diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 196a0eb79272535559390fdcc1daf30830e7c61e..5a103496423c7477c6657371246b4d81472081d5 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -7887,11 +7887,9 @@ enum {
 #define _TRANS_DP_CTL_C		0xe2300
 #define TRANS_DP_CTL(pipe)	_MMIO_PIPE(pipe, _TRANS_DP_CTL_A, _TRANS_DP_CTL_B)
 #define  TRANS_DP_OUTPUT_ENABLE	(1<<31)
-#define  TRANS_DP_PORT_SEL_B	(0<<29)
-#define  TRANS_DP_PORT_SEL_C	(1<<29)
-#define  TRANS_DP_PORT_SEL_D	(2<<29)
-#define  TRANS_DP_PORT_SEL_NONE	(3<<29)
-#define  TRANS_DP_PORT_SEL_MASK	(3<<29)
+#define  TRANS_DP_PORT_SEL_MASK		(3 << 29)
+#define  TRANS_DP_PORT_SEL_NONE		(3 << 29)
+#define  TRANS_DP_PORT_SEL(port)	(((port) - PORT_B) << 29)
 #define  TRANS_DP_PIPE_TO_PORT(val)	((((val) & TRANS_DP_PORT_SEL_MASK) >> 29) + PORT_B)
 #define  TRANS_DP_AUDIO_ONLY	(1<<26)
 #define  TRANS_DP_ENH_FRAMING	(1<<18)
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 16f9a9b3364a772f192798e0909a02b862c8dc43..68d48b7445e90a2c0acd985a66853e0c887e3258 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -1360,9 +1360,9 @@ static void assert_pch_ports_disabled(struct drm_i915_private *dev_priv,
 {
 	enum pipe port_pipe;
 
-	assert_pch_dp_disabled(dev_priv, pipe, PCH_DP_B, TRANS_DP_PORT_SEL_B);
-	assert_pch_dp_disabled(dev_priv, pipe, PCH_DP_C, TRANS_DP_PORT_SEL_C);
-	assert_pch_dp_disabled(dev_priv, pipe, PCH_DP_D, TRANS_DP_PORT_SEL_D);
+	assert_pch_dp_disabled(dev_priv, pipe, PCH_DP_B, TRANS_DP_PORT_SEL(PORT_B));
+	assert_pch_dp_disabled(dev_priv, pipe, PCH_DP_C, TRANS_DP_PORT_SEL(PORT_C));
+	assert_pch_dp_disabled(dev_priv, pipe, PCH_DP_D, TRANS_DP_PORT_SEL(PORT_D));
 
 	I915_STATE_WARN(intel_crt_port_enabled(dev_priv, PCH_ADPA, &port_pipe) &&
 			port_pipe == pipe,
@@ -4702,6 +4702,8 @@ static void ironlake_pch_enable(const struct intel_crtc_state *crtc_state)
 			&crtc_state->base.adjusted_mode;
 		u32 bpc = (I915_READ(PIPECONF(pipe)) & PIPECONF_BPC_MASK) >> 5;
 		i915_reg_t reg = TRANS_DP_CTL(pipe);
+		enum port port;
+
 		temp = I915_READ(reg);
 		temp &= ~(TRANS_DP_PORT_SEL_MASK |
 			  TRANS_DP_SYNC_MASK |
@@ -4714,19 +4716,9 @@ static void ironlake_pch_enable(const struct intel_crtc_state *crtc_state)
 		if (adjusted_mode->flags & DRM_MODE_FLAG_PVSYNC)
 			temp |= TRANS_DP_VSYNC_ACTIVE_HIGH;
 
-		switch (intel_trans_dp_port_sel(crtc)) {
-		case PORT_B:
-			temp |= TRANS_DP_PORT_SEL_B;
-			break;
-		case PORT_C:
-			temp |= TRANS_DP_PORT_SEL_C;
-			break;
-		case PORT_D:
-			temp |= TRANS_DP_PORT_SEL_D;
-			break;
-		default:
-			BUG();
-		}
+		port = intel_trans_dp_port_sel(crtc);
+		WARN_ON(port < PORT_B || port > PORT_D);
+		temp |= TRANS_DP_PORT_SEL(port);
 
 		I915_WRITE(reg, temp);
 	}