Re: [PATCH 2/2] backlight: pwm_bl: add configurable delay between re-enabling PWM and switching backlight power on
From: Lee Jones
Date: Mon Oct 30 2017 - 06:33:53 EST
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?
> > [0]: Documentation/devicetree/bindings/pwm/pwm.txt
> > [1]: Documentation/devicetree/bindings/gpio/gpio.txt
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org â Open source software for ARM SoCs
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