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Mon, 31 Mar 2025 08:39:46 -0700 (PDT) Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250327-wip-obbardc-qcom-t14s-oled-panel-v3-0-45d5f2747398@linaro.org> <20250327-wip-obbardc-qcom-t14s-oled-panel-v3-1-45d5f2747398@linaro.org> In-Reply-To: From: Christopher Obbard Date: Mon, 31 Mar 2025 17:39:35 +0200 X-Gm-Features: AQ5f1JoEit7j_TzMlyZa7QbfN6E0NDm9GuAOKbUqEfVJoM1pbPZfw3UrD5vfGmY Message-ID: Subject: Re: [PATCH v3 1/2] arm64: dts: qcom: x1e78100-t14s: add hpd gpio to eDP panel To: Johan Hovold Cc: Douglas Anderson , Neil Armstrong , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Dmitry Baryshkov , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, Rui Miguel Silva , Abel Vesa , devicetree@vger.kernel.org, "Bryan O'Donoghue" Content-Type: text/plain; charset="UTF-8" Hi Johan, On Mon, 31 Mar 2025 at 09:50, Johan Hovold wrote: > > On Thu, Mar 27, 2025 at 04:56:53PM +0000, Christopher Obbard wrote: > > The eDP panel has an HPD GPIO. Describe it in the device tree > > for the generic T14s model, as the HPD GPIO property is used in > > both the OLED and LCD models which inherit this device tree. > > AFAICT, this patch is not correct as the hotplug detect signal is > connected directly to the display controller on (these) Qualcomm SoCs > and is already handled by its driver. > > Describing it as you do here leads to less accurate delays, see commits: > > 2327b13d6c47 ("drm/panel-edp: Take advantage of wait_hpd_asserted() in struct drm_dp_aux"). > 3b5765df375c ("drm/panel: atna33xc20: Take advantage of wait_hpd_asserted() in struct drm_dp_aux") > > Perhaps you lose some other functionality too. > > > Reviewed-by: Bryan O'Donoghue > > Signed-off-by: Christopher Obbard > > --- > > arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi | 11 +++++++++++ > > 1 file changed, 11 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 962fb050c55c4fd33f480a21a8c47a484d0c82b8..46c73f5c039ed982b553636cf8c4237a20ba7687 100644 > > --- a/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi > > +++ b/arch/arm64/boot/dts/qcom/x1e78100-lenovo-thinkpad-t14s.dtsi > > @@ -980,8 +980,12 @@ &mdss_dp3 { > > aux-bus { > > panel: panel { > > compatible = "edp-panel"; > > + hpd-gpios = <&tlmm 119 GPIO_ACTIVE_HIGH>; > > power-supply = <&vreg_edp_3p3>; > > > > + pinctrl-0 = <&edp_hpd_n_default>; > > + pinctrl-names = "default"; > > + > > port { > > edp_panel_in: endpoint { > > remote-endpoint = <&mdss_dp3_out>; > > @@ -1286,6 +1290,13 @@ hall_int_n_default: hall-int-n-state { > > bias-disable; > > }; > > > > + edp_hpd_n_default: edp-hpd-n-state { > > + pins = "gpio119"; > > + function = "gpio"; > > + drive-strength = <2>; > > + bias-pull-up; > > + }; > > I checked the firmware configuration for this pin on my T14s, which > does not match what you have here. Instead the function is set to > "edp0_hot" which forwards the signal to the display controller which > already handles the signal on panel power on. (And there is also no > internal pull up enabled). > > We may want to describe this pin configuration somewhere, but that's a > separate issue. Thanks for your review, I will send another version in coming days and drop this first patch (adding hpd to the T14s DTSI). As a consequence I will need to add no-hpd property to the panel node. I will add a short comment about how the hpd signal is handled by the driver already. Thanks! Chris