1/*
  2 * Broadcom tag support
  3 *
  4 * Copyright (C) 2014 Broadcom Corporation
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License as published by
  8 * the Free Software Foundation; either version 2 of the License, or
  9 * (at your option) any later version.
 10 */
 11
 12#include <linux/etherdevice.h>
 13#include <linux/list.h>
 14#include <linux/slab.h>
 15#include "dsa_priv.h"
 16
 17/* This tag length is 4 bytes, older ones were 6 bytes, we do not
 18 * handle them
 19 */
 20#define BRCM_TAG_LEN	4
 21
 22/* Tag is constructed and desconstructed using byte by byte access
 23 * because the tag is placed after the MAC Source Address, which does
 24 * not make it 4-bytes aligned, so this might cause unaligned accesses
 25 * on most systems where this is used.
 26 */
 27
 28/* Ingress and egress opcodes */
 29#define BRCM_OPCODE_SHIFT	5
 30#define BRCM_OPCODE_MASK	0x7
 31
 32/* Ingress fields */
 33/* 1st byte in the tag */
 34#define BRCM_IG_TC_SHIFT	2
 35#define BRCM_IG_TC_MASK		0x7
 36/* 2nd byte in the tag */
 37#define BRCM_IG_TE_MASK		0x3
 38#define BRCM_IG_TS_SHIFT	7
 39/* 3rd byte in the tag */
 40#define BRCM_IG_DSTMAP2_MASK	1
 41#define BRCM_IG_DSTMAP1_MASK	0xff
 42
 43/* Egress fields */
 44
 45/* 2nd byte in the tag */
 46#define BRCM_EG_CID_MASK	0xff
 47
 48/* 3rd byte in the tag */
 49#define BRCM_EG_RC_MASK		0xff
 50#define  BRCM_EG_RC_RSVD	(3 << 6)
 51#define  BRCM_EG_RC_EXCEPTION	(1 << 5)
 52#define  BRCM_EG_RC_PROT_SNOOP	(1 << 4)
 53#define  BRCM_EG_RC_PROT_TERM	(1 << 3)
 54#define  BRCM_EG_RC_SWITCH	(1 << 2)
 55#define  BRCM_EG_RC_MAC_LEARN	(1 << 1)
 56#define  BRCM_EG_RC_MIRROR	(1 << 0)
 57#define BRCM_EG_TC_SHIFT	5
 58#define BRCM_EG_TC_MASK		0x7
 59#define BRCM_EG_PID_MASK	0x1f
 60
 61static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb, struct net_device *dev)
 62{
 63	struct dsa_slave_priv *p = netdev_priv(dev);
 64	u8 *brcm_tag;
 65
 66	if (skb_cow_head(skb, BRCM_TAG_LEN) < 0)
 67		goto out_free;
 68
 69	skb_push(skb, BRCM_TAG_LEN);
 70
 71	memmove(skb->data, skb->data + BRCM_TAG_LEN, 2 * ETH_ALEN);
 72
 73	/* Build the tag after the MAC Source Address */
 74	brcm_tag = skb->data + 2 * ETH_ALEN;
 75
 76	/* Set the ingress opcode, traffic class, tag enforcment is
 77	 * deprecated
 78	 */
 79	brcm_tag[0] = (1 << BRCM_OPCODE_SHIFT) |
 80			((skb->priority << BRCM_IG_TC_SHIFT) & BRCM_IG_TC_MASK);
 81	brcm_tag[1] = 0;
 82	brcm_tag[2] = 0;
 83	if (p->port == 8)
 84		brcm_tag[2] = BRCM_IG_DSTMAP2_MASK;
 85	brcm_tag[3] = (1 << p->port) & BRCM_IG_DSTMAP1_MASK;
 86
 87	return skb;
 88
 89out_free:
 90	kfree_skb(skb);
 91	return NULL;
 92}
 93
 94static int brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 95			struct packet_type *pt, struct net_device *orig_dev)
 96{
 97	struct dsa_switch_tree *dst = dev->dsa_ptr;
 98	struct dsa_switch *ds;
 99	int source_port;
100	u8 *brcm_tag;
101
102	if (unlikely(dst == NULL))
103		goto out_drop;
104
105	ds = dst->ds[0];
106
107	skb = skb_unshare(skb, GFP_ATOMIC);
108	if (skb == NULL)
109		goto out;
110
111	if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
112		goto out_drop;
113
114	/* skb->data points to the EtherType, the tag is right before it */
115	brcm_tag = skb->data - 2;
116
117	/* The opcode should never be different than 0b000 */
118	if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
119		goto out_drop;
120
121	/* We should never see a reserved reason code without knowing how to
122	 * handle it
123	 */
124	WARN_ON(brcm_tag[2] & BRCM_EG_RC_RSVD);
125
126	/* Locate which port this is coming from */
127	source_port = brcm_tag[3] & BRCM_EG_PID_MASK;
128
129	/* Validate port against switch setup, either the port is totally */
130	if (source_port >= DSA_MAX_PORTS || !ds->ports[source_port].netdev)
131		goto out_drop;
132
133	/* Remove Broadcom tag and update checksum */
134	skb_pull_rcsum(skb, BRCM_TAG_LEN);
135
136	/* Move the Ethernet DA and SA */
137	memmove(skb->data - ETH_HLEN,
138		skb->data - ETH_HLEN - BRCM_TAG_LEN,
139		2 * ETH_ALEN);
140
141	skb_push(skb, ETH_HLEN);
142	skb->pkt_type = PACKET_HOST;
143	skb->dev = ds->ports[source_port].netdev;
144	skb->protocol = eth_type_trans(skb, skb->dev);
145
146	skb->dev->stats.rx_packets++;
147	skb->dev->stats.rx_bytes += skb->len;
148
149	netif_receive_skb(skb);
150
151	return 0;
152
153out_drop:
154	kfree_skb(skb);
155out:
156	return 0;
157}
158
159const struct dsa_device_ops brcm_netdev_ops = {
160	.xmit	= brcm_tag_xmit,
161	.rcv	= brcm_tag_rcv,
162};