I am having extreme difficulty getting X working with hwacceleration. I have followed a bit of a different route than you and there is good reasons for that. I have a debian 9 debootstrapped system with all the required X libraries installed. I have successfully installed the imx-viv gpu libraries and compiled the Xorg drivers and pulled the kernel drivers (kernel-module-imx-gpu-viv-upstream-6.2.4.p1.8) and patched the kernel.
Debian 9 rootfs
Kernel: Kernel 4.9.88
GPU Libs: imx-gpu-viv-6.2.4.p2.3
Xorg drivers: xserver-xorg-video-imx-viv-6.2.4.p2.3
Xorg version : X.Org X Server 1.20.4
Now everything seem to be starting up and vivante xorg driver is loaded and it opens up the drm devices see Xorg.log attached but then I experience a crash in second after startup.
[ 288.537] (EE) Segmentation fault at address 0xc0000000
I have done a backtrace on the crash and end up with the following, does anyone have any advice on how to debug or trace the issue ?
#0 0xc0000000 in ()
#1 0x004ff592 in DRIBlockHandler ()
#2 0x0043f6b0 in BlockHandler ()
#3 0x0051f992 in WaitForSomething ()
#4 0x0043c1d4 in ()