linux-kernel - Re: [PATCH 0/2] backlight: pwm_bl: prevent backlight flicker when switching PWM on

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Message-ID: <20171114085616.3dfe6f03@karo-electronics.de>
Date:   Tue, 14 Nov 2017 08:56:16 +0100
From:   Lothar Waßmann <LW@...O-electronics.de>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Daniel Thompson <daniel.thompson@...aro.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Jingoo Han <jingoohan1@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Pavel Machek <pavel@....cz>,
        Richard Purdie <rpurdie@...ys.net>,
        Rob Herring <robh+dt@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        devicetree@...r.kernel.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org,
        linux-pwm@...r.kernel.org
Subject: Re: [PATCH 0/2] backlight: pwm_bl: prevent backlight flicker when
 switching PWM on

Hi,

On Fri, 10 Nov 2017 12:22:15 +0100 Enric Balletbo i Serra wrote:
> Hi all,
> 
> On 08/11/17 11:48, Daniel Thompson wrote:
> > On 26/10/17 13:49, Lothar Waßmann wrote:
> >> These patches implement some measures to prevent backlight flicker
> >> when the backlight is being switched on for a display with an active
> >> low brightness control pin.
> >> GIT: [PATCH 1/2] backlight: pwm_bl: Enable PWM before switching regulator
> >> GIT: [PATCH 2/2] backlight: pwm_bl: add configurable delay between
> > 
> > Other than hoisting the pwm_enable() even earlier in the setup sequence this
> > patchset seems to have a significant overlap with Enric's recent posting:
> > 
> >   https://lkml.org/lkml/2017/7/21/211
> > 
> > Any chance of a shared view on this, especially on the DT bindings?
> > 
> 
> The DT binding were discussed some time ago for the patch series I sent, though
> there isn't a final ack from DT maintainer.
> 
> Lothar, the series I sent have been reviewed and acked, can you test if the
> series fixes the problem for you too?
> 
I'll try to test it within the next couple of days and will report back.


Lothar Waßmann