X.org graphics driver for OMAP AM57x

Features:
- EXA and Xv GC320 2D acceleration with etnaviv
- DRI2 & DRI3

Kernel version note for etnaviv driver:
- 4.4x is not tested anymore
- There is a bug in etnaviv driver in 4.9x, missing mutex make kernel to hang : https://github.com/torvalds/linux/blob/v4.9/drivers/gpu/drm/etnaviv/etnaviv_gem.c#L557
- It seems this is fixed in 4.14x (untested): https://github.com/torvalds/linux/blob/v4.14/drivers/gpu/drm/etnaviv/etnaviv_gem.c#L561

This driver only use GC320 2D capabilities to provide X11 acceleration, it does not give any 3D acceleration.
For 3D acceleration, you could use https://github.com/TexasInstruments/dri3wsegl which is a DRI3 plugin for PVR SGX 544MP 3D chip available in AM57x. You just need to install SGX drivers and dri3wsegl as documented in the repository. Once done, just restart the X server to activate acceleration in omap5 X11. You can then check if the driver is activated using eglinfo:
$ eglinfo
EGL config number: 0
EGL vendor string: Imagination Technologies
EGL version string: 1.4 build 1.14@3699939 (MAIN)
EGL extensions: EGL_IMG_client_api_ogl EGL_KHR_image EGL_KHR_image_base EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_vg_parent_image EGL_IMG_cl_image EGL_KHR_fence_sync EGL_IMG_context_priority EGL_IMG_hibernate_process EGL_IMG_image_plane_attribs EGL_KHR_surfaceless_context EGL_KHR_wait_sync EGL_KHR_create_context EGL_WL_bind_wayland_display EGL_EXT_image_dma_buf_import
EGL client APIs are: OpenGL_ES

Install:
./autogen.sh
./configure --prefix=/usr
make
sudo make install

xorg.conf configuration:

Section "Device"
    Identifier  "Builtin Default fbdev Device 0"
	Driver		"omap5"
	Option 		"DRICard" "1" # must point to the /dev/dri/cardX corresponding to omapdrm because detection can sometimes fail
	Option		"SoftEXA" "FALSE" # will disable etnaviv acceleration. CPU only EXA is actually faster, but let all the work to A15 core
EndSection

Based on 
- https://cgit.freedesktop.org/xorg/driver/xf86-video-armsoc
- https://github.com/xobs/xserver-xorg-video-armada
- https://github.com/mxOBS/deb-pkg_xserver-xorg-video-imx-viv
- https://github.com/endlessm/xf86-video-armsoc
- https://github.com/tobiasjakobi/xf86-video-armsoc