Created attachment 75196 [details] [review]
Fixes on the Workaround

Ok, there were some minor issues with the workaround which are fixed here

The output is:
[drm] ring test on 3 succeeded in 1 usecs
[drm] GRPH_PRIMARY_SURFACE[ 0]   0x0000000000000000
[drm] GRPH_SECONDARY_SURFACE[ 0] 0x0000000000000000
[drm] GRPH_PRIMARY_SURFACE[ 1]   0x0000000000000000
[drm] GRPH_SECONDARY_SURFACE[ 1] 0x0000000000000000
[drm] GRPH_PRIMARY_SURFACE[ 2]   0x0000000000000000
[drm] GRPH_SECONDARY_SURFACE[ 2] 0x0000000000000000
[drm] GRPH_PRIMARY_SURFACE[ 3]   0x0000000000000000
[drm] GRPH_SECONDARY_SURFACE[ 3] 0x0000000000000000
[drm] ib test on ring 0 succeeded in 0 usecs

And there's no longer a "stuck in loop" message, but the registers do become
all f's. I'm investigating exactly where, to see if it's still the same issue.