1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2017 Pengutronix, Juergen Borleis <jbe@pengutronix.de>
4 */
5 #include <linux/dsa/lan9303.h>
6 #include <linux/etherdevice.h>
7 #include <linux/list.h>
8 #include <linux/slab.h>
9
10 #include "dsa_priv.h"
11
12 /* To define the outgoing port and to discover the incoming port a regular
13 * VLAN tag is used by the LAN9303. But its VID meaning is 'special':
14 *
15 * Dest MAC Src MAC TAG Type
16 * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 | 1 2 |...
17 * |<------->|
18 * TAG:
19 * |<------------->|
20 * | 1 2 | 3 4 |
21 * TPID VID
22 * 0x8100
23 *
24 * VID bit 3 indicates a request for an ALR lookup.
25 *
26 * If VID bit 3 is zero, then bits 0 and 1 specify the destination port
27 * (0, 1, 2) or broadcast (3) or the source port (1, 2).
28 *
29 * VID bit 4 is used to specify if the STP port state should be overridden.
30 * Required when no forwarding between the external ports should happen.
31 */
32
33 #define LAN9303_TAG_LEN 4
34 # define LAN9303_TAG_TX_USE_ALR BIT(3)
35 # define LAN9303_TAG_TX_STP_OVERRIDE BIT(4)
36 # define LAN9303_TAG_RX_IGMP BIT(3)
37 # define LAN9303_TAG_RX_STP BIT(4)
38 # define LAN9303_TAG_RX_TRAPPED_TO_CPU (LAN9303_TAG_RX_IGMP | \
39 LAN9303_TAG_RX_STP)
40
41 /* Decide whether to transmit using ALR lookup, or transmit directly to
42 * port using tag. ALR learning is performed only when using ALR lookup.
43 * If the two external ports are bridged and the frame is unicast,
44 * then use ALR lookup to allow ALR learning on CPU port.
45 * Otherwise transmit directly to port with STP state override.
46 * See also: lan9303_separate_ports() and lan9303.pdf 6.4.10.1
47 */
lan9303_xmit_use_arl(struct dsa_port * dp,u8 * dest_addr)48 static int lan9303_xmit_use_arl(struct dsa_port *dp, u8 *dest_addr)
49 {
50 struct lan9303 *chip = dp->ds->priv;
51
52 return chip->is_bridged && !is_multicast_ether_addr(dest_addr);
53 }
54
lan9303_xmit(struct sk_buff * skb,struct net_device * dev)55 static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
56 {
57 struct dsa_port *dp = dsa_slave_to_port(dev);
58 __be16 *lan9303_tag;
59 u16 tag;
60
61 /* insert a special VLAN tag between the MAC addresses
62 * and the current ethertype field.
63 */
64 if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
65 dev_dbg(&dev->dev,
66 "Cannot make room for the special tag. Dropping packet\n");
67 return NULL;
68 }
69
70 /* provide 'LAN9303_TAG_LEN' bytes additional space */
71 skb_push(skb, LAN9303_TAG_LEN);
72
73 /* make room between MACs and Ether-Type */
74 memmove(skb->data, skb->data + LAN9303_TAG_LEN, 2 * ETH_ALEN);
75
76 lan9303_tag = (__be16 *)(skb->data + 2 * ETH_ALEN);
77 tag = lan9303_xmit_use_arl(dp, skb->data) ?
78 LAN9303_TAG_TX_USE_ALR :
79 dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
80 lan9303_tag[0] = htons(ETH_P_8021Q);
81 lan9303_tag[1] = htons(tag);
82
83 return skb;
84 }
85
lan9303_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt)86 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev,
87 struct packet_type *pt)
88 {
89 __be16 *lan9303_tag;
90 u16 lan9303_tag1;
91 unsigned int source_port;
92
93 if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
94 dev_warn_ratelimited(&dev->dev,
95 "Dropping packet, cannot pull\n");
96 return NULL;
97 }
98
99 /* '->data' points into the middle of our special VLAN tag information:
100 *
101 * ~ MAC src | 0x81 | 0x00 | 0xyy | 0xzz | ether type
102 * ^
103 * ->data
104 */
105 lan9303_tag = (__be16 *)(skb->data - 2);
106
107 if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
108 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
109 return NULL;
110 }
111
112 lan9303_tag1 = ntohs(lan9303_tag[1]);
113 source_port = lan9303_tag1 & 0x3;
114
115 skb->dev = dsa_master_find_slave(dev, 0, source_port);
116 if (!skb->dev) {
117 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
118 return NULL;
119 }
120
121 /* remove the special VLAN tag between the MAC addresses
122 * and the current ethertype field.
123 */
124 skb_pull_rcsum(skb, 2 + 2);
125 memmove(skb->data - ETH_HLEN, skb->data - (ETH_HLEN + LAN9303_TAG_LEN),
126 2 * ETH_ALEN);
127 skb->offload_fwd_mark = !(lan9303_tag1 & LAN9303_TAG_RX_TRAPPED_TO_CPU);
128
129 return skb;
130 }
131
132 static const struct dsa_device_ops lan9303_netdev_ops = {
133 .name = "lan9303",
134 .proto = DSA_TAG_PROTO_LAN9303,
135 .xmit = lan9303_xmit,
136 .rcv = lan9303_rcv,
137 .overhead = LAN9303_TAG_LEN,
138 };
139
140 MODULE_LICENSE("GPL");
141 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN9303);
142
143 module_dsa_tag_driver(lan9303_netdev_ops);
144
