// SPDX-License-Identifier: GPL-2.0
/*
 * net.c - Networking component for Mostcore
 *
 * Copyright (C) 2015, Microchip Technology Germany II GmbH & Co. KG
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/wait.h>
#include <linux/kobject.h>
#include <linux/most.h>

#define MEP_HDR_LEN 8
#define MDP_HDR_LEN 16
#define MAMAC_DATA_LEN (1024 - MDP_HDR_LEN)

#define PMHL 5

#define PMS_TELID_UNSEGM_MAMAC  0x0A
#define PMS_FIFONO_MDP          0x01
#define PMS_FIFONO_MEP          0x04
#define PMS_MSGTYPE_DATA        0x04
#define PMS_DEF_PRIO            0
#define MEP_DEF_RETRY           15

#define PMS_FIFONO_MASK         0x07
#define PMS_FIFONO_SHIFT        3
#define PMS_RETRY_SHIFT         4
#define PMS_TELID_MASK          0x0F
#define PMS_TELID_SHIFT         4

#define HB(value)               ((u8)((u16)(value) >> 8))
#define LB(value)               ((u8)(value))

#define EXTRACT_BIT_SET(bitset_name, value) \
        (((value) >> bitset_name##_SHIFT) & bitset_name##_MASK)

#define PMS_IS_MEP(buf, len) \
        ((len) > MEP_HDR_LEN && \
         EXTRACT_BIT_SET(PMS_FIFONO, (buf)[3]) == PMS_FIFONO_MEP)

static inline bool pms_is_mamac(char *buf, u32 len)
{
        return (len > MDP_HDR_LEN &&
                EXTRACT_BIT_SET(PMS_FIFONO, buf[3]) == PMS_FIFONO_MDP &&
                EXTRACT_BIT_SET(PMS_TELID, buf[14]) == PMS_TELID_UNSEGM_MAMAC);
}

struct net_dev_channel {
        bool linked;
        int ch_id;
};

struct net_dev_context {
        struct most_interface *iface;
        bool is_mamac;
        struct net_device *dev;
        struct net_dev_channel rx;
        struct net_dev_channel tx;
        struct list_head list;
};

static LIST_HEAD(net_devices);
static DEFINE_MUTEX(probe_disc_mt); /* ch->linked = true, most_nd_open */
static DEFINE_SPINLOCK(list_lock); /* list_head, ch->linked = false, dev_hold */
static struct most_component comp;

static int skb_to_mamac(const struct sk_buff *skb, struct mbo *mbo)
{
        u8 *buff = mbo->virt_address;
        static const u8 broadcast[] = { 0x03, 0xFF };
        const u8 *dest_addr = skb->data + 4;
        const u8 *eth_type = skb->data + 12;
        unsigned int payload_len = skb->len - ETH_HLEN;
        unsigned int mdp_len = payload_len + MDP_HDR_LEN;

        if (mdp_len < skb->len) {
                pr_err("drop: too large packet! (%u)\n", skb->len);
                return -EINVAL;
        }

        if (mbo->buffer_length < mdp_len) {
                pr_err("drop: too small buffer! (%d for %d)\n",
                       mbo->buffer_length, mdp_len);
                return -EINVAL;
        }

        if (skb->len < ETH_HLEN) {
                pr_err("drop: too small packet! (%d)\n", skb->len);
                return -EINVAL;
        }

        if (dest_addr[0] == 0xFF && dest_addr[1] == 0xFF)
                dest_addr = broadcast;

        *buff++ = HB(mdp_len - 2);
        *buff++ = LB(mdp_len - 2);

        *buff++ = PMHL;
        *buff++ = (PMS_FIFONO_MDP << PMS_FIFONO_SHIFT) | PMS_MSGTYPE_DATA;
        *buff++ = PMS_DEF_PRIO;
        *buff++ = dest_addr[0];
        *buff++ = dest_addr[1];
        *buff++ = 0x00;

        *buff++ = HB(payload_len + 6);
        *buff++ = LB(payload_len + 6);

        /* end of FPH here */

        *buff++ = eth_type[0];
        *buff++ = eth_type[1];
        *buff++ = 0;
        *buff++ = 0;

        *buff++ = PMS_TELID_UNSEGM_MAMAC << 4 | HB(payload_len);
        *buff++ = LB(payload_len);

        memcpy(buff, skb->data + ETH_HLEN, payload_len);
        mbo->buffer_length = mdp_len;
        return 0;
}

static int skb_to_mep(const struct sk_buff *skb, struct mbo *mbo)
{
        u8 *buff = mbo->virt_address;
        unsigned int mep_len = skb->len + MEP_HDR_LEN;

        if (mep_len < skb->len) {
                pr_err("drop: too large packet! (%u)\n", skb->len);
                return -EINVAL;
        }

        if (mbo->buffer_length < mep_len) {
                pr_err("drop: too small buffer! (%d for %d)\n",
                       mbo->buffer_length, mep_len);
                return -EINVAL;
        }

        *buff++ = HB(mep_len - 2);
        *buff++ = LB(mep_len - 2);

        *buff++ = PMHL;
        *buff++ = (PMS_FIFONO_MEP << PMS_FIFONO_SHIFT) | PMS_MSGTYPE_DATA;
        *buff++ = (MEP_DEF_RETRY << PMS_RETRY_SHIFT) | PMS_DEF_PRIO;
        *buff++ = 0;
        *buff++ = 0;
        *buff++ = 0;

        memcpy(buff, skb->data, skb->len);
        mbo->buffer_length = mep_len;
        return 0;
}

static int most_nd_set_mac_address(struct net_device *dev, void *p)
{
        struct net_dev_context *nd = netdev_priv(dev);
        int err = eth_mac_addr(dev, p);

        if (err)
                return err;

        nd->is_mamac =
                (dev->dev_addr[0] == 0 && dev->dev_addr[1] == 0 &&
                 dev->dev_addr[2] == 0 && dev->dev_addr[3] == 0);

        /*
         * Set default MTU for the given packet type.
         * It is still possible to change MTU using ip tools afterwards.
         */
        dev->mtu = nd->is_mamac ? MAMAC_DATA_LEN : ETH_DATA_LEN;

        return 0;
}

static void on_netinfo(struct most_interface *iface,
                       unsigned char link_stat, unsigned char *mac_addr);

static int most_nd_open(struct net_device *dev)
{
        struct net_dev_context *nd = netdev_priv(dev);
        int ret = 0;

        mutex_lock(&probe_disc_mt);

        if (most_start_channel(nd->iface, nd->rx.ch_id, &comp)) {
                netdev_err(dev, "most_start_channel() failed\n");
                ret = -EBUSY;
                goto unlock;
        }

        if (most_start_channel(nd->iface, nd->tx.ch_id, &comp)) {
                netdev_err(dev, "most_start_channel() failed\n");
                most_stop_channel(nd->iface, nd->rx.ch_id, &comp);
                ret = -EBUSY;
                goto unlock;
        }

        netif_carrier_off(dev);
        if (is_valid_ether_addr(dev->dev_addr))
                netif_dormant_off(dev);
        else
                netif_dormant_on(dev);
        netif_wake_queue(dev);
        if (nd->iface->request_netinfo)
                nd->iface->request_netinfo(nd->iface, nd->tx.ch_id, on_netinfo);

unlock:
        mutex_unlock(&probe_disc_mt);
        return ret;
}

static int most_nd_stop(struct net_device *dev)
{
        struct net_dev_context *nd = netdev_priv(dev);

        netif_stop_queue(dev);
        if (nd->iface->request_netinfo)
                nd->iface->request_netinfo(nd->iface, nd->tx.ch_id, NULL);
        most_stop_channel(nd->iface, nd->rx.ch_id, &comp);
        most_stop_channel(nd->iface, nd->tx.ch_id, &comp);

        return 0;
}

static netdev_tx_t most_nd_start_xmit(struct sk_buff *skb,
                                      struct net_device *dev)
{
        struct net_dev_context *nd = netdev_priv(dev);
        struct mbo *mbo;
        int ret;

        mbo = most_get_mbo(nd->iface, nd->tx.ch_id, &comp);

        if (!mbo) {
                netif_stop_queue(dev);
                dev->stats.tx_fifo_errors++;
                return NETDEV_TX_BUSY;
        }

        if (nd->is_mamac)
                ret = skb_to_mamac(skb, mbo);
        else
                ret = skb_to_mep(skb, mbo);

        if (ret) {
                most_put_mbo(mbo);
                dev->stats.tx_dropped++;
                kfree_skb(skb);
                return NETDEV_TX_OK;
        }

        most_submit_mbo(mbo);
        dev->stats.tx_packets++;
        dev->stats.tx_bytes += skb->len;
        kfree_skb(skb);
        return NETDEV_TX_OK;
}

static const struct net_device_ops most_nd_ops = {
        .ndo_open = most_nd_open,
        .ndo_stop = most_nd_stop,
        .ndo_start_xmit = most_nd_start_xmit,
        .ndo_set_mac_address = most_nd_set_mac_address,
};

static void most_nd_setup(struct net_device *dev)
{
        ether_setup(dev);
        dev->netdev_ops = &most_nd_ops;
}

static struct net_dev_context *get_net_dev(struct most_interface *iface)
{
        struct net_dev_context *nd;

        list_for_each_entry(nd, &net_devices, list)
                if (nd->iface == iface)
                        return nd;
        return NULL;
}

static struct net_dev_context *get_net_dev_hold(struct most_interface *iface)
{
        struct net_dev_context *nd;
        unsigned long flags;

        spin_lock_irqsave(&list_lock, flags);
        nd = get_net_dev(iface);
        if (nd && nd->rx.linked && nd->tx.linked)
                dev_hold(nd->dev);
        else
                nd = NULL;
        spin_unlock_irqrestore(&list_lock, flags);
        return nd;
}

static int comp_probe_channel(struct most_interface *iface, int channel_idx,
                              struct most_channel_config *ccfg, char *name,
                              char *args)
{
        struct net_dev_context *nd;
        struct net_dev_channel *ch;
        struct net_device *dev;
        unsigned long flags;
        int ret = 0;

        if (!iface)
                return -EINVAL;

        if (ccfg->data_type != MOST_CH_ASYNC)
                return -EINVAL;

        mutex_lock(&probe_disc_mt);
        nd = get_net_dev(iface);
        if (!nd) {
                dev = alloc_netdev(sizeof(struct net_dev_context), "meth%d",
                                   NET_NAME_UNKNOWN, most_nd_setup);
                if (!dev) {
                        ret = -ENOMEM;
                        goto unlock;
                }

                nd = netdev_priv(dev);
                nd->iface = iface;
                nd->dev = dev;

                spin_lock_irqsave(&list_lock, flags);
                list_add(&nd->list, &net_devices);
                spin_unlock_irqrestore(&list_lock, flags);

                ch = ccfg->direction == MOST_CH_TX ? &nd->tx : &nd->rx;
        } else {
                ch = ccfg->direction == MOST_CH_TX ? &nd->tx : &nd->rx;
                if (ch->linked) {
                        pr_err("direction is allocated\n");
                        ret = -EINVAL;
                        goto unlock;
                }

                if (register_netdev(nd->dev)) {
                        pr_err("register_netdev() failed\n");
                        ret = -EINVAL;
                        goto unlock;
                }
        }
        ch->ch_id = channel_idx;
        ch->linked = true;

unlock:
        mutex_unlock(&probe_disc_mt);
        return ret;
}

static int comp_disconnect_channel(struct most_interface *iface,
                                   int channel_idx)
{
        struct net_dev_context *nd;
        struct net_dev_channel *ch;
        unsigned long flags;
        int ret = 0;

        mutex_lock(&probe_disc_mt);
        nd = get_net_dev(iface);
        if (!nd) {
                ret = -EINVAL;
                goto unlock;
        }

        if (nd->rx.linked && channel_idx == nd->rx.ch_id) {
                ch = &nd->rx;
        } else if (nd->tx.linked && channel_idx == nd->tx.ch_id) {
                ch = &nd->tx;
        } else {
                ret = -EINVAL;
                goto unlock;
        }

        if (nd->rx.linked && nd->tx.linked) {
                spin_lock_irqsave(&list_lock, flags);
                ch->linked = false;
                spin_unlock_irqrestore(&list_lock, flags);

                /*
                 * do not call most_stop_channel() here, because channels are
                 * going to be closed in ndo_stop() after unregister_netdev()
                 */
                unregister_netdev(nd->dev);
        } else {
                spin_lock_irqsave(&list_lock, flags);
                list_del(&nd->list);
                spin_unlock_irqrestore(&list_lock, flags);

                free_netdev(nd->dev);
        }

unlock:
        mutex_unlock(&probe_disc_mt);
        return ret;
}

static int comp_resume_tx_channel(struct most_interface *iface,
                                  int channel_idx)
{
        struct net_dev_context *nd;

        nd = get_net_dev_hold(iface);
        if (!nd)
                return 0;

        if (nd->tx.ch_id != channel_idx)
                goto put_nd;

        netif_wake_queue(nd->dev);

put_nd:
        dev_put(nd->dev);
        return 0;
}

static int comp_rx_data(struct mbo *mbo)
{
        const u32 zero = 0;
        struct net_dev_context *nd;
        char *buf = mbo->virt_address;
        u32 len = mbo->processed_length;
        struct sk_buff *skb;
        struct net_device *dev;
        unsigned int skb_len;
        int ret = 0;

        nd = get_net_dev_hold(mbo->ifp);
        if (!nd)
                return -EIO;

        if (nd->rx.ch_id != mbo->hdm_channel_id) {
                ret = -EIO;
                goto put_nd;
        }

        dev = nd->dev;

        if (nd->is_mamac) {
                if (!pms_is_mamac(buf, len)) {
                        ret = -EIO;
                        goto put_nd;
                }

                skb = dev_alloc_skb(len - MDP_HDR_LEN + 2 * ETH_ALEN + 2);
        } else {
                if (!PMS_IS_MEP(buf, len)) {
                        ret = -EIO;
                        goto put_nd;
                }

                skb = dev_alloc_skb(len - MEP_HDR_LEN);
        }

        if (!skb) {
                dev->stats.rx_dropped++;
                pr_err_once("drop packet: no memory for skb\n");
                goto out;
        }

        skb->dev = dev;

        if (nd->is_mamac) {
                /* dest */
                ether_addr_copy(skb_put(skb, ETH_ALEN), dev->dev_addr);

                /* src */
                skb_put_data(skb, &zero, 4);
                skb_put_data(skb, buf + 5, 2);

                /* eth type */
                skb_put_data(skb, buf + 10, 2);

                buf += MDP_HDR_LEN;
                len -= MDP_HDR_LEN;
        } else {
                buf += MEP_HDR_LEN;
                len -= MEP_HDR_LEN;
        }

        skb_put_data(skb, buf, len);
        skb->protocol = eth_type_trans(skb, dev);
        skb_len = skb->len;
        if (netif_rx(skb) == NET_RX_SUCCESS) {
                dev->stats.rx_packets++;
                dev->stats.rx_bytes += skb_len;
        } else {
                dev->stats.rx_dropped++;
        }

out:
        most_put_mbo(mbo);

put_nd:
        dev_put(nd->dev);
        return ret;
}

static struct most_component comp = {
        .mod = THIS_MODULE,
        .name = "net",
        .probe_channel = comp_probe_channel,
        .disconnect_channel = comp_disconnect_channel,
        .tx_completion = comp_resume_tx_channel,
        .rx_completion = comp_rx_data,
};

static int __init most_net_init(void)
{
        int err;

        err = most_register_component(&comp);
        if (err)
                return err;
        err = most_register_configfs_subsys(&comp);
        if (err) {
                most_deregister_component(&comp);
                return err;
        }
        return 0;
}

static void __exit most_net_exit(void)
{
        most_deregister_configfs_subsys(&comp);
        most_deregister_component(&comp);
}

/**
 * on_netinfo - callback for HDM to be informed about HW's MAC
 * @iface: most interface instance
 * @link_stat: link status
 * @mac_addr: MAC address
 */
static void on_netinfo(struct most_interface *iface,
                       unsigned char link_stat, unsigned char *mac_addr)
{
        struct net_dev_context *nd;
        struct net_device *dev;
        const u8 *m = mac_addr;

        nd = get_net_dev_hold(iface);
        if (!nd)
                return;

        dev = nd->dev;

        if (link_stat)
                netif_carrier_on(dev);
        else
                netif_carrier_off(dev);

        if (m && is_valid_ether_addr(m)) {
                if (!is_valid_ether_addr(dev->dev_addr)) {
                        netdev_info(dev, "set mac %pM\n", m);
                        eth_hw_addr_set(dev, m);
                        netif_dormant_off(dev);
                } else if (!ether_addr_equal(dev->dev_addr, m)) {
                        netdev_warn(dev, "reject mac %pM\n", m);
                }
        }

        dev_put(nd->dev);
}

module_init(most_net_init);
module_exit(most_net_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Andrey Shvetsov <andrey.shvetsov@k2l.de>");
MODULE_DESCRIPTION("Networking Component Module for Mostcore");