net/dsa/tag_lan9303.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Copyright (C) 2017 Pengutronix, Juergen Borleis <jbe@pengutronix.de>
0004  */
0005 #include <linux/dsa/lan9303.h>
0006 #include <linux/etherdevice.h>
0007 #include <linux/list.h>
0008 #include <linux/slab.h>
0009
0010 #include "dsa_priv.h"
0011
0012 /* To define the outgoing port and to discover the incoming port a regular
0013  * VLAN tag is used by the LAN9303. But its VID meaning is 'special':
0014  *
0015  *       Dest MAC       Src MAC        TAG    Type
0016  * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 | 1 2 |...
0017  *                                |<------->|
0018  * TAG:
0019  *    |<------------->|
0020  *    |  1  2 | 3  4  |
0021  *      TPID    VID
0022  *     0x8100
0023  *
0024  * VID bit 3 indicates a request for an ALR lookup.
0025  *
0026  * If VID bit 3 is zero, then bits 0 and 1 specify the destination port
0027  * (0, 1, 2) or broadcast (3) or the source port (1, 2).
0028  *
0029  * VID bit 4 is used to specify if the STP port state should be overridden.
0030  * Required when no forwarding between the external ports should happen.
0031  */
0032
0033 #define LAN9303_TAG_LEN 4
0034 # define LAN9303_TAG_TX_USE_ALR BIT(3)
0035 # define LAN9303_TAG_TX_STP_OVERRIDE BIT(4)
0036 # define LAN9303_TAG_RX_IGMP BIT(3)
0037 # define LAN9303_TAG_RX_STP BIT(4)
0038 # define LAN9303_TAG_RX_TRAPPED_TO_CPU (LAN9303_TAG_RX_IGMP | \
0039                     LAN9303_TAG_RX_STP)
0040
0041 /* Decide whether to transmit using ALR lookup, or transmit directly to
0042  * port using tag. ALR learning is performed only when using ALR lookup.
0043  * If the two external ports are bridged and the frame is unicast,
0044  * then use ALR lookup to allow ALR learning on CPU port.
0045  * Otherwise transmit directly to port with STP state override.
0046  * See also: lan9303_separate_ports() and lan9303.pdf 6.4.10.1
0047  */
0048 static int lan9303_xmit_use_arl(struct dsa_port *dp, u8 *dest_addr)
0049 {
0050     struct lan9303 *chip = dp->ds->priv;
0051
0052     return chip->is_bridged && !is_multicast_ether_addr(dest_addr);
0053 }
0054
0055 static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
0056 {
0057     struct dsa_port *dp = dsa_slave_to_port(dev);
0058     __be16 *lan9303_tag;
0059     u16 tag;
0060
0061     /* provide 'LAN9303_TAG_LEN' bytes additional space */
0062     skb_push(skb, LAN9303_TAG_LEN);
0063
0064     /* make room between MACs and Ether-Type */
0065     dsa_alloc_etype_header(skb, LAN9303_TAG_LEN);
0066
0067     lan9303_tag = dsa_etype_header_pos_tx(skb);
0068
0069     tag = lan9303_xmit_use_arl(dp, skb->data) ?
0070         LAN9303_TAG_TX_USE_ALR :
0071         dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
0072     lan9303_tag[0] = htons(ETH_P_8021Q);
0073     lan9303_tag[1] = htons(tag);
0074
0075     return skb;
0076 }
0077
0078 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
0079 {
0080     u16 lan9303_tag1;
0081     unsigned int source_port;
0082
0083     if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
0084         dev_warn_ratelimited(&dev->dev,
0085                      "Dropping packet, cannot pull\n");
0086         return NULL;
0087     }
0088
0089     if (skb_vlan_tag_present(skb)) {
0090         lan9303_tag1 = skb_vlan_tag_get(skb);
0091         __vlan_hwaccel_clear_tag(skb);
0092     } else {
0093         skb_push_rcsum(skb, ETH_HLEN);
0094         __skb_vlan_pop(skb, &lan9303_tag1);
0095         skb_pull_rcsum(skb, ETH_HLEN);
0096     }
0097
0098     source_port = lan9303_tag1 & 0x3;
0099
0100     skb->dev = dsa_master_find_slave(dev, 0, source_port);
0101     if (!skb->dev) {
0102         dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
0103         return NULL;
0104     }
0105
0106     if (!(lan9303_tag1 & LAN9303_TAG_RX_TRAPPED_TO_CPU))
0107         dsa_default_offload_fwd_mark(skb);
0108
0109     return skb;
0110 }
0111
0112 static const struct dsa_device_ops lan9303_netdev_ops = {
0113     .name = "lan9303",
0114     .proto  = DSA_TAG_PROTO_LAN9303,
0115     .xmit = lan9303_xmit,
0116     .rcv = lan9303_rcv,
0117     .needed_headroom = LAN9303_TAG_LEN,
0118 };
0119
0120 MODULE_LICENSE("GPL");
0121 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN9303);
0122
0123 module_dsa_tag_driver(lan9303_netdev_ops);