EDIT 2: I couldn't reproduce the issue on 4.17 this time even after 2 wakeups.
However, the issue I encountered was similar (system apparently froze when
trying to wake up the screen). 

After looking into it, I found that along with the errors that showed up like
that in Comment 16 (which did not crash the system), there was an additional
"kernel BUG" related to dm_update_crtcs_state which was called by
amdgpu_dm_atomic_check, but the log appeared to have been cut (the log entries
between the two errors were apparently unrelated to the error so I did not
include them, and the new error began with a "--[ cut here ]--"). This
additional error (not 100% reproducible) might be what actually crashed the
system that time.