net/dsa/tag_brcm.c

   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
  62 static 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
 111 static 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
 148 static 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
 156 static 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
 174 const 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
 181 static 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
 188 static 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
 196 const struct dsa_device_ops brcm_prepend_netdev_ops = {
 197         .xmit   = brcm_tag_xmit_prepend,
 198         .rcv    = brcm_tag_rcv_prepend,
 199 };
 200 #endif