diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3a0709a6e4a0b3910d6d3ffc6a42c5d41dd148c1..aab1c6c58edf612c8f9f5386a34213fa3f334210 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1236,7 +1236,12 @@ void assert_panel_unlocked(struct drm_i915_private *dev_priv, enum pipe pipe)
 		pp_reg = PP_CONTROL(pipe);
 		panel_pipe = pipe;
 	} else {
+		u32 port_sel;
+
 		pp_reg = PP_CONTROL(0);
+		port_sel = I915_READ(PP_ON_DELAYS(0)) & PANEL_PORT_SELECT_MASK;
+
+		WARN_ON(port_sel != PANEL_PORT_SELECT_LVDS);
 		intel_lvds_port_enabled(dev_priv, LVDS, &panel_pipe);
 	}