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[2001:4dd6:393b:ff:f59e:4402:63f8:7ff5]) by smtp.gmail.com with ESMTPSA id e6-20020a5d5306000000b003110ab70a4fsm2341094wrv.83.2023.06.14.12.08.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jun 2023 12:08:58 -0700 (PDT) From: Maximilian Weigand Subject: [PATCH 0/3] backlight: lm3630a: add functionality to change boost converter frequency Date: Wed, 14 Jun 2023 21:08:51 +0200 Message-Id: <20230602-lm3630a_boost_frequency-v1-0-076472036d1a@mweigand.net> MIME-Version: 1.0 X-B4-Tracking: v=1; b=H4sIAEMQimQC/x2N0QrCMAwAf2Xk2UJtWWX+ishIa+YCrtVkE2Xs3 +18PI7jVlASJoVzs4LQm5VLrnA8NJBGzHcyfKsMzjpvg3XmMfngLfaxFJ37Qei1UE5fE5G60AZ Kp7aDWkdUMlEwp3HvJ9SZZBdPoYE//+Xlum0/AtvEh4IAAAA= To: Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Pavel Machek , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Heiko Stuebner Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, Maximilian Weigand X-Mailer: b4 0.12.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1686769738; l=2088; i=mweigand@mweigand.net; s=20230601; h=from:subject:message-id; bh=EEQE3qlxnzvPdxyG2oGt17X4etiM2QkOKRdSulvTDt8=; b=QDW3TR3W/883zra37WNEzh+EauPKNzzRyQ0jUD+mJkih625wuoYVOam6dW69idKvEE8TnOpGi voO1JiSbRG6CGLieSDFKFKTLpGGwPABCsKlTwIlwrEUtY7qvyzobyJx X-Developer-Key: i=mweigand@mweigand.net; a=ed25519; pk=Tjuj6PXmCCxzGTRw+9suZuZ41q/etgDHrIbPdkAaTpM= Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org For certain brightness settings the Pine64 PineNote exhibits quite visible flickering of the led backlights, leading to an unpleasant user experience. It is understood that flickering is caused by certain power line ripples interacting with the led driver, inherent to the specific hardware. The lm3630a led driver is able to change the boost converter switching frequency. Among other things, changing the boost frequency can also greatly improve visible flickering issues. This patchset enables dts control of two frequency modifications that the hardware is capable of: Switch from a base frequency of 500 kHz to 1 MHz, and activate a frequency shift to 560 kHz or 1.12 MHz, respectively. As flickering characteristics are mainly hardware dependent, this should warrant the inclusion of two dts entries for the lm3630a led driver to control the boost frequency of the chip on a per-device basis. Changes were tested on a Pine64 PineNote. The following brightness settings were found to exhibit serious flickering without either the frequency shift or the higher boost frequency: echo 186 > /sys/class/backlight/backlight_warm/brightness echo 255 > /sys/class/backlight/backlight_cool/brightness Signed-off-by: Maximilian Weigand --- Maximilian Weigand (3): backlight: lm3630a: add support for changing the boost frequency dt-bindings: backlight: lm3630a: add entries to control boost frequency arm64: dts: rockchip: shift boost frequency for rk3566-pinenote backlight .../bindings/leds/backlight/lm3630a-backlight.yaml | 12 ++++++++++++ arch/arm64/boot/dts/rockchip/rk3566-pinenote.dtsi | 1 + drivers/video/backlight/lm3630a_bl.c | 9 ++++++++- include/linux/platform_data/lm3630a_bl.h | 5 +++++ 4 files changed, 26 insertions(+), 1 deletion(-) --- base-commit: 858fd168a95c5b9669aac8db6c14a9aeab446375 change-id: 20230602-lm3630a_boost_frequency-bae9656ec759 Best regards,