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[2a01:cb08:52d:7400:bbd7:ca83:de4a:f625]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49033dab0besm74323395e9.15.2026.05.21.10.57.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 May 2026 10:57:37 -0700 (PDT) Message-ID: <9eddfa15-ec2e-4d3c-8d55-2be5a974866f@gmail.com> Date: Thu, 21 May 2026 19:57:36 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 02/11] arm64: dts: qcom: sc8280xp-arcata: Enable backlight To: Konrad Dybcio , Douglas Anderson , Neil Armstrong , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , Conor Dooley Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, Krzysztof Kozlowski References: <20260520-surface-sp9-5g-for-next-v1-0-9df52552bf87@gmail.com> <20260520-surface-sp9-5g-for-next-v1-2-9df52552bf87@gmail.com> <624a780c-0b22-45e3-aec5-e61c319de901@oss.qualcomm.com> Content-Language: en-US From: =?UTF-8?Q?J=C3=A9r=C3=B4me_de_Bretagne?= In-Reply-To: <624a780c-0b22-45e3-aec5-e61c319de901@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/21/26 10:48, Konrad Dybcio wrote: > On 5/21/26 12:26 AM, Jérôme de Bretagne wrote: >> On 5/20/26 18:40, Jérôme de Bretagne via B4 Relay wrote: >>> From: Jérôme de Bretagne >>> >>> Add backlight nodes and enable backlight so that it can be controlled >>> with the corresponding buttons found on Surface Pro Type Cover keyboards. >>> >>> The nodes are almost identical to the ones from the ThinkPad X13s with >>> a different enable GPIO for the vreg_edp_bl node. >>> >>> The difference was found by looking at the output of /sys/kernel/debug/gpio >>> on the ThinkPad X13s to see the properties of its enable gpio9: > > [...] > >> and ... backlight still works! It can also be enabled/disabled with: >>    /sys/class/backlight/backlight/bl_power >> as expected. >> >> I have no clue why both gpio6 on pmc8280_2 and gpio6 on pmc8280c can enable and disable the backlight. Is it a common scenario? > > Could it be that one of them is an ENABLE_BL pin, while the other one > enables the regulator? > > Konrad I've looked at more device trees and seen that quite a few of them simply don't have a "power-supply = <&vreg_edp_bl>" property in their backlight node. Trying a similar approach, the backlight still works so the gpio6 I was adding wasn't used (or even useful). I will send a simpler patch in v2, removing the power-supply property and the vreg_edp_bl & edp_bl_reg_en nodes. Jérôme