etnaviv: fbdev kms and eglfs issue

[Christoph Fritz]

On Fri, 2018-01-12 at 14:13 +0100, Lucas Stach wrote:
> Hi Christoph,
> 
> Am Freitag, den 12.01.2018, 12:09 +0100 schrieb Christoph Fritz:
> > Hi,
> > 
> >  while using CONFIG_DRM_ETNAVIV in conjunction with
> > CONFIG_DRM_FBDEV_EMULATION eglfs programs like qt5-opengles2-test can
> > fail to display any content so that the screen just stays black.
> > 
> > To get to this point, gstreamer with kms sink has to be executed
> > before:
> > 
> >  1. boot system
> >  2. $ qt5-opengles2-test
> >     -> works and displays fine
> >  3. $ gst-launch-1.0 filesrc location=/home/test.webm ! decodebin ! \
> >       videoconvert ! kmssink connector-id=41 name=imx-drm sync=0
> >     -> works and displays fine
> 
> This is a wild guess, but maybe the overlay plane used by kmssink isn't
> getting disabled properly when fbdev emulation takes over the display
> again.

It really looks that way, setting gstreamer's kmssink option
force-modesetting=1 disables overlay usage and bypasses this issue.

Any hints how to debug this further?

By the way (and I'm pretty sure this isn't the right place to ask :) ...
What's here the best gstreamer sink for qt to play hw accelerated
videos?

thanks
  -- Christoph