[PATCH V9 23/24] arm64: dts: allwinner: rg35xx: Add GPIO backlight control

[Chris Morgan]

On Fri, May 09, 2025 at 03:32:04PM +0100, Andre Przywara wrote:
> On Wed,  7 May 2025 15:19:42 -0500
> Chris Morgan <macroalpha82 at gmail.com> wrote:
> 
> Hi Chris,
> 
> > From: Chris Morgan <macromorgan at hotmail.com>
> > 
> > The LCD backlight for this device can be exposed as a simple GPIO-
> > controlled device. It would be more accurately modelled using PWM to
> > enable brightness control, however the PWM driver design for the H616 is
> > not yet upstreamed.
> 
> I don't think this is right then: First there should be no notion of a
> "driver being upstreamed" in a *DT* patch, as "the driver" is a Linux
> speciality, which the DT itself doesn't care about.
> And secondly we should not chicken out and go with an interim solution.
> 
> So I guess we need to wait for the PWM binding to appear.
> 
> Cheers,
> Andre

Okay, so then I can drop the backlight (and might as well drop the
LCD bindings as well) until the PWM is upstreamed. I just figured
"something" for now is okay, but we can wait.

This is the specific series I'm tracking [1]... adding support for the
H616 would just require a little bit of boilerplate code and a new
compatible string once that gets upstreamed.

[1] https://lore.kernel.org/linux-sunxi/20250427142500.151925-3-privatesub2@gmail.com/

Thank you,
Chris

> 
> > Add a GPIO backlight node to the DTS.
> > 
> > Signed-off-by: Ryan Walklin <ryan at testtoast.com>
> > Signed-off-by: Chris Morgan <macromorgan at hotmail.com>
> > ---
> >  .../boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts b/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts
> > index 7e17ca07892d..95f2ae04bd95 100644
> > --- a/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts
> > +++ b/arch/arm64/boot/dts/allwinner/sun50i-h700-anbernic-rg35xx-2024.dts
> > @@ -21,6 +21,12 @@ aliases {
> >  		serial0 = &uart0;
> >  	};
> >  
> > +	backlight: backlight {
> > +		compatible = "gpio-backlight";
> > +		gpios = <&pio 3 28 GPIO_ACTIVE_HIGH>; // PD28
> > +		default-on;
> > +	};
> > +
> >  	battery: battery {
> >  		compatible = "simple-battery";
> >  		constant-charge-current-max-microamp = <1024000>;
>