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Date: Thu, 30 Oct 2025 11:51:07 +0000
From: Daniel Thompson <danielt@kernel.org>
To: Michael Grzeschik <m.grzeschik@pengutronix.de>
Cc: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= <ukleinek@kernel.org>,
	Lee Jones <lee@kernel.org>, Jingoo Han <jingoohan1@gmail.com>,
	Helge Deller <deller@gmx.de>, Pengutronix <kernel@pengutronix.de>,
	linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] backlight: pwm_bl: apply the initial backlight state
 with sane defaults
Message-ID: <aQNRK5ksNDMMve0x@aspen.lan>
References: <20250731-blpwm-v1-1-0171fd31bff9@pengutronix.de>
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In-Reply-To: <20250731-blpwm-v1-1-0171fd31bff9@pengutronix.de>

On Thu, Jul 31, 2025 at 10:47:18AM +0200, Michael Grzeschik wrote:
> 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 <m.grzeschik@pengutronix.de>

Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>


Daniel.