Cairo with image backend makes no difference. I actually have no text console
either, but I'm pretty sure I run weston the right way. Weston and gdm
(wayland) run just fine, but just don't show up on the screen.

I actually think it's a general problem with initializing, since I have no text
console as well or plymouth splash if enabled. The machine is usually connected
trough HDMI to a nobrand HD720 TV. When I connect the same setup through VGA it
does give an image (however the image is positioned wrong). I explicitly
disable the VGA output when using HDMI trough the kernel command line :
 video=HDMI-A-1:1280x720@60 video=VGA-1:d radeon.audio=1 radeon.modeset=1
radeon.dpm=1 .

The weird thing is that if I start X it does show up and subsequent runs of
weston or gdm on wayland are just fine, so it just happens after a fresh boot.

Attached 2 more logs with drm.debug=0xe, one for a boot with HDMI and one for
boot with VGA into gdm on wayland.

By the way, the invalid ioctl message in #1 disappeared since switching to the
4.0 kernel.