[Intel-gfx] [PATCH 0/2] drm/i915: Ring buffer stuff

[ville.syrjala at linux.intel.com]

After getting slightly confused by the values of the ring registers
in the error state dumps, I started to actually read the specs and
compare what I learned with the code.

I spotted one possible issue with the head and tail handling. But I
don't know if my patch might fix some obscure bug, or not.
gem_ringfill seems to work equally well with and without the patch.