Hi,

On Mon, Jul 29, 2019 at 03:55:23PM +0200, Pavel Machek wrote:
> > Oh and the new backlight module comes up blanked right now so it
> > needs to be manually enabled via sysfs.
>
> Or you can enable ledtrig-backlight and apply this.
>
> (I know, we need better solution).

https://lore.kernel.org/lkml/20190717141514.21171-1-jjhiblot@ti.com/

The above patchset is the proper solution. It is a backlight
driver, which takes the LED driver as input and exposes a
proper backlight device. This makes it possible to reference
the backlight in DT:

----------------
led-node {
    blabla;
};

backlight-node {
    blabla;
    led = <&led-node>;
};

panel-node {
    backlight = <&backlight-node>;
};
----------------

That way the kernel has a known link between the LCD panel and the
backlight and eveything should work smoothly :) I suggest to wait
for it to land and carry any Droid 4 specific hacks downstream until
that happens. This will also remove the bogus DSI backlight from sysfs.
Without the backlight reference the panel driver assumes, that native
DSI backlight is used.

-- Sebastian