Re: [PATCH 2/2] backlight: pwm_bl: add configurable delay between re-enabling PWM and switching back

[Rob Herring <robh@kernel.org>]

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@KARO-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