linux-kernel - Re: [PATCH 2/2] arm64: dts: qcom: x1p42100-lenovo-thinkbook-16: add hdmi bridge with enable pin

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Message-ID: <x2zwsjk4vv73a4i4pj2aphvajtjgkw6mkzs5brg6adlm4gnxpu@r7pbypzvcsi6>
Date: Sun, 21 Dec 2025 04:49:01 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Jens Glathe <jens.glathe@...schoolsolutions.biz>
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,
        Val Packett <val@...kett.cool>
Subject: Re: [PATCH 2/2] arm64: dts: qcom: x1p42100-lenovo-thinkbook-16: add
 hdmi bridge with enable pin

On Sat, Dec 20, 2025 at 09:17:16PM +0100, Jens Glathe wrote:
> On 20.12.25 19:52, Dmitry Baryshkov wrote:
> > On Sat, Dec 20, 2025 at 06:47:10PM +0100, Jens Glathe via B4 Relay wrote:
> > > From: Jens Glathe <jens.glathe@...schoolsolutions.biz>
> > > 
> > > Add TLMM 119 for hdmi bridge enable. AeoB has this gpio.
> > Whaat is AeoB? I don't see the GPIO being used in other place.
> 
> AeoB is a resource format used by the QCom Windows drivers to add /
> overwrite definitions coming from the ACPI tables. [1] It had the info that
> was not to be found in the DSDT. Actually, x1e80100.dtsi has the
> edp0_hpd_default pinctrl which is required for the display to work with the
> function edp_hot. I verified this, you need both. I can use that definition
> in this patchset, too, but its not for HDMI.
> 
> [1]: https://github.com/alexVinarskis/qcom-aeob-dumps/tree/master/lenovo-thinkbook-16-g7-qoy
> 
> > > In general this is the same setup as on the T14s. Since its using simple-bridge
> > > and also is Lenovo, we also use the same realtek,rtd2171 compatible.
> > > The real chip identity is not known yet. The bridge is wired with un-swapped
> > > lanes, though.
> > Is the chip marked anyhow?
> I don't know. Haven't looked inside.

Photos / scans of the mainboard?

> > > As for gpio119 being used twice: It doesn't work if you don't, so it may be a case
> > > of TLMM multiplexing hpd for both ports.
> > What is the relationship between enable and HPD?
> 
> Yeah, good question. Actually HDMI hpd is wired to gpio126, and works
> without the enable pin. But no link training succeeds, no display coming up.
> With enable set on probe() this works. If you have the lane order right. The
> HDMI socket  is "above" the type-c ports on the TB16, compared to the T14s
> where it is "below" the type-c ports, so swapped lanes sounds reasonable.

Okay, I might be misunderstanding something. What do you mean here by
"gpio119 being used twice"?

> 
> [...]
> 

-- 
With best wishes
Dmitry