// SPDX-License-Identifier: GPL-2.0+
/*
 * Broadcom tag support
 *
 * Copyright (C) 2014 Broadcom Corporation
 */

#include <linux/etherdevice.h>
#include <linux/list.h>
#include <linux/slab.h>

#include "dsa_priv.h"

/* This tag length is 4 bytes, older ones were 6 bytes, we do not
 * handle them
 */
#define BRCM_TAG_LEN    4

/* Tag is constructed and desconstructed using byte by byte access
 * because the tag is placed after the MAC Source Address, which does
 * not make it 4-bytes aligned, so this might cause unaligned accesses
 * on most systems where this is used.
 */

/* Ingress and egress opcodes */
#define BRCM_OPCODE_SHIFT       5
#define BRCM_OPCODE_MASK        0x7

/* Ingress fields */
/* 1st byte in the tag */
#define BRCM_IG_TC_SHIFT        2
#define BRCM_IG_TC_MASK         0x7
/* 2nd byte in the tag */
#define BRCM_IG_TE_MASK         0x3
#define BRCM_IG_TS_SHIFT        7
/* 3rd byte in the tag */
#define BRCM_IG_DSTMAP2_MASK    1
#define BRCM_IG_DSTMAP1_MASK    0xff

/* Egress fields */

/* 2nd byte in the tag */
#define BRCM_EG_CID_MASK        0xff

/* 3rd byte in the tag */
#define BRCM_EG_RC_MASK         0xff
#define  BRCM_EG_RC_RSVD        (3 << 6)
#define  BRCM_EG_RC_EXCEPTION   (1 << 5)
#define  BRCM_EG_RC_PROT_SNOOP  (1 << 4)
#define  BRCM_EG_RC_PROT_TERM   (1 << 3)
#define  BRCM_EG_RC_SWITCH      (1 << 2)
#define  BRCM_EG_RC_MAC_LEARN   (1 << 1)
#define  BRCM_EG_RC_MIRROR      (1 << 0)
#define BRCM_EG_TC_SHIFT        5
#define BRCM_EG_TC_MASK         0x7
#define BRCM_EG_PID_MASK        0x1f

#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM) || \
        IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)

static struct sk_buff *brcm_tag_xmit_ll(struct sk_buff *skb,
                                        struct net_device *dev,
                                        unsigned int offset)
{
        struct dsa_port *dp = dsa_slave_to_port(dev);
        u16 queue = skb_get_queue_mapping(skb);
        u8 *brcm_tag;

        if (skb_cow_head(skb, BRCM_TAG_LEN) < 0)
                return NULL;

        /* The Ethernet switch we are interfaced with needs packets to be at
         * least 64 bytes (including FCS) otherwise they will be discarded when
         * they enter the switch port logic. When Broadcom tags are enabled, we
         * need to make sure that packets are at least 68 bytes
         * (including FCS and tag) because the length verification is done after
         * the Broadcom tag is stripped off the ingress packet.
         *
         * Let dsa_slave_xmit() free the SKB
         */
        if (__skb_put_padto(skb, ETH_ZLEN + BRCM_TAG_LEN, false))
                return NULL;

        skb_push(skb, BRCM_TAG_LEN);

        if (offset)
                memmove(skb->data, skb->data + BRCM_TAG_LEN, offset);

        brcm_tag = skb->data + offset;

        /* Set the ingress opcode, traffic class, tag enforcment is
         * deprecated
         */
        brcm_tag[0] = (1 << BRCM_OPCODE_SHIFT) |
                       ((queue & BRCM_IG_TC_MASK) << BRCM_IG_TC_SHIFT);
        brcm_tag[1] = 0;
        brcm_tag[2] = 0;
        if (dp->index == 8)
                brcm_tag[2] = BRCM_IG_DSTMAP2_MASK;
        brcm_tag[3] = (1 << dp->index) & BRCM_IG_DSTMAP1_MASK;

        /* Now tell the master network device about the desired output queue
         * as well
         */
        skb_set_queue_mapping(skb, BRCM_TAG_SET_PORT_QUEUE(dp->index, queue));

        return skb;
}

/* Frames with this tag have one of these two layouts:
 * -----------------------------------
 * | MAC DA | MAC SA | 4b tag | Type | DSA_TAG_PROTO_BRCM
 * -----------------------------------
 * -----------------------------------
 * | 4b tag | MAC DA | MAC SA | Type | DSA_TAG_PROTO_BRCM_PREPEND
 * -----------------------------------
 * In both cases, at receive time, skb->data points 2 bytes before the actual
 * Ethernet type field and we have an offset of 4bytes between where skb->data
 * and where the payload starts. So the same low-level receive function can be
 * used.
 */
static struct sk_buff *brcm_tag_rcv_ll(struct sk_buff *skb,
                                       struct net_device *dev,
                                       struct packet_type *pt,
                                       unsigned int offset)
{
        int source_port;
        u8 *brcm_tag;

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

        brcm_tag = skb->data - offset;

        /* The opcode should never be different than 0b000 */
        if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
                return NULL;

        /* We should never see a reserved reason code without knowing how to
         * handle it
         */
        if (unlikely(brcm_tag[2] & BRCM_EG_RC_RSVD))
                return NULL;

        /* Locate which port this is coming from */
        source_port = brcm_tag[3] & BRCM_EG_PID_MASK;

        skb->dev = dsa_master_find_slave(dev, 0, source_port);
        if (!skb->dev)
                return NULL;

        /* Remove Broadcom tag and update checksum */
        skb_pull_rcsum(skb, BRCM_TAG_LEN);

        skb->offload_fwd_mark = 1;

        return skb;
}
#endif

#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM)
static struct sk_buff *brcm_tag_xmit(struct sk_buff *skb,
                                     struct net_device *dev)
{
        /* Build the tag after the MAC Source Address */
        return brcm_tag_xmit_ll(skb, dev, 2 * ETH_ALEN);
}


static struct sk_buff *brcm_tag_rcv(struct sk_buff *skb, struct net_device *dev,
                                    struct packet_type *pt)
{
        struct sk_buff *nskb;

        /* skb->data points to the EtherType, the tag is right before it */
        nskb = brcm_tag_rcv_ll(skb, dev, pt, 2);
        if (!nskb)
                return nskb;

        /* Move the Ethernet DA and SA */
        memmove(nskb->data - ETH_HLEN,
                nskb->data - ETH_HLEN - BRCM_TAG_LEN,
                2 * ETH_ALEN);

        return nskb;
}

static const struct dsa_device_ops brcm_netdev_ops = {
        .name   = "brcm",
        .proto  = DSA_TAG_PROTO_BRCM,
        .xmit   = brcm_tag_xmit,
        .rcv    = brcm_tag_rcv,
        .overhead = BRCM_TAG_LEN,
};

DSA_TAG_DRIVER(brcm_netdev_ops);
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM);
#endif

#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)
static struct sk_buff *brcm_tag_xmit_prepend(struct sk_buff *skb,
                                             struct net_device *dev)
{
        /* tag is prepended to the packet */
        return brcm_tag_xmit_ll(skb, dev, 0);
}

static struct sk_buff *brcm_tag_rcv_prepend(struct sk_buff *skb,
                                            struct net_device *dev,
                                            struct packet_type *pt)
{
        /* tag is prepended to the packet */
        return brcm_tag_rcv_ll(skb, dev, pt, ETH_HLEN);
}

static const struct dsa_device_ops brcm_prepend_netdev_ops = {
        .name   = "brcm-prepend",
        .proto  = DSA_TAG_PROTO_BRCM_PREPEND,
        .xmit   = brcm_tag_xmit_prepend,
        .rcv    = brcm_tag_rcv_prepend,
        .overhead = BRCM_TAG_LEN,
};

DSA_TAG_DRIVER(brcm_prepend_netdev_ops);
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_BRCM_PREPEND);
#endif

static struct dsa_tag_driver *dsa_tag_driver_array[] =  {
#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM)
        &DSA_TAG_DRIVER_NAME(brcm_netdev_ops),
#endif
#if IS_ENABLED(CONFIG_NET_DSA_TAG_BRCM_PREPEND)
        &DSA_TAG_DRIVER_NAME(brcm_prepend_netdev_ops),
#endif
};

module_dsa_tag_drivers(dsa_tag_driver_array);

MODULE_LICENSE("GPL");