drm/i915: make sure VDD AUX power has time to settle

When turning on or off the VDD AUX bit, we need to give the panel time
to start or stop or AUX transactions may fail.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

drivers/gpu/drm/i915/intel_dp.c

@@ -825,6 +825,7 @@ static void ironlake_edp_panel_vdd_on(struct drm_device *dev)
 	pp |= EDP_FORCE_VDD;
 	I915_WRITE(PCH_PP_CONTROL, pp);
 	POSTING_READ(PCH_PP_CONTROL);
+	msleep(300);
 }
 
 static void ironlake_edp_panel_vdd_off(struct drm_device *dev)
@@ -836,6 +837,7 @@ static void ironlake_edp_panel_vdd_off(struct drm_device *dev)
 	pp &= ~EDP_FORCE_VDD;
 	I915_WRITE(PCH_PP_CONTROL, pp);
 	POSTING_READ(PCH_PP_CONTROL);
+	msleep(300);
 }
 
 static void ironlake_edp_backlight_on (struct drm_device *dev)