# Re: \[PATCH v6 2/5\] dt-bindings: pwm-backlight: add PWM delay proprieties.

- From: Daniel Thompson \<hidden\>
- Date: 2018-03-26 15:07:15 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2018/03/5243465
- Thread: https://ratatoskr.run/linux-pwm/2018/03/5243290/t.md

```text
On Mon, Mar 26, 2018 at 11:52:10AM +0200, Enric Balletbo i Serra wrote:
> Hardware needs a delay between setting an initial (non-zero) PWM and
> enabling the backlight using GPIO. The post-pwm-on-delay-ms specifies
> this delay in milli seconds. Hardware also needs a delay between disabing
> the backlight using GPIO and setting PWM value to 0. The pwm-off-delay-ms
> is this delay in milli seconds.
> 
> Signed-off-by: Enric Balletbo i Serra <redacted>
> Acked-by: Pavel Machek <redacted>
> Acked-by: Thierry Reding <redacted>

Acked-by: Daniel Thompson <redacted>

> ---
> Based on the original Huang Lin [ref] work.
> Changes since v5:
>  - Add Acked-by: Thierry Reding [ref]
>  - CC DT mainling list (for some reason dropped at some point, my
>    fault)
> Changes since v4:
>  - Rebase on top of mainline.
> Changes since v3:
>  - Replace us for ms.
>  - Add Acked-by: Pavel Machek [ref]
> Changes since v2:
>  - Use separate properties (Rob Herring)
> Changes since v1:
>  - As suggested by Daniel Thompson
>    - Do not assume power-on delay and power-off delay will be the same
> ---
>  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 764db86d441a..310810906613 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])
> +  - post-pwm-on-delay-ms: Delay in ms between setting an initial (non-zero) PWM
> +                          and enabling the backlight using GPIO.
> +  - pwm-off-delay-ms: Delay in ms between disabling the backlight using GPIO
> +                      and setting PWM value to 0.
>  
>  [0]: Documentation/devicetree/bindings/pwm/pwm.txt
>  [1]: Documentation/devicetree/bindings/gpio/gpio.txt
> @@ -32,4 +36,6 @@ Example:
>  
>  		power-supply = <&vdd_bl_reg>;
>  		enable-gpios = <&gpio 58 0>;
> +		post-pwm-on-delay-ms = <10>;
> +		pwm-off-delay-ms = <10>;
>  	};
> -- 
> 2.16.2
> 
```