[PATCH] drm/panel: Avoid warnings w/ panel-simple/panel-edp at shutdown

[Linus Walleij]

On Fri, Jun 21, 2024 at 10:45 PM Douglas Anderson <dianders at chromium.org> wrote:

> At shutdown if you've got a _properly_ coded DRM modeset driver then
> you'll get these two warnings at shutdown time:
>
>   Skipping disable of already disabled panel
>   Skipping unprepare of already unprepared panel
>
> These warnings are ugly and sound concerning, but they're actually a
> sign of a properly working system. That's not great.
>
> We're not ready to get rid of the calls to drm_panel_disable() and
> drm_panel_unprepare() because we're not 100% convinced that all DRM
> modeset drivers are properly calling drm_atomic_helper_shutdown() or
> drm_helper_force_disable_all() at the right times. However, having the
> warning show up for correctly working systems is bad.
>
> As a bit of a workaround, add some "if" tests to try to avoid the
> warning on correctly working systems. Also add some comments and
> update the TODO items in the hopes that future developers won't be too
> confused by what's going on here.
>
> Suggested-by: Daniel Vetter <daniel at ffwll.ch>
> Signed-off-by: Douglas Anderson <dianders at chromium.org>

Reviewed-by: Linus Walleij <linus.walleij at linaro.org>

This is the right thing to do.

Yours,
Linus Walleij