Steps to reproduce:

1) Have dual monitors
2) Enable PP_OVERDRIVE_MASK by flipping the appropriate bit in
amdgpu.ppfeaturemask. (For my configuration I used: 0xfffd7fff)
3) See artifacting.

When using default featuremask, or when using a single monitor with the
overdrive bit enabled behaves correctly. I heard multiple people who have the
same issue, so it does not seem related to my setup.

Setup:
RX480
Linux 4.20-rc5


If additional information is needed please let me know.