[Letux-kernel] backlight woes

[Andreas Kemnade]

On Thu, 21 Mar 2019 22:15:59 +0100
Andreas Kemnade <andreas at kemnade.info> wrote:

> Hi,
> 
> I finally debugged a bit more the backlight thing.
> What fails:
> 
> drivers/video/backlight/pwm_bl.c
> static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb)
> ...
> /* The PWM is disabled, keep it like this */
>    if (!pwm_is_enabled(pb->pwm))
>         return FB_BLANK_POWERDOWN;
> 
> 
> That sets power state to 4 initially.
> If we have
> drm/omap: panel-tpo-td028ttec1: add backlight support
> in, it will be enabled later on.
> 
> So the interesting thing is whether the whole thing can be considered
> a regression and that panel patch the solution...
> So we could have some arguments to bring it into 5.1.
> Next question: why does this pwm_is_enabled fail.
> Maybe the problem was already there is 5.0...
> 

5.0.2+5.1-rc1 dt = trouble
5.0.2+5.0.2 dt = ok

both mainline, dtb binaries are different.

Regards,
Andreas