net-next: dsa: add Qualcomm tag RX/TX handler

Add support for the 2-bytes Qualcomm tag that gigabit switches such as
the QCA8337/N might insert when receiving packets, or that we need
to insert while targeting specific switch ports. The tag is inserted
directly behind the ethernet header.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/dsa.h

@@ -26,6 +26,7 @@ enum dsa_tag_protocol {
 	DSA_TAG_PROTO_TRAILER,
 	DSA_TAG_PROTO_EDSA,
 	DSA_TAG_PROTO_BRCM,
+	DSA_TAG_PROTO_QCA,
 	DSA_TAG_LAST,		/* MUST BE LAST */
 };
 

net/dsa/Kconfig

@@ -38,4 +38,7 @@ config NET_DSA_TAG_EDSA
 config NET_DSA_TAG_TRAILER
 	bool
 
+config NET_DSA_TAG_QCA
+	bool
+
 endif

net/dsa/Makefile

@@ -7,3 +7,4 @@ dsa_core-$(CONFIG_NET_DSA_TAG_BRCM) += tag_brcm.o
 dsa_core-$(CONFIG_NET_DSA_TAG_DSA) += tag_dsa.o
 dsa_core-$(CONFIG_NET_DSA_TAG_EDSA) += tag_edsa.o
 dsa_core-$(CONFIG_NET_DSA_TAG_TRAILER) += tag_trailer.o
+dsa_core-$(CONFIG_NET_DSA_TAG_QCA) += tag_qca.o

net/dsa/dsa.c

@@ -53,6 +53,9 @@ const struct dsa_device_ops *dsa_device_ops[DSA_TAG_LAST] = {
 #endif
 #ifdef CONFIG_NET_DSA_TAG_BRCM
 	[DSA_TAG_PROTO_BRCM] = &brcm_netdev_ops,
+#endif
+#ifdef CONFIG_NET_DSA_TAG_QCA
+	[DSA_TAG_PROTO_QCA] = &qca_netdev_ops,
 #endif
 	[DSA_TAG_PROTO_NONE] = &none_ops,
 };

net/dsa/dsa_priv.h

@@ -81,5 +81,7 @@ extern const struct dsa_device_ops trailer_netdev_ops;
 /* tag_brcm.c */
 extern const struct dsa_device_ops brcm_netdev_ops;
 
+/* tag_qca.c */
+extern const struct dsa_device_ops qca_netdev_ops;
 
 #endif

net/dsa/tag_qca.c

@@ -0,0 +1,138 @@
+/*
+ * Copyright (c) 2015, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/etherdevice.h>
+#include "dsa_priv.h"
+
+#define QCA_HDR_LEN	2
+#define QCA_HDR_VERSION	0x2
+
+#define QCA_HDR_RECV_VERSION_MASK	GENMASK(15, 14)
+#define QCA_HDR_RECV_VERSION_S		14
+#define QCA_HDR_RECV_PRIORITY_MASK	GENMASK(13, 11)
+#define QCA_HDR_RECV_PRIORITY_S		11
+#define QCA_HDR_RECV_TYPE_MASK		GENMASK(10, 6)
+#define QCA_HDR_RECV_TYPE_S		6
+#define QCA_HDR_RECV_FRAME_IS_TAGGED	BIT(3)
+#define QCA_HDR_RECV_SOURCE_PORT_MASK	GENMASK(2, 0)
+
+#define QCA_HDR_XMIT_VERSION_MASK	GENMASK(15, 14)
+#define QCA_HDR_XMIT_VERSION_S		14
+#define QCA_HDR_XMIT_PRIORITY_MASK	GENMASK(13, 11)
+#define QCA_HDR_XMIT_PRIORITY_S		11
+#define QCA_HDR_XMIT_CONTROL_MASK	GENMASK(10, 8)
+#define QCA_HDR_XMIT_CONTROL_S		8
+#define QCA_HDR_XMIT_FROM_CPU		BIT(7)
+#define QCA_HDR_XMIT_DP_BIT_MASK	GENMASK(6, 0)
+
+static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct dsa_slave_priv *p = netdev_priv(dev);
+	u16 *phdr, hdr;
+
+	dev->stats.tx_packets++;
+	dev->stats.tx_bytes += skb->len;
+
+	if (skb_cow_head(skb, 0) < 0)
+		goto out_free;
+
+	skb_push(skb, QCA_HDR_LEN);
+
+	memmove(skb->data, skb->data + QCA_HDR_LEN, 2 * ETH_ALEN);
+	phdr = (u16 *)(skb->data + 2 * ETH_ALEN);
+
+	/* Set the version field, and set destination port information */
+	hdr = QCA_HDR_VERSION << QCA_HDR_XMIT_VERSION_S |
+		QCA_HDR_XMIT_FROM_CPU |
+		BIT(p->port);
+
+	*phdr = htons(hdr);
+
+	return skb;
+
+out_free:
+	kfree_skb(skb);
+	return NULL;
+}
+
+static int qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
+		       struct packet_type *pt, struct net_device *orig_dev)
+{
+	struct dsa_switch_tree *dst = dev->dsa_ptr;
+	struct dsa_switch *ds;
+	u8 ver;
+	int port;
+	__be16 *phdr, hdr;
+
+	if (unlikely(!dst))
+		goto out_drop;
+
+	skb = skb_unshare(skb, GFP_ATOMIC);
+	if (!skb)
+		goto out;
+
+	if (unlikely(!pskb_may_pull(skb, QCA_HDR_LEN)))
+		goto out_drop;
+
+	/* The QCA header is added by the switch between src addr and Ethertype
+	 * At this point, skb->data points to ethertype so header should be
+	 * right before
+	 */
+	phdr = (__be16 *)(skb->data - 2);
+	hdr = ntohs(*phdr);
+
+	/* Make sure the version is correct */
+	ver = (hdr & QCA_HDR_RECV_VERSION_MASK) >> QCA_HDR_RECV_VERSION_S;
+	if (unlikely(ver != QCA_HDR_VERSION))
+		goto out_drop;
+
+	/* Remove QCA tag and recalculate checksum */
+	skb_pull_rcsum(skb, QCA_HDR_LEN);
+	memmove(skb->data - ETH_HLEN, skb->data - ETH_HLEN - QCA_HDR_LEN,
+		ETH_HLEN - QCA_HDR_LEN);
+
+	/* This protocol doesn't support cascading multiple switches so it's
+	 * safe to assume the switch is first in the tree
+	 */
+	ds = dst->ds[0];
+	if (!ds)
+		goto out_drop;
+
+	/* Get source port information */
+	port = (hdr & QCA_HDR_RECV_SOURCE_PORT_MASK);
+	if (!ds->ports[port].netdev)
+		goto out_drop;
+
+	/* Update skb & forward the frame accordingly */
+	skb_push(skb, ETH_HLEN);
+	skb->pkt_type = PACKET_HOST;
+	skb->dev = ds->ports[port].netdev;
+	skb->protocol = eth_type_trans(skb, skb->dev);
+
+	skb->dev->stats.rx_packets++;
+	skb->dev->stats.rx_bytes += skb->len;
+
+	netif_receive_skb(skb);
+
+	return 0;
+
+out_drop:
+	kfree_skb(skb);
+out:
+	return 0;
+}
+
+const struct dsa_device_ops qca_netdev_ops = {
+	.xmit	= qca_tag_xmit,
+	.rcv	= qca_tag_rcv,
+};