diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
index 7c223520ad6b..eb420069a469 100644
--- a/drivers/gpu/drm/i915/display/intel_ddi.c
+++ b/drivers/gpu/drm/i915/display/intel_ddi.c
@@ -2659,38 +2659,66 @@ static u32 intel_ddi_dp_level(struct intel_dp *intel_dp)
 	return translate_signal_level(signal_levels);
 }
 
-u32 bxt_signal_levels(struct intel_dp *intel_dp)
+static void
+tgl_set_signal_levels(struct intel_dp *intel_dp)
 {
-	struct intel_digital_port *dport = dp_to_dig_port(intel_dp);
-	struct drm_i915_private *dev_priv = to_i915(dport->base.base.dev);
-	struct intel_encoder *encoder = &dport->base;
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
 	int level = intel_ddi_dp_level(intel_dp);
 
-	if (INTEL_GEN(dev_priv) >= 12)
-		tgl_ddi_vswing_sequence(encoder, intel_dp->link_rate,
-					level, encoder->type);
-	else if (INTEL_GEN(dev_priv) >= 11)
-		icl_ddi_vswing_sequence(encoder, intel_dp->link_rate,
-					level, encoder->type);
-	else if (IS_CANNONLAKE(dev_priv))
-		cnl_ddi_vswing_sequence(encoder, level, encoder->type);
-	else
-		bxt_ddi_vswing_sequence(encoder, level, encoder->type);
-
-	return 0;
+	tgl_ddi_vswing_sequence(encoder, intel_dp->link_rate,
+				level, encoder->type);
 }
 
-u32 ddi_signal_levels(struct intel_dp *intel_dp)
+static void
+icl_set_signal_levels(struct intel_dp *intel_dp)
 {
-	struct intel_digital_port *dport = dp_to_dig_port(intel_dp);
-	struct drm_i915_private *dev_priv = to_i915(dport->base.base.dev);
-	struct intel_encoder *encoder = &dport->base;
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
 	int level = intel_ddi_dp_level(intel_dp);
 
+	icl_ddi_vswing_sequence(encoder, intel_dp->link_rate,
+				level, encoder->type);
+}
+
+static void
+cnl_set_signal_levels(struct intel_dp *intel_dp)
+{
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	int level = intel_ddi_dp_level(intel_dp);
+
+	cnl_ddi_vswing_sequence(encoder, level, encoder->type);
+}
+
+static void
+bxt_set_signal_levels(struct intel_dp *intel_dp)
+{
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	int level = intel_ddi_dp_level(intel_dp);
+
+	bxt_ddi_vswing_sequence(encoder, level, encoder->type);
+}
+
+static void
+hsw_set_signal_levels(struct intel_dp *intel_dp)
+{
+	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
+	struct drm_i915_private *dev_priv = to_i915(encoder->base.dev);
+	int level = intel_ddi_dp_level(intel_dp);
+	enum port port = encoder->port;
+	u32 signal_levels;
+
+	signal_levels = DDI_BUF_TRANS_SELECT(level);
+
+	drm_dbg_kms(&dev_priv->drm, "Using signal levels %08x\n",
+		    signal_levels);
+
+	intel_dp->DP &= ~DDI_BUF_EMP_MASK;
+	intel_dp->DP |= signal_levels;
+
 	if (IS_GEN9_BC(dev_priv))
 		skl_ddi_set_iboost(encoder, level, encoder->type);
 
-	return DDI_BUF_TRANS_SELECT(level);
+	intel_de_write(dev_priv, DDI_BUF_CTL(port), intel_dp->DP);
+	intel_de_posting_read(dev_priv, DDI_BUF_CTL(port));
 }
 
 static inline
@@ -4435,6 +4463,17 @@ intel_ddi_init_dp_connector(struct intel_digital_port *intel_dig_port)
 		intel_ddi_prepare_link_retrain;
 	intel_dig_port->dp.set_link_train = intel_ddi_set_link_train;
 
+	if (INTEL_GEN(dev_priv) >= 12)
+		intel_dig_port->dp.set_signal_levels = tgl_set_signal_levels;
+	else if (INTEL_GEN(dev_priv) >= 11)
+		intel_dig_port->dp.set_signal_levels = icl_set_signal_levels;
+	else if (IS_CANNONLAKE(dev_priv))
+		intel_dig_port->dp.set_signal_levels = cnl_set_signal_levels;
+	else if (IS_GEN9_LP(dev_priv))
+		intel_dig_port->dp.set_signal_levels = bxt_set_signal_levels;
+	else
+		intel_dig_port->dp.set_signal_levels = hsw_set_signal_levels;
+
 	if (INTEL_GEN(dev_priv) < 12) {
 		intel_dig_port->dp.regs.dp_tp_ctl = DP_TP_CTL(port);
 		intel_dig_port->dp.regs.dp_tp_status = DP_TP_STATUS(port);
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
index 616850cc66bb..960ba14f01c8 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1369,6 +1369,7 @@ struct intel_dp {
 	/* This is called before a link training is starterd */
 	void (*prepare_link_retrain)(struct intel_dp *intel_dp);
 	void (*set_link_train)(struct intel_dp *intel_dp, u8 dp_train_pat);
+	void (*set_signal_levels)(struct intel_dp *intel_dp);
 
 	/* Displayport compliance testing */
 	struct intel_dp_compliance compliance;
diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
index f120e2881f77..7d5e1e857ba7 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -4033,7 +4033,7 @@ intel_dp_pre_emphasis_max(struct intel_dp *intel_dp, u8 voltage_swing)
 	}
 }
 
-static u32 vlv_signal_levels(struct intel_dp *intel_dp)
+static void vlv_set_signal_levels(struct intel_dp *intel_dp)
 {
 	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
 	unsigned long demph_reg_value, preemph_reg_value,
@@ -4061,7 +4061,7 @@ static u32 vlv_signal_levels(struct intel_dp *intel_dp)
 			uniqtranscale_reg_value = 0x5598DA3A;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	case DP_TRAIN_PRE_EMPH_LEVEL_1:
@@ -4080,7 +4080,7 @@ static u32 vlv_signal_levels(struct intel_dp *intel_dp)
 			uniqtranscale_reg_value = 0x55ADDA3A;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	case DP_TRAIN_PRE_EMPH_LEVEL_2:
@@ -4095,7 +4095,7 @@ static u32 vlv_signal_levels(struct intel_dp *intel_dp)
 			uniqtranscale_reg_value = 0x55ADDA3A;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	case DP_TRAIN_PRE_EMPH_LEVEL_3:
@@ -4106,20 +4106,18 @@ static u32 vlv_signal_levels(struct intel_dp *intel_dp)
 			uniqtranscale_reg_value = 0x55ADDA3A;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	default:
-		return 0;
+		return;
 	}
 
 	vlv_set_phy_signal_level(encoder, demph_reg_value, preemph_reg_value,
 				 uniqtranscale_reg_value, 0);
-
-	return 0;
 }
 
-static u32 chv_signal_levels(struct intel_dp *intel_dp)
+static void chv_set_signal_levels(struct intel_dp *intel_dp)
 {
 	struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
 	u32 deemph_reg_value, margin_reg_value;
@@ -4147,7 +4145,7 @@ static u32 chv_signal_levels(struct intel_dp *intel_dp)
 			uniq_trans_scale = true;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	case DP_TRAIN_PRE_EMPH_LEVEL_1:
@@ -4165,7 +4163,7 @@ static u32 chv_signal_levels(struct intel_dp *intel_dp)
 			margin_reg_value = 154;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	case DP_TRAIN_PRE_EMPH_LEVEL_2:
@@ -4179,7 +4177,7 @@ static u32 chv_signal_levels(struct intel_dp *intel_dp)
 			margin_reg_value = 154;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	case DP_TRAIN_PRE_EMPH_LEVEL_3:
@@ -4189,21 +4187,18 @@ static u32 chv_signal_levels(struct intel_dp *intel_dp)
 			margin_reg_value = 154;
 			break;
 		default:
-			return 0;
+			return;
 		}
 		break;
 	default:
-		return 0;
+		return;
 	}
 
 	chv_set_phy_signal_level(encoder, deemph_reg_value,
 				 margin_reg_value, uniq_trans_scale);
-
-	return 0;
 }
 
-static u32
-g4x_signal_levels(u8 train_set)
+static u32 g4x_signal_levels(u8 train_set)
 {
 	u32 signal_levels = 0;
 
@@ -4240,12 +4235,31 @@ g4x_signal_levels(u8 train_set)
 	return signal_levels;
 }
 
+static void
+g4x_set_signal_levels(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+	u8 train_set = intel_dp->train_set[0];
+	u32 signal_levels;
+
+	signal_levels = g4x_signal_levels(train_set);
+
+	drm_dbg_kms(&dev_priv->drm, "Using signal levels %08x\n",
+		    signal_levels);
+
+	intel_dp->DP &= ~(DP_VOLTAGE_MASK | DP_PRE_EMPHASIS_MASK);
+	intel_dp->DP |= signal_levels;
+
+	intel_de_write(dev_priv, intel_dp->output_reg, intel_dp->DP);
+	intel_de_posting_read(dev_priv, intel_dp->output_reg);
+}
+
 /* SNB CPU eDP voltage swing and pre-emphasis control */
-static u32
-snb_cpu_edp_signal_levels(u8 train_set)
+static u32 snb_cpu_edp_signal_levels(u8 train_set)
 {
-	int signal_levels = train_set & (DP_TRAIN_VOLTAGE_SWING_MASK |
-					 DP_TRAIN_PRE_EMPHASIS_MASK);
+	u8 signal_levels = train_set & (DP_TRAIN_VOLTAGE_SWING_MASK |
+					DP_TRAIN_PRE_EMPHASIS_MASK);
+
 	switch (signal_levels) {
 	case DP_TRAIN_VOLTAGE_SWING_LEVEL_0 | DP_TRAIN_PRE_EMPH_LEVEL_0:
 	case DP_TRAIN_VOLTAGE_SWING_LEVEL_1 | DP_TRAIN_PRE_EMPH_LEVEL_0:
@@ -4268,12 +4282,31 @@ snb_cpu_edp_signal_levels(u8 train_set)
 	}
 }
 
+static void
+snb_cpu_edp_set_signal_levels(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+	u8 train_set = intel_dp->train_set[0];
+	u32 signal_levels;
+
+	signal_levels = snb_cpu_edp_signal_levels(train_set);
+
+	drm_dbg_kms(&dev_priv->drm, "Using signal levels %08x\n",
+		    signal_levels);
+
+	intel_dp->DP &= ~EDP_LINK_TRAIN_VOL_EMP_MASK_SNB;
+	intel_dp->DP |= signal_levels;
+
+	intel_de_write(dev_priv, intel_dp->output_reg, intel_dp->DP);
+	intel_de_posting_read(dev_priv, intel_dp->output_reg);
+}
+
 /* IVB CPU eDP voltage swing and pre-emphasis control */
-static u32
-ivb_cpu_edp_signal_levels(u8 train_set)
+static u32 ivb_cpu_edp_signal_levels(u8 train_set)
 {
-	int signal_levels = train_set & (DP_TRAIN_VOLTAGE_SWING_MASK |
-					 DP_TRAIN_PRE_EMPHASIS_MASK);
+	u8 signal_levels = train_set & (DP_TRAIN_VOLTAGE_SWING_MASK |
+					DP_TRAIN_PRE_EMPHASIS_MASK);
+
 	switch (signal_levels) {
 	case DP_TRAIN_VOLTAGE_SWING_LEVEL_0 | DP_TRAIN_PRE_EMPH_LEVEL_0:
 		return EDP_LINK_TRAIN_400MV_0DB_IVB;
@@ -4299,38 +4332,29 @@ ivb_cpu_edp_signal_levels(u8 train_set)
 	}
 }
 
-void
-intel_dp_set_signal_levels(struct intel_dp *intel_dp)
+static void
+ivb_cpu_edp_set_signal_levels(struct intel_dp *intel_dp)
 {
 	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
-	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
-	enum port port = intel_dig_port->base.port;
-	u32 signal_levels, mask = 0;
 	u8 train_set = intel_dp->train_set[0];
+	u32 signal_levels;
 
-	if (IS_GEN9_LP(dev_priv) || INTEL_GEN(dev_priv) >= 10) {
-		signal_levels = bxt_signal_levels(intel_dp);
-	} else if (HAS_DDI(dev_priv)) {
-		signal_levels = ddi_signal_levels(intel_dp);
-		mask = DDI_BUF_EMP_MASK;
-	} else if (IS_CHERRYVIEW(dev_priv)) {
-		signal_levels = chv_signal_levels(intel_dp);
-	} else if (IS_VALLEYVIEW(dev_priv)) {
-		signal_levels = vlv_signal_levels(intel_dp);
-	} else if (IS_IVYBRIDGE(dev_priv) && port == PORT_A) {
-		signal_levels = ivb_cpu_edp_signal_levels(train_set);
-		mask = EDP_LINK_TRAIN_VOL_EMP_MASK_IVB;
-	} else if (IS_GEN(dev_priv, 6) && port == PORT_A) {
-		signal_levels = snb_cpu_edp_signal_levels(train_set);
-		mask = EDP_LINK_TRAIN_VOL_EMP_MASK_SNB;
-	} else {
-		signal_levels = g4x_signal_levels(train_set);
-		mask = DP_VOLTAGE_MASK | DP_PRE_EMPHASIS_MASK;
-	}
+	signal_levels = ivb_cpu_edp_signal_levels(train_set);
 
-	if (mask)
-		drm_dbg_kms(&dev_priv->drm, "Using signal levels %08x\n",
-			    signal_levels);
+	drm_dbg_kms(&dev_priv->drm, "Using signal levels %08x\n",
+		    signal_levels);
+
+	intel_dp->DP &= ~EDP_LINK_TRAIN_VOL_EMP_MASK_IVB;
+	intel_dp->DP |= signal_levels;
+
+	intel_de_write(dev_priv, intel_dp->output_reg, intel_dp->DP);
+	intel_de_posting_read(dev_priv, intel_dp->output_reg);
+}
+
+void intel_dp_set_signal_levels(struct intel_dp *intel_dp)
+{
+	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
+	u8 train_set = intel_dp->train_set[0];
 
 	drm_dbg_kms(&dev_priv->drm, "Using vswing level %d%s\n",
 		    train_set & DP_TRAIN_VOLTAGE_SWING_MASK,
@@ -4341,10 +4365,7 @@ intel_dp_set_signal_levels(struct intel_dp *intel_dp)
 		    train_set & DP_TRAIN_MAX_PRE_EMPHASIS_REACHED ?
 		    " (max)" : "");
 
-	intel_dp->DP = (intel_dp->DP & ~mask) | signal_levels;
-
-	intel_de_write(dev_priv, intel_dp->output_reg, intel_dp->DP);
-	intel_de_posting_read(dev_priv, intel_dp->output_reg);
+	intel_dp->set_signal_levels(intel_dp);
 }
 
 void
@@ -8515,6 +8536,17 @@ bool intel_dp_init(struct drm_i915_private *dev_priv,
 	else
 		intel_dig_port->dp.set_link_train = g4x_set_link_train;
 
+	if (IS_CHERRYVIEW(dev_priv))
+		intel_dig_port->dp.set_signal_levels = chv_set_signal_levels;
+	else if (IS_VALLEYVIEW(dev_priv))
+		intel_dig_port->dp.set_signal_levels = vlv_set_signal_levels;
+	else if (IS_IVYBRIDGE(dev_priv) && port == PORT_A)
+		intel_dig_port->dp.set_signal_levels = ivb_cpu_edp_set_signal_levels;
+	else if (IS_GEN(dev_priv, 6) && port == PORT_A)
+		intel_dig_port->dp.set_signal_levels = snb_cpu_edp_set_signal_levels;
+	else
+		intel_dig_port->dp.set_signal_levels = g4x_set_signal_levels;
+
 	intel_dig_port->dp.output_reg = output_reg;
 	intel_dig_port->max_lanes = 4;
 	intel_dig_port->dp.regs.dp_tp_ctl = DP_TP_CTL(port);
