Re: [PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us property

From: Pavel Machek <pavel@ucw.cz>
To: Enric Balletbo i Serra
	<enric.balletbo-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>
Cc: linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Daniel Thompson
	<daniel.thompson-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>,
	Bartlomiej Zolnierkiewicz
	<b.zolnierkie-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
	Jingoo Han <jingoohan1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	Thierry Reding
	<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Richard Purdie <rpurdie-Fm38FmjxZ/leoWH0uzbU5w@public.gmane.org>,
	Jacek Anaszewski
	<jacek.anaszewski-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	groeck-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org,
	Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	huang lin <hl-TNX95d0MmH7DzftRWevZcw@public.gmane.org>
Subject: Re: [PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us property
Date: Fri, 30 Jun 2017 11:25:05 +0000	[thread overview]
Message-ID: <20170630112505.GA18448@amd> (raw)
In-Reply-To: <20170630112109.13785-1-enric.balletbo-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>

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On Fri 2017-06-30 13:21:06, Enric Balletbo i Serra wrote:
> From: huang lin <hl@rock-chips.com>
> 
> Add a pwm-delay-us property to specify the delay between setting an
> initial (non-zero) PWM value and enabling the backlight, and also the
> delay between disabling the backlight and setting PWM value to 0.
> 
> Signed-off-by: huang lin <hl@rock-chips.com>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> ---
> Changes since v1:
>  - As suggested by Daniel Thompson
>    - Do not assume power-on delay and power-off delay will be the same
> 
> v1: https://lkml.org/lkml/2017/6/28/219
> 
>  Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> index 764db86..49b037e 100644
> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> @@ -17,6 +17,11 @@ 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])
> +  - pwm-delay-us: delay between setting an initial (non-zero) PWM value and
> +                  enabling the backlight, and also the delay between disabling
> +                  the backlight and setting PWM value to 0.

"Hardware needs a delay between setting an initial (non-zero) PWM and
enabling the backlight using GPIO. The 1st cell specifies this delay
in micro seconds. Hardware also needs a delay between disabing the
backlight using GPIO and setting PWM value to 0. The 2nd cell is this
delay in micro seconds."

Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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