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
mtk_tag_xmit(struct sk_buff * skb,struct net_device * dev)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
mtk_tag_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt)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
mtk_tag_flow_dissect(const struct sk_buff * skb,__be16 * proto,int * offset)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 };
113
