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
mtk_tag_xmit(struct sk_buff * skb,struct net_device * dev)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 unsigned char *dest = eth_hdr(skb)->h_dest;
28 bool is_multicast_skb = is_multicast_ether_addr(dest) &&
29 !is_broadcast_ether_addr(dest);
30
31 /* Build the special tag after the MAC Source Address. If VLAN header
32 * is present, it's required that VLAN header and special tag is
33 * being combined. Only in this way we can allow the switch can parse
34 * the both special and VLAN tag at the same time and then look up VLAN
35 * table with VID.
36 */
37 switch (skb->protocol) {
38 case htons(ETH_P_8021Q):
39 xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_8100;
40 break;
41 case htons(ETH_P_8021AD):
42 xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_88A8;
43 break;
44 default:
45 xmit_tpid = MTK_HDR_XMIT_UNTAGGED;
46 skb_push(skb, MTK_HDR_LEN);
47 memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
48 }
49
50 mtk_tag = skb->data + 2 * ETH_ALEN;
51
52 /* Mark tag attribute on special tag insertion to notify hardware
53 * whether that's a combined special tag with 802.1Q header.
54 */
55 mtk_tag[0] = xmit_tpid;
56 mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
57
58 /* Disable SA learning for multicast frames */
59 if (unlikely(is_multicast_skb))
60 mtk_tag[1] |= MTK_HDR_XMIT_SA_DIS;
61
62 /* Tag control information is kept for 802.1Q */
63 if (xmit_tpid == MTK_HDR_XMIT_UNTAGGED) {
64 mtk_tag[2] = 0;
65 mtk_tag[3] = 0;
66 }
67
68 return skb;
69 }
70
mtk_tag_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt)71 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
72 struct packet_type *pt)
73 {
74 u16 hdr;
75 int port;
76 __be16 *phdr;
77 unsigned char *dest = eth_hdr(skb)->h_dest;
78 bool is_multicast_skb = is_multicast_ether_addr(dest) &&
79 !is_broadcast_ether_addr(dest);
80
81 if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
82 return NULL;
83
84 /* The MTK header is added by the switch between src addr
85 * and ethertype at this point, skb->data points to 2 bytes
86 * after src addr so header should be 2 bytes right before.
87 */
88 phdr = (__be16 *)(skb->data - 2);
89 hdr = ntohs(*phdr);
90
91 /* Remove MTK tag and recalculate checksum. */
92 skb_pull_rcsum(skb, MTK_HDR_LEN);
93
94 memmove(skb->data - ETH_HLEN,
95 skb->data - ETH_HLEN - MTK_HDR_LEN,
96 2 * ETH_ALEN);
97
98 /* Get source port information */
99 port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
100
101 skb->dev = dsa_master_find_slave(dev, 0, port);
102 if (!skb->dev)
103 return NULL;
104
105 /* Only unicast or broadcast frames are offloaded */
106 if (likely(!is_multicast_skb))
107 skb->offload_fwd_mark = 1;
108
109 return skb;
110 }
111
112 static const struct dsa_device_ops mtk_netdev_ops = {
113 .name = "mtk",
114 .proto = DSA_TAG_PROTO_MTK,
115 .xmit = mtk_tag_xmit,
116 .rcv = mtk_tag_rcv,
117 .overhead = MTK_HDR_LEN,
118 };
119
120 MODULE_LICENSE("GPL");
121 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
122
123 module_dsa_tag_driver(mtk_netdev_ops);
124