AW: drm/panel: panel-simple power-off sequencing

[Jonas Mark (BT-FS/ENG1-GRB)]

Hi Doug,

> > I guess, in summary, I'm hoping you'll look again and find that this
> > really is a backlight enable. If not, I'd probably advocate for a
> > per-panel boolean.
> 
> Circling back, I'm curious what ended up happening here. Did you
> decide that it actually was a backlight enable GPIO, or are you
> planning on sending a patch?

Thank you for coming back to this topic.

We agree that linking the enable signal of "old school" parallel panels with the enable of the backlight would work. We tested it and it works with our panels.

Yet, we are not convinced that the backlight is part of the panel. And thus, architecturally, this should be kept separate. For us, a display is the combination of a backlight and a panel.

For adding support of the kind of enable signal required for our "old school" parallel panels into panel-simple we see the following possibilities:

- Add another GPIO with a tight coupling to the prepare and unprepare state.
- Add a flag which signals to prepare/ unprepare to handle the existing GPIO synchronously.

But we are not convinced that this is in the spirit of a panel *simple*. Short-term we will now create our own panel driver which will support our parallel panels. Mid-term we would like to revisit the topic and hopefully come up with a patch for panel-simple.

Cheers,
Mark