...we need to apply exactly the same workaround for missing interrupts
from BSD as for the BLT ring, apparently.
See also commit 
498e720b96379d8ee9c294950a01534a73defcf3
(drm/i915: Fix gen6 (SNB) missed BLT ring interrupts).
Reported-and-tested-by: nkalkhof@web.de
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38529
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Keith Packard <keithp@keithp.com>
                 * happens.
                 */
                I915_WRITE(GEN6_BLITTER_HWSTAM, ~GEN6_BLITTER_USER_INTERRUPT);
+               I915_WRITE(GEN6_BSD_HWSTAM, ~GEN6_BSD_USER_INTERRUPT);
        }
 
        /* XXX hotplug from PCH */
 
 #define   GEN6_BSD_SLEEP_PSMI_CONTROL_RC_ILDL_MESSAGE_ENABLE           0
 #define   GEN6_BSD_SLEEP_PSMI_CONTROL_IDLE_INDICATOR                   (1 << 3)
 
+#define GEN6_BSD_HWSTAM                        0x12098
 #define GEN6_BSD_IMR                   0x120a8
 #define   GEN6_BSD_USER_INTERRUPT      (1 << 12)