Can you provide the command line needed to reproduce the problem?
Sure. I can reproduce it here using something as simple as:
./qemu-system-ppc -cdrom /dev/null -boot d -vnc :1
What you'll see is that the framebuffer remains black in your VNC
client, as opposed to displaying the OpenBIOS startup banner.
Note that de58ac72b6a062d1a61478284c0c0f8a0428613e (and the previous
commit) have a qdev bug which segfaults qemu-system-ppc on startup,
however the attached patch will resolve this for you.
I've also confirmed over the weekend that the bug also affects
SPARC64, although testing shows that SPARC32 still seems to work okay.