drm/i915: Implement WaVSRefCountFullforceMissDisable

Implements WaVSRefCountFullforceMissDisable as documented in the BSpec
3D workarounds chapter.

Cc: Paulo Zanoni <[e-mail]>
Signed-off-by: Ben Widawsky <[e-mail]>
Reviewed-by: Ville Syrjälä <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>

drivers/gpu/drm/i915/i915_reg.h

···
 #define   GEN7_FF_TS_SCHED_HS0		(0x3<<16)
 #define   GEN7_FF_TS_SCHED_LOAD_BALANCE	(0x1<<16)
 #define   GEN7_FF_TS_SCHED_HW		(0x0<<16) /* Default */
+#define   GEN7_FF_VS_REF_CNT_FFME	(1 << 15)
 #define   GEN7_FF_VS_SCHED_HS1		(0x5<<12)
 #define   GEN7_FF_VS_SCHED_HS0		(0x3<<12)
 #define   GEN7_FF_VS_SCHED_LOAD_BALANCE	(0x1<<12) /* Default */

drivers/gpu/drm/i915/intel_pm.c

···
 	reg |= GEN7_FF_VS_SCHED_HW;
 	reg |= GEN7_FF_DS_SCHED_HW;
 
+	/* WaVSRefCountFullforceMissDisable */
+	if (IS_HASWELL(dev_priv->dev))
+		reg &= ~GEN7_FF_VS_REF_CNT_FFME;
+
 	I915_WRITE(GEN7_FF_THREAD_MODE, reg);
 }