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
mtk_tag_xmit(struct sk_buff * skb,struct net_device * dev)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
mtk_tag_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt)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
mtk_tag_flow_dissect(const struct sk_buff * skb,__be16 * proto,int * offset)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);
114