net/dsa/tag_mtk.c

   1 /*
   2  * Mediatek DSA Tag support
   3  * Copyright (C) 2017 Landen Chao <landen.chao@mediatek.com>
   4  *                    Sean Wang <sean.wang@mediatek.com>
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 and
   7  * only version 2 as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #include <linux/etherdevice.h>
  16 #include <linux/if_vlan.h>
  17
  18 #include "dsa_priv.h"
  19
  20 #define MTK_HDR_LEN             4
  21 #define MTK_HDR_XMIT_UNTAGGED           0
  22 #define MTK_HDR_XMIT_TAGGED_TPID_8100   1
  23 #define MTK_HDR_RECV_SOURCE_PORT_MASK   GENMASK(2, 0)
  24 #define MTK_HDR_XMIT_DP_BIT_MASK        GENMASK(5, 0)
  25
  26 static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  27                                     struct net_device *dev)
  28 {
  29         struct dsa_port *dp = dsa_slave_to_port(dev);
  30         u8 *mtk_tag;
  31         bool is_vlan_skb = true;
  32
  33         /* Build the special tag after the MAC Source Address. If VLAN header
  34          * is present, it's required that VLAN header and special tag is
  35          * being combined. Only in this way we can allow the switch can parse
  36          * the both special and VLAN tag at the same time and then look up VLAN
  37          * table with VID.
  38          */
  39         if (!skb_vlan_tagged(skb)) {
  40                 if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  41                         return NULL;
  42
  43                 skb_push(skb, MTK_HDR_LEN);
  44                 memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  45                 is_vlan_skb = false;
  46         }
  47
  48         mtk_tag = skb->data + 2 * ETH_ALEN;
  49
  50         /* Mark tag attribute on special tag insertion to notify hardware
  51          * whether that's a combined special tag with 802.1Q header.
  52          */
  53         mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
  54                      MTK_HDR_XMIT_UNTAGGED;
  55         mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  56
  57         /* Tag control information is kept for 802.1Q */
  58         if (!is_vlan_skb) {
  59                 mtk_tag[2] = 0;
  60                 mtk_tag[3] = 0;
  61         }
  62
  63         return skb;
  64 }
  65
  66 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  67                                    struct packet_type *pt)
  68 {
  69         int port;
  70         __be16 *phdr, hdr;
  71
  72         if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  73                 return NULL;
  74
  75         /* The MTK header is added by the switch between src addr
  76          * and ethertype at this point, skb->data points to 2 bytes
  77          * after src addr so header should be 2 bytes right before.
  78          */
  79         phdr = (__be16 *)(skb->data - 2);
  80         hdr = ntohs(*phdr);
  81
  82         /* Remove MTK tag and recalculate checksum. */
  83         skb_pull_rcsum(skb, MTK_HDR_LEN);
  84
  85         memmove(skb->data - ETH_HLEN,
  86                 skb->data - ETH_HLEN - MTK_HDR_LEN,
  87                 2 * ETH_ALEN);
  88
  89         /* Get source port information */
  90         port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  91
  92         skb->dev = dsa_master_find_slave(dev, 0, port);
  93         if (!skb->dev)
  94                 return NULL;
  95
  96         return skb;
  97 }
  98
  99 static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 100                                 int *offset)
 101 {
 102         *offset = 4;
 103         *proto = ((__be16 *)skb->data)[1];
 104
 105         return 0;
 106 }
 107
 108 const struct dsa_device_ops mtk_netdev_ops = {
 109         .xmit           = mtk_tag_xmit,
 110         .rcv            = mtk_tag_rcv,
 111         .flow_dissect   = mtk_tag_flow_dissect,
 112 };