_l4a>;
> +
> +	status = "okay";
> +};
> +
>  &iris {
>  	status = "okay";
>  };
>  
> +&qup_i2c0_data_clk {
> +	drive-strength = <2>;
> +	bias-pull-up;
> +};
> +
>  &qupv3_id_0 {
>  	firmware-name = "qcom/qcs8300/qupv3fw.elf";
>  	status = "okay";
> diff --git a/arch/arm64/boot/dts/qcom/monaco.dtsi b/arch/arm64/boot/dts/qcom/monaco.dtsi
> index e44fd5c33816..7f6c681fb1b4 100644
> --- a/arch/arm64/boot/dts/qcom/monaco.dtsi
> +++ b/arch/arm64/boot/dts/qcom/monaco.dtsi
> @@ -5117,6 +5117,12 @@ tlmm: pinctrl@...0000 {
>  			#interrupt-cells = <2>;
>  			wakeup-parent = <&pdc>;
>  
> +			dp_hot_plug_det: dp-hot-plug-det-state {
> +				pins = "gpio94";
> +				function = "edp0_hot";
> +				bias-disable;
> +			};
> +
>  			hs0_mi2s_active: hs0-mi2s-active-state {
>  				pins = "gpio106", "gpio107", "gpio108", "gpio109";
>  				function = "hs0_mi2s";
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry