Re: [PATCH v2 1/4] dt-bindings: pwm-backlight: add pwm-delay-us property
From: Pavel Machek
Date: Thu Jul 13 2017 - 03:40:09 EST
On Thu 2017-07-13 09:22:15, Enric Balletbo Serra wrote:
> 2017-07-06 20:23 GMT+02:00 Enric Balletbo Serra <eballetbo@xxxxxxxxx>:
> > Hi Rob,
> > 2017-07-06 19:07 GMT+02:00 Rob Herring <robh+dt@xxxxxxxxxx>:
> >> On Fri, Jun 30, 2017 at 6:21 AM, Enric Balletbo i Serra
> >> <enric.balletbo@xxxxxxxxxxxxx> wrote:
> >>> From: huang lin <hl@xxxxxxxxxxxxxx>
> >>> Add a pwm-delay-us property to specify the delay between setting an
> >>> initial (non-zero) PWM value and enabling the backlight, and also the
> >>> delay between disabling the backlight and setting PWM value to 0.
> >>> Signed-off-by: huang lin <hl@xxxxxxxxxxxxxx>
> >>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
> >>> ---
> >>> Changes since v1:
> >>> - As suggested by Daniel Thompson
> >>> - Do not assume power-on delay and power-off delay will be the same
> >>> v1: https://lkml.org/lkml/2017/6/28/219
> >>> 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 764db86..49b037e 100644
> >>> --- a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> >>> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.txt
> >>> @@ -17,6 +17,11 @@ Optional properties:
> >>> "pwms" property (see PWM binding)
> >>> - enable-gpios: contains a single GPIO specifier for the GPIO which enables
> >>> and disables the backlight (see GPIO binding)
> >>> + - pwm-delay-us: delay between setting an initial (non-zero) PWM value and
> >>> + enabling the backlight, and also the delay between disabling
> >>> + the backlight and setting PWM value to 0.
> >>> + The 1st cell is the pre-delay in micro seconds.
> >>> + The 2nd cell is the post-delay in micro seconds.
> >> pre and post imply a time before and after a certain event, but these
> >> are for 2 different events. These are more like an enable/on delay and
> >> disable/off delay which probably should be separate properties. What
> >> happens when we need the opposite sequence or a different sequence?
> >> Maybe some panel requires the PWM to be 0 until some time after
> >> enabling.
> A second proposal, what do you think?
> - post-pwm-on-delay-us: Delay in us after setting an initial (non-zero) PWM
> and enabling the backlight using GPIO.
This says "PWM on", "enable GPIO", "delay". Which is not what you
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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