| Message ID | 20170524121320.4171-3-icenowy@aosc.io (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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
On Mon, May 29, 2017 at 3:41 PM, Maxime Ripard <maxime.ripard@free-electrons.com> wrote: > 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. I think the backlight is a functional part of the panel. It probably belongs in the panel's overlay. ChenYu
On Mon, May 29, 2017 at 04:16:51PM +0800, Chen-Yu Tsai wrote: > On Mon, May 29, 2017 at 3:41 PM, Maxime Ripard > <maxime.ripard@free-electrons.com> wrote: > > 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. > > I think the backlight is a functional part of the panel. It probably > belongs in the panel's overlay. Yeah, that's also true. Maxime
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>; + default-brightness-level = <8>; + status = "disabled"; + }; + chosen { stdout-path = "serial0:115200n8"; }; @@ -86,6 +94,12 @@ status = "okay"; }; +&pwm { + pinctrl-0 = <&pwm0_pins>; + pinctrl-names = "default"; + status = "disabled"; +}; + &uart0 { pinctrl-0 = <&uart0_pins_a>; pinctrl-names = "default";
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(+)