drm/radeon: rework panel mode setup

Adjust the panel mode setup to match the behavior
of the vbios.  Rather than checking for specific
bridge chip ids, just check the eDP configuration register.
This saves extra aux transactions and works across
DP bridge chips without requiring additional per chip
id checking.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/atombios_dp.c

@@ -577,30 +577,25 @@ int radeon_dp_get_panel_mode(struct drm_encoder *encoder,
 	struct radeon_device *rdev = dev->dev_private;
 	struct radeon_connector *radeon_connector = to_radeon_connector(connector);
 	int panel_mode = DP_PANEL_MODE_EXTERNAL_DP_MODE;
+	u16 dp_bridge = radeon_connector_encoder_get_dp_bridge_encoder_id(connector);
+	u8 tmp;
 
 	if (!ASIC_IS_DCE4(rdev))
 		return panel_mode;
 
-	if (radeon_connector_encoder_get_dp_bridge_encoder_id(connector) ==
-	    ENCODER_OBJECT_ID_NUTMEG)
-		panel_mode = DP_PANEL_MODE_INTERNAL_DP1_MODE;
-	else if (radeon_connector_encoder_get_dp_bridge_encoder_id(connector) ==
-		 ENCODER_OBJECT_ID_TRAVIS) {
-		u8 id[6];
-		int i;
-		for (i = 0; i < 6; i++)
-			id[i] = radeon_read_dpcd_reg(radeon_connector, 0x503 + i);
-		if (id[0] == 0x73 &&
-		    id[1] == 0x69 &&
-		    id[2] == 0x76 &&
-		    id[3] == 0x61 &&
-		    id[4] == 0x72 &&
-		    id[5] == 0x54)
+	if (dp_bridge != ENCODER_OBJECT_ID_NONE) {
+		/* DP bridge chips */
+		tmp = radeon_read_dpcd_reg(radeon_connector, DP_EDP_CONFIGURATION_CAP);
+		if (tmp & 1)
+			panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
+		else if ((dp_bridge == ENCODER_OBJECT_ID_NUTMEG) ||
+			 (dp_bridge == ENCODER_OBJECT_ID_TRAVIS))
 			panel_mode = DP_PANEL_MODE_INTERNAL_DP1_MODE;
 		else
-			panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
+			panel_mode = DP_PANEL_MODE_EXTERNAL_DP_MODE;
 	} else if (connector->connector_type == DRM_MODE_CONNECTOR_eDP) {
-		u8 tmp = radeon_read_dpcd_reg(radeon_connector, DP_EDP_CONFIGURATION_CAP);
+		/* eDP */
+		tmp = radeon_read_dpcd_reg(radeon_connector, DP_EDP_CONFIGURATION_CAP);
 		if (tmp & 1)
 			panel_mode = DP_PANEL_MODE_INTERNAL_DP2_MODE;
 	}