[RFC PATCH net-next 01/11] net: dsa: microchip: lan937x: add cascade tailtag

@@ -56,6 +56,7 @@ struct phylink_link_state;
 #define DSA_TAG_PROTO_RTL8_4T_VALUE		25
 #define DSA_TAG_PROTO_RZN1_A5PSW_VALUE		26
 #define DSA_TAG_PROTO_LAN937X_VALUE		27
+#define DSA_TAG_PROTO_LAN937X_CASCADE_VALUE     28
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,

@@ -86,6 +87,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_RTL8_4T		= DSA_TAG_PROTO_RTL8_4T_VALUE,
 	DSA_TAG_PROTO_RZN1_A5PSW	= DSA_TAG_PROTO_RZN1_A5PSW_VALUE,
 	DSA_TAG_PROTO_LAN937X		= DSA_TAG_PROTO_LAN937X_VALUE,
+	DSA_TAG_PROTO_LAN937X_CASCADE   = DSA_TAG_PROTO_LAN937X_CASCADE_VALUE,
 };
 
 struct dsa_switch;

@@ -16,6 +16,7 @@
 #define KSZ9477_NAME "ksz9477"
 #define KSZ9893_NAME "ksz9893"
 #define LAN937X_NAME "lan937x"
+#define LAN937X_CASCADE_NAME "lan937x_cascade"
 
 /* Typically only one byte is used for tail tag. */
 #define KSZ_PTP_TAG_LEN			4

@@ -24,6 +25,9 @@
 
 #define KSZ_HWTS_EN  0
 
+#define SWITCH_0       0
+#define SWITCH_1       1
+
 struct ksz_tagger_private {
 	struct ksz_tagger_data data; /* Must be first */
 	unsigned long state;

@@ -84,10 +88,10 @@ static int ksz_connect(struct dsa_switch *ds)
 }
 
 static struct sk_buff *ksz_common_rcv(struct sk_buff *skb,
-				      struct net_device *dev,
-				      unsigned int port, unsigned int len)
+				      struct net_device *dev, unsigned int port,
+				      unsigned int len, u8 device)
 {
-	skb->dev = dsa_master_find_slave(dev, 0, port);
+	skb->dev = dsa_master_find_slave(dev, device, port);
 	if (!skb->dev)
 		return NULL;
 

@@ -141,7 +145,7 @@ static struct sk_buff *ksz8795_rcv(struct sk_buff *skb, struct net_device *dev)
 {
 	u8 *tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
 
-	return ksz_common_rcv(skb, dev, tag[0] & 7, KSZ_EGRESS_TAG_LEN);
+	return ksz_common_rcv(skb, dev, tag[0] & 7, KSZ_EGRESS_TAG_LEN, SWITCH_0);
 }
 
 static const struct dsa_device_ops ksz8795_netdev_ops = {

@@ -177,6 +181,7 @@ MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ8795, KSZ8795_NAME);
 #define KSZ9477_INGRESS_TAG_LEN		2
 #define KSZ9477_PTP_TAG_LEN		4
 #define KSZ9477_PTP_TAG_INDICATION	0x80
+#define LAN937X_CASCADE_CHIP		0x40
 
 #define KSZ9477_TAIL_TAG_PRIO		GENMASK(8, 7)
 #define KSZ9477_TAIL_TAG_OVERRIDE	BIT(9)

@@ -304,6 +309,7 @@ static struct sk_buff *ksz9477_rcv(struct sk_buff *skb, struct net_device *dev)
 	u8 *tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
 	unsigned int port = tag[0] & 7;
 	unsigned int len = KSZ_EGRESS_TAG_LEN;
+	u8 device = SWITCH_0;
 
 	/* Extra 4-bytes PTP timestamp */
 	if (tag[0] & KSZ9477_PTP_TAG_INDICATION) {

@@ -311,7 +317,10 @@ static struct sk_buff *ksz9477_rcv(struct sk_buff *skb, struct net_device *dev)
 		len += KSZ_PTP_TAG_LEN;
 	}
 
-	return ksz_common_rcv(skb, dev, port, len);
+	if (tag[0] & LAN937X_CASCADE_CHIP)
+		device = SWITCH_1;
+
+	return ksz_common_rcv(skb, dev, port, len, device);
 }
 
 static const struct dsa_device_ops ksz9477_netdev_ops = {

@@ -390,6 +399,7 @@ MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893, KSZ9893_NAME);
  *	  (eg, 0x00=port1, 0x02=port3, 0x07=port8)
  */
 #define LAN937X_EGRESS_TAG_LEN		2
+#define LAN937X_CASCADE_TAG_LEN		3
 
 #define LAN937X_TAIL_TAG_BLOCKING_OVERRIDE	BIT(11)
 #define LAN937X_TAIL_TAG_LOOKUP			BIT(12)

@@ -442,11 +452,71 @@ static const struct dsa_device_ops lan937x_netdev_ops = {
 DSA_TAG_DRIVER(lan937x_netdev_ops);
 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN937X, LAN937X_NAME);
 
+/* For xmit, 3/7 bytes are added before FCS.
+ * ---------------------------------------------------------------------------
+ * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|ts(4bytes)|tag0(1byte)|tag1(1byte)|
+ * tag2(1byte)|FCS(4bytes)
+ * ---------------------------------------------------------------------------
+ * ts   : time stamp (Present only if PTP is enabled in the Hardware)
+ * tag0 : represents tag override, lookup and valid
+ * tag1 : each bit represents destination port map through switch 2
+ *	  (eg, 0x01=port1, 0x02=port2, 0x80=port8)
+ * tag2 : each bit represents destination port map through switch 1
+ *	  (eg, 0x01=port1, 0x02=port2, 0x80=port8)
+ *
+ * For rcv, 1/5 bytes is added before FCS.
+ * ---------------------------------------------------------------------------
+ * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|ts(4bytes)|tag0(1byte)|FCS(4bytes)
+ * ---------------------------------------------------------------------------
+ * ts   : time stamp (Present only if bit 7 of tag0 is set)
+ * tag0 : zero-based value represents port
+ *	  (eg, 0x00=port1, 0x02=port3, 0x07=port8)
+ */
+static struct sk_buff *lan937x_cascade_xmit(struct sk_buff *skb,
+					    struct net_device *dev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	const struct ethhdr *hdr = eth_hdr(skb);
+	__be32 *tag;
+	u32 val;
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
+		return NULL;
+
+	tag = skb_put(skb, LAN937X_CASCADE_TAG_LEN);
+
+	val |= BIT((dp->index + (8 * dp->ds->index)));
+
+	if (is_link_local_ether_addr(hdr->h_dest))
+		val |= (LAN937X_TAIL_TAG_BLOCKING_OVERRIDE << 8);
+
+	val |= (LAN937X_TAIL_TAG_VALID << 8);
+
+	put_unaligned_be24(val, tag);
+
+	return skb;
+}
+
+static const struct dsa_device_ops lan937x_cascade_netdev_ops = {
+	.name   = LAN937X_CASCADE_NAME,
+	.proto  = DSA_TAG_PROTO_LAN937X_CASCADE,
+	.xmit   = lan937x_cascade_xmit,
+	.rcv    = ksz9477_rcv,
+	.connect = ksz_connect,
+	.disconnect = ksz_disconnect,
+	.needed_tailroom = LAN937X_CASCADE_TAG_LEN,
+};
+
+DSA_TAG_DRIVER(lan937x_cascade_netdev_ops);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN937x_CASCADE,
+			    LAN937X_CASCADE_NAME);
+
 static struct dsa_tag_driver *dsa_tag_driver_array[] = {
 	&DSA_TAG_DRIVER_NAME(ksz8795_netdev_ops),
 	&DSA_TAG_DRIVER_NAME(ksz9477_netdev_ops),
 	&DSA_TAG_DRIVER_NAME(ksz9893_netdev_ops),
 	&DSA_TAG_DRIVER_NAME(lan937x_netdev_ops),
+	&DSA_TAG_DRIVER_NAME(lan937x_cascade_netdev_ops),
 };
 
 module_dsa_tag_drivers(dsa_tag_driver_array);