// SPDX-License-Identifier: GPL-2.0+
/*
 * net/dsa/tag_ksz.c - Microchip KSZ Switch tag format handling
 * Copyright (c) 2017 Microchip Technology
 */

#include <linux/etherdevice.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <net/dsa.h>
#include "dsa_priv.h"

/* Typically only one byte is used for tail tag. */
#define KSZ_EGRESS_TAG_LEN              1
#define KSZ_INGRESS_TAG_LEN             1

static struct sk_buff *ksz_common_xmit(struct sk_buff *skb,
                                       struct net_device *dev, int len)
{
        struct sk_buff *nskb;
        int padlen;

        padlen = (skb->len >= ETH_ZLEN) ? 0 : ETH_ZLEN - skb->len;

        if (skb_tailroom(skb) >= padlen + len) {
                /* Let dsa_slave_xmit() free skb */
                if (__skb_put_padto(skb, skb->len + padlen, false))
                        return NULL;

                nskb = skb;
        } else {
                nskb = alloc_skb(NET_IP_ALIGN + skb->len +
                                 padlen + len, GFP_ATOMIC);
                if (!nskb)
                        return NULL;
                skb_reserve(nskb, NET_IP_ALIGN);

                skb_reset_mac_header(nskb);
                skb_set_network_header(nskb,
                                       skb_network_header(skb) - skb->head);
                skb_set_transport_header(nskb,
                                         skb_transport_header(skb) - skb->head);
                skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));

                /* Let skb_put_padto() free nskb, and let dsa_slave_xmit() free
                 * skb
                 */
                if (skb_put_padto(nskb, nskb->len + padlen))
                        return NULL;

                consume_skb(skb);
        }

        return nskb;
}

static struct sk_buff *ksz_common_rcv(struct sk_buff *skb,
                                      struct net_device *dev,
                                      unsigned int port, unsigned int len)
{
        skb->dev = dsa_master_find_slave(dev, 0, port);
        if (!skb->dev)
                return NULL;

        pskb_trim_rcsum(skb, skb->len - len);

        skb->offload_fwd_mark = true;

        return skb;
}

/*
 * For Ingress (Host -> KSZ9477), 2 bytes are added before FCS.
 * ---------------------------------------------------------------------------
 * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|tag1(1byte)|FCS(4bytes)
 * ---------------------------------------------------------------------------
 * tag0 : Prioritization (not used now)
 * tag1 : each bit represents port (eg, 0x01=port1, 0x02=port2, 0x10=port5)
 *
 * For Egress (KSZ9477 -> Host), 1 byte is added before FCS.
 * ---------------------------------------------------------------------------
 * DA(6bytes)|SA(6bytes)|....|Data(nbytes)|tag0(1byte)|FCS(4bytes)
 * ---------------------------------------------------------------------------
 * tag0 : zero-based value represents port
 *        (eg, 0x00=port1, 0x02=port3, 0x06=port7)
 */

#define KSZ9477_INGRESS_TAG_LEN         2
#define KSZ9477_PTP_TAG_LEN             4
#define KSZ9477_PTP_TAG_INDICATION      0x80

#define KSZ9477_TAIL_TAG_OVERRIDE       BIT(9)
#define KSZ9477_TAIL_TAG_LOOKUP         BIT(10)

static struct sk_buff *ksz9477_xmit(struct sk_buff *skb,
                                    struct net_device *dev)
{
        struct dsa_port *dp = dsa_slave_to_port(dev);
        struct sk_buff *nskb;
        u16 *tag;
        u8 *addr;

        nskb = ksz_common_xmit(skb, dev, KSZ9477_INGRESS_TAG_LEN);
        if (!nskb)
                return NULL;

        /* Tag encoding */
        tag = skb_put(nskb, KSZ9477_INGRESS_TAG_LEN);
        addr = skb_mac_header(nskb);

        *tag = BIT(dp->index);

        if (is_link_local_ether_addr(addr))
                *tag |= KSZ9477_TAIL_TAG_OVERRIDE;

        *tag = cpu_to_be16(*tag);

        return nskb;
}

static struct sk_buff *ksz9477_rcv(struct sk_buff *skb, struct net_device *dev,
                                   struct packet_type *pt)
{
        /* Tag decoding */
        u8 *tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN;
        unsigned int port = tag[0] & 7;
        unsigned int len = KSZ_EGRESS_TAG_LEN;

        /* Extra 4-bytes PTP timestamp */
        if (tag[0] & KSZ9477_PTP_TAG_INDICATION)
                len += KSZ9477_PTP_TAG_LEN;

        return ksz_common_rcv(skb, dev, port, len);
}

static const struct dsa_device_ops ksz9477_netdev_ops = {
        .name   = "ksz9477",
        .proto  = DSA_TAG_PROTO_KSZ9477,
        .xmit   = ksz9477_xmit,
        .rcv    = ksz9477_rcv,
        .overhead = KSZ9477_INGRESS_TAG_LEN,
};

DSA_TAG_DRIVER(ksz9477_netdev_ops);
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9477);

#define KSZ9893_TAIL_TAG_OVERRIDE       BIT(5)
#define KSZ9893_TAIL_TAG_LOOKUP         BIT(6)

static struct sk_buff *ksz9893_xmit(struct sk_buff *skb,
                                    struct net_device *dev)
{
        struct dsa_port *dp = dsa_slave_to_port(dev);
        struct sk_buff *nskb;
        u8 *addr;
        u8 *tag;

        nskb = ksz_common_xmit(skb, dev, KSZ_INGRESS_TAG_LEN);
        if (!nskb)
                return NULL;

        /* Tag encoding */
        tag = skb_put(nskb, KSZ_INGRESS_TAG_LEN);
        addr = skb_mac_header(nskb);

        *tag = BIT(dp->index);

        if (is_link_local_ether_addr(addr))
                *tag |= KSZ9893_TAIL_TAG_OVERRIDE;

        return nskb;
}

static const struct dsa_device_ops ksz9893_netdev_ops = {
        .name   = "ksz9893",
        .proto  = DSA_TAG_PROTO_KSZ9893,
        .xmit   = ksz9893_xmit,
        .rcv    = ksz9477_rcv,
        .overhead = KSZ_INGRESS_TAG_LEN,
};

DSA_TAG_DRIVER(ksz9893_netdev_ops);
MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893);

static struct dsa_tag_driver *dsa_tag_driver_array[] = {
        &DSA_TAG_DRIVER_NAME(ksz9477_netdev_ops),
        &DSA_TAG_DRIVER_NAME(ksz9893_netdev_ops),
};

module_dsa_tag_drivers(dsa_tag_driver_array);

MODULE_LICENSE("GPL");