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#define MTK_HDR_XMIT_SA_DIS		BIT(6)
 19
 20static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
 21				    struct net_device *dev)
 22{
 23	struct dsa_port *dp = dsa_slave_to_port(dev);
 24	u8 *mtk_tag;
 25	bool is_vlan_skb = true;
 26	unsigned char *dest = eth_hdr(skb)->h_dest;
 27	bool is_multicast_skb = is_multicast_ether_addr(dest) &&
 28				!is_broadcast_ether_addr(dest);
 29
 30	/* Build the special tag after the MAC Source Address. If VLAN header
 31	 * is present, it's required that VLAN header and special tag is
 32	 * being combined. Only in this way we can allow the switch can parse
 33	 * the both special and VLAN tag at the same time and then look up VLAN
 34	 * table with VID.
 35	 */
 36	if (!skb_vlan_tagged(skb)) {
 37		if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
 38			return NULL;
 39
 40		skb_push(skb, MTK_HDR_LEN);
 41		memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
 42		is_vlan_skb = false;
 43	}
 44
 45	mtk_tag = skb->data + 2 * ETH_ALEN;
 46
 47	/* Mark tag attribute on special tag insertion to notify hardware
 48	 * whether that's a combined special tag with 802.1Q header.
 49	 */
 50	mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
 51		     MTK_HDR_XMIT_UNTAGGED;
 52	mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
 53
 54	/* Disable SA learning for multicast frames */
 55	if (unlikely(is_multicast_skb))
 56		mtk_tag[1] |= MTK_HDR_XMIT_SA_DIS;
 57
 58	/* Tag control information is kept for 802.1Q */
 59	if (!is_vlan_skb) {
 60		mtk_tag[2] = 0;
 61		mtk_tag[3] = 0;
 62	}
 63
 64	return skb;
 65}
 66
 67static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 68				   struct packet_type *pt)
 69{
 70	u16 hdr;
 71	int port;
 72	__be16 *phdr;
 73	unsigned char *dest = eth_hdr(skb)->h_dest;
 74	bool is_multicast_skb = is_multicast_ether_addr(dest) &&
 75				!is_broadcast_ether_addr(dest);
 76
 77	if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
 78		return NULL;
 79
 80	/* The MTK header is added by the switch between src addr
 81	 * and ethertype at this point, skb->data points to 2 bytes
 82	 * after src addr so header should be 2 bytes right before.
 83	 */
 84	phdr = (__be16 *)(skb->data - 2);
 85	hdr = ntohs(*phdr);
 86
 87	/* Remove MTK tag and recalculate checksum. */
 88	skb_pull_rcsum(skb, MTK_HDR_LEN);
 89
 90	memmove(skb->data - ETH_HLEN,
 91		skb->data - ETH_HLEN - MTK_HDR_LEN,
 92		2 * ETH_ALEN);
 93
 94	/* Get source port information */
 95	port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
 96
 97	skb->dev = dsa_master_find_slave(dev, 0, port);
 98	if (!skb->dev)
 99		return NULL;
100
101	/* Only unicast or broadcast frames are offloaded */
102	if (likely(!is_multicast_skb))
103		skb->offload_fwd_mark = 1;
104
105	return skb;
106}
107
108static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
109				int *offset)
110{
111	*offset = 4;
112	*proto = ((__be16 *)skb->data)[1];
113
114	return 0;
115}
116
117static const struct dsa_device_ops mtk_netdev_ops = {
118	.name		= "mtk",
119	.proto		= DSA_TAG_PROTO_MTK,
120	.xmit		= mtk_tag_xmit,
121	.rcv		= mtk_tag_rcv,
122	.flow_dissect	= mtk_tag_flow_dissect,
123	.overhead	= MTK_HDR_LEN,
124};
125
126MODULE_LICENSE("GPL");
127MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
128
129module_dsa_tag_driver(mtk_netdev_ops);