I've just compiled your hns/work/omapdrm kernel, and things seem to work reasonably well.
I get the "atomic complete timeout" thing all over the place when using the omap5-pyra.dtb, but when using omap5-uevm.dtb things work fine (although a lot slower than when using the turbofb driver)
I also tried the xf86-video-omap driver, but there were no noticable differences between that and the debian xserver-xorg-video-omap package (no surprise, since the debian package comes from the same place)