xref: /openbmc/linux/net/dsa/tag_lan9303.c (revision bd954b82)
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 "tag.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_NAME "lan9303"
34 
35 #define LAN9303_TAG_LEN 4
36 # define LAN9303_TAG_TX_USE_ALR BIT(3)
37 # define LAN9303_TAG_TX_STP_OVERRIDE BIT(4)
38 # define LAN9303_TAG_RX_IGMP BIT(3)
39 # define LAN9303_TAG_RX_STP BIT(4)
40 # define LAN9303_TAG_RX_TRAPPED_TO_CPU (LAN9303_TAG_RX_IGMP | \
41 					LAN9303_TAG_RX_STP)
42 
43 /* Decide whether to transmit using ALR lookup, or transmit directly to
44  * port using tag. ALR learning is performed only when using ALR lookup.
45  * If the two external ports are bridged and the frame is unicast,
46  * then use ALR lookup to allow ALR learning on CPU port.
47  * Otherwise transmit directly to port with STP state override.
48  * See also: lan9303_separate_ports() and lan9303.pdf 6.4.10.1
49  */
lan9303_xmit_use_arl(struct dsa_port * dp,u8 * dest_addr)50 static int lan9303_xmit_use_arl(struct dsa_port *dp, u8 *dest_addr)
51 {
52 	struct lan9303 *chip = dp->ds->priv;
53 
54 	return chip->is_bridged && !is_multicast_ether_addr(dest_addr);
55 }
56 
lan9303_xmit(struct sk_buff * skb,struct net_device * dev)57 static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
58 {
59 	struct dsa_port *dp = dsa_slave_to_port(dev);
60 	__be16 *lan9303_tag;
61 	u16 tag;
62 
63 	/* provide 'LAN9303_TAG_LEN' bytes additional space */
64 	skb_push(skb, LAN9303_TAG_LEN);
65 
66 	/* make room between MACs and Ether-Type */
67 	dsa_alloc_etype_header(skb, LAN9303_TAG_LEN);
68 
69 	lan9303_tag = dsa_etype_header_pos_tx(skb);
70 
71 	tag = lan9303_xmit_use_arl(dp, skb->data) ?
72 		LAN9303_TAG_TX_USE_ALR :
73 		dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
74 	lan9303_tag[0] = htons(ETH_P_8021Q);
75 	lan9303_tag[1] = htons(tag);
76 
77 	return skb;
78 }
79 
lan9303_rcv(struct sk_buff * skb,struct net_device * dev)80 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
81 {
82 	u16 lan9303_tag1;
83 	unsigned int source_port;
84 
85 	if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
86 		dev_warn_ratelimited(&dev->dev,
87 				     "Dropping packet, cannot pull\n");
88 		return NULL;
89 	}
90 
91 	if (skb_vlan_tag_present(skb)) {
92 		lan9303_tag1 = skb_vlan_tag_get(skb);
93 		__vlan_hwaccel_clear_tag(skb);
94 	} else {
95 		skb_push_rcsum(skb, ETH_HLEN);
96 		__skb_vlan_pop(skb, &lan9303_tag1);
97 		skb_pull_rcsum(skb, ETH_HLEN);
98 	}
99 
100 	source_port = lan9303_tag1 & 0x3;
101 
102 	skb->dev = dsa_master_find_slave(dev, 0, source_port);
103 	if (!skb->dev) {
104 		dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
105 		return NULL;
106 	}
107 
108 	if (!(lan9303_tag1 & LAN9303_TAG_RX_TRAPPED_TO_CPU))
109 		dsa_default_offload_fwd_mark(skb);
110 
111 	return skb;
112 }
113 
114 static const struct dsa_device_ops lan9303_netdev_ops = {
115 	.name = LAN9303_NAME,
116 	.proto	= DSA_TAG_PROTO_LAN9303,
117 	.xmit = lan9303_xmit,
118 	.rcv = lan9303_rcv,
119 	.needed_headroom = LAN9303_TAG_LEN,
120 };
121 
122 MODULE_LICENSE("GPL");
123 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN9303, LAN9303_NAME);
124 
125 module_dsa_tag_driver(lan9303_netdev_ops);
126