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_XMIT_TAGGED_TPID_88A8	2
 17#define MTK_HDR_RECV_SOURCE_PORT_MASK	GENMASK(2, 0)
 18#define MTK_HDR_XMIT_DP_BIT_MASK	GENMASK(5, 0)
 19#define MTK_HDR_XMIT_SA_DIS		BIT(6)
 20
 21static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
 22				    struct net_device *dev)
 23{
 24	struct dsa_port *dp = dsa_slave_to_port(dev);
 25	u8 xmit_tpid;
 26	u8 *mtk_tag;
 27
 28	/* Build the special tag after the MAC Source Address. If VLAN header
 29	 * is present, it's required that VLAN header and special tag is
 30	 * being combined. Only in this way we can allow the switch can parse
 31	 * the both special and VLAN tag at the same time and then look up VLAN
 32	 * table with VID.
 33	 */
 34	switch (skb->protocol) {
 35	case htons(ETH_P_8021Q):
 36		xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_8100;
 37		break;
 38	case htons(ETH_P_8021AD):
 39		xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_88A8;
 40		break;
 41	default:
 42		xmit_tpid = MTK_HDR_XMIT_UNTAGGED;
 43		skb_push(skb, MTK_HDR_LEN);
 44		memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
 45	}
 46
 47	mtk_tag = skb->data + 2 * ETH_ALEN;
 48
 49	/* Mark tag attribute on special tag insertion to notify hardware
 50	 * whether that's a combined special tag with 802.1Q header.
 51	 */
 52	mtk_tag[0] = xmit_tpid;
 53	mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
 54
 55	/* Tag control information is kept for 802.1Q */
 56	if (xmit_tpid == MTK_HDR_XMIT_UNTAGGED) {
 57		mtk_tag[2] = 0;
 58		mtk_tag[3] = 0;
 59	}
 60
 61	return skb;
 62}
 63
 64static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 65				   struct packet_type *pt)
 66{
 67	u16 hdr;
 68	int port;
 69	__be16 *phdr;
 70
 71	if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
 72		return NULL;
 73
 74	/* The MTK header is added by the switch between src addr
 75	 * and ethertype at this point, skb->data points to 2 bytes
 76	 * after src addr so header should be 2 bytes right before.
 77	 */
 78	phdr = (__be16 *)(skb->data - 2);
 79	hdr = ntohs(*phdr);
 80
 81	/* Remove MTK tag and recalculate checksum. */
 82	skb_pull_rcsum(skb, MTK_HDR_LEN);
 83
 84	memmove(skb->data - ETH_HLEN,
 85		skb->data - ETH_HLEN - MTK_HDR_LEN,
 86		2 * ETH_ALEN);
 87
 88	/* Get source port information */
 89	port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
 90
 91	skb->dev = dsa_master_find_slave(dev, 0, port);
 92	if (!skb->dev)
 93		return NULL;
 94
 95	skb->offload_fwd_mark = 1;
 96
 97	return skb;
 98}
 99
100static const struct dsa_device_ops mtk_netdev_ops = {
101	.name		= "mtk",
102	.proto		= DSA_TAG_PROTO_MTK,
103	.xmit		= mtk_tag_xmit,
104	.rcv		= mtk_tag_rcv,
105	.needed_headroom = MTK_HDR_LEN,
106};
107
108MODULE_LICENSE("GPL");
109MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
110
111module_dsa_tag_driver(mtk_netdev_ops);