/*
 * This file is provided under a dual BSD/GPLv2 license.  When using or
 *   redistributing this file, you may do so under either license.
 *
 *   GPL LICENSE SUMMARY
 *
 *   Copyright(c) 2012 Intel Corporation. All rights reserved.
 *   Copyright (C) 2015 EMC Corporation. All Rights Reserved.
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of version 2 of the GNU General Public License as
 *   published by the Free Software Foundation.
 *
 *   BSD LICENSE
 *
 *   Copyright(c) 2012 Intel Corporation. All rights reserved.
 *   Copyright (C) 2015 EMC Corporation. All Rights Reserved.
 *
 *   Redistribution and use in source and binary forms, with or without
 *   modification, are permitted provided that the following conditions
 *   are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copy
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *     * Neither the name of Intel Corporation nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * PCIe NTB Network Linux driver
 *
 * Contact Information:
 * Jon Mason <jon.mason@intel.com>
 */
#include <linux/etherdevice.h>
#include <linux/ethtool.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/ntb.h>
#include <linux/ntb_transport.h>

#define NTB_NETDEV_VER  "0.7"

MODULE_DESCRIPTION(KBUILD_MODNAME);
MODULE_VERSION(NTB_NETDEV_VER);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Intel Corporation");

/* Time in usecs for tx resource reaper */
static unsigned int tx_time = 1;

/* Number of descriptors to free before resuming tx */
static unsigned int tx_start = 10;

/* Number of descriptors still available before stop upper layer tx */
static unsigned int tx_stop = 5;

struct ntb_netdev {
        struct list_head list;
        struct pci_dev *pdev;
        struct net_device *ndev;
        struct ntb_transport_qp *qp;
        struct timer_list tx_timer;
};

#define NTB_TX_TIMEOUT_MS       1000
#define NTB_RXQ_SIZE            100

static LIST_HEAD(dev_list);

static void ntb_netdev_event_handler(void *data, int link_is_up)
{
        struct net_device *ndev = data;
        struct ntb_netdev *dev = netdev_priv(ndev);

        netdev_dbg(ndev, "Event %x, Link %x\n", link_is_up,
                   ntb_transport_link_query(dev->qp));

        if (link_is_up) {
                if (ntb_transport_link_query(dev->qp))
                        netif_carrier_on(ndev);
        } else {
                netif_carrier_off(ndev);
        }
}

static void ntb_netdev_rx_handler(struct ntb_transport_qp *qp, void *qp_data,
                                  void *data, int len)
{
        struct net_device *ndev = qp_data;
        struct sk_buff *skb;
        int rc;

        skb = data;
        if (!skb)
                return;

        netdev_dbg(ndev, "%s: %d byte payload received\n", __func__, len);

        if (len < 0) {
                ndev->stats.rx_errors++;
                ndev->stats.rx_length_errors++;
                goto enqueue_again;
        }

        skb_put(skb, len);
        skb->protocol = eth_type_trans(skb, ndev);
        skb->ip_summed = CHECKSUM_NONE;

        if (netif_rx(skb) == NET_RX_DROP) {
                ndev->stats.rx_errors++;
                ndev->stats.rx_dropped++;
        } else {
                ndev->stats.rx_packets++;
                ndev->stats.rx_bytes += len;
        }

        skb = netdev_alloc_skb(ndev, ndev->mtu + ETH_HLEN);
        if (!skb) {
                ndev->stats.rx_errors++;
                ndev->stats.rx_frame_errors++;
                return;
        }

enqueue_again:
        rc = ntb_transport_rx_enqueue(qp, skb, skb->data, ndev->mtu + ETH_HLEN);
        if (rc) {
                dev_kfree_skb(skb);
                ndev->stats.rx_errors++;
                ndev->stats.rx_fifo_errors++;
        }
}

static int __ntb_netdev_maybe_stop_tx(struct net_device *netdev,
                                      struct ntb_transport_qp *qp, int size)
{
        struct ntb_netdev *dev = netdev_priv(netdev);

        netif_stop_queue(netdev);
        /* Make sure to see the latest value of ntb_transport_tx_free_entry()
         * since the queue was last started.
         */
        smp_mb();

        if (likely(ntb_transport_tx_free_entry(qp) < size)) {
                mod_timer(&dev->tx_timer, jiffies + usecs_to_jiffies(tx_time));
                return -EBUSY;
        }

        netif_start_queue(netdev);
        return 0;
}

static int ntb_netdev_maybe_stop_tx(struct net_device *ndev,
                                    struct ntb_transport_qp *qp, int size)
{
        if (netif_queue_stopped(ndev) ||
            (ntb_transport_tx_free_entry(qp) >= size))
                return 0;

        return __ntb_netdev_maybe_stop_tx(ndev, qp, size);
}

static void ntb_netdev_tx_handler(struct ntb_transport_qp *qp, void *qp_data,
                                  void *data, int len)
{
        struct net_device *ndev = qp_data;
        struct sk_buff *skb;
        struct ntb_netdev *dev = netdev_priv(ndev);

        skb = data;
        if (!skb || !ndev)
                return;

        if (len > 0) {
                ndev->stats.tx_packets++;
                ndev->stats.tx_bytes += skb->len;
        } else {
                ndev->stats.tx_errors++;
                ndev->stats.tx_aborted_errors++;
        }

        dev_kfree_skb(skb);

        if (ntb_transport_tx_free_entry(dev->qp) >= tx_start) {
                /* Make sure anybody stopping the queue after this sees the new
                 * value of ntb_transport_tx_free_entry()
                 */
                smp_mb();
                if (netif_queue_stopped(ndev))
                        netif_wake_queue(ndev);
        }
}

static netdev_tx_t ntb_netdev_start_xmit(struct sk_buff *skb,
                                         struct net_device *ndev)
{
        struct ntb_netdev *dev = netdev_priv(ndev);
        int rc;

        ntb_netdev_maybe_stop_tx(ndev, dev->qp, tx_stop);

        rc = ntb_transport_tx_enqueue(dev->qp, skb, skb->data, skb->len);
        if (rc)
                goto err;

        /* check for next submit */
        ntb_netdev_maybe_stop_tx(ndev, dev->qp, tx_stop);

        return NETDEV_TX_OK;

err:
        ndev->stats.tx_dropped++;
        ndev->stats.tx_errors++;
        return NETDEV_TX_BUSY;
}

static void ntb_netdev_tx_timer(unsigned long data)
{
        struct net_device *ndev = (struct net_device *)data;
        struct ntb_netdev *dev = netdev_priv(ndev);

        if (ntb_transport_tx_free_entry(dev->qp) < tx_stop) {
                mod_timer(&dev->tx_timer, jiffies + msecs_to_jiffies(tx_time));
        } else {
                /* Make sure anybody stopping the queue after this sees the new
                 * value of ntb_transport_tx_free_entry()
                 */
                smp_mb();
                if (netif_queue_stopped(ndev))
                        netif_wake_queue(ndev);
        }
}

static int ntb_netdev_open(struct net_device *ndev)
{
        struct ntb_netdev *dev = netdev_priv(ndev);
        struct sk_buff *skb;
        int rc, i, len;

        /* Add some empty rx bufs */
        for (i = 0; i < NTB_RXQ_SIZE; i++) {
                skb = netdev_alloc_skb(ndev, ndev->mtu + ETH_HLEN);
                if (!skb) {
                        rc = -ENOMEM;
                        goto err;
                }

                rc = ntb_transport_rx_enqueue(dev->qp, skb, skb->data,
                                              ndev->mtu + ETH_HLEN);
                if (rc) {
                        dev_kfree_skb(skb);
                        goto err;
                }
        }

        setup_timer(&dev->tx_timer, ntb_netdev_tx_timer, (unsigned long)ndev);

        netif_carrier_off(ndev);
        ntb_transport_link_up(dev->qp);
        netif_start_queue(ndev);

        return 0;

err:
        while ((skb = ntb_transport_rx_remove(dev->qp, &len)))
                dev_kfree_skb(skb);
        return rc;
}

static int ntb_netdev_close(struct net_device *ndev)
{
        struct ntb_netdev *dev = netdev_priv(ndev);
        struct sk_buff *skb;
        int len;

        ntb_transport_link_down(dev->qp);

        while ((skb = ntb_transport_rx_remove(dev->qp, &len)))
                dev_kfree_skb(skb);

        del_timer_sync(&dev->tx_timer);

        return 0;
}

static int ntb_netdev_change_mtu(struct net_device *ndev, int new_mtu)
{
        struct ntb_netdev *dev = netdev_priv(ndev);
        struct sk_buff *skb;
        int len, rc;

        if (new_mtu > ntb_transport_max_size(dev->qp) - ETH_HLEN)
                return -EINVAL;

        if (!netif_running(ndev)) {
                ndev->mtu = new_mtu;
                return 0;
        }

        /* Bring down the link and dispose of posted rx entries */
        ntb_transport_link_down(dev->qp);

        if (ndev->mtu < new_mtu) {
                int i;

                for (i = 0; (skb = ntb_transport_rx_remove(dev->qp, &len)); i++)
                        dev_kfree_skb(skb);

                for (; i; i--) {
                        skb = netdev_alloc_skb(ndev, new_mtu + ETH_HLEN);
                        if (!skb) {
                                rc = -ENOMEM;
                                goto err;
                        }

                        rc = ntb_transport_rx_enqueue(dev->qp, skb, skb->data,
                                                      new_mtu + ETH_HLEN);
                        if (rc) {
                                dev_kfree_skb(skb);
                                goto err;
                        }
                }
        }

        ndev->mtu = new_mtu;

        ntb_transport_link_up(dev->qp);

        return 0;

err:
        ntb_transport_link_down(dev->qp);

        while ((skb = ntb_transport_rx_remove(dev->qp, &len)))
                dev_kfree_skb(skb);

        netdev_err(ndev, "Error changing MTU, device inoperable\n");
        return rc;
}

static const struct net_device_ops ntb_netdev_ops = {
        .ndo_open = ntb_netdev_open,
        .ndo_stop = ntb_netdev_close,
        .ndo_start_xmit = ntb_netdev_start_xmit,
        .ndo_change_mtu = ntb_netdev_change_mtu,
        .ndo_set_mac_address = eth_mac_addr,
};

static void ntb_get_drvinfo(struct net_device *ndev,
                            struct ethtool_drvinfo *info)
{
        struct ntb_netdev *dev = netdev_priv(ndev);

        strlcpy(info->driver, KBUILD_MODNAME, sizeof(info->driver));
        strlcpy(info->version, NTB_NETDEV_VER, sizeof(info->version));
        strlcpy(info->bus_info, pci_name(dev->pdev), sizeof(info->bus_info));
}

static int ntb_get_settings(struct net_device *dev, struct ethtool_cmd *cmd)
{
        cmd->supported = SUPPORTED_Backplane;
        cmd->advertising = ADVERTISED_Backplane;
        ethtool_cmd_speed_set(cmd, SPEED_UNKNOWN);
        cmd->duplex = DUPLEX_FULL;
        cmd->port = PORT_OTHER;
        cmd->phy_address = 0;
        cmd->transceiver = XCVR_DUMMY1;
        cmd->autoneg = AUTONEG_ENABLE;
        cmd->maxtxpkt = 0;
        cmd->maxrxpkt = 0;

        return 0;
}

static const struct ethtool_ops ntb_ethtool_ops = {
        .get_drvinfo = ntb_get_drvinfo,
        .get_link = ethtool_op_get_link,
        .get_settings = ntb_get_settings,
};

static const struct ntb_queue_handlers ntb_netdev_handlers = {
        .tx_handler = ntb_netdev_tx_handler,
        .rx_handler = ntb_netdev_rx_handler,
        .event_handler = ntb_netdev_event_handler,
};

static int ntb_netdev_probe(struct device *client_dev)
{
        struct ntb_dev *ntb;
        struct net_device *ndev;
        struct pci_dev *pdev;
        struct ntb_netdev *dev;
        int rc;

        ntb = dev_ntb(client_dev->parent);
        pdev = ntb->pdev;
        if (!pdev)
                return -ENODEV;

        ndev = alloc_etherdev(sizeof(*dev));
        if (!ndev)
                return -ENOMEM;

        dev = netdev_priv(ndev);
        dev->ndev = ndev;
        dev->pdev = pdev;
        ndev->features = NETIF_F_HIGHDMA;

        ndev->priv_flags |= IFF_LIVE_ADDR_CHANGE;

        ndev->hw_features = ndev->features;
        ndev->watchdog_timeo = msecs_to_jiffies(NTB_TX_TIMEOUT_MS);

        random_ether_addr(ndev->perm_addr);
        memcpy(ndev->dev_addr, ndev->perm_addr, ndev->addr_len);

        ndev->netdev_ops = &ntb_netdev_ops;
        ndev->ethtool_ops = &ntb_ethtool_ops;

        dev->qp = ntb_transport_create_queue(ndev, client_dev,
                                             &ntb_netdev_handlers);
        if (!dev->qp) {
                rc = -EIO;
                goto err;
        }

        ndev->mtu = ntb_transport_max_size(dev->qp) - ETH_HLEN;

        rc = register_netdev(ndev);
        if (rc)
                goto err1;

        list_add(&dev->list, &dev_list);
        dev_info(&pdev->dev, "%s created\n", ndev->name);
        return 0;

err1:
        ntb_transport_free_queue(dev->qp);
err:
        free_netdev(ndev);
        return rc;
}

static void ntb_netdev_remove(struct device *client_dev)
{
        struct ntb_dev *ntb;
        struct net_device *ndev;
        struct pci_dev *pdev;
        struct ntb_netdev *dev;
        bool found = false;

        ntb = dev_ntb(client_dev->parent);
        pdev = ntb->pdev;

        list_for_each_entry(dev, &dev_list, list) {
                if (dev->pdev == pdev) {
                        found = true;
                        break;
                }
        }
        if (!found)
                return;

        list_del(&dev->list);

        ndev = dev->ndev;

        unregister_netdev(ndev);
        ntb_transport_free_queue(dev->qp);
        free_netdev(ndev);
}

static struct ntb_transport_client ntb_netdev_client = {
        .driver.name = KBUILD_MODNAME,
        .driver.owner = THIS_MODULE,
        .probe = ntb_netdev_probe,
        .remove = ntb_netdev_remove,
};

static int __init ntb_netdev_init_module(void)
{
        int rc;

        rc = ntb_transport_register_client_dev(KBUILD_MODNAME);
        if (rc)
                return rc;
        return ntb_transport_register_client(&ntb_netdev_client);
}
module_init(ntb_netdev_init_module);

static void __exit ntb_netdev_exit_module(void)
{
        ntb_transport_unregister_client(&ntb_netdev_client);
        ntb_transport_unregister_client_dev(KBUILD_MODNAME);
}
module_exit(ntb_netdev_exit_module);