drm/i915: Change BDW WIZ hashing mode to 16x4

BSpec recommends using 8x4 hashing mode when MSAA is used. But in
practice 16x4 seems to have a slight edge in performance (on IVB and
HSW at least). So just use 16x4.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Antti Koskipää <antti.koskipaa@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 7da7360fea359077c4e0fd5e47c0bc599f14c075..151afe53cc7cff1afd35e071c6e26d22d786c737 100644 (file)
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4843,6 +4843,13 @@ static void gen8_init_clock_gating(struct drm_device *dev)
        I915_WRITE(GEN7_FF_THREAD_MODE,
                   I915_READ(GEN7_FF_THREAD_MODE) &
                   ~(GEN8_FF_DS_REF_CNT_FFME | GEN7_FF_VS_REF_CNT_FFME));
+
+       /*
+        * BSpec recommends 8x4 when MSAA is used,
+        * however in practice 16x4 seems fastest.
+        */
+       I915_WRITE(GEN7_GT_MODE,
+                  GEN6_WIZ_HASHING_MASK | GEN6_WIZ_HASHING_16x4);
 }
 
 static void haswell_init_clock_gating(struct drm_device *dev)