[PATCH 4/6] drm/i915: Bump reserved size for legacy gen8 semaphore emission

[Chris Wilson]

With 5 rings and a flush, we need 168 bytes of space to emit the
breadcrumb.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_ringbuffer.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 3adce83cfcfc..6e3ea4ec7df1 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -492,8 +492,10 @@ static inline u32 intel_ring_get_tail(struct intel_ringbuffer *ringbuf)
  * is ILK at 136 words. Reserving too much is better than reserving too little
  * as that allows for corner cases that might have been missed. So the figure
  * has been rounded up to 160 words.
+ * Broadwell then manages to top that by requiring a whooping 168 bytes to emit
+ * a semaphore to each ring and flush before the breadcrumb.
  */
-#define MIN_SPACE_FOR_ADD_REQUEST	160
+#define MIN_SPACE_FOR_ADD_REQUEST	168
 
 /*
  * Reserve space in the ring to guarantee that the i915_add_request() call
-- 
2.8.0.rc3