drm/i915/chv: Implement WaDisableSamplerPowerBypass for CHV

Cherryview also needs this WA.
Signed-off-by: Rafael Barbalho <rafael.barbalho@intel.com>
[vsyrjala: Looks like it's for pre-prodution hw only]
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_pm.c

@@ -5401,6 +5401,10 @@ static void cherryview_init_clock_gating(struct drm_device *dev)
 	/* WaDisableSDEUnitClockGating:chv */
 	I915_WRITE(GEN8_UCGCTL6, I915_READ(GEN8_UCGCTL6) |
 		   GEN8_SDEUNIT_CLOCK_GATE_DISABLE);
+
+	/* WaDisableSamplerPowerBypass:chv (pre-production hw) */
+	I915_WRITE(HALF_SLICE_CHICKEN3,
+		   _MASKED_BIT_ENABLE(GEN8_SAMPLER_POWER_BYPASS_DIS));
 }
 
 static void g4x_init_clock_gating(struct drm_device *dev)