[PATCH v4 net-next 04/10] net: dsa: tag_ksz: add tag handling for Microchip LAN937x

[Prasanna Vengateshan <prasanna.vengateshan@microchip.com>]

The Microchip LAN937X switches have a tagging protocol which is
very similar to KSZ tagging. So that the implementation is added to
tag_ksz.c and reused common APIs

Signed-off-by: Prasanna Vengateshan <prasanna.vengateshan@microchip.com>
---
 include/net/dsa.h |  2 ++
 net/dsa/Kconfig   |  4 ++--
 net/dsa/tag_ksz.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 2 deletions(-)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index d784e76113b8..0b5eda0021e7 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -51,6 +51,7 @@ struct phylink_link_state;
 #define DSA_TAG_PROTO_SEVILLE_VALUE		21
 #define DSA_TAG_PROTO_BRCM_LEGACY_VALUE		22
 #define DSA_TAG_PROTO_SJA1110_VALUE		23
+#define DSA_TAG_PROTO_LAN937X_VALUE		24
 
 enum dsa_tag_protocol {
 	DSA_TAG_PROTO_NONE		= DSA_TAG_PROTO_NONE_VALUE,
@@ -77,6 +78,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_OCELOT_8021Q	= DSA_TAG_PROTO_OCELOT_8021Q_VALUE,
 	DSA_TAG_PROTO_SEVILLE		= DSA_TAG_PROTO_SEVILLE_VALUE,
 	DSA_TAG_PROTO_SJA1110		= DSA_TAG_PROTO_SJA1110_VALUE,
+	DSA_TAG_PROTO_LAN937X		= DSA_TAG_PROTO_LAN937X_VALUE,
 };
 
 struct dsa_switch;
diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index bca1b5d66df2..f728e60e0bd3 100644
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -87,10 +87,10 @@ config NET_DSA_TAG_MTK
 	  Mediatek switches.
 
 config NET_DSA_TAG_KSZ
-	tristate "Tag driver for Microchip 8795/9477/9893 families of switches"
+	tristate "Tag driver for Microchip 8795/937x/9477/9893 families of switches"
 	help
 	  Say Y if you want to enable support for tagging frames for the
-	  Microchip 8795/9477/9893 families of switches.
+	  Microchip 8795/937x/9477/9893 families of switches.
 
 config NET_DSA_TAG_RTL4_A
 	tristate "Tag driver for Realtek 4 byte protocol A tags"
diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
index 3509fc967ca9..38fa19c1e2d5 100644
--- a/net/dsa/tag_ksz.c
+++ b/net/dsa/tag_ksz.c
@@ -193,10 +193,69 @@ static const struct dsa_device_ops ksz9893_netdev_ops = {
 DSA_TAG_DRIVER(ksz9893_netdev_ops);
 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893);
 
+/* For xmit, 2 bytes are added before FCS.
+ * ---------------------------------------------------------------------------
+ * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|tag1(1byte)|FCS(4bytes)
+ * ---------------------------------------------------------------------------
+ * tag0 : represents tag override, lookup and valid
+ * tag1 : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x80=port8)
+ *
+ * For rcv, 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, 0x07=port8)
+ */
+#define LAN937X_EGRESS_TAG_LEN		2
+
+#define LAN937X_TAIL_TAG_BLOCKING_OVERRIDE	BIT(11)
+#define LAN937X_TAIL_TAG_LOOKUP			BIT(12)
+#define LAN937X_TAIL_TAG_VALID			BIT(13)
+#define LAN937X_TAIL_TAG_PORT_MASK		7
+
+static struct sk_buff *lan937x_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);
+	__be16 *tag;
+	u16 val;
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL && skb_checksum_help(skb))
+		return NULL;
+
+	tag = skb_put(skb, LAN937X_EGRESS_TAG_LEN);
+
+	val = BIT(dp->index);
+
+	if (is_link_local_ether_addr(hdr->h_dest))
+		val |= LAN937X_TAIL_TAG_BLOCKING_OVERRIDE;
+
+	/* Tail tag valid bit - This bit should always be set by the CPU */
+	val |= LAN937X_TAIL_TAG_VALID;
+
+	put_unaligned_be16(val, tag);
+
+	return skb;
+}
+
+static const struct dsa_device_ops lan937x_netdev_ops = {
+	.name	= "lan937x",
+	.proto	= DSA_TAG_PROTO_LAN937X,
+	.xmit	= lan937x_xmit,
+	.rcv	= ksz9477_rcv,
+	.needed_tailroom = LAN937X_EGRESS_TAG_LEN,
+};
+
+DSA_TAG_DRIVER(lan937x_netdev_ops);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN937X);
+
 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),
 };
 
 module_dsa_tag_drivers(dsa_tag_driver_array);
-- 
2.27.0