net/dsa/tag_mtk.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Mediatek DSA Tag support
   4  * Copyright (C) 2017 Landen Chao <landen.chao@mediatek.com>
   5  *                    Sean Wang <sean.wang@mediatek.com>
   6  */
   7
   8 #include <linux/etherdevice.h>
   9 #include <linux/if_vlan.h>
  10
  11 #include "dsa_priv.h"
  12
  13 #define MTK_HDR_LEN             4
  14 #define MTK_HDR_XMIT_UNTAGGED           0
  15 #define MTK_HDR_XMIT_TAGGED_TPID_8100   1
  16 #define MTK_HDR_RECV_SOURCE_PORT_MASK   GENMASK(2, 0)
  17 #define MTK_HDR_XMIT_DP_BIT_MASK        GENMASK(5, 0)
  18 #define MTK_HDR_XMIT_SA_DIS             BIT(6)
  19
  20 static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  21                                     struct net_device *dev)
  22 {
  23         struct dsa_port *dp = dsa_slave_to_port(dev);
  24         u8 *mtk_tag;
  25         bool is_vlan_skb = true;
  26         unsigned char *dest = eth_hdr(skb)->h_dest;
  27         bool is_multicast_skb = is_multicast_ether_addr(dest) &&
  28                                 !is_broadcast_ether_addr(dest);
  29
  30         /* Build the special tag after the MAC Source Address. If VLAN header
  31          * is present, it's required that VLAN header and special tag is
  32          * being combined. Only in this way we can allow the switch can parse
  33          * the both special and VLAN tag at the same time and then look up VLAN
  34          * table with VID.
  35          */
  36         if (!skb_vlan_tagged(skb)) {
  37                 if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  38                         return NULL;
  39
  40                 skb_push(skb, MTK_HDR_LEN);
  41                 memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  42                 is_vlan_skb = false;
  43         }
  44
  45         mtk_tag = skb->data + 2 * ETH_ALEN;
  46
  47         /* Mark tag attribute on special tag insertion to notify hardware
  48          * whether that's a combined special tag with 802.1Q header.
  49          */
  50         mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
  51                      MTK_HDR_XMIT_UNTAGGED;
  52         mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  53
  54         /* Disable SA learning for multicast frames */
  55         if (unlikely(is_multicast_skb))
  56                 mtk_tag[1] |= MTK_HDR_XMIT_SA_DIS;
  57
  58         /* Tag control information is kept for 802.1Q */
  59         if (!is_vlan_skb) {
  60                 mtk_tag[2] = 0;
  61                 mtk_tag[3] = 0;
  62         }
  63
  64         return skb;
  65 }
  66
  67 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  68                                    struct packet_type *pt)
  69 {
  70         int port;
  71         __be16 *phdr, hdr;
  72         unsigned char *dest = eth_hdr(skb)->h_dest;
  73         bool is_multicast_skb = is_multicast_ether_addr(dest) &&
  74                                 !is_broadcast_ether_addr(dest);
  75
  76         if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  77                 return NULL;
  78
  79         /* The MTK header is added by the switch between src addr
  80          * and ethertype at this point, skb->data points to 2 bytes
  81          * after src addr so header should be 2 bytes right before.
  82          */
  83         phdr = (__be16 *)(skb->data - 2);
  84         hdr = ntohs(*phdr);
  85
  86         /* Remove MTK tag and recalculate checksum. */
  87         skb_pull_rcsum(skb, MTK_HDR_LEN);
  88
  89         memmove(skb->data - ETH_HLEN,
  90                 skb->data - ETH_HLEN - MTK_HDR_LEN,
  91                 2 * ETH_ALEN);
  92
  93         /* Get source port information */
  94         port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  95
  96         skb->dev = dsa_master_find_slave(dev, 0, port);
  97         if (!skb->dev)
  98                 return NULL;
  99
 100         /* Only unicast or broadcast frames are offloaded */
 101         if (likely(!is_multicast_skb))
 102                 skb->offload_fwd_mark = 1;
 103
 104         return skb;
 105 }
 106
 107 static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 108                                 int *offset)
 109 {
 110         *offset = 4;
 111         *proto = ((__be16 *)skb->data)[1];
 112
 113         return 0;
 114 }
 115
 116 static const struct dsa_device_ops mtk_netdev_ops = {
 117         .name           = "mtk",
 118         .proto          = DSA_TAG_PROTO_MTK,
 119         .xmit           = mtk_tag_xmit,
 120         .rcv            = mtk_tag_rcv,
 121         .flow_dissect   = mtk_tag_flow_dissect,
 122         .overhead       = MTK_HDR_LEN,
 123 };
 124
 125 MODULE_LICENSE("GPL");
 126 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
 127
 128 module_dsa_tag_driver(mtk_netdev_ops);