diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index 4a7c86f190873..509330b8041aa 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -10354,10 +10354,9 @@ static void haswell_get_ddi_port_state(struct intel_crtc *crtc,
 	tmp = I915_READ(TRANS_DDI_FUNC_CTL(pipe_config->cpu_transcoder));
 
 	if (INTEL_GEN(dev_priv) >= 12)
-		port = (tmp & TGL_TRANS_DDI_PORT_MASK) >>
-			TGL_TRANS_DDI_PORT_SHIFT;
+		port = TGL_TRANS_DDI_FUNC_CTL_VAL_TO_PORT(tmp);
 	else
-		port = (tmp & TRANS_DDI_PORT_MASK) >> TRANS_DDI_PORT_SHIFT;
+		port = TRANS_DDI_FUNC_CTL_VAL_TO_PORT(tmp);
 
 	if (INTEL_GEN(dev_priv) >= 11)
 		icelake_get_ddi_pll(dev_priv, port, pipe_config);
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index b362ca0663a60..4a947bd0a294d 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -9432,6 +9432,8 @@ enum skl_power_gate {
 #define  TGL_TRANS_DDI_PORT_MASK	(0xf << TGL_TRANS_DDI_PORT_SHIFT)
 #define  TRANS_DDI_SELECT_PORT(x)	((x) << TRANS_DDI_PORT_SHIFT)
 #define  TGL_TRANS_DDI_SELECT_PORT(x)	(((x) + 1) << TGL_TRANS_DDI_PORT_SHIFT)
+#define  TRANS_DDI_FUNC_CTL_VAL_TO_PORT(val)	 (((val) & TRANS_DDI_PORT_MASK) >> TRANS_DDI_PORT_SHIFT)
+#define  TGL_TRANS_DDI_FUNC_CTL_VAL_TO_PORT(val) (((val) & TGL_TRANS_DDI_PORT_MASK >> TGL_TRANS_DDI_PORT_SHIFT) - 1)
 #define  TRANS_DDI_MODE_SELECT_MASK	(7 << 24)
 #define  TRANS_DDI_MODE_SELECT_HDMI	(0 << 24)
 #define  TRANS_DDI_MODE_SELECT_DVI	(1 << 24)