linux-kernel - Re: [PATCH 2/2] backlight: pwm_bl: add configurable delay between re-enabling PWM and switching backlight power on

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20171027140307.x7mtgvy5py7l5nqf@rob-hp-laptop>
Date:   Fri, 27 Oct 2017 09:38:11 -0500
From:   Rob Herring <robh@...nel.org>
To:     Lothar Waßmann <LW@...O-electronics.de>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        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>,
        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 2/2] backlight: pwm_bl: add configurable delay between
 re-enabling PWM and switching backlight power on

On Thu, Oct 26, 2017 at 02:49:46PM +0200, Lothar Waßmann wrote:
> When switching the backlight on, the LCD may need some time to adjust
> to the configured PWM duty cycle. Add a configurable delay between
> configuring the PWM and enabling the backlight regulator to account
> for this.
> 
> Signed-off-by: Lothar Waßmann <LW@...O-electronics.de>
> ---
>  .../bindings/leds/backlight/pwm-backlight.txt      |  4 ++++
>  drivers/video/backlight/pwm_bl.c                   | 22 +++++++++++++++++++---
>  2 files changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> index 764db86..95594c3 100644
> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> @@ -17,6 +17,10 @@ Optional properties:
>                 "pwms" property (see PWM binding[0])
>    - enable-gpios: contains a single GPIO specifier for the GPIO which enables
>                    and disables the backlight (see GPIO binding[1])
> +  - turn-on-delay-ms: delay in milliseconds between configuring the PWM
> +		  and switching PWM on. This may be required to eliminate
> +		  flicker when switching the PWM on after it has been
> +		  disabled.

The subject talks about turning on the backlight regulator, but this 
only talks about the PWM.

>  
>  [0]: Documentation/devicetree/bindings/pwm/pwm.txt
>  [1]: Documentation/devicetree/bindings/gpio/gpio.txt