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
 16#include "dsa_priv.h"
 17
 18/* This tag length is 4 bytes, older ones were 6 bytes, we do not
 19 * handle them
 20 */
 21#define BRCM_TAG_LEN	4
 22
 23/* Tag is constructed and desconstructed using byte by byte access
 24 * because the tag is placed after the MAC Source Address, which does
 25 * not make it 4-bytes aligned, so this might cause unaligned accesses
 26 * on most systems where this is used.
 27 */
 28
 29/* Ingress and egress opcodes */
 30#define BRCM_OPCODE_SHIFT	5
 31#define BRCM_OPCODE_MASK	0x7
 32
 33/* Ingress fields */
 34/* 1st byte in the tag */
 35#define BRCM_IG_TC_SHIFT	2
 36#define BRCM_IG_TC_MASK		0x7
 37/* 2nd byte in the tag */
 38#define BRCM_IG_TE_MASK		0x3
 39#define BRCM_IG_TS_SHIFT	7
 40/* 3rd byte in the tag */
 41#define BRCM_IG_DSTMAP2_MASK	1
 42#define BRCM_IG_DSTMAP1_MASK	0xff
 43
 44/* Egress fields */
 45
 46/* 2nd byte in the tag */
 47#define BRCM_EG_CID_MASK	0xff
 48
 49/* 3rd byte in the tag */
 50#define BRCM_EG_RC_MASK		0xff
 51#define  BRCM_EG_RC_RSVD	(3 << 6)
 52#define  BRCM_EG_RC_EXCEPTION	(1 << 5)
 53#define  BRCM_EG_RC_PROT_SNOOP	(1 << 4)
 54#define  BRCM_EG_RC_PROT_TERM	(1 << 3)
 55#define  BRCM_EG_RC_SWITCH	(1 << 2)
 56#define  BRCM_EG_RC_MAC_LEARN	(1 << 1)
 57#define  BRCM_EG_RC_MIRROR	(1 << 0)
 58#define BRCM_EG_TC_SHIFT	5
 59#define BRCM_EG_TC_MASK		0x7
 60#define BRCM_EG_PID_MASK	0x1f
 61
 62static struct sk_buff *brcm_tag_xmit_ll(struct sk_buff *skb,
 63					struct net_device *dev,
 64					unsigned int offset)
 65{
 66	struct dsa_port *dp = dsa_slave_to_port(dev);
 67	u16 queue = skb_get_queue_mapping(skb);
 68	u8 *brcm_tag;
 69
 70	if (skb_cow_head(skb, BRCM_TAG_LEN) < 0)
 71		return NULL;
 72
 73	/* The Ethernet switch we are interfaced with needs packets to be at
 74	 * least 64 bytes (including FCS) otherwise they will be discarded when
 75	 * they enter the switch port logic. When Broadcom tags are enabled, we
 76	 * need to make sure that packets are at least 68 bytes
 77	 * (including FCS and tag) because the length verification is done after
 78	 * the Broadcom tag is stripped off the ingress packet.
 79	 *
 80	 * Let dsa_slave_xmit() free the SKB
 81	 */
 82	if (__skb_put_padto(skb, ETH_ZLEN + BRCM_TAG_LEN, false))
 83		return NULL;
 84
 85	skb_push(skb, BRCM_TAG_LEN);
 86
 87	if (offset)
 88		memmove(skb->data, skb->data + BRCM_TAG_LEN, offset);
 89
 90	brcm_tag = skb->data + offset;
 91
 92	/* Set the ingress opcode, traffic class, tag enforcment is
 93	 * deprecated
 94	 */
 95	brcm_tag[0] = (1 << BRCM_OPCODE_SHIFT) |
 96		       ((queue & BRCM_IG_TC_MASK) << BRCM_IG_TC_SHIFT);
 97	brcm_tag[1] = 0;
 98	brcm_tag[2] = 0;
 99	if (dp->index == 8)
100		brcm_tag[2] = BRCM_IG_DSTMAP2_MASK;
101	brcm_tag[3] = (1 << dp->index) & BRCM_IG_DSTMAP1_MASK;
102
103	/* Now tell the master network device about the desired output queue
104	 * as well
105	 */
106	skb_set_queue_mapping(skb, BRCM_TAG_SET_PORT_QUEUE(dp->index, queue));
107
108	return skb;
109}
110
111static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
112				       struct net_device *dev,
113				       struct packet_type *pt,
114				       unsigned int offset)
115{
116	int source_port;
117	u8 *brcm_tag;
118
119	if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
120		return NULL;
121
122	brcm_tag = skb->data - offset;
123
124	/* The opcode should never be different than 0b000 */
125	if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
126		return NULL;
127
128	/* We should never see a reserved reason code without knowing how to
129	 * handle it
130	 */
131	if (unlikely(brcm_tag[2] & BRCM_EG_RC_RSVD))
132		return NULL;
133
134	/* Locate which port this is coming from */
135	source_port = brcm_tag[3] & BRCM_EG_PID_MASK;
136
137	skb->dev = dsa_master_find_slave(dev, 0, source_port);
138	if (!skb->dev)
139		return NULL;
140
141	/* Remove Broadcom tag and update checksum */
142	skb_pull_rcsum(skb, BRCM_TAG_LEN);
143
144	return skb;
145}
146
147#ifdef CONFIG_NET_DSA_TAG_BRCM
148static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb,
149				     struct net_device *dev)
150{
151	/* Build the tag after the MAC Source Address */
152	return brcm_tag_xmit_ll(skb, dev, 2 * ETH_ALEN);
153}
154
155
156static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
157				    struct packet_type *pt)
158{
159	struct sk_buff *nskb;
160
161	/* skb->data points to the EtherType, the tag is right before it */
162	nskb = brcm_tag_rcv_ll(skb, dev, pt, 2);
163	if (!nskb)
164		return nskb;
165
166	/* Move the Ethernet DA and SA */
167	memmove(nskb->data - ETH_HLEN,
168		nskb->data - ETH_HLEN - BRCM_TAG_LEN,
169		2 * ETH_ALEN);
170
171	return nskb;
172}
173
174const struct dsa_device_ops brcm_netdev_ops = {
175	.xmit	= brcm_tag_xmit,
176	.rcv	= brcm_tag_rcv,
177};
178#endif
179
180#ifdef CONFIG_NET_DSA_TAG_BRCM_PREPEND
181static struct sk_buff *brcm_tag_xmit_prepend(struct sk_buff *skb,
182					     struct net_device *dev)
183{
184	/* tag is prepended to the packet */
185	return brcm_tag_xmit_ll(skb, dev, 0);
186}
187
188static struct sk_buff *brcm_tag_rcv_prepend(struct sk_buff *skb,
189					    struct net_device *dev,
190					    struct packet_type *pt)
191{
192	/* tag is prepended to the packet */
193	return brcm_tag_rcv_ll(skb, dev, pt, ETH_HLEN);
194}
195
196const struct dsa_device_ops brcm_prepend_netdev_ops = {
197	.xmit	= brcm_tag_xmit_prepend,
198	.rcv	= brcm_tag_rcv_prepend,
199};
200#endif