drm/i915: Check for FIFO underruns after modeset on IVB/HSW and CPT/PPT

Due to the shared error interrupt on IVB/HSW and CPT/PPT we may not
always get an interrupt on a FIFO underrun. But we can always do an
explicit check (like we do on GMCH platforms that have no underrun
interrupt).

v2: Drop stale kerneldoc for i9xx_check_fifo_underruns() (Daniel)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1446225741-11070-1-git-send-email-ville.syrjala@linux.intel.com
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index f859f86..5046b99 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4688,9 +4688,9 @@
 	if (IS_GEN2(dev))
 		intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
 
-	/* Underruns don't raise interrupts, so check manually. */
-	if (HAS_GMCH_DISPLAY(dev))
-		i9xx_check_fifo_underruns(dev_priv);
+	/* Underruns don't always raise interrupts, so check manually. */
+	intel_check_cpu_fifo_underruns(dev_priv);
+	intel_check_pch_fifo_underruns(dev_priv);
 }
 
 /**