It seems this Monk's patch series is problematic, for me "4/9 drm/amdgpu:keep bo pinned in prefered domain" is causing ring test failures on polaris 10, the one in this bug report is 1/9. bug 98016 might also be related to this, I've also had a hang once while bisecting, but then it just went away without changing anything. I wasn't doing cold boots though, bug 98016 suggests that may be required to fully reproduce this.