etnaviv: fbdev kms and eglfs issue

[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
 4. $ qt5-opengles2-test
    -> FAILS to display any content (but starts and runs fine)

Is this a known issue?

Disabling CONFIG_DRM_FBDEV_EMULATION bypasses this issue.

Any ideas?

Thanks
  -- Christoph