https://bugzilla.kernel.org/show_bug.cgi?id=203471
--- Comment #12 from Michel Dänzer (michel@daenzer.net) --- (In reply to vr00m from comment #11)
ICYMI, I was able to solve the tearing problem with raven ridge using iommu=soft boot param.
Tearing isn't related to the IOMMU. Scatter/gather scanout support for Raven Ridge is landing now, maybe you're running a development snapshot kernel which has it already?