// SPDX-License-Identifier: GPL-2.0

  /*
   * Mediatek DSA Tag support
   * Copyright (C) 2017 Landen Chao <landen.chao@mediatek.com>
   *		      Sean Wang <sean.wang@mediatek.com>

   */
  
  #include <linux/etherdevice.h>

  #include <linux/if_vlan.h>

  #include "dsa_priv.h"
  
  #define MTK_HDR_LEN		4

  #define MTK_HDR_XMIT_UNTAGGED		0
  #define MTK_HDR_XMIT_TAGGED_TPID_8100	1

  #define MTK_HDR_RECV_SOURCE_PORT_MASK	GENMASK(2, 0)
  #define MTK_HDR_XMIT_DP_BIT_MASK	GENMASK(5, 0)

  #define MTK_HDR_XMIT_SA_DIS		BIT(6)

  
  static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  				    struct net_device *dev)
  {

  	struct dsa_port *dp = dsa_slave_to_port(dev);

  	u8 *mtk_tag;

  	bool is_vlan_skb = true;

  	unsigned char *dest = eth_hdr(skb)->h_dest;
  	bool is_multicast_skb = is_multicast_ether_addr(dest) &&
  				!is_broadcast_ether_addr(dest);

  	/* Build the special tag after the MAC Source Address. If VLAN header
  	 * is present, it's required that VLAN header and special tag is
  	 * being combined. Only in this way we can allow the switch can parse
  	 * the both special and VLAN tag at the same time and then look up VLAN
  	 * table with VID.
  	 */
  	if (!skb_vlan_tagged(skb)) {
  		if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  			return NULL;

  		skb_push(skb, MTK_HDR_LEN);
  		memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  		is_vlan_skb = false;
  	}

  	mtk_tag = skb->data + 2 * ETH_ALEN;

  
  	/* Mark tag attribute on special tag insertion to notify hardware
  	 * whether that's a combined special tag with 802.1Q header.
  	 */
  	mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
  		     MTK_HDR_XMIT_UNTAGGED;

  	mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;

  	/* Disable SA learning for multicast frames */
  	if (unlikely(is_multicast_skb))
  		mtk_tag[1] |= MTK_HDR_XMIT_SA_DIS;

  	/* Tag control information is kept for 802.1Q */
  	if (!is_vlan_skb) {
  		mtk_tag[2] = 0;
  		mtk_tag[3] = 0;
  	}

  
  	return skb;

  }

  static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,

  				   struct packet_type *pt)

  {

  	u16 hdr;

  	int port;

  	__be16 *phdr;

  	unsigned char *dest = eth_hdr(skb)->h_dest;
  	bool is_multicast_skb = is_multicast_ether_addr(dest) &&
  				!is_broadcast_ether_addr(dest);

  	if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))

  		return NULL;

  
  	/* The MTK header is added by the switch between src addr
  	 * and ethertype at this point, skb->data points to 2 bytes
  	 * after src addr so header should be 2 bytes right before.
  	 */
  	phdr = (__be16 *)(skb->data - 2);
  	hdr = ntohs(*phdr);
  
  	/* Remove MTK tag and recalculate checksum. */
  	skb_pull_rcsum(skb, MTK_HDR_LEN);
  
  	memmove(skb->data - ETH_HLEN,
  		skb->data - ETH_HLEN - MTK_HDR_LEN,
  		2 * ETH_ALEN);

  	/* Get source port information */
  	port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);

  	skb->dev = dsa_master_find_slave(dev, 0, port);

  	if (!skb->dev)
  		return NULL;

  	/* Only unicast or broadcast frames are offloaded */
  	if (likely(!is_multicast_skb))
  		skb->offload_fwd_mark = 1;

  	return skb;

  }

  static const struct dsa_device_ops mtk_netdev_ops = {

  	.name		= "mtk",

  	.proto		= DSA_TAG_PROTO_MTK,

  	.xmit		= mtk_tag_xmit,
  	.rcv		= mtk_tag_rcv,

  	.overhead	= MTK_HDR_LEN,

  };

  MODULE_LICENSE("GPL");

  MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);

  
  module_dsa_tag_driver(mtk_netdev_ops);