If your X11 server is not working, check the syslog with
logread and the
/var/log/Xorg.0.log files via SSH for helpful messages.
Example output from running XFCE4:
(xfwm4:2538): xfwm4-WARNING **: Cannot find visual format on screen 0 (EE) Segmentation fault at address 0x4 (EE) Fatal server error: (EE) Caught signal 11 (Segmentation fault). Server aborting
Strange refresh rate
Android devices seem to usually have a refresh rate of 60 Hz. If you have a very high or low refresh rate, that does not make any sense, try the patch from #348. If that also fails, try to add a X11 modeline with the correct refresh rate.
Output isn't displayed right for other reasons
Try the patches from Troubleshooting:display.
Is TWRP working?
Try to compare its framebuffer output code with xf86-video-fbdev. If you go down this road, please expand this idea with more information.