> I'm confused. Why would you want to call into pwm_bl directly? If we're
> going to split this up into separate platform devices, why not look up a
> given backlight device and use the backlight API on that? The pieces of
> the puzzle are all there: you can use of_find_backlight_by_node() to
> obtain a backlight device from a device tree node, so I'd expect the DT
> to look something like this:
>
> backlight: backlight {
> compatible = "pwm-backlight";
> ...
> };
This would still prevent any power control from the backlight driver. I.e. if
someone sets the brightness to 0 through sysfs, we cannot power the backlight
off as pwm-backlight cannot control more than the PWM without platform
callbacks. Backlight could only be powered off as a result of a fb blank event.
> panel: panel {
> compatible = "...";
> ...
> backlight = <&backlight>;
> ...
> };
So all the power control of both the panel and backlight would be performed
from this device's driver. How would it plug into tegra-drm? I would see
tegra_panel as a new member of the tegra_output structure, with one callback
invoked from tegra_encoder_dpms(). Does that look sane?
> After that you can wire it up with host1x using something like:
>
> host1x {
> dc@54200000 {
> rgb {
> status = "okay";
>
> nvidia,panel = <&panel>;
> };
> };
> };
Indeed. So if we do that, the DRM DPMS functions would take care of the
panel/backlight powering and the backlight driver will control the PWM after
this, through the FB notifier. This is a little bit different from the
"official"
power sequence, but I just tested controlling the PWM at the very end of the
sequence and it works just as well. If you think this looks better I don't
mind doing it that way, it is actually a good excuse for me to dive into the
DRM code.
Anyway, this will only be a temporary solution, CDF is the only way to do this
right.
Alex.
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