net: dsa: ksz: Add KSZ8795 tag code

Add DSA tag code for Microchip KSZ8795 switch. The switch is simpler
and the tag is only 1 byte, instead of 2 as is the case with KSZ9477.
Signed-off-by: Tristram Ha <Tristram.Ha@microchip.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: David S. Miller <davem@davemloft.net>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Tristram Ha <Tristram.Ha@microchip.com>
Cc: Vivien Didelot <vivien.didelot@gmail.com>
Cc: Woojung Huh <woojung.huh@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -41,6 +41,7 @@ struct phylink_link_state;
 #define DSA_TAG_PROTO_TRAILER_VALUE		11
 #define DSA_TAG_PROTO_8021Q_VALUE		12
 #define DSA_TAG_PROTO_SJA1105_VALUE		13
+#define DSA_TAG_PROTO_KSZ8795_VALUE		14
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
@@ -57,6 +58,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_TRAILER		= DSA_TAG_PROTO_TRAILER_VALUE,
 	DSA_TAG_PROTO_8021Q		= DSA_TAG_PROTO_8021Q_VALUE,
 	DSA_TAG_PROTO_SJA1105		= DSA_TAG_PROTO_SJA1105_VALUE,
+	DSA_TAG_PROTO_KSZ8795		= DSA_TAG_PROTO_KSZ8795_VALUE,
 };
 
 struct packet_type;

net/dsa/tag_ksz.c

@@ -69,6 +69,67 @@ static struct sk_buff *ksz_common_rcv(struct sk_buff *skb,
 	return skb;
 }
 
+/*
+ * For Ingress (Host -> KSZ8795), 1 byte is added before FCS.
+ * ---------------------------------------------------------------------------
+ * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag(1byte)|FCS(4bytes)
+ * ---------------------------------------------------------------------------
+ * tag : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x10=port5)
+ *
+ * For Egress (KSZ8795 -> Host), 1 byte is added before FCS.
+ * ---------------------------------------------------------------------------
+ * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|FCS(4bytes)
+ * ---------------------------------------------------------------------------
+ * tag0 : zero-based value represents port
+ *	  (eg, 0x00=port1, 0x02=port3, 0x06=port7)
+ */
+
+#define KSZ8795_INGRESS_TAG_LEN		1
+
+#define KSZ8795_TAIL_TAG_OVERRIDE	BIT(6)
+#define KSZ8795_TAIL_TAG_LOOKUP		BIT(7)
+
+static struct sk_buff *ksz8795_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	struct sk_buff *nskb;
+	u8 *tag;
+	u8 *addr;
+
+	nskb = ksz_common_xmit(skb, dev, KSZ8795_INGRESS_TAG_LEN);
+	if (!nskb)
+		return NULL;
+
+	/* Tag encoding */
+	tag = skb_put(nskb, KSZ8795_INGRESS_TAG_LEN);
+	addr = skb_mac_header(nskb);
+
+	*tag = 1 << dp->index;
+	if (is_link_local_ether_addr(addr))
+		*tag |= KSZ8795_TAIL_TAG_OVERRIDE;
+
+	return nskb;
+}
+
+static struct sk_buff *ksz8795_rcv(struct sk_buff *skb, struct net_device *dev,
+				  struct packet_type *pt)
+{
+	u8 *tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
+
+	return ksz_common_rcv(skb, dev, tag[0] & 7, KSZ_EGRESS_TAG_LEN);
+}
+
+static const struct dsa_device_ops ksz8795_netdev_ops = {
+	.name	= "ksz8795",
+	.proto	= DSA_TAG_PROTO_KSZ8795,
+	.xmit	= ksz8795_xmit,
+	.rcv	= ksz8795_rcv,
+	.overhead = KSZ8795_INGRESS_TAG_LEN,
+};
+
+DSA_TAG_DRIVER(ksz8795_netdev_ops);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ8795);
+
 /*
  * For Ingress (Host -> KSZ9477), 2 bytes are added before FCS.
  * ---------------------------------------------------------------------------
@@ -183,6 +244,7 @@ DSA_TAG_DRIVER(ksz9893_netdev_ops);
 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893);
 
 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),
 };