drm/i915: Don't vblank wait on ilk-ivb after pipe enable

Like on hsw/bdw the pipe isn't actually running yet at this point.
This holds for both pch ports and the cpu edp port according to my
testing on ilk, snb and ivb.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=77297
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -1804,16 +1804,6 @@ static void intel_enable_pipe(struct intel_crtc *crtc)
 
 	I915_WRITE(reg, val | PIPECONF_ENABLE);
 	POSTING_READ(reg);
-
-	/*
-	 * There's no guarantee the pipe will really start running now. It
-	 * depends on the Gen, the output type and the relative order between
-	 * pipe and plane enabling. Avoid waiting on HSW+ since it's not
-	 * necessary.
-	 * TODO: audit the previous gens.
-	 */
-	if (INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev))
-		intel_wait_for_vblank(dev_priv->dev, pipe);
 }
 
 /**
@@ -4369,7 +4359,9 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
 
 	intel_update_watermarks(crtc);
 	intel_enable_pipe(intel_crtc);
+	intel_wait_for_vblank(dev_priv->dev, pipe);
 	intel_set_cpu_fifo_underrun_reporting(dev, pipe, true);
+
 	intel_enable_primary_hw_plane(dev_priv, plane, pipe);
 	intel_enable_planes(crtc);
 	intel_crtc_update_cursor(crtc, true);
@@ -4408,7 +4400,9 @@ static void i9xx_crtc_enable(struct drm_crtc *crtc)
 
 	intel_update_watermarks(crtc);
 	intel_enable_pipe(intel_crtc);
+	intel_wait_for_vblank(dev_priv->dev, pipe);
 	intel_set_cpu_fifo_underrun_reporting(dev, pipe, true);
+
 	intel_enable_primary_hw_plane(dev_priv, plane, pipe);
 	intel_enable_planes(crtc);
 	/* The fixup needs to happen before cursor is enabled */