linux-kernel - Re: [PATCH v6 1/2] arm64: dts: qcom: x1e78100-t14s: add hpd gpio to dp controller

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Message-ID: <aJ325wUrBjydnc1m@linaro.org>
Date: Thu, 14 Aug 2025 16:47:25 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Neil Armstrong <neil.armstrong@...aro.org>,
	Christopher Obbard <christopher.obbard@...aro.org>
Cc: Johan Hovold <johan@...nel.org>,
	Douglas Anderson <dianders@...omium.org>,
	Jessica Zhang <quic_jesszhan@...cinc.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	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>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	Rui Miguel Silva <rui.silva@...aro.org>,
	Abel Vesa <abel.vesa@...aro.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v6 1/2] arm64: dts: qcom: x1e78100-t14s: add hpd gpio to
 dp controller

On Thu, Aug 14, 2025 at 04:21:09PM +0200, Neil Armstrong wrote:
> On 09/08/2025 00:28, Christopher Obbard wrote:
> > On Mon, 4 Aug 2025 at 14:13, Johan Hovold <johan@...nel.org> wrote:
> > > 
> > > On Thu, Jul 31, 2025 at 09:51:26PM +0100, Christopher Obbard wrote:
> > > > The eDP controller has an HPD GPIO. Describe it in the device tree
> > > > for the generic T14s model, as the HPD GPIO is used in both the
> > > > OLED and LCD models which inherit this device tree.
> > > 
> > > > @@ -5779,6 +5779,11 @@ tlmm: pinctrl@...0000 {
> > > >                        gpio-ranges = <&tlmm 0 0 239>;
> > > >                        wakeup-parent = <&pdc>;
> > > > 
> > > > +                     edp_hpd_active: edp-hpd-active-state {
> > > 
> > > The node name and label needs an index as this SoC has two edp hpd pins
> > > as I already pointed out.
> > 
> > Sure. After looking at the schematics this should be called
> > edp0_hpd_active. I will fix this in the next revision.
> > 
> > 
> > > > +                             pins = "gpio119";
> > > > +                             function = "edp0_hot";
> > > 
> > > And you also need to configure the bias somewhere as you should not rely
> > > on the firmware having configured things for you (as I also pointed out
> > > before).
> > > 
> > > On my T14s the internal pull-up has been disabled.
> > 
> > I am still unsure of what else needs to be set here. Can you help me
> > with the correct settings?
> 
> Just add bias-disable;
> 

I sent a patch fixing this for all the X1 devices upstream earlier [1],
so you could also just send v7 with just the second patch of your
series.

The bias-disable is really somewhat device-specific (what if there is no
pull down on the device side and someone disconnects the panel
entirely?), so I put it into each board DT separately like Johan
requested on v5. We have the same for the PCIe pinctrl.

Thanks,
Stephan

[1]: https://lore.kernel.org/linux-arm-msm/20250814-x1e80100-add-edp-hpd-v1-0-a52804db53f6@linaro.org/T/