linux-kernel - Re: [PATCH 1/2] dt-bindings: pwm-backlight: Add pwm-delay-us property

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Date:   Wed, 28 Jun 2017 14:16:58 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Rob Herring <robh+dt@...nel.org>, Pavel Machek <pavel@....cz>,
        Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>
Cc:     linux-pwm@...r.kernel.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, groeck@...omium.org,
        huang lin <hl@...k-chips.com>
Subject: Re: [PATCH 1/2] dt-bindings: pwm-backlight: Add pwm-delay-us property

On 28/06/17 12:16, Enric Balletbo i Serra wrote:
> From: huang lin <hl@...k-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@...k-chips.com>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
>   Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> index 764db86..f75b08f 100644
> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> @@ -17,6 +17,9 @@ 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.

If is safe to assume power-on delay and power-off delay will be the same?

I've only took a quick look but several backlight controllers support 
asymetric power-on/off sequences...


Daniel.


>   
>   [0]: Documentation/devicetree/bindings/pwm/pwm.txt
>   [1]: Documentation/devicetree/bindings/gpio/gpio.txt
> @@ -32,4 +35,5 @@ Example:
>   
>   		power-supply = <&vdd_bl_reg>;
>   		enable-gpios = <&gpio 58 0>;
> +		pwm-delay-us = <10000>;
>   	};
>