diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 2a3f707caab..96cea08b10c 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -5808,12 +5808,15 @@ static int ironlake_crtc_mode_set(struct drm_crtc *crtc,
 	if (is_lvds) {
 		temp = I915_READ(PCH_LVDS);
 		temp |= LVDS_PORT_EN | LVDS_A0A2_CLKA_POWER_UP;
-		if (HAS_PCH_CPT(dev))
+		if (HAS_PCH_CPT(dev)) {
+			temp &= ~PORT_TRANS_SEL_MASK;
 			temp |= PORT_TRANS_SEL_CPT(pipe);
-		else if (pipe == 1)
-			temp |= LVDS_PIPEB_SELECT;
-		else
-			temp &= ~LVDS_PIPEB_SELECT;
+		} else {
+			if (pipe == 1)
+				temp |= LVDS_PIPEB_SELECT;
+			else
+				temp &= ~LVDS_PIPEB_SELECT;
+		}
 
 		/* set the corresponsding LVDS_BORDER bit */
 		temp |= dev_priv->lvds_border_bits;