linux-kernel - Re: [PATCH v2] arm64: dts: qcom: x1e80100-lenovo-yoga-slim7x: add retimers, dp altmode support

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Message-ID: <sassa62hyh2six6dbn6qgz7eobzt4z2p3eyqz3uaifcglwmf42@ckdaonsd3roe>
Date: Fri, 26 Dec 2025 19:02:51 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Shawn Guo <shawnguo@...nel.org>
Cc: Krzysztof Kozlowski <krzk@...nel.org>, jens.glathe@...schoolsolutions.biz,
        Abel Vesa <abel.vesa@....qualcomm.com>,
        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,
        Rob Clark <robdclark@...il.com>, Jos Dehaes <jos.dehaes@...il.com>
Subject: Re: [PATCH v2] arm64: dts: qcom: x1e80100-lenovo-yoga-slim7x: add
 retimers, dp altmode support

On Fri, Dec 26, 2025 at 09:15:23PM +0800, Shawn Guo wrote:
> On Thu, Dec 25, 2025 at 09:33:59AM +0100, Krzysztof Kozlowski wrote:
> > On 25/12/2025 04:29, Shawn Guo wrote:
> > > On Fri, Apr 18, 2025 at 12:35 AM Jens Glathe via B4 Relay
> > > <devnull+jens.glathe.oldschoolsolutions.biz@...nel.org> wrote:
> > >>
> > >> From: Jens Glathe <jens.glathe@...schoolsolutions.biz>
> > >>
> > >> comparing with CRD and other dts for a more complete support of the 7X
> > >> only retimers, gpios, regulators, dp outputs
> > >>
> > >> Tested-by: Rob Clark <robdclark@...il.com>
> > >> Tested-by: Jos Dehaes <jos.dehaes@...il.com>
> > >> Signed-off-by: Jens Glathe <jens.glathe@...schoolsolutions.biz>
> > >> ---
> > >> This patch adds the required nodes to support DP Altmode on all three type-c
> > >> ports. The definition is derived from the CRD. Since they are all marked 40Gbps,
> > >> I assume there are 3 PS8830 retimers.
> > >> This modification is now for ~8 weeks in my tree with little to no complaints. I
> > >> don't have access to a Yoga Slim 7X, however many people on #aarch64-laptops do
> > >> and some are using this patch.
> > >> ---
> > >> Changes in v2:
> > >> - removed changes not relevant to retimers and dp altmode (thanks Johan)
> > >> - Link to v1: https://lore.kernel.org/r/20250417-slim7x-retimer-v1-1-5813a7835903@oldschoolsolutions.biz
> > >> ---
> > >>  .../boot/dts/qcom/x1e80100-lenovo-yoga-slim7x.dts  | 476 ++++++++++++++++++++-
> > >>  1 file changed, 470 insertions(+), 6 deletions(-)
> > > 
> > > Hi,
> > > 
> > > I'm running a Slim7x China variant (Yoga Air 14s) with Debian 13.
> > > While the Debian stock 6.12 kernel works fine to bring up the display
> > > (AMOLED eDP panel), newer kernels like 6.18 loses display during boot.
> > > I can do either of the following to get the display back to work.
> > > 
> > > - Enable PS883X driver (Yes, CONFIG_TYPEC_MUX_PS883X is missing from
> > > Debian config [1])
> > 
> > Obviously.
> > 
> > > 
> > > OR
> > > 
> > > - Revert commit 299038d82418 ("arm64: dts: qcom:
> > > x1e80100-lenovo-yoga-slim7x: add retimers, dp altmode support")
> > > 
> > > My understanding is that a PS883X driver is required only for external
> > > DP support.  Why would the driver missing impact/break the internal
> > > panel support?  Do you guys have any insight on this?  Thanks!
> > > 
> > 
> > You need all drivers to avoid probe deferrals.
> 
> Ah, yes!  The display subsystem/card is wired up with all 4 eDP/DP
> ports.  A probe failure on any of the ports will cause the display
> card fail out, even though the eDP port has all the dependencies in
> place.

Unfortunately, that's a requirement for now. It might change in future,
once Luca finishes his hotplug bridges rework, but for now we have to
have all drivers in place.

Please send a patch to Debian kernel build system (ping me if you need
any help or if you'd need to convince Ben that we need it).

-- 
With best wishes
Dmitry