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

[Rob Herring]

On Mon, Oct 30, 2017 at 5:33 AM, Lee Jones <lee.jones@xxxxxxxxxx> wrote:
> On Fri, 27 Oct 2017, Rob Herring wrote:
>
>> On Thu, Oct 26, 2017 at 02:49:46PM +0200, Lothar WaÃmann 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 WaÃmann <LW@xxxxxxxxxxxxxxxxxxx>
>> > ---
>> >  .../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.
>
> From my understanding "switching PWM on" == enabling the regulator.
>
> I don't see any disparity here.  Or am I missing something?

The delay is from (re-)enabling the PWM (turning it on) to switching
backlight power on. That sounds like 2 different things to me.

Rob