drm/i915/cnl: Move voltage check into ddi buf trans functions.

Let's start converging CNL buf translations to same style
used on previous platforms. So first thing is to use the
standard signature so we don't need to propagate the voltage
check into other parts of the code, but only on the parts
that it is really useful.
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170829232230.23051-5-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_ddi.c

@@ -1830,9 +1830,10 @@ u8 intel_ddi_dp_voltage_max(struct intel_encoder *encoder)
 }
 
 static const struct cnl_ddi_buf_trans *
-cnl_get_buf_trans_hdmi(struct drm_i915_private *dev_priv,
-		       u32 voltage, int *n_entries)
+cnl_get_buf_trans_hdmi(struct drm_i915_private *dev_priv, int *n_entries)
 {
+	u32 voltage = I915_READ(CNL_PORT_COMP_DW3) & VOLTAGE_INFO_MASK;
+
 	if (voltage == VOLTAGE_INFO_0_85V) {
 		*n_entries = ARRAY_SIZE(cnl_ddi_translations_hdmi_0_85V);
 		return cnl_ddi_translations_hdmi_0_85V;
@@ -1842,14 +1843,16 @@ cnl_get_buf_trans_hdmi(struct drm_i915_private *dev_priv,
 	} else if (voltage == VOLTAGE_INFO_1_05V) {
 		*n_entries = ARRAY_SIZE(cnl_ddi_translations_hdmi_1_05V);
 		return cnl_ddi_translations_hdmi_1_05V;
-	}
+	} else
+		MISSING_CASE(voltage);
 	return NULL;
 }
 
 static const struct cnl_ddi_buf_trans *
-cnl_get_buf_trans_dp(struct drm_i915_private *dev_priv,
-		     u32 voltage, int *n_entries)
+cnl_get_buf_trans_dp(struct drm_i915_private *dev_priv, int *n_entries)
 {
+	u32 voltage = I915_READ(CNL_PORT_COMP_DW3) & VOLTAGE_INFO_MASK;
+
 	if (voltage == VOLTAGE_INFO_0_85V) {
 		*n_entries = ARRAY_SIZE(cnl_ddi_translations_dp_0_85V);
 		return cnl_ddi_translations_dp_0_85V;
@@ -1859,14 +1862,16 @@ cnl_get_buf_trans_dp(struct drm_i915_private *dev_priv,
 	} else if (voltage == VOLTAGE_INFO_1_05V) {
 		*n_entries = ARRAY_SIZE(cnl_ddi_translations_dp_1_05V);
 		return cnl_ddi_translations_dp_1_05V;
-	}
+	} else
+		MISSING_CASE(voltage);
 	return NULL;
 }
 
 static const struct cnl_ddi_buf_trans *
-cnl_get_buf_trans_edp(struct drm_i915_private *dev_priv,
-		      u32 voltage, int *n_entries)
+cnl_get_buf_trans_edp(struct drm_i915_private *dev_priv, int *n_entries)
 {
+	u32 voltage = I915_READ(CNL_PORT_COMP_DW3) & VOLTAGE_INFO_MASK;
+
 	if (dev_priv->vbt.edp.low_vswing) {
 		if (voltage == VOLTAGE_INFO_0_85V) {
 			*n_entries = ARRAY_SIZE(cnl_ddi_translations_edp_0_85V);
@@ -1877,10 +1882,11 @@ cnl_get_buf_trans_edp(struct drm_i915_private *dev_priv,
 		} else if (voltage == VOLTAGE_INFO_1_05V) {
 			*n_entries = ARRAY_SIZE(cnl_ddi_translations_edp_1_05V);
 			return cnl_ddi_translations_edp_1_05V;
-		}
+		} else
+			MISSING_CASE(voltage);
 		return NULL;
 	} else {
-		return cnl_get_buf_trans_dp(dev_priv, voltage, n_entries);
+		return cnl_get_buf_trans_dp(dev_priv, n_entries);
 	}
 }
 
@@ -1888,31 +1894,19 @@ static void cnl_ddi_vswing_program(struct drm_i915_private *dev_priv,
 				    u32 level, enum port port, int type)
 {
 	const struct cnl_ddi_buf_trans *ddi_translations = NULL;
-	u32 n_entries, val, voltage;
+	u32 n_entries, val;
 	int ln;
 
-	/*
-	 * Values for each port type are listed in
-	 * voltage swing programming tables.
-	 * Vccio voltage found in PORT_COMP_DW3.
-	 */
-	voltage = I915_READ(CNL_PORT_COMP_DW3) & VOLTAGE_INFO_MASK;
-
 	if (type == INTEL_OUTPUT_HDMI) {
-		ddi_translations = cnl_get_buf_trans_hdmi(dev_priv,
-							  voltage, &n_entries);
+		ddi_translations = cnl_get_buf_trans_hdmi(dev_priv, &n_entries);
 	} else if (type == INTEL_OUTPUT_DP) {
-		ddi_translations = cnl_get_buf_trans_dp(dev_priv,
-							voltage, &n_entries);
+		ddi_translations = cnl_get_buf_trans_dp(dev_priv, &n_entries);
 	} else if (type == INTEL_OUTPUT_EDP) {
-		ddi_translations = cnl_get_buf_trans_edp(dev_priv,
-							 voltage, &n_entries);
+		ddi_translations = cnl_get_buf_trans_edp(dev_priv, &n_entries);
 	}
 
-	if (ddi_translations == NULL) {
-		MISSING_CASE(voltage);
+	if (WARN_ON(ddi_translations == NULL))
 		return;
-	}
 
 	if (level >= n_entries) {
 		DRM_DEBUG_KMS("DDI translation not found for level %d. Using %d instead.", level, n_entries - 1);