/*
   * 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
  ", 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
  ", __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
  ");
  	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
  ", 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);