I have enormous issues with an MSI R9 390 8GB card on linux. I've tried pretty much everything (amdgpu, amdgpu-pro, a plethora of kernel versions, versions of Mesa, llvm, enabling/disabling iommu, etc, etc...) but this card simply does not want to work the the open source amgpu driver.
The only solution that works for me thus far is this:
I read that kernel 4.13 is the first in which official support for Hawaii series GPUs has been enabled, with regard to the amdgpu open source driver.
I'd like to know if this is a known issue and maybe if there is something else I might try to have the card work with amdgpu, or if I should at least expect better support with future kernel versions.
Also, I wanted to underline a problem that apparently is felt by other users as well: