Hi, On Tue, 7 Nov 2017 18:46:18 -0600 Rob Herring wrote: > 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 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@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. > The text should better read: + - turn-on-delay-ms: delay in milliseconds between configuring the PWM + and switching the backlight regulator on. This may be + required to eliminate flicker when switching the backlight + on after it had been disabled. Lothar Waßmann
