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

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Message-ID: <7462e29c-7602-45fc-b8f6-31e881ef3fc4@linaro.org>
Date: Mon, 8 Sep 2025 14:37:19 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Jens Glathe <jens.glathe@...schoolsolutions.biz>,
 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>
Cc: 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 06/09/2025 10:41, Jens Glathe wrote:
> On 21.08.25 15:53, Neil Armstrong wrote:
>> The Thinkpad T14s embeds a transparent 4lanes DP->HDMI transceiver
>> connected to the third QMP Combo PHY 4 lanes.
>>
> [...]
>>   .../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
> [...]
>> +&mdss_dp2 {
>> +    status = "okay";
>> +};
>> +
>> +&mdss_dp2_out {
>> +    data-lanes = <0 1 2 3>;
>> +};
>> +
> 
> Hi Neil,
> 
> shouldn't mdss_dp2_out also have the link-frequencies property?
> 
> +    link-frequencies = /bits/ 64 <1620000000 2700000000 5400000000 8100000000>;
> 
> Or is it something the bridge already negotiates?

No, indeed I'll add it, it will fall back to HBR2 anyway (as actually) if the link quality is low.

Neil

> 
> with best regards
> 
> Jens
>