Nouveau - Jan 2016 - Issues with GeForce 6800 Ultra (NV40) and nouveau on linux 4.4 (powerpc)

I recently acquired an old PowerMac G5 that has an AGP GeForce 6800 Ultra
(NV40) in it. I put debian stretch (testing) on it and am having issues
getting the 6800 Ultra working with nouveau.

Software versions:
linux: 4.4.0 (powerpc)
libdrm: 2.4.65
mesa: 11.0.8
nouveau: 1.0.12

On boot when the system starts Xorg I get an initially black screen that
finally changes to a screen that has distorted multicolored bars in the
screen.

Two interesting lines from dmesg:

[   25.965156] nouveau 0000:f0:10.0: gr: intr 00100000 [ERROR] nsource
00000010 [LIMIT_COLOR] nstatus 04000000 [PROTECTION_FAULT] ch 1 [0008e000
Xorg[847]] subc 4 class 009f mthd 0308 data 04380780


[   67.550355] nouveau 0000:f0:10.0: DRM: GPU lockup - switching to
software fbcon


Full dmesg:

http://pastebin.com/WhfMbu9M

Full Xorg.0.log:

http://pastebin.com/2nn4CVkx

lspci -v:

http://pastebin.com/wRK9PwdZ


Please let me know if there is any other information that would be helpful.
I hope someone has some ideas of what to try next. Thanks in advance for
everyone's time!


Logan
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