https://bugs.freedesktop.org/show_bug.cgi?id=109628
--- Comment #4 from Nicholas Kazlauskas nicholas.kazlauskas@amd.com --- There were some patches recently for Raven that fixed some programming sequence issues during changes for dpms / suspend. I wonder if these would help fix what you're reporting - the pstate warnings usually indicate that something went wrong in the programming sequence and the hardware has potentially hung but it won't always happen consistently.
https://patchwork.freedesktop.org/patch/282418/
I think there was another related to this as well that might be in amd-staging-drm-next
https://cgit.freedesktop.org/~agd5f/linux/log/?h=amd-staging-drm-next
If you can still reproduce the issue consistently I'd give this tree a try and see if you still have the issue.