LXR linux/net/dsa/tag

   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
  20static 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                skb_push(skb, MTK_HDR_LEN);
  38                memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  39                is_vlan_skb = false;
  40        }
  41
  42        mtk_tag = skb->data + 2 * ETH_ALEN;
  43
  44        /* Mark tag attribute on special tag insertion to notify hardware
  45         * whether that's a combined special tag with 802.1Q header.
  46         */
  47        mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
  48                     MTK_HDR_XMIT_UNTAGGED;
  49        mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  50
  51        /* Disable SA learning for multicast frames */
  52        if (unlikely(is_multicast_skb))
  53                mtk_tag[1] |= MTK_HDR_XMIT_SA_DIS;
  54
  55        /* Tag control information is kept for 802.1Q */
  56        if (!is_vlan_skb) {
  57                mtk_tag[2] = 0;
  58                mtk_tag[3] = 0;
  59        }
  60
  61        return skb;
  62}
  63
  64static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  65                                   struct packet_type *pt)
  66{
  67        u16 hdr;
  68        int port;
  69        __be16 *phdr;
  70        unsigned char *dest = eth_hdr(skb)->h_dest;
  71        bool is_multicast_skb = is_multicast_ether_addr(dest) &&
  72                                !is_broadcast_ether_addr(dest);
  73
  74        if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  75                return NULL;
  76
  77        /* The MTK header is added by the switch between src addr
  78         * and ethertype at this point, skb->data points to 2 bytes
  79         * after src addr so header should be 2 bytes right before.
  80         */
  81        phdr = (__be16 *)(skb->data - 2);
  82        hdr = ntohs(*phdr);
  83
  84        /* Remove MTK tag and recalculate checksum. */
  85        skb_pull_rcsum(skb, MTK_HDR_LEN);
  86
  87        memmove(skb->data - ETH_HLEN,
  88                skb->data - ETH_HLEN - MTK_HDR_LEN,
  89                2 * ETH_ALEN);
  90
  91        /* Get source port information */
  92        port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  93
  94        skb->dev = dsa_master_find_slave(dev, 0, port);
  95        if (!skb->dev)
  96                return NULL;
  97
  98        /* Only unicast or broadcast frames are offloaded */
  99        if (likely(!is_multicast_skb))
 100                skb->offload_fwd_mark = 1;
 101
 102        return skb;
 103}
 104
 105static const struct dsa_device_ops mtk_netdev_ops = {
 106        .name           = "mtk",
 107        .proto          = DSA_TAG_PROTO_MTK,
 108        .xmit           = mtk_tag_xmit,
 109        .rcv            = mtk_tag_rcv,
 110        .overhead       = MTK_HDR_LEN,
 111};
 112
 113MODULE_LICENSE("GPL");
 114MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
 115
 116module_dsa_tag_driver(mtk_netdev_ops);
 117