Summary: black screen after starting Xorg
- System boots fine, loads i915 and switches to display native resolutio but when X starts it shows only black screen on connected HDMI display
- Xorg UI works, screenshot taken using xwd utility shows proper application UI
- drm status of attached display is "connected", EDID is valid
- xrandr output looks normal: HDMI port status, modes, and active mode look correct
- Switching to console using "Ctrl-Alt-Fn" works, login prompt is present and screen displays typed characters
- Switching back to Xorg displays static snapshot of Xorg UI. Our app runs progress animation, the snapshot displays one frame from this animation.
- Swtiching to console again and switching back fixes the problem and get Xorg into working state
- Changing mode (i.e. from 1080 to 4k) using xrandr also fixes the problem
- dmesg does not have any WARN messages or any other traces of kernel problems
- System is booted with "quiet splash" kernel parameters
Note: This problem is intermittent, our platform is Linux 4.14.15 with custom Yocto build on SkyLake i3 6100U (Graphics 520).
