1/*
  2 * Mediatek DSA Tag support
  3 * Copyright (C) 2017 Landen Chao <landen.chao@mediatek.com>
  4 *		      Sean Wang <sean.wang@mediatek.com>
  5 * This program is free software; you can redistribute it and/or modify
  6 * it under the terms of the GNU General Public License version 2 and
  7 * only version 2 as published by the Free Software Foundation.
  8 *
  9 * This program is distributed in the hope that it will be useful,
 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12 * GNU General Public License for more details.
 13 */
 14
 15#include <linux/etherdevice.h>
 16#include <linux/if_vlan.h>
 17
 18#include "dsa_priv.h"
 19
 20#define MTK_HDR_LEN		4
 21#define MTK_HDR_XMIT_UNTAGGED		0
 22#define MTK_HDR_XMIT_TAGGED_TPID_8100	1
 23#define MTK_HDR_RECV_SOURCE_PORT_MASK	GENMASK(2, 0)
 24#define MTK_HDR_XMIT_DP_BIT_MASK	GENMASK(5, 0)
 25
 26static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
 27				    struct net_device *dev)
 28{
 29	struct dsa_port *dp = dsa_slave_to_port(dev);
 30	u8 *mtk_tag;
 31	bool is_vlan_skb = true;
 32
 33	/* Build the special tag after the MAC Source Address. If VLAN header
 34	 * is present, it's required that VLAN header and special tag is
 35	 * being combined. Only in this way we can allow the switch can parse
 36	 * the both special and VLAN tag at the same time and then look up VLAN
 37	 * table with VID.
 38	 */
 39	if (!skb_vlan_tagged(skb)) {
 40		if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
 41			return NULL;
 42
 43		skb_push(skb, MTK_HDR_LEN);
 44		memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
 45		is_vlan_skb = false;
 46	}
 47
 48	mtk_tag = skb->data + 2 * ETH_ALEN;
 49
 50	/* Mark tag attribute on special tag insertion to notify hardware
 51	 * whether that's a combined special tag with 802.1Q header.
 52	 */
 53	mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
 54		     MTK_HDR_XMIT_UNTAGGED;
 55	mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
 56
 57	/* Tag control information is kept for 802.1Q */
 58	if (!is_vlan_skb) {
 59		mtk_tag[2] = 0;
 60		mtk_tag[3] = 0;
 61	}
 62
 63	return skb;
 64}
 65
 66static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 67				   struct packet_type *pt)
 68{
 69	int port;
 70	__be16 *phdr, hdr;
 71
 72	if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
 73		return NULL;
 74
 75	/* The MTK header is added by the switch between src addr
 76	 * and ethertype at this point, skb->data points to 2 bytes
 77	 * after src addr so header should be 2 bytes right before.
 78	 */
 79	phdr = (__be16 *)(skb->data - 2);
 80	hdr = ntohs(*phdr);
 81
 82	/* Remove MTK tag and recalculate checksum. */
 83	skb_pull_rcsum(skb, MTK_HDR_LEN);
 84
 85	memmove(skb->data - ETH_HLEN,
 86		skb->data - ETH_HLEN - MTK_HDR_LEN,
 87		2 * ETH_ALEN);
 88
 89	/* Get source port information */
 90	port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
 91
 92	skb->dev = dsa_master_find_slave(dev, 0, port);
 93	if (!skb->dev)
 94		return NULL;
 95
 96	return skb;
 97}
 98
 99static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
100				int *offset)
101{
102	*offset = 4;
103	*proto = ((__be16 *)skb->data)[1];
104
105	return 0;
106}
107
108const struct dsa_device_ops mtk_netdev_ops = {
109	.xmit		= mtk_tag_xmit,
110	.rcv		= mtk_tag_rcv,
111	.flow_dissect	= mtk_tag_flow_dissect,
112};