linux-kernel - Re: [PATCH v3 0/6] arm64: qcom: allow up to 4 lanes for the Type-C DisplayPort Altmode

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Message-ID: <d435fda2-1471-4561-b7a0-ee831a8f0909@oldschoolsolutions.biz>
Date: Thu, 29 May 2025 10:43:27 +0200
From: Jens Glathe <jens.glathe@...schoolsolutions.biz>
To: Konrad Dybcio <konradybcio@...nel.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>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>,
 linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Krzysztof Kozlowski <krzk@...nel.org>, Dmitry Baryshkov <lumag@...nel.org>
Subject: Re: [PATCH v3 0/6] arm64: qcom: allow up to 4 lanes for the Type-C
 DisplayPort Altmode

On 27.05.25 22:40, Konrad Dybcio wrote:
> The DisplayPort 4 lanes setup can be check with:
> $ cat /sys/kernel/debug/dri/ae01000.display-controller/DP-1/dp_debug
> 	name = msm_dp
> 	drm_dp_link
> 		rate = 540000
> 		num_lanes = 4
> ...

Hi Konrad,

thank you for the patch. I applied it, added `mode-switch;` to all combo 
qmpphys in sc8280xp.dtsi, enabled 4 lanes on the mdss_dp's, and it works 
on the windows Dev Kit 2023 (Blackrock) on usb1, with both orientations. 
Getting 4k@60 with 4 lanes. DPMS suspend/wakeup works, too. usb0 does 
only data, as before (need to investigate).

My suggestion would be to put the `mode-switch;` into the SoC dtsi 
(sc8280xp and x1e80100, maybe more?). Shouldn't hurt IMO.

Tested-by: Jens Glathe <jens.glathe@...schoolsolutions.biz>

with best regards

Jens