Messages in this thread | | | Date | Mon, 29 May 2017 09:41:17 +0200 | From | Maxime Ripard <> | Subject | Re: [PATCH 3/3] ARM: sun8i: v3s: add backlight device node for Lichee Pi Zero LCD |
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Hi,
On Wed, May 24, 2017 at 08:13:20PM +0800, Icenowy Zheng wrote: > The 40-pin LCD connector on Lichee Pi Zero has backlight pins, which is > controlled by the PWM0 controller of the V3s SoC, and the controlling > part is on the board. > > Add the PWM and backlight device nodes in the device tree file, but > leave them disabled, as they can only be useful when the LCD is > attached. The LCD device tree overlay files can enable these controllers > and make use of them. > > Signed-off-by: Icenowy Zheng <icenowy@aosc.io> > --- > arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts b/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts > index 387fc2aa546d..e0721bf725d1 100644 > --- a/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts > +++ b/arch/arm/boot/dts/sun8i-v3s-licheepi-zero.dts > @@ -52,6 +52,14 @@ > serial0 = &uart0; > }; > > + backlight: backlight { > + compatible = "pwm-backlight"; > + pwms = <&pwm 0 50000 0>; > + brightness-levels = <0 10 20 30 40 50 60 70 80 90 100>;
This is unlikely, the perceived brightness by the human eye is not linear, and is actually much closer to a logarithmic function, which means you should have use an exponential function here in order to appear that your brightness increase is linear.
Maxime
-- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com [unhandled content-type:application/pgp-signature] | |