// 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 "tag.h"

#define MTK_NAME                "mtk"

#define MTK_HDR_LEN             4
#define MTK_HDR_XMIT_UNTAGGED           0
#define MTK_HDR_XMIT_TAGGED_TPID_8100   1
#define MTK_HDR_XMIT_TAGGED_TPID_88A8   2
#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_user_to_port(dev);
        u8 xmit_tpid;
        u8 *mtk_tag;

        skb_set_queue_mapping(skb, dp->index);

        /* 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.
         */
        switch (skb->protocol) {
        case htons(ETH_P_8021Q):
                xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_8100;
                break;
        case htons(ETH_P_8021AD):
                xmit_tpid = MTK_HDR_XMIT_TAGGED_TPID_88A8;
                break;
        default:
                xmit_tpid = MTK_HDR_XMIT_UNTAGGED;
                skb_push(skb, MTK_HDR_LEN);
                dsa_alloc_etype_header(skb, MTK_HDR_LEN);
        }

        mtk_tag = dsa_etype_header_pos_tx(skb);

        /* Mark tag attribute on special tag insertion to notify hardware
         * whether that's a combined special tag with 802.1Q header.
         */
        mtk_tag[0] = xmit_tpid;
        mtk_tag[1] = FIELD_PREP(MTK_HDR_XMIT_DP_BIT_MASK,
                                dsa_xmit_port_mask(skb, dev));

        /* Tag control information is kept for 802.1Q */
        if (xmit_tpid == MTK_HDR_XMIT_UNTAGGED) {
                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)
{
        u16 hdr;
        int port;
        __be16 *phdr;

        if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
                return NULL;

        phdr = dsa_etype_header_pos_rx(skb);
        hdr = ntohs(*phdr);

        /* Remove MTK tag and recalculate checksum. */
        skb_pull_rcsum(skb, MTK_HDR_LEN);

        dsa_strip_etype_header(skb, MTK_HDR_LEN);

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

        skb->dev = dsa_conduit_find_user(dev, 0, port);
        if (!skb->dev)
                return NULL;

        dsa_default_offload_fwd_mark(skb);

        return skb;
}

static const struct dsa_device_ops mtk_netdev_ops = {
        .name           = MTK_NAME,
        .proto          = DSA_TAG_PROTO_MTK,
        .xmit           = mtk_tag_xmit,
        .rcv            = mtk_tag_rcv,
        .needed_headroom = MTK_HDR_LEN,
};

MODULE_DESCRIPTION("DSA tag driver for Mediatek switches");
MODULE_LICENSE("GPL");
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK, MTK_NAME);

module_dsa_tag_driver(mtk_netdev_ops);