drm/i915: implement WaMbcDriverBootEnable on Haswell

Also document the WA name for the previous gens that implement it.
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -3519,6 +3519,7 @@ static void gen6_init_clock_gating(struct drm_device *dev)
 		   ILK_DPARBUNIT_CLOCK_GATE_ENABLE  |
 		   ILK_DPFDUNIT_CLOCK_GATE_ENABLE);
 
+	/* WaMbcDriverBootEnable */
 	I915_WRITE(GEN6_MBCTL, I915_READ(GEN6_MBCTL) |
 		   GEN6_MBCTL_ENABLE_BOOT_FETCH);
 
@@ -3605,6 +3606,10 @@ static void haswell_init_clock_gating(struct drm_device *dev)
 	I915_WRITE(CACHE_MODE_1,
 		   _MASKED_BIT_ENABLE(PIXEL_SUBSPAN_COLLECT_OPT_DISABLE));
 
+	/* WaMbcDriverBootEnable */
+	I915_WRITE(GEN6_MBCTL, I915_READ(GEN6_MBCTL) |
+		   GEN6_MBCTL_ENABLE_BOOT_FETCH);
+
 	/* XXX: This is a workaround for early silicon revisions and should be
 	 * removed later.
 	 */
@@ -3696,6 +3701,7 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
 		intel_flush_display_plane(dev_priv, pipe);
 	}
 
+	/* WaMbcDriverBootEnable */
 	I915_WRITE(GEN6_MBCTL, I915_READ(GEN6_MBCTL) |
 		   GEN6_MBCTL_ENABLE_BOOT_FETCH);
 
@@ -3761,6 +3767,7 @@ static void valleyview_init_clock_gating(struct drm_device *dev)
 		   I915_READ(GEN7_SQ_CHICKEN_MBCUNIT_CONFIG) |
 		   GEN7_SQ_CHICKEN_MBCUNIT_SQINTMOB);
 
+	/* WaMbcDriverBootEnable */
 	I915_WRITE(GEN6_MBCTL, I915_READ(GEN6_MBCTL) |
 		   GEN6_MBCTL_ENABLE_BOOT_FETCH);