@@ -524,9 +524,7 @@ enum rtl8365mb_cpu_rxlen {
  * @mask: port mask of ports that parse should parse CPU tags
  * @trap_port: forward trapped frames to this port
  * @insert: CPU tag insertion mode in switch->CPU frames
- * @position: position of CPU tag in frame
  * @rx_length: minimum CPU RX length
- * @format: CPU tag format
  *
  * Represents the CPU tagging and CPU port configuration of the switch. These
  * settings are configurable at runtime.

@@ -536,9 +534,7 @@ struct rtl8365mb_cpu {
 	u32 mask;
 	u32 trap_port;
 	enum rtl8365mb_cpu_insert insert;
-	enum rtl8365mb_cpu_position position;
 	enum rtl8365mb_cpu_rxlen rx_length;
-	enum rtl8365mb_cpu_format format;
 };
 
 /**

@@ -566,6 +562,7 @@ struct rtl8365mb_port {
  * @chip_ver: chip silicon revision
  * @port_mask: mask of all ports
  * @learn_limit_max: maximum number of L2 addresses the chip can learn
+ * @tag_protocol: current switch CPU tag protocol
  * @mib_lock: prevent concurrent reads of MIB counters
  * @ports: per-port data
  * @jam_table: chip-specific initialization jam table

@@ -580,6 +577,7 @@ struct rtl8365mb {
 	u32 chip_ver;
 	u32 port_mask;
 	u32 learn_limit_max;
+	enum dsa_tag_protocol tag_protocol;
 	struct mutex mib_lock;
 	struct rtl8365mb_port ports[RTL8365MB_MAX_NUM_PORTS];
 	const struct rtl8365mb_jam_tbl_entry *jam_table;

@@ -770,7 +768,54 @@ static enum dsa_tag_protocol
 rtl8365mb_get_tag_protocol(struct dsa_switch *ds, int port,
 			   enum dsa_tag_protocol mp)
 {
-	return DSA_TAG_PROTO_RTL8_4;
+	struct realtek_priv *priv = ds->priv;
+	struct rtl8365mb *chip_data;
+
+	chip_data = priv->chip_data;
+
+	return chip_data->tag_protocol;
+}
+
+static int rtl8365mb_change_tag_protocol(struct dsa_switch *ds, int cpu,
+					 enum dsa_tag_protocol proto)
+{
+	struct realtek_priv *priv = ds->priv;
+	struct rtl8365mb *chip_data;
+	int tag_position;
+	int tag_format;
+	int ret;
+
+	switch (proto) {
+	case DSA_TAG_PROTO_RTL8_4:
+		tag_format = RTL8365MB_CPU_FORMAT_8BYTES;
+		tag_position = RTL8365MB_CPU_POS_AFTER_SA;
+		break;
+	case DSA_TAG_PROTO_RTL8_4T:
+		tag_format = RTL8365MB_CPU_FORMAT_8BYTES;
+		tag_position = RTL8365MB_CPU_POS_BEFORE_CRC;
+		break;
+	/* The switch also supports a 4-byte format, similar to rtl4a but with
+	 * the same 0x04 8-bit version and probably 8-bit port source/dest.
+	 * There is no public doc about it. Not supported yet.
+	 */
+	default:
+		return -EPROTONOSUPPORT;
+	}
+
+	ret = regmap_update_bits(priv->map, RTL8365MB_CPU_CTRL_REG,
+				 RTL8365MB_CPU_CTRL_TAG_POSITION_MASK |
+				 RTL8365MB_CPU_CTRL_TAG_FORMAT_MASK,
+				 FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_POSITION_MASK,
+					    tag_position) |
+				 FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_FORMAT_MASK,
+					    tag_format));
+	if (ret)
+		return ret;
+
+	chip_data = priv->chip_data;
+	chip_data->tag_protocol = proto;
+
+	return 0;
 }
 
 static int rtl8365mb_ext_config_rgmii(struct realtek_priv *priv, int port,

@@ -1739,13 +1784,18 @@ static int rtl8365mb_cpu_config(struct realtek_priv *priv, const struct rtl8365m
 
 	val = FIELD_PREP(RTL8365MB_CPU_CTRL_EN_MASK, cpu->enable ? 1 : 0) |
 	      FIELD_PREP(RTL8365MB_CPU_CTRL_INSERTMODE_MASK, cpu->insert) |
-	      FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_POSITION_MASK, cpu->position) |
 	      FIELD_PREP(RTL8365MB_CPU_CTRL_RXBYTECOUNT_MASK, cpu->rx_length) |
-	      FIELD_PREP(RTL8365MB_CPU_CTRL_TAG_FORMAT_MASK, cpu->format) |
 	      FIELD_PREP(RTL8365MB_CPU_CTRL_TRAP_PORT_MASK, cpu->trap_port & 0x7) |
 	      FIELD_PREP(RTL8365MB_CPU_CTRL_TRAP_PORT_EXT_MASK,
 			 cpu->trap_port >> 3 & 0x1);
-	ret = regmap_write(priv->map, RTL8365MB_CPU_CTRL_REG, val);
+
+	ret = regmap_update_bits(priv->map, RTL8365MB_CPU_CTRL_REG,
+				 RTL8365MB_CPU_CTRL_EN_MASK |
+				 RTL8365MB_CPU_CTRL_INSERTMODE_MASK |
+				 RTL8365MB_CPU_CTRL_RXBYTECOUNT_MASK |
+				 RTL8365MB_CPU_CTRL_TRAP_PORT_MASK |
+				 RTL8365MB_CPU_CTRL_TRAP_PORT_EXT_MASK,
+				 val);
 	if (ret)
 		return ret;
 

@@ -1827,6 +1877,11 @@ static int rtl8365mb_setup(struct dsa_switch *ds)
 		dev_info(priv->dev, "no interrupt support\n");
 
 	/* Configure CPU tagging */
+	ret = rtl8365mb_change_tag_protocol(priv->ds, -1, DSA_TAG_PROTO_RTL8_4);
+	if (ret) {
+		dev_err(priv->dev, "failed to set default tag protocol: %d\n", ret);
+		return ret;
+	}
 	cpu.trap_port = RTL8365MB_MAX_NUM_PORTS;
 	dsa_switch_for_each_cpu_port(cpu_dp, priv->ds) {
 		cpu.mask |= BIT(cpu_dp->index);

@@ -1834,13 +1889,9 @@ static int rtl8365mb_setup(struct dsa_switch *ds)
 		if (cpu.trap_port == RTL8365MB_MAX_NUM_PORTS)
 			cpu.trap_port = cpu_dp->index;
 	}
-
 	cpu.enable = cpu.mask > 0;
 	cpu.insert = RTL8365MB_CPU_INSERT_TO_ALL;
-	cpu.position = RTL8365MB_CPU_POS_AFTER_SA;
 	cpu.rx_length = RTL8365MB_CPU_RXLEN_64BYTES;
-	cpu.format = RTL8365MB_CPU_FORMAT_8BYTES;
-
 	ret = rtl8365mb_cpu_config(priv, &cpu);
 	if (ret)
 		goto out_teardown_irq;

@@ -1982,6 +2033,7 @@ static int rtl8365mb_detect(struct realtek_priv *priv)
 		mb->learn_limit_max = RTL8365MB_LEARN_LIMIT_MAX;
 		mb->jam_table = rtl8365mb_init_jam_8365mb_vc;
 		mb->jam_size = ARRAY_SIZE(rtl8365mb_init_jam_8365mb_vc);
+		mb->tag_protocol = DSA_TAG_PROTO_RTL8_4;
 
 		break;
 	default:

@@ -1996,6 +2048,7 @@ static int rtl8365mb_detect(struct realtek_priv *priv)
 
 static const struct dsa_switch_ops rtl8365mb_switch_ops_smi = {
 	.get_tag_protocol = rtl8365mb_get_tag_protocol,
+	.change_tag_protocol = rtl8365mb_change_tag_protocol,
 	.setup = rtl8365mb_setup,
 	.teardown = rtl8365mb_teardown,
 	.phylink_get_caps = rtl8365mb_phylink_get_caps,

@@ -2014,6 +2067,7 @@ static const struct dsa_switch_ops rtl8365mb_switch_ops_smi = {
 
 static const struct dsa_switch_ops rtl8365mb_switch_ops_mdio = {
 	.get_tag_protocol = rtl8365mb_get_tag_protocol,
+	.change_tag_protocol = rtl8365mb_change_tag_protocol,
 	.setup = rtl8365mb_setup,
 	.teardown = rtl8365mb_teardown,
 	.phylink_get_caps = rtl8365mb_phylink_get_caps,