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Mon, 31 Mar 2025 14:38:50 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@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 23:38:39 +0200 X-Gm-Features: AQ5f1JqS7_0iOlATZpsQl1aZ_ovAj_zC9EkVcEt6c_OLO56CTepuvb55ZRJsI1s Message-ID: Subject: Re: [PATCH v3 1/2] arm64: dts: qcom: x1e78100-t14s: add hpd gpio to eDP panel To: Dmitry Baryshkov Cc: Johan Hovold , 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 , 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 Dmitry, On Mon, 31 Mar 2025 at 17:49, Dmitry Baryshkov wrote: > > On 31/03/2025 18:39, Christopher Obbard wrote: > > 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. > No, you won't. There is a HPD line and it is routed to the DP controller. OK, I think I misunderstand what Johan said. After taking some time to think about it in more detail: - The first commit will be changed so that the hpd GPIO will be added to the X1E DP controller instead of the panel. grepping the source for dp_hot_plug_det shows me how to do that. This part is clear. - The panel node in the generic T14s DTSI should not have the hpd-gpios property / pinctrl set. - The panel node should not have the hpd-gpios property / pinctrl set. I hope I understand that correctly. I will send a new series in the morning unless there is any objection. Thanks Chris