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_XMIT_TAGGED_TPID_88A8   2
  17 #define MTK_HDR_RECV_SOURCE_PORT_MASK   GENMASK(2, 0)
  18 #define MTK_HDR_XMIT_DP_BIT_MASK        GENMASK(5, 0)
  19 #define MTK_HDR_XMIT_SA_DIS             BIT(6)
  20
  21 static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  22                                     struct net_device *dev)
  23 {
  24         struct dsa_port *dp = dsa_slave_to_port(dev);
  25         u8 xmit_tpid;
  26         u8 *mtk_tag;
  27
  28         /* Build the special tag after the MAC Source Address. If VLAN header
  29          * is present, it's required that VLAN header and special tag is
  30          * being combined. Only in this way we can allow the switch can parse
  31          * the both special and VLAN tag at the same time and then look up VLAN
  32          * table with VID.
  33          */
  34         switch (skb->protocol) {
  35         case htons(ETH_P_8021Q):
  36                 xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_8100;
  37                 break;
  38         case htons(ETH_P_8021AD):
  39                 xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_88A8;
  40                 break;
  41         default:
  42                 xmit_tpid = MTK_HDR_XMIT_UNTAGGED;
  43                 skb_push(skb, MTK_HDR_LEN);
  44                 dsa_alloc_etype_header(skb, MTK_HDR_LEN);
  45         }
  46
  47         mtk_tag = dsa_etype_header_pos_tx(skb);
  48
  49         /* Mark tag attribute on special tag insertion to notify hardware
  50          * whether that's a combined special tag with 802.1Q header.
  51          */
  52         mtk_tag[0] = xmit_tpid;
  53         mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  54
  55         /* Tag control information is kept for 802.1Q */
  56         if (xmit_tpid == MTK_HDR_XMIT_UNTAGGED) {
  57                 mtk_tag[2] = 0;
  58                 mtk_tag[3] = 0;
  59         }
  60
  61         return skb;
  62 }
  63
  64 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev)
  65 {
  66         u16 hdr;
  67         int port;
  68         __be16 *phdr;
  69
  70         if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  71                 return NULL;
  72
  73         phdr = dsa_etype_header_pos_rx(skb);
  74         hdr = ntohs(*phdr);
  75
  76         /* Remove MTK tag and recalculate checksum. */
  77         skb_pull_rcsum(skb, MTK_HDR_LEN);
  78
  79         dsa_strip_etype_header(skb, MTK_HDR_LEN);
  80
  81         /* Get source port information */
  82         port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  83
  84         skb->dev = dsa_master_find_slave(dev, 0, port);
  85         if (!skb->dev)
  86                 return NULL;
  87
  88         dsa_default_offload_fwd_mark(skb);
  89
  90         return skb;
  91 }
  92
  93 static const struct dsa_device_ops mtk_netdev_ops = {
  94         .name           = "mtk",
  95         .proto          = DSA_TAG_PROTO_MTK,
  96         .xmit           = mtk_tag_xmit,
  97         .rcv            = mtk_tag_rcv,
  98         .needed_headroom = MTK_HDR_LEN,
  99 };
 100
 101 MODULE_LICENSE("GPL");
 102 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
 103
 104 module_dsa_tag_driver(mtk_netdev_ops);