net: dsa: add Broadcom tag RX/TX handler

Add support for the 4-bytes Broadcom tag that built-in switches such as
the Starfighter 2 might insert when receiving packets, or that we need
to insert while targetting specific switch ports. We use a fake local
EtherType value for this 4-bytes switch tag: ETH_P_BRCMTAG to make sure
we can assign DSA-specific network operations within the DSA drivers.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 185 insertions, 0 deletions

diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index f5eede1d6cb8..a585fd6352eb 100644
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -12,6 +12,9 @@ config NET_DSA
 if NET_DSA
 
 # tagging formats
+config NET_DSA_TAG_BRCM
+        bool
+
 config NET_DSA_TAG_DSA
         bool
 
diff --git a/net/dsa/Makefile b/net/dsa/Makefile
index 7b9fcbbeda5d..da06ed1df620 100644
--- a/net/dsa/Makefile
+++ b/net/dsa/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_NET_DSA) += dsa_core.o
 dsa_core-y += dsa.o slave.o
 
 # tagging formats
+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
diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index d20364ac1574..98afed4d92ba 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -57,5 +57,8 @@ extern const struct dsa_device_ops edsa_netdev_ops;
 /* tag_trailer.c */
 extern const struct dsa_device_ops trailer_netdev_ops;
 
+/* tag_brcm.c */
+extern const struct dsa_device_ops brcm_netdev_ops;
+
 
 #endif
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 18ff53836fe3..7333a4aebb7d 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -451,6 +451,11 @@ dsa_slave_create(struct dsa_switch *ds, struct device *parent,
                 ds->dst->ops = &trailer_netdev_ops;
                 break;
 #endif
+#ifdef CONFIG_NET_DSA_TAG_BRCM
+        case htons(ETH_P_BRCMTAG):
+                ds->dst->ops = &brcm_netdev_ops;
+                break;
+#endif
         default:
                 ds->dst->ops = &notag_netdev_ops;
                 break;
diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c
new file mode 100644
index 000000000000..e0b759ec209e
--- /dev/null
+++ b/net/dsa/tag_brcm.c
@@ -0,0 +1,173 @@
+/*
+ * Broadcom tag support
+ *
+ * Copyright (C) 2014 Broadcom Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include <linux/slab.h>
+#include "dsa_priv.h"
+
+/* This tag length is 4 bytes, older ones were 6 bytes, we do not
+ * handle them
+ */
+#define BRCM_TAG_LEN    4
+
+/* Tag is constructed and desconstructed using byte by byte access
+ * because the tag is placed after the MAC Source Address, which does
+ * not make it 4-bytes aligned, so this might cause unaligned accesses
+ * on most systems where this is used.
+ */
+
+/* Ingress and egress opcodes */
+#define BRCM_OPCODE_SHIFT       5
+#define BRCM_OPCODE_MASK        0x7
+
+/* Ingress fields */
+/* 1st byte in the tag */
+#define BRCM_IG_TC_SHIFT        2
+#define BRCM_IG_TC_MASK         0x7
+/* 2nd byte in the tag */
+#define BRCM_IG_TE_MASK         0x3
+#define BRCM_IG_TS_SHIFT        7
+/* 3rd byte in the tag */
+#define BRCM_IG_DSTMAP2_MASK    1
+#define BRCM_IG_DSTMAP1_MASK    0xff
+
+/* Egress fields */
+
+/* 2nd byte in the tag */
+#define BRCM_EG_CID_MASK        0xff
+
+/* 3rd byte in the tag */
+#define BRCM_EG_RC_MASK         0xff
+#define  BRCM_EG_RC_RSVD        (3 << 6)
+#define  BRCM_EG_RC_EXCEPTION   (1 << 5)
+#define  BRCM_EG_RC_PROT_SNOOP  (1 << 4)
+#define  BRCM_EG_RC_PROT_TERM   (1 << 3)
+#define  BRCM_EG_RC_SWITCH      (1 << 2)
+#define  BRCM_EG_RC_MAC_LEARN   (1 << 1)
+#define  BRCM_EG_RC_MIRROR      (1 << 0)
+#define BRCM_EG_TC_SHIFT        5
+#define BRCM_EG_TC_MASK         0x7
+#define BRCM_EG_PID_MASK        0x1f
+
+static netdev_tx_t brcm_tag_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+        struct dsa_slave_priv *p = netdev_priv(dev);
+        u8 *brcm_tag;
+
+        dev->stats.tx_packets++;
+        dev->stats.tx_bytes += skb->len;
+
+        if (skb_cow_head(skb, BRCM_TAG_LEN) < 0)
+                goto out_free;
+
+        skb_push(skb, BRCM_TAG_LEN);
+
+        memmove(skb->data, skb->data + BRCM_TAG_LEN, 2 * ETH_ALEN);
+
+        /* Build the tag after the MAC Source Address */
+        brcm_tag = skb->data + 2 * ETH_ALEN;
+
+        /* Set the ingress opcode, traffic class, tag enforcment is
+         * deprecated
+         */
+        brcm_tag[0] = (1 << BRCM_OPCODE_SHIFT) |
+                        ((skb->priority << BRCM_IG_TC_SHIFT) & BRCM_IG_TC_MASK);
+        brcm_tag[1] = 0;
+        brcm_tag[2] = 0;
+        if (p->port == 8)
+                brcm_tag[2] = BRCM_IG_DSTMAP2_MASK;
+        brcm_tag[3] = (1 << p->port) & BRCM_IG_DSTMAP1_MASK;
+
+        /* Queue the SKB for transmission on the parent interface, but
+         * do not modify its EtherType
+         */
+        skb->protocol = htons(ETH_P_BRCMTAG);
+        skb->dev = p->parent->dst->master_netdev;
+        dev_queue_xmit(skb);
+
+        return NETDEV_TX_OK;
+
+out_free:
+        kfree_skb(skb);
+        return NETDEV_TX_OK;
+}
+
+static int brcm_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;
+        int source_port;
+        u8 *brcm_tag;
+
+        if (unlikely(dst == NULL))
+                goto out_drop;
+
+        ds = dst->ds[0];
+
+        skb = skb_unshare(skb, GFP_ATOMIC);
+        if (skb == NULL)
+                goto out;
+
+        if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
+                goto out_drop;
+
+        /* skb->data points to the EtherType, the tag is right before it */
+        brcm_tag = skb->data - 2;
+
+        /* The opcode should never be different than 0b000 */
+        if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
+                goto out_drop;
+
+        /* We should never see a reserved reason code without knowing how to
+         * handle it
+         */
+        WARN_ON(brcm_tag[2] & BRCM_EG_RC_RSVD);
+
+        /* Locate which port this is coming from */
+        source_port = brcm_tag[3] & BRCM_EG_PID_MASK;
+
+        /* Validate port against switch setup, either the port is totally */
+        if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
+                goto out_drop;
+
+        /* Remove Broadcom tag and update checksum */
+        skb_pull_rcsum(skb, BRCM_TAG_LEN);
+
+        /* Move the Ethernet DA and SA */
+        memmove(skb->data - ETH_HLEN,
+                skb->data - ETH_HLEN - BRCM_TAG_LEN,
+                2 * ETH_ALEN);
+
+        skb_push(skb, ETH_HLEN);
+        skb->pkt_type = PACKET_HOST;
+        skb->dev = ds->ports[source_port];
+        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 brcm_netdev_ops = {
+        .xmit   = brcm_tag_xmit,
+        .rcv    = brcm_tag_rcv,
+};