Regression: Black screen after resume from powersave

[Martin Babutzka]

Hello,

I tracked down another regression affecting my PC with R9 380 GPU,
running the amd-staging-4.11 kernel on Xubuntu 17.04:

After resume from powersave, display freezes when the powersave is
triggered from the lightdm locked screen or stays completely black if
the powersave was triggered from a logged in user.

The regression occurs the first time when I build the kernel including
commit 323a1cc8f7d3c40a8e77751d62545de43fa52653. Here is the result
from the testing series:
8. Step - crashes
bfd40a54f781899ee5b9ddffc459a6eafe2bba86
11. Step - crashes
dde557132beb2cfb9e98046936cb3565b21d6f9c
12. Step - crashes
323a1cc8f7d3c40a8e77751d62545de43fa52653
10. Step - works
19993e3a86268a30c8b1c31c4518fc403431efe2
3af79f94b85557d26d53909ed85526ec980ffd7f
b81aface585aab7262a830aa2f93ff53d4baf3c0
9. Step - works
8d1610a0f3b99e3f950064dc4c476000d3b6ba02
d36719c5ea181601f47e2d056a444d025a5247c6
2247dfee70a96025ba389f363b9088e2d377c7cc
239e79555c7e490823582b9a66390e76ebabb9ab

Maybe this is also linked to:
"iMac 10,1 with Ubuntu 16.04: black screen after suspend (Florian
Echtler)"

If you fix this successfully I would be very glad if you push the
commit to amd-staging-4.11 again.

Many regards,
Martin Babutzka