11caf5517c
An interesting snippet from Sandybridge's prm: "Although a Ring Buffer can be enabled in the non-empty state, it must not be disabled unless it is empty. Attempting to disable a Ring Buffer in the non-empty state is UNDEFINED." Let's avoid the undefined behaviour as we disable the rings prior to reset and resume. v2: Tell HEAD to catch up to TAIL (empty ring) first, then reset both to 0 (supposedly while stopped). Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20171027094311.30380-1-chris@chris-wilson.co.uk