[PATCH V3 2/3] net: dsa: ksz: Factor out common tag code

[Marek Vasut <marex@denx.de>]

From: Tristram Ha <Tristram.Ha@microchip.com>

Factor out common code from the tag_ksz , so that the code can be used
with other KSZ family switches which use differenly sized tags.

Signed-off-by: Tristram Ha <Tristram.Ha@microchip.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Cc: Woojung Huh <woojung.huh@microchip.com>
Cc: David S. Miller <davem@davemloft.net>
--
V2: - Rebase on next/master
    - Redo the code refactoring again, this by pulling out common pieces
      of the xmit, receive functions, to avoid function calls through
      pointers.
V3: - Check return value of ksz_common_xmit()
---
 net/dsa/tag_ksz.c | 112 ++++++++++++++++++++++++++++++----------------
 1 file changed, 73 insertions(+), 39 deletions(-)

diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
index c24a333e55bd..c98b53f691bd 100644
--- a/net/dsa/tag_ksz.c
+++ b/net/dsa/tag_ksz.c
@@ -14,34 +14,18 @@
 #include <net/dsa.h>
 #include "dsa_priv.h"
 
-/* For Ingress (Host -> KSZ), 2 bytes are added before FCS.
- * ---------------------------------------------------------------------------
- * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|tag1(1byte)|FCS(4bytes)
- * ---------------------------------------------------------------------------
- * tag0 : Prioritization (not used now)
- * tag1 : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x10=port5)
- *
- * For Egress (KSZ -> 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)
- */
+/* Typically only one byte is used for tail tag. */
+#define KSZ_EGRESS_TAG_LEN		1
 
-#define	KSZ_INGRESS_TAG_LEN	2
-#define	KSZ_EGRESS_TAG_LEN	1
-
-static struct sk_buff *ksz_xmit(struct sk_buff *skb, struct net_device *dev)
+static struct sk_buff *ksz_common_xmit(struct sk_buff *skb,
+				       struct net_device *dev, int len)
 {
-	struct dsa_port *dp = dsa_slave_to_port(dev);
 	struct sk_buff *nskb;
 	int padlen;
-	u8 *tag;
 
 	padlen = (skb->len >= ETH_ZLEN) ? 0 : ETH_ZLEN - skb->len;
 
-	if (skb_tailroom(skb) >= padlen + KSZ_INGRESS_TAG_LEN) {
+	if (skb_tailroom(skb) >= padlen + len) {
 		/* Let dsa_slave_xmit() free skb */
 		if (__skb_put_padto(skb, skb->len + padlen, false))
 			return NULL;
@@ -49,7 +33,7 @@ static struct sk_buff *ksz_xmit(struct sk_buff *skb, struct net_device *dev)
 		nskb = skb;
 	} else {
 		nskb = alloc_skb(NET_IP_ALIGN + skb->len +
-				 padlen + KSZ_INGRESS_TAG_LEN, GFP_ATOMIC);
+				 padlen + len, GFP_ATOMIC);
 		if (!nskb)
 			return NULL;
 		skb_reserve(nskb, NET_IP_ALIGN);
@@ -70,34 +54,84 @@ static struct sk_buff *ksz_xmit(struct sk_buff *skb, struct net_device *dev)
 		consume_skb(skb);
 	}
 
-	tag = skb_put(nskb, KSZ_INGRESS_TAG_LEN);
-	tag[0] = 0;
-	tag[1] = 1 << dp->index; /* destination port */
-
 	return nskb;
 }
 
-static struct sk_buff *ksz_rcv(struct sk_buff *skb, struct net_device *dev,
-			       struct packet_type *pt)
+static struct sk_buff *ksz_common_rcv(struct sk_buff *skb,
+				      struct net_device *dev,
+				      unsigned int port, unsigned int len)
 {
-	u8 *tag;
-	int source_port;
+	skb->dev = dsa_master_find_slave(dev, 0, port);
+	if (!skb->dev)
+		return NULL;
 
-	tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
+	pskb_trim_rcsum(skb, skb->len - len);
 
-	source_port = tag[0] & 7;
+	return skb;
+}
 
-	skb->dev = dsa_master_find_slave(dev, 0, source_port);
-	if (!skb->dev)
+/*
+ * For Ingress (Host -> KSZ9477), 2 bytes are added before FCS.
+ * ---------------------------------------------------------------------------
+ * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|tag1(1byte)|FCS(4bytes)
+ * ---------------------------------------------------------------------------
+ * tag0 : Prioritization (not used now)
+ * tag1 : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x10=port5)
+ *
+ * For Egress (KSZ9477 -> 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 KSZ9477_INGRESS_TAG_LEN		2
+#define KSZ9477_PTP_TAG_LEN		4
+#define KSZ9477_PTP_TAG_INDICATION	0x80
+
+#define KSZ9477_TAIL_TAG_OVERRIDE	BIT(9)
+#define KSZ9477_TAIL_TAG_LOOKUP		BIT(10)
+
+static struct sk_buff *ksz9477_xmit(struct sk_buff *skb,
+				    struct net_device *dev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	struct sk_buff *nskb;
+	u16 *tag;
+	u8 *addr;
+
+	nskb = ksz_common_xmit(skb, dev, KSZ9477_INGRESS_TAG_LEN);
+	if (!nskb)
 		return NULL;
 
-	pskb_trim_rcsum(skb, skb->len - KSZ_EGRESS_TAG_LEN);
+	/* Tag encoding */
+	tag = skb_put(nskb, KSZ9477_INGRESS_TAG_LEN);
+	addr = skb_mac_header(nskb);
 
-	return skb;
+	*tag = BIT(dp->index);
+	*tag = cpu_to_be16(*tag);
+
+	return nskb;
+}
+
+static struct sk_buff *ksz9477_rcv(struct sk_buff *skb, struct net_device *dev,
+				   struct packet_type *pt)
+{
+	/* Tag decoding */
+	u8 *tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
+	unsigned int port = tag[0] & 7;
+	unsigned int len = KSZ_EGRESS_TAG_LEN;
+
+	/* Extra 4-bytes PTP timestamp */
+	if (tag[0] & KSZ9477_PTP_TAG_INDICATION)
+		len += KSZ9477_PTP_TAG_LEN;
+
+	return ksz_common_rcv(skb, dev, port, len);
 }
 
 const struct dsa_device_ops ksz9477_netdev_ops = {
-	.xmit	= ksz_xmit,
-	.rcv	= ksz_rcv,
-	.overhead = KSZ_INGRESS_TAG_LEN,
+	.xmit	= ksz9477_xmit,
+	.rcv	= ksz9477_rcv,
+	.overhead = KSZ9477_INGRESS_TAG_LEN,
 };
-- 
2.18.0