From nobody Sun Oct 5 18:12:35 2025 Received: from metis.whiteo.stw.pengutronix.de (metis.whiteo.stw.pengutronix.de [185.203.201.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C773A1E7C19 for ; Thu, 31 Jul 2025 08:47:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.203.201.7 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753951652; cv=none; b=h35arZWs2dNY+LRg/N4JH3iKC01v3NQndlryaxlKcOcdjWiOoGg/C+d9GKbxo6h0pLf1bTOt7gfM37PhU5tt/qsFtOn8urvJEXJQk5N2i10BTbfrGXYJ+Z5CXFYZa0c0GCDw9N+ZuLN9YkMQNMn9UY0K81gRsPg4owv6YV6j3oM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753951652; c=relaxed/simple; bh=bOmDtkbd0RHffi0gOqZgUXs/Axzd8xlgdMd6KON8a7Q=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=p3mU79B7t0MuJoOLfhCkS+GB/cSps6cXjmTqpwKif0syrAUrocF87PsgXSRnzwZ2YQdZtmHRVmPY5lhNjQUDCOY759qU104l7yPVl96WRaTS9sbZiR+UekmuXkaHy8G4ZvE+kXF5Ceqvb+ze0Mz98+3KHPI6lE2RIZN/QwJePAM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de; spf=pass smtp.mailfrom=pengutronix.de; arc=none smtp.client-ip=185.203.201.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=pengutronix.de Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1uhOwf-0007I2-K4; Thu, 31 Jul 2025 10:47:25 +0200 Received: from dude04.red.stw.pengutronix.de ([2a0a:edc0:0:1101:1d::ac]) by drehscheibe.grey.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1uhOwf-00BBL9-0K; Thu, 31 Jul 2025 10:47:25 +0200 Received: from localhost ([::1] helo=dude04.red.stw.pengutronix.de) by dude04.red.stw.pengutronix.de with esmtp (Exim 4.96) (envelope-from ) id 1uhOwf-00ENqd-05; Thu, 31 Jul 2025 10:47:25 +0200 From: Michael Grzeschik Date: Thu, 31 Jul 2025 10:47:18 +0200 Subject: [PATCH] backlight: pwm_bl: apply the initial backlight state with sane defaults Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250731-blpwm-v1-1-0171fd31bff9@pengutronix.de> X-B4-Tracking: v=1; b=H4sIAJUti2gC/x2MSQqAMBDAviJztmBd0PoV8dBl1IFapcUFxL87e EwIeSBhJEzQZw9EPCnRFhhknoFddJhRkGOGsiiboq2kMH6/VtGoDq12qrK1A26NTihM1MEuXIf De5Z7xInufz6M7/sBizVVlWwAAAA= To: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= , Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller Cc: Pengutronix , linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Grzeschik X-Mailer: b4 0.12.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2042; i=m.grzeschik@pengutronix.de; h=from:subject:message-id; bh=bOmDtkbd0RHffi0gOqZgUXs/Axzd8xlgdMd6KON8a7Q=; b=owEBbQKS/ZANAwAKAb9pWET5cfSrAcsmYgBoiy2c+7jsNb6oW5if001bv1SF04cbIfTveDwqA ZfjiWLs9MGJAjMEAAEKAB0WIQQV2+2Fpbqd6fvv0Gi/aVhE+XH0qwUCaIstnAAKCRC/aVhE+XH0 q6+LD/9G4mbLXal5Mo9BUyS72SWmZYnXX6CGHACo9HiLFRQbANW9bJZ2oYPp8n4oRljM2RxnkyY uQ3mPrdwE9FEkfAi3YyKM0Mob0T7Smci66r1iN0raJeaw8g6i6m7gWf4eRs4Tm0OsNlIxBMHk15 9HN3yx8AlShEwY73dSy9CGT8Kc03A+TwvLVep4ykNtkCoH5g9cji9ydU4bzB8Bl/NLGqs/bepmS RLxuhkQlgLQCk766Dlwafm11I6aez3Zc1g70WcHu+Fq+Qd2cE8T5HRMivBDLhfmT1yToRZNq/q+ m1qj0RKXlwva2E9TW/WZve8WVqemfJBPzCkws3tY21mumDA8Iz5NYaoBt/LBCa1epp6ProOjfBl WZ0LOXicoP+q8vtx9i4A0Nl/eiLXk/ptox2fV2ldQe5gktJ+d3FaydcbR+PyRUCRh+oAV+c7Ha7 LWb4rV+l42E8yF3CzqXbVggxZLys0m87b2BgCD1NuYX0xS1Y+YeOWzqVlHwgqNGZy+x38Bexpwe p1dsZXM8Vte16ZVjCNqkyjjbfOkwmmVHVJ2Qj+r/4S0HSW5Zzso9sC59dOeuknyNXcJ1L+tzaeq Cj3p/KLVrl8lXZjJHtcXI728PonvVXv8Vj2XZy+WrJfF+UtFl0t2sbLT7/BlXyznTp1x/LfryY9 vITN1nvyJzpWTkA== X-Developer-Key: i=m.grzeschik@pengutronix.de; a=openpgp; fpr=957BC452CE953D7EA60CF4FC0BE9E3157A1E2C64 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: m.grzeschik@pengutronix.de X-SA-Exim-Scanned: No (on metis.whiteo.stw.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Currently when calling pwm_apply_might_sleep in the probe routine the pwm will be configured with an not fully defined state. The duty_cycle is not yet set in that moment. There is a final backlight_update_status call that will have a properly setup state. However this change in the backlight can create a short flicker if the backlight was already preinitialised. We fix the flicker by moving the pwm_apply after the default duty_cycle can be calculated. Signed-off-by: Michael Grzeschik --- drivers/video/backlight/pwm_bl.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm= _bl.c index 237d3d3f3bb1a..5924e0b9f01e7 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -518,13 +518,6 @@ static int pwm_backlight_probe(struct platform_device = *pdev) if (!state.period && (data->pwm_period_ns > 0)) state.period =3D data->pwm_period_ns; =20 - ret =3D pwm_apply_might_sleep(pb->pwm, &state); - if (ret) { - dev_err_probe(&pdev->dev, ret, - "failed to apply initial PWM state"); - goto err_alloc; - } - memset(&props, 0, sizeof(struct backlight_properties)); =20 if (data->levels) { @@ -582,6 +575,15 @@ static int pwm_backlight_probe(struct platform_device = *pdev) pb->lth_brightness =3D data->lth_brightness * (div_u64(state.period, pb->scale)); =20 + state.duty_cycle =3D compute_duty_cycle(pb, data->dft_brightness, &state); + + ret =3D pwm_apply_might_sleep(pb->pwm, &state); + if (ret) { + dev_err_probe(&pdev->dev, ret, + "failed to apply initial PWM state"); + goto err_alloc; + } + props.type =3D BACKLIGHT_RAW; props.max_brightness =3D data->max_brightness; bl =3D backlight_device_register(dev_name(&pdev->dev), &pdev->dev, pb, --- base-commit: 739a6c93cc755c0daf3a7e57e018a8c61047cd90 change-id: 20250731-blpwm-598ecad93c4d Best regards, --=20 Michael Grzeschik