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
  19 static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  20                                     struct net_device *dev)
  21 {
  22         struct dsa_port *dp = dsa_slave_to_port(dev);
  23         u8 *mtk_tag;
  24         bool is_vlan_skb = true;
  25
  26         /* Build the special tag after the MAC Source Address. If VLAN header
  27          * is present, it's required that VLAN header and special tag is
  28          * being combined. Only in this way we can allow the switch can parse
  29          * the both special and VLAN tag at the same time and then look up VLAN
  30          * table with VID.
  31          */
  32         if (!skb_vlan_tagged(skb)) {
  33                 if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  34                         return NULL;
  35
  36                 skb_push(skb, MTK_HDR_LEN);
  37                 memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  38                 is_vlan_skb = false;
  39         }
  40
  41         mtk_tag = skb->data + 2 * ETH_ALEN;
  42
  43         /* Mark tag attribute on special tag insertion to notify hardware
  44          * whether that's a combined special tag with 802.1Q header.
  45          */
  46         mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
  47                      MTK_HDR_XMIT_UNTAGGED;
  48         mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  49
  50         /* Tag control information is kept for 802.1Q */
  51         if (!is_vlan_skb) {
  52                 mtk_tag[2] = 0;
  53                 mtk_tag[3] = 0;
  54         }
  55
  56         return skb;
  57 }
  58
  59 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  60                                    struct packet_type *pt)
  61 {
  62         int port;
  63         __be16 *phdr, hdr;
  64
  65         if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  66                 return NULL;
  67
  68         /* The MTK header is added by the switch between src addr
  69          * and ethertype at this point, skb->data points to 2 bytes
  70          * after src addr so header should be 2 bytes right before.
  71          */
  72         phdr = (__be16 *)(skb->data - 2);
  73         hdr = ntohs(*phdr);
  74
  75         /* Remove MTK tag and recalculate checksum. */
  76         skb_pull_rcsum(skb, MTK_HDR_LEN);
  77
  78         memmove(skb->data - ETH_HLEN,
  79                 skb->data - ETH_HLEN - MTK_HDR_LEN,
  80                 2 * ETH_ALEN);
  81
  82         /* Get source port information */
  83         port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  84
  85         skb->dev = dsa_master_find_slave(dev, 0, port);
  86         if (!skb->dev)
  87                 return NULL;
  88
  89         return skb;
  90 }
  91
  92 static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
  93                                 int *offset)
  94 {
  95         *offset = 4;
  96         *proto = ((__be16 *)skb->data)[1];
  97
  98         return 0;
  99 }
 100
 101 static const struct dsa_device_ops mtk_netdev_ops = {
 102         .name           = "mtk",
 103         .proto          = DSA_TAG_PROTO_MTK,
 104         .xmit           = mtk_tag_xmit,
 105         .rcv            = mtk_tag_rcv,
 106         .flow_dissect   = mtk_tag_flow_dissect,
 107         .overhead       = MTK_HDR_LEN,
 108 };
 109
 110 MODULE_LICENSE("GPL");
 111 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
 112
 113 module_dsa_tag_driver(mtk_netdev_ops);