/*
 * 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 Transport Linux driver
 *
 * Contact Information:
 * Jon Mason <jon.mason@intel.com>
 */
#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/dmaengine.h>
#include <linux/dma-mapping.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include "linux/ntb.h"
#include "linux/ntb_transport.h"

#define NTB_TRANSPORT_VERSION   4
#define NTB_TRANSPORT_VER       "4"
#define NTB_TRANSPORT_NAME      "ntb_transport"
#define NTB_TRANSPORT_DESC      "Software Queue-Pair Transport over NTB"
#define NTB_TRANSPORT_MIN_SPADS (MW0_SZ_HIGH + 2)

MODULE_DESCRIPTION(NTB_TRANSPORT_DESC);
MODULE_VERSION(NTB_TRANSPORT_VER);
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Intel Corporation");

static unsigned long max_mw_size;
module_param(max_mw_size, ulong, 0644);
MODULE_PARM_DESC(max_mw_size, "Limit size of large memory windows");

static unsigned int transport_mtu = 0x10000;
module_param(transport_mtu, uint, 0644);
MODULE_PARM_DESC(transport_mtu, "Maximum size of NTB transport packets");

static unsigned char max_num_clients;
module_param(max_num_clients, byte, 0644);
MODULE_PARM_DESC(max_num_clients, "Maximum number of NTB transport clients");

static unsigned int copy_bytes = 1024;
module_param(copy_bytes, uint, 0644);
MODULE_PARM_DESC(copy_bytes, "Threshold under which NTB will use the CPU to copy instead of DMA");

static bool use_dma;
module_param(use_dma, bool, 0644);
MODULE_PARM_DESC(use_dma, "Use DMA engine to perform large data copy");

static bool use_msi;
#ifdef CONFIG_NTB_MSI
module_param(use_msi, bool, 0644);
MODULE_PARM_DESC(use_msi, "Use MSI interrupts instead of doorbells");
#endif

static struct dentry *nt_debugfs_dir;

/* Only two-ports NTB devices are supported */
#define PIDX            NTB_DEF_PEER_IDX

struct ntb_queue_entry {
        /* ntb_queue list reference */
        struct list_head entry;
        /* pointers to data to be transferred */
        void *cb_data;
        void *buf;
        unsigned int len;
        unsigned int flags;
        int retries;
        int errors;
        unsigned int tx_index;
        unsigned int rx_index;

        struct ntb_transport_qp *qp;
        union {
                struct ntb_payload_header __iomem *tx_hdr;
                struct ntb_payload_header *rx_hdr;
        };
};

struct ntb_rx_info {
        unsigned int entry;
};

struct ntb_transport_qp {
        struct ntb_transport_ctx *transport;
        struct ntb_dev *ndev;
        void *cb_data;
        struct dma_chan *tx_dma_chan;
        struct dma_chan *rx_dma_chan;

        bool client_ready;
        bool link_is_up;
        bool active;

        u8 qp_num;      /* Only 64 QP's are allowed.  0-63 */
        u64 qp_bit;

        struct ntb_rx_info __iomem *rx_info;
        struct ntb_rx_info *remote_rx_info;

        void (*tx_handler)(struct ntb_transport_qp *qp, void *qp_data,
                           void *data, int len);
        struct list_head tx_free_q;
        spinlock_t ntb_tx_free_q_lock;
        void __iomem *tx_mw;
        phys_addr_t tx_mw_phys;
        size_t tx_mw_size;
        dma_addr_t tx_mw_dma_addr;
        unsigned int tx_index;
        unsigned int tx_max_entry;
        unsigned int tx_max_frame;

        void (*rx_handler)(struct ntb_transport_qp *qp, void *qp_data,
                           void *data, int len);
        struct list_head rx_post_q;
        struct list_head rx_pend_q;
        struct list_head rx_free_q;
        /* ntb_rx_q_lock: synchronize access to rx_XXXX_q */
        spinlock_t ntb_rx_q_lock;
        void *rx_buff;
        unsigned int rx_index;
        unsigned int rx_max_entry;
        unsigned int rx_max_frame;
        unsigned int rx_alloc_entry;
        dma_cookie_t last_cookie;
        struct tasklet_struct rxc_db_work;

        void (*event_handler)(void *data, int status);
        struct delayed_work link_work;
        struct work_struct link_cleanup;

        struct dentry *debugfs_dir;
        struct dentry *debugfs_stats;

        /* Stats */
        u64 rx_bytes;
        u64 rx_pkts;
        u64 rx_ring_empty;
        u64 rx_err_no_buf;
        u64 rx_err_oflow;
        u64 rx_err_ver;
        u64 rx_memcpy;
        u64 rx_async;
        u64 tx_bytes;
        u64 tx_pkts;
        u64 tx_ring_full;
        u64 tx_err_no_buf;
        u64 tx_memcpy;
        u64 tx_async;

        bool use_msi;
        int msi_irq;
        struct ntb_msi_desc msi_desc;
        struct ntb_msi_desc peer_msi_desc;
};

struct ntb_transport_mw {
        phys_addr_t phys_addr;
        resource_size_t phys_size;
        void __iomem *vbase;
        size_t xlat_size;
        size_t buff_size;
        size_t alloc_size;
        void *alloc_addr;
        void *virt_addr;
        dma_addr_t dma_addr;
};

struct ntb_transport_client_dev {
        struct list_head entry;
        struct ntb_transport_ctx *nt;
        struct device dev;
};

struct ntb_transport_ctx {
        struct list_head entry;
        struct list_head client_devs;

        struct ntb_dev *ndev;

        struct ntb_transport_mw *mw_vec;
        struct ntb_transport_qp *qp_vec;
        unsigned int mw_count;
        unsigned int qp_count;
        u64 qp_bitmap;
        u64 qp_bitmap_free;

        bool use_msi;
        unsigned int msi_spad_offset;
        u64 msi_db_mask;

        bool link_is_up;
        struct delayed_work link_work;
        struct work_struct link_cleanup;

        struct dentry *debugfs_node_dir;
};

enum {
        DESC_DONE_FLAG = BIT(0),
        LINK_DOWN_FLAG = BIT(1),
};

struct ntb_payload_header {
        unsigned int ver;
        unsigned int len;
        unsigned int flags;
};

enum {
        VERSION = 0,
        QP_LINKS,
        NUM_QPS,
        NUM_MWS,
        MW0_SZ_HIGH,
        MW0_SZ_LOW,
};

#define dev_client_dev(__dev) \
        container_of((__dev), struct ntb_transport_client_dev, dev)

#define drv_client(__drv) \
        container_of((__drv), struct ntb_transport_client, driver)

#define QP_TO_MW(nt, qp)        ((qp) % nt->mw_count)
#define NTB_QP_DEF_NUM_ENTRIES  100
#define NTB_LINK_DOWN_TIMEOUT   10

static void ntb_transport_rxc_db(unsigned long data);
static const struct ntb_ctx_ops ntb_transport_ops;
static struct ntb_client ntb_transport_client;
static int ntb_async_tx_submit(struct ntb_transport_qp *qp,
                               struct ntb_queue_entry *entry);
static void ntb_memcpy_tx(struct ntb_queue_entry *entry, void __iomem *offset);
static int ntb_async_rx_submit(struct ntb_queue_entry *entry, void *offset);
static void ntb_memcpy_rx(struct ntb_queue_entry *entry, void *offset);


static int ntb_transport_bus_match(struct device *dev,
                                   struct device_driver *drv)
{
        return !strncmp(dev_name(dev), drv->name, strlen(drv->name));
}

static int ntb_transport_bus_probe(struct device *dev)
{
        const struct ntb_transport_client *client;
        int rc = -EINVAL;

        get_device(dev);

        client = drv_client(dev->driver);
        rc = client->probe(dev);
        if (rc)
                put_device(dev);

        return rc;
}

static int ntb_transport_bus_remove(struct device *dev)
{
        const struct ntb_transport_client *client;

        client = drv_client(dev->driver);
        client->remove(dev);

        put_device(dev);

        return 0;
}

static struct bus_type ntb_transport_bus = {
        .name = "ntb_transport",
        .match = ntb_transport_bus_match,
        .probe = ntb_transport_bus_probe,
        .remove = ntb_transport_bus_remove,
};

static LIST_HEAD(ntb_transport_list);

static int ntb_bus_init(struct ntb_transport_ctx *nt)
{
        list_add_tail(&nt->entry, &ntb_transport_list);
        return 0;
}

static void ntb_bus_remove(struct ntb_transport_ctx *nt)
{
        struct ntb_transport_client_dev *client_dev, *cd;

        list_for_each_entry_safe(client_dev, cd, &nt->client_devs, entry) {
                dev_err(client_dev->dev.parent, "%s still attached to bus, removing\n",
                        dev_name(&client_dev->dev));
                list_del(&client_dev->entry);
                device_unregister(&client_dev->dev);
        }

        list_del(&nt->entry);
}

static void ntb_transport_client_release(struct device *dev)
{
        struct ntb_transport_client_dev *client_dev;

        client_dev = dev_client_dev(dev);
        kfree(client_dev);
}

/**
 * ntb_transport_unregister_client_dev - Unregister NTB client device
 * @device_name: Name of NTB client device
 *
 * Unregister an NTB client device with the NTB transport layer
 */
void ntb_transport_unregister_client_dev(char *device_name)
{
        struct ntb_transport_client_dev *client, *cd;
        struct ntb_transport_ctx *nt;

        list_for_each_entry(nt, &ntb_transport_list, entry)
                list_for_each_entry_safe(client, cd, &nt->client_devs, entry)
                        if (!strncmp(dev_name(&client->dev), device_name,
                                     strlen(device_name))) {
                                list_del(&client->entry);
                                device_unregister(&client->dev);
                        }
}
EXPORT_SYMBOL_GPL(ntb_transport_unregister_client_dev);

/**
 * ntb_transport_register_client_dev - Register NTB client device
 * @device_name: Name of NTB client device
 *
 * Register an NTB client device with the NTB transport layer
 */
int ntb_transport_register_client_dev(char *device_name)
{
        struct ntb_transport_client_dev *client_dev;
        struct ntb_transport_ctx *nt;
        int node;
        int rc, i = 0;

        if (list_empty(&ntb_transport_list))
                return -ENODEV;

        list_for_each_entry(nt, &ntb_transport_list, entry) {
                struct device *dev;

                node = dev_to_node(&nt->ndev->dev);

                client_dev = kzalloc_node(sizeof(*client_dev),
                                          GFP_KERNEL, node);
                if (!client_dev) {
                        rc = -ENOMEM;
                        goto err;
                }

                dev = &client_dev->dev;

                /* setup and register client devices */
                dev_set_name(dev, "%s%d", device_name, i);
                dev->bus = &ntb_transport_bus;
                dev->release = ntb_transport_client_release;
                dev->parent = &nt->ndev->dev;

                rc = device_register(dev);
                if (rc) {
                        kfree(client_dev);
                        goto err;
                }

                list_add_tail(&client_dev->entry, &nt->client_devs);
                i++;
        }

        return 0;

err:
        ntb_transport_unregister_client_dev(device_name);

        return rc;
}
EXPORT_SYMBOL_GPL(ntb_transport_register_client_dev);

/**
 * ntb_transport_register_client - Register NTB client driver
 * @drv: NTB client driver to be registered
 *
 * Register an NTB client driver with the NTB transport layer
 *
 * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
 */
int ntb_transport_register_client(struct ntb_transport_client *drv)
{
        drv->driver.bus = &ntb_transport_bus;

        if (list_empty(&ntb_transport_list))
                return -ENODEV;

        return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(ntb_transport_register_client);

/**
 * ntb_transport_unregister_client - Unregister NTB client driver
 * @drv: NTB client driver to be unregistered
 *
 * Unregister an NTB client driver with the NTB transport layer
 *
 * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
 */
void ntb_transport_unregister_client(struct ntb_transport_client *drv)
{
        driver_unregister(&drv->driver);
}
EXPORT_SYMBOL_GPL(ntb_transport_unregister_client);

static ssize_t debugfs_read(struct file *filp, char __user *ubuf, size_t count,
                            loff_t *offp)
{
        struct ntb_transport_qp *qp;
        char *buf;
        ssize_t ret, out_offset, out_count;

        qp = filp->private_data;

        if (!qp || !qp->link_is_up)
                return 0;

        out_count = 1000;

        buf = kmalloc(out_count, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        out_offset = 0;
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "\nNTB QP stats:\n\n");
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_bytes - \t%llu\n", qp->rx_bytes);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_pkts - \t%llu\n", qp->rx_pkts);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_memcpy - \t%llu\n", qp->rx_memcpy);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_async - \t%llu\n", qp->rx_async);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_ring_empty - %llu\n", qp->rx_ring_empty);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_err_no_buf - %llu\n", qp->rx_err_no_buf);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_err_oflow - \t%llu\n", qp->rx_err_oflow);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_err_ver - \t%llu\n", qp->rx_err_ver);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_buff - \t0x%p\n", qp->rx_buff);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_index - \t%u\n", qp->rx_index);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_max_entry - \t%u\n", qp->rx_max_entry);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "rx_alloc_entry - \t%u\n\n", qp->rx_alloc_entry);

        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_bytes - \t%llu\n", qp->tx_bytes);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_pkts - \t%llu\n", qp->tx_pkts);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_memcpy - \t%llu\n", qp->tx_memcpy);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_async - \t%llu\n", qp->tx_async);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_ring_full - \t%llu\n", qp->tx_ring_full);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_err_no_buf - %llu\n", qp->tx_err_no_buf);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_mw - \t0x%p\n", qp->tx_mw);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_index (H) - \t%u\n", qp->tx_index);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "RRI (T) - \t%u\n",
                               qp->remote_rx_info->entry);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_max_entry - \t%u\n", qp->tx_max_entry);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "free tx - \t%u\n",
                               ntb_transport_tx_free_entry(qp));

        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "\n");
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "Using TX DMA - \t%s\n",
                               qp->tx_dma_chan ? "Yes" : "No");
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "Using RX DMA - \t%s\n",
                               qp->rx_dma_chan ? "Yes" : "No");
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "QP Link - \t%s\n",
                               qp->link_is_up ? "Up" : "Down");
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "\n");

        if (out_offset > out_count)
                out_offset = out_count;

        ret = simple_read_from_buffer(ubuf, count, offp, buf, out_offset);
        kfree(buf);
        return ret;
}

static const struct file_operations ntb_qp_debugfs_stats = {
        .owner = THIS_MODULE,
        .open = simple_open,
        .read = debugfs_read,
};

static void ntb_list_add(spinlock_t *lock, struct list_head *entry,
                         struct list_head *list)
{
        unsigned long flags;

        spin_lock_irqsave(lock, flags);
        list_add_tail(entry, list);
        spin_unlock_irqrestore(lock, flags);
}

static struct ntb_queue_entry *ntb_list_rm(spinlock_t *lock,
                                           struct list_head *list)
{
        struct ntb_queue_entry *entry;
        unsigned long flags;

        spin_lock_irqsave(lock, flags);
        if (list_empty(list)) {
                entry = NULL;
                goto out;
        }
        entry = list_first_entry(list, struct ntb_queue_entry, entry);
        list_del(&entry->entry);

out:
        spin_unlock_irqrestore(lock, flags);

        return entry;
}

static struct ntb_queue_entry *ntb_list_mv(spinlock_t *lock,
                                           struct list_head *list,
                                           struct list_head *to_list)
{
        struct ntb_queue_entry *entry;
        unsigned long flags;

        spin_lock_irqsave(lock, flags);

        if (list_empty(list)) {
                entry = NULL;
        } else {
                entry = list_first_entry(list, struct ntb_queue_entry, entry);
                list_move_tail(&entry->entry, to_list);
        }

        spin_unlock_irqrestore(lock, flags);

        return entry;
}

static int ntb_transport_setup_qp_mw(struct ntb_transport_ctx *nt,
                                     unsigned int qp_num)
{
        struct ntb_transport_qp *qp = &nt->qp_vec[qp_num];
        struct ntb_transport_mw *mw;
        struct ntb_dev *ndev = nt->ndev;
        struct ntb_queue_entry *entry;
        unsigned int rx_size, num_qps_mw;
        unsigned int mw_num, mw_count, qp_count;
        unsigned int i;
        int node;

        mw_count = nt->mw_count;
        qp_count = nt->qp_count;

        mw_num = QP_TO_MW(nt, qp_num);
        mw = &nt->mw_vec[mw_num];

        if (!mw->virt_addr)
                return -ENOMEM;

        if (mw_num < qp_count % mw_count)
                num_qps_mw = qp_count / mw_count + 1;
        else
                num_qps_mw = qp_count / mw_count;

        rx_size = (unsigned int)mw->xlat_size / num_qps_mw;
        qp->rx_buff = mw->virt_addr + rx_size * (qp_num / mw_count);
        rx_size -= sizeof(struct ntb_rx_info);

        qp->remote_rx_info = qp->rx_buff + rx_size;

        /* Due to housekeeping, there must be atleast 2 buffs */
        qp->rx_max_frame = min(transport_mtu, rx_size / 2);
        qp->rx_max_entry = rx_size / qp->rx_max_frame;
        qp->rx_index = 0;

        /*
         * Checking to see if we have more entries than the default.
         * We should add additional entries if that is the case so we
         * can be in sync with the transport frames.
         */
        node = dev_to_node(&ndev->dev);
        for (i = qp->rx_alloc_entry; i < qp->rx_max_entry; i++) {
                entry = kzalloc_node(sizeof(*entry), GFP_KERNEL, node);
                if (!entry)
                        return -ENOMEM;

                entry->qp = qp;
                ntb_list_add(&qp->ntb_rx_q_lock, &entry->entry,
                             &qp->rx_free_q);
                qp->rx_alloc_entry++;
        }

        qp->remote_rx_info->entry = qp->rx_max_entry - 1;

        /* setup the hdr offsets with 0's */
        for (i = 0; i < qp->rx_max_entry; i++) {
                void *offset = (qp->rx_buff + qp->rx_max_frame * (i + 1) -
                                sizeof(struct ntb_payload_header));
                memset(offset, 0, sizeof(struct ntb_payload_header));
        }

        qp->rx_pkts = 0;
        qp->tx_pkts = 0;
        qp->tx_index = 0;

        return 0;
}

static irqreturn_t ntb_transport_isr(int irq, void *dev)
{
        struct ntb_transport_qp *qp = dev;

        tasklet_schedule(&qp->rxc_db_work);

        return IRQ_HANDLED;
}

static void ntb_transport_setup_qp_peer_msi(struct ntb_transport_ctx *nt,
                                            unsigned int qp_num)
{
        struct ntb_transport_qp *qp = &nt->qp_vec[qp_num];
        int spad = qp_num * 2 + nt->msi_spad_offset;

        if (!nt->use_msi)
                return;

        if (spad >= ntb_spad_count(nt->ndev))
                return;

        qp->peer_msi_desc.addr_offset =
                ntb_peer_spad_read(qp->ndev, PIDX, spad);
        qp->peer_msi_desc.data =
                ntb_peer_spad_read(qp->ndev, PIDX, spad + 1);

        dev_dbg(&qp->ndev->pdev->dev, "QP%d Peer MSI addr=%x data=%x\n",
                qp_num, qp->peer_msi_desc.addr_offset, qp->peer_msi_desc.data);

        if (qp->peer_msi_desc.addr_offset) {
                qp->use_msi = true;
                dev_info(&qp->ndev->pdev->dev,
                         "Using MSI interrupts for QP%d\n", qp_num);
        }
}

static void ntb_transport_setup_qp_msi(struct ntb_transport_ctx *nt,
                                       unsigned int qp_num)
{
        struct ntb_transport_qp *qp = &nt->qp_vec[qp_num];
        int spad = qp_num * 2 + nt->msi_spad_offset;
        int rc;

        if (!nt->use_msi)
                return;

        if (spad >= ntb_spad_count(nt->ndev)) {
                dev_warn_once(&qp->ndev->pdev->dev,
                              "Not enough SPADS to use MSI interrupts\n");
                return;
        }

        ntb_spad_write(qp->ndev, spad, 0);
        ntb_spad_write(qp->ndev, spad + 1, 0);

        if (!qp->msi_irq) {
                qp->msi_irq = ntbm_msi_request_irq(qp->ndev, ntb_transport_isr,
                                                   KBUILD_MODNAME, qp,
                                                   &qp->msi_desc);
                if (qp->msi_irq < 0) {
                        dev_warn(&qp->ndev->pdev->dev,
                                 "Unable to allocate MSI interrupt for qp%d\n",
                                 qp_num);
                        return;
                }
        }

        rc = ntb_spad_write(qp->ndev, spad, qp->msi_desc.addr_offset);
        if (rc)
                goto err_free_interrupt;

        rc = ntb_spad_write(qp->ndev, spad + 1, qp->msi_desc.data);
        if (rc)
                goto err_free_interrupt;

        dev_dbg(&qp->ndev->pdev->dev, "QP%d MSI %d addr=%x data=%x\n",
                qp_num, qp->msi_irq, qp->msi_desc.addr_offset,
                qp->msi_desc.data);

        return;

err_free_interrupt:
        devm_free_irq(&nt->ndev->dev, qp->msi_irq, qp);
}

static void ntb_transport_msi_peer_desc_changed(struct ntb_transport_ctx *nt)
{
        int i;

        dev_dbg(&nt->ndev->pdev->dev, "Peer MSI descriptors changed");

        for (i = 0; i < nt->qp_count; i++)
                ntb_transport_setup_qp_peer_msi(nt, i);
}

static void ntb_transport_msi_desc_changed(void *data)
{
        struct ntb_transport_ctx *nt = data;
        int i;

        dev_dbg(&nt->ndev->pdev->dev, "MSI descriptors changed");

        for (i = 0; i < nt->qp_count; i++)
                ntb_transport_setup_qp_msi(nt, i);

        ntb_peer_db_set(nt->ndev, nt->msi_db_mask);
}

static void ntb_free_mw(struct ntb_transport_ctx *nt, int num_mw)
{
        struct ntb_transport_mw *mw = &nt->mw_vec[num_mw];
        struct pci_dev *pdev = nt->ndev->pdev;

        if (!mw->virt_addr)
                return;

        ntb_mw_clear_trans(nt->ndev, PIDX, num_mw);
        dma_free_coherent(&pdev->dev, mw->alloc_size,
                          mw->alloc_addr, mw->dma_addr);
        mw->xlat_size = 0;
        mw->buff_size = 0;
        mw->alloc_size = 0;
        mw->alloc_addr = NULL;
        mw->virt_addr = NULL;
}

static int ntb_alloc_mw_buffer(struct ntb_transport_mw *mw,
                               struct device *dma_dev, size_t align)
{
        dma_addr_t dma_addr;
        void *alloc_addr, *virt_addr;
        int rc;

        alloc_addr = dma_alloc_coherent(dma_dev, mw->alloc_size,
                                        &dma_addr, GFP_KERNEL);
        if (!alloc_addr) {
                dev_err(dma_dev, "Unable to alloc MW buff of size %zu\n",
                        mw->alloc_size);
                return -ENOMEM;
        }
        virt_addr = alloc_addr;

        /*
         * we must ensure that the memory address allocated is BAR size
         * aligned in order for the XLAT register to take the value. This
         * is a requirement of the hardware. It is recommended to setup CMA
         * for BAR sizes equal or greater than 4MB.
         */
        if (!IS_ALIGNED(dma_addr, align)) {
                if (mw->alloc_size > mw->buff_size) {
                        virt_addr = PTR_ALIGN(alloc_addr, align);
                        dma_addr = ALIGN(dma_addr, align);
                } else {
                        rc = -ENOMEM;
                        goto err;
                }
        }

        mw->alloc_addr = alloc_addr;
        mw->virt_addr = virt_addr;
        mw->dma_addr = dma_addr;

        return 0;

err:
        dma_free_coherent(dma_dev, mw->alloc_size, alloc_addr, dma_addr);

        return rc;
}

static int ntb_set_mw(struct ntb_transport_ctx *nt, int num_mw,
                      resource_size_t size)
{
        struct ntb_transport_mw *mw = &nt->mw_vec[num_mw];
        struct pci_dev *pdev = nt->ndev->pdev;
        size_t xlat_size, buff_size;
        resource_size_t xlat_align;
        resource_size_t xlat_align_size;
        int rc;

        if (!size)
                return -EINVAL;

        rc = ntb_mw_get_align(nt->ndev, PIDX, num_mw, &xlat_align,
                              &xlat_align_size, NULL);
        if (rc)
                return rc;

        xlat_size = round_up(size, xlat_align_size);
        buff_size = round_up(size, xlat_align);

        /* No need to re-setup */
        if (mw->xlat_size == xlat_size)
                return 0;

        if (mw->buff_size)
                ntb_free_mw(nt, num_mw);

        /* Alloc memory for receiving data.  Must be aligned */
        mw->xlat_size = xlat_size;
        mw->buff_size = buff_size;
        mw->alloc_size = buff_size;

        rc = ntb_alloc_mw_buffer(mw, &pdev->dev, xlat_align);
        if (rc) {
                mw->alloc_size *= 2;
                rc = ntb_alloc_mw_buffer(mw, &pdev->dev, xlat_align);
                if (rc) {
                        dev_err(&pdev->dev,
                                "Unable to alloc aligned MW buff\n");
                        mw->xlat_size = 0;
                        mw->buff_size = 0;
                        mw->alloc_size = 0;
                        return rc;
                }
        }

        /* Notify HW the memory location of the receive buffer */
        rc = ntb_mw_set_trans(nt->ndev, PIDX, num_mw, mw->dma_addr,
                              mw->xlat_size);
        if (rc) {
                dev_err(&pdev->dev, "Unable to set mw%d translation", num_mw);
                ntb_free_mw(nt, num_mw);
                return -EIO;
        }

        return 0;
}

static void ntb_qp_link_down_reset(struct ntb_transport_qp *qp)
{
        qp->link_is_up = false;
        qp->active = false;

        qp->tx_index = 0;
        qp->rx_index = 0;
        qp->rx_bytes = 0;
        qp->rx_pkts = 0;
        qp->rx_ring_empty = 0;
        qp->rx_err_no_buf = 0;
        qp->rx_err_oflow = 0;
        qp->rx_err_ver = 0;
        qp->rx_memcpy = 0;
        qp->rx_async = 0;
        qp->tx_bytes = 0;
        qp->tx_pkts = 0;
        qp->tx_ring_full = 0;
        qp->tx_err_no_buf = 0;
        qp->tx_memcpy = 0;
        qp->tx_async = 0;
}

static void ntb_qp_link_cleanup(struct ntb_transport_qp *qp)
{
        struct ntb_transport_ctx *nt = qp->transport;
        struct pci_dev *pdev = nt->ndev->pdev;

        dev_info(&pdev->dev, "qp %d: Link Cleanup\n", qp->qp_num);

        cancel_delayed_work_sync(&qp->link_work);
        ntb_qp_link_down_reset(qp);

        if (qp->event_handler)
                qp->event_handler(qp->cb_data, qp->link_is_up);
}

static void ntb_qp_link_cleanup_work(struct work_struct *work)
{
        struct ntb_transport_qp *qp = container_of(work,
                                                   struct ntb_transport_qp,
                                                   link_cleanup);
        struct ntb_transport_ctx *nt = qp->transport;

        ntb_qp_link_cleanup(qp);

        if (nt->link_is_up)
                schedule_delayed_work(&qp->link_work,
                                      msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
}

static void ntb_qp_link_down(struct ntb_transport_qp *qp)
{
        schedule_work(&qp->link_cleanup);
}

static void ntb_transport_link_cleanup(struct ntb_transport_ctx *nt)
{
        struct ntb_transport_qp *qp;
        u64 qp_bitmap_alloc;
        unsigned int i, count;

        qp_bitmap_alloc = nt->qp_bitmap & ~nt->qp_bitmap_free;

        /* Pass along the info to any clients */
        for (i = 0; i < nt->qp_count; i++)
                if (qp_bitmap_alloc & BIT_ULL(i)) {
                        qp = &nt->qp_vec[i];
                        ntb_qp_link_cleanup(qp);
                        cancel_work_sync(&qp->link_cleanup);
                        cancel_delayed_work_sync(&qp->link_work);
                }

        if (!nt->link_is_up)
                cancel_delayed_work_sync(&nt->link_work);

        for (i = 0; i < nt->mw_count; i++)
                ntb_free_mw(nt, i);

        /* The scratchpad registers keep the values if the remote side
         * goes down, blast them now to give them a sane value the next
         * time they are accessed
         */
        count = ntb_spad_count(nt->ndev);
        for (i = 0; i < count; i++)
                ntb_spad_write(nt->ndev, i, 0);
}

static void ntb_transport_link_cleanup_work(struct work_struct *work)
{
        struct ntb_transport_ctx *nt =
                container_of(work, struct ntb_transport_ctx, link_cleanup);

        ntb_transport_link_cleanup(nt);
}

static void ntb_transport_event_callback(void *data)
{
        struct ntb_transport_ctx *nt = data;

        if (ntb_link_is_up(nt->ndev, NULL, NULL) == 1)
                schedule_delayed_work(&nt->link_work, 0);
        else
                schedule_work(&nt->link_cleanup);
}

static void ntb_transport_link_work(struct work_struct *work)
{
        struct ntb_transport_ctx *nt =
                container_of(work, struct ntb_transport_ctx, link_work.work);
        struct ntb_dev *ndev = nt->ndev;
        struct pci_dev *pdev = ndev->pdev;
        resource_size_t size;
        u32 val;
        int rc = 0, i, spad;

        /* send the local info, in the opposite order of the way we read it */

        if (nt->use_msi) {
                rc = ntb_msi_setup_mws(ndev);
                if (rc) {
                        dev_warn(&pdev->dev,
                                 "Failed to register MSI memory window: %d\n",
                                 rc);
                        nt->use_msi = false;
                }
        }

        for (i = 0; i < nt->qp_count; i++)
                ntb_transport_setup_qp_msi(nt, i);

        for (i = 0; i < nt->mw_count; i++) {
                size = nt->mw_vec[i].phys_size;

                if (max_mw_size && size > max_mw_size)
                        size = max_mw_size;

                spad = MW0_SZ_HIGH + (i * 2);
                ntb_peer_spad_write(ndev, PIDX, spad, upper_32_bits(size));

                spad = MW0_SZ_LOW + (i * 2);
                ntb_peer_spad_write(ndev, PIDX, spad, lower_32_bits(size));
        }

        ntb_peer_spad_write(ndev, PIDX, NUM_MWS, nt->mw_count);

        ntb_peer_spad_write(ndev, PIDX, NUM_QPS, nt->qp_count);

        ntb_peer_spad_write(ndev, PIDX, VERSION, NTB_TRANSPORT_VERSION);

        /* Query the remote side for its info */
        val = ntb_spad_read(ndev, VERSION);
        dev_dbg(&pdev->dev, "Remote version = %d\n", val);
        if (val != NTB_TRANSPORT_VERSION)
                goto out;

        val = ntb_spad_read(ndev, NUM_QPS);
        dev_dbg(&pdev->dev, "Remote max number of qps = %d\n", val);
        if (val != nt->qp_count)
                goto out;

        val = ntb_spad_read(ndev, NUM_MWS);
        dev_dbg(&pdev->dev, "Remote number of mws = %d\n", val);
        if (val != nt->mw_count)
                goto out;

        for (i = 0; i < nt->mw_count; i++) {
                u64 val64;

                val = ntb_spad_read(ndev, MW0_SZ_HIGH + (i * 2));
                val64 = (u64)val << 32;

                val = ntb_spad_read(ndev, MW0_SZ_LOW + (i * 2));
                val64 |= val;

                dev_dbg(&pdev->dev, "Remote MW%d size = %#llx\n", i, val64);

                rc = ntb_set_mw(nt, i, val64);
                if (rc)
                        goto out1;
        }

        nt->link_is_up = true;

        for (i = 0; i < nt->qp_count; i++) {
                struct ntb_transport_qp *qp = &nt->qp_vec[i];

                ntb_transport_setup_qp_mw(nt, i);
                ntb_transport_setup_qp_peer_msi(nt, i);

                if (qp->client_ready)
                        schedule_delayed_work(&qp->link_work, 0);
        }

        return;

out1:
        for (i = 0; i < nt->mw_count; i++)
                ntb_free_mw(nt, i);

        /* if there's an actual failure, we should just bail */
        if (rc < 0)
                return;

out:
        if (ntb_link_is_up(ndev, NULL, NULL) == 1)
                schedule_delayed_work(&nt->link_work,
                                      msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
}

static void ntb_qp_link_work(struct work_struct *work)
{
        struct ntb_transport_qp *qp = container_of(work,
                                                   struct ntb_transport_qp,
                                                   link_work.work);
        struct pci_dev *pdev = qp->ndev->pdev;
        struct ntb_transport_ctx *nt = qp->transport;
        int val;

        WARN_ON(!nt->link_is_up);

        val = ntb_spad_read(nt->ndev, QP_LINKS);

        ntb_peer_spad_write(nt->ndev, PIDX, QP_LINKS, val | BIT(qp->qp_num));

        /* query remote spad for qp ready bits */
        dev_dbg_ratelimited(&pdev->dev, "Remote QP link status = %x\n", val);

        /* See if the remote side is up */
        if (val & BIT(qp->qp_num)) {
                dev_info(&pdev->dev, "qp %d: Link Up\n", qp->qp_num);
                qp->link_is_up = true;
                qp->active = true;

                if (qp->event_handler)
                        qp->event_handler(qp->cb_data, qp->link_is_up);

                if (qp->active)
                        tasklet_schedule(&qp->rxc_db_work);
        } else if (nt->link_is_up)
                schedule_delayed_work(&qp->link_work,
                                      msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
}

static int ntb_transport_init_queue(struct ntb_transport_ctx *nt,
                                    unsigned int qp_num)
{
        struct ntb_transport_qp *qp;
        phys_addr_t mw_base;
        resource_size_t mw_size;
        unsigned int num_qps_mw, tx_size;
        unsigned int mw_num, mw_count, qp_count;
        u64 qp_offset;

        mw_count = nt->mw_count;
        qp_count = nt->qp_count;

        mw_num = QP_TO_MW(nt, qp_num);

        qp = &nt->qp_vec[qp_num];
        qp->qp_num = qp_num;
        qp->transport = nt;
        qp->ndev = nt->ndev;
        qp->client_ready = false;
        qp->event_handler = NULL;
        ntb_qp_link_down_reset(qp);

        if (mw_num < qp_count % mw_count)
                num_qps_mw = qp_count / mw_count + 1;
        else
                num_qps_mw = qp_count / mw_count;

        mw_base = nt->mw_vec[mw_num].phys_addr;
        mw_size = nt->mw_vec[mw_num].phys_size;

        if (max_mw_size && mw_size > max_mw_size)
                mw_size = max_mw_size;

        tx_size = (unsigned int)mw_size / num_qps_mw;
        qp_offset = tx_size * (qp_num / mw_count);

        qp->tx_mw_size = tx_size;
        qp->tx_mw = nt->mw_vec[mw_num].vbase + qp_offset;
        if (!qp->tx_mw)
                return -EINVAL;

        qp->tx_mw_phys = mw_base + qp_offset;
        if (!qp->tx_mw_phys)
                return -EINVAL;

        tx_size -= sizeof(struct ntb_rx_info);
        qp->rx_info = qp->tx_mw + tx_size;

        /* Due to housekeeping, there must be atleast 2 buffs */
        qp->tx_max_frame = min(transport_mtu, tx_size / 2);
        qp->tx_max_entry = tx_size / qp->tx_max_frame;

        if (nt->debugfs_node_dir) {
                char debugfs_name[4];

                snprintf(debugfs_name, 4, "qp%d", qp_num);
                qp->debugfs_dir = debugfs_create_dir(debugfs_name,
                                                     nt->debugfs_node_dir);

                qp->debugfs_stats = debugfs_create_file("stats", S_IRUSR,
                                                        qp->debugfs_dir, qp,
                                                        &ntb_qp_debugfs_stats);
        } else {
                qp->debugfs_dir = NULL;
                qp->debugfs_stats = NULL;
        }

        INIT_DELAYED_WORK(&qp->link_work, ntb_qp_link_work);
        INIT_WORK(&qp->link_cleanup, ntb_qp_link_cleanup_work);

        spin_lock_init(&qp->ntb_rx_q_lock);
        spin_lock_init(&qp->ntb_tx_free_q_lock);

        INIT_LIST_HEAD(&qp->rx_post_q);
        INIT_LIST_HEAD(&qp->rx_pend_q);
        INIT_LIST_HEAD(&qp->rx_free_q);
        INIT_LIST_HEAD(&qp->tx_free_q);

        tasklet_init(&qp->rxc_db_work, ntb_transport_rxc_db,
                     (unsigned long)qp);

        return 0;
}

static int ntb_transport_probe(struct ntb_client *self, struct ntb_dev *ndev)
{
        struct ntb_transport_ctx *nt;
        struct ntb_transport_mw *mw;
        unsigned int mw_count, qp_count, spad_count, max_mw_count_for_spads;
        u64 qp_bitmap;
        int node;
        int rc, i;

        mw_count = ntb_peer_mw_count(ndev);

        if (!ndev->ops->mw_set_trans) {
                dev_err(&ndev->dev, "Inbound MW based NTB API is required\n");
                return -EINVAL;
        }

        if (ntb_db_is_unsafe(ndev))
                dev_dbg(&ndev->dev,
                        "doorbell is unsafe, proceed anyway...\n");
        if (ntb_spad_is_unsafe(ndev))
                dev_dbg(&ndev->dev,
                        "scratchpad is unsafe, proceed anyway...\n");

        if (ntb_peer_port_count(ndev) != NTB_DEF_PEER_CNT)
                dev_warn(&ndev->dev, "Multi-port NTB devices unsupported\n");

        node = dev_to_node(&ndev->dev);

        nt = kzalloc_node(sizeof(*nt), GFP_KERNEL, node);
        if (!nt)
                return -ENOMEM;

        nt->ndev = ndev;

        /*
         * If we are using MSI, and have at least one extra memory window,
         * we will reserve the last MW for the MSI window.
         */
        if (use_msi && mw_count > 1) {
                rc = ntb_msi_init(ndev, ntb_transport_msi_desc_changed);
                if (!rc) {
                        mw_count -= 1;
                        nt->use_msi = true;
                }
        }

        spad_count = ntb_spad_count(ndev);

        /* Limit the MW's based on the availability of scratchpads */

        if (spad_count < NTB_TRANSPORT_MIN_SPADS) {
                nt->mw_count = 0;
                rc = -EINVAL;
                goto err;
        }

        max_mw_count_for_spads = (spad_count - MW0_SZ_HIGH) / 2;
        nt->mw_count = min(mw_count, max_mw_count_for_spads);

        nt->msi_spad_offset = nt->mw_count * 2 + MW0_SZ_HIGH;

        nt->mw_vec = kcalloc_node(mw_count, sizeof(*nt->mw_vec),
                                  GFP_KERNEL, node);
        if (!nt->mw_vec) {
                rc = -ENOMEM;
                goto err;
        }

        for (i = 0; i < mw_count; i++) {
                mw = &nt->mw_vec[i];

                rc = ntb_peer_mw_get_addr(ndev, i, &mw->phys_addr,
                                          &mw->phys_size);
                if (rc)
                        goto err1;

                mw->vbase = ioremap_wc(mw->phys_addr, mw->phys_size);
                if (!mw->vbase) {
                        rc = -ENOMEM;
                        goto err1;
                }

                mw->buff_size = 0;
                mw->xlat_size = 0;
                mw->virt_addr = NULL;
                mw->dma_addr = 0;
        }

        qp_bitmap = ntb_db_valid_mask(ndev);

        qp_count = ilog2(qp_bitmap);
        if (nt->use_msi) {
                qp_count -= 1;
                nt->msi_db_mask = 1 << qp_count;
                ntb_db_clear_mask(ndev, nt->msi_db_mask);
        }

        if (max_num_clients && max_num_clients < qp_count)
                qp_count = max_num_clients;
        else if (nt->mw_count < qp_count)
                qp_count = nt->mw_count;

        qp_bitmap &= BIT_ULL(qp_count) - 1;

        nt->qp_count = qp_count;
        nt->qp_bitmap = qp_bitmap;
        nt->qp_bitmap_free = qp_bitmap;

        nt->qp_vec = kcalloc_node(qp_count, sizeof(*nt->qp_vec),
                                  GFP_KERNEL, node);
        if (!nt->qp_vec) {
                rc = -ENOMEM;
                goto err1;
        }

        if (nt_debugfs_dir) {
                nt->debugfs_node_dir =
                        debugfs_create_dir(pci_name(ndev->pdev),
                                           nt_debugfs_dir);
        }

        for (i = 0; i < qp_count; i++) {
                rc = ntb_transport_init_queue(nt, i);
                if (rc)
                        goto err2;
        }

        INIT_DELAYED_WORK(&nt->link_work, ntb_transport_link_work);
        INIT_WORK(&nt->link_cleanup, ntb_transport_link_cleanup_work);

        rc = ntb_set_ctx(ndev, nt, &ntb_transport_ops);
        if (rc)
                goto err2;

        INIT_LIST_HEAD(&nt->client_devs);
        rc = ntb_bus_init(nt);
        if (rc)
                goto err3;

        nt->link_is_up = false;
        ntb_link_enable(ndev, NTB_SPEED_AUTO, NTB_WIDTH_AUTO);
        ntb_link_event(ndev);

        return 0;

err3:
        ntb_clear_ctx(ndev);
err2:
        kfree(nt->qp_vec);
err1:
        while (i--) {
                mw = &nt->mw_vec[i];
                iounmap(mw->vbase);
        }
        kfree(nt->mw_vec);
err:
        kfree(nt);
        return rc;
}

static void ntb_transport_free(struct ntb_client *self, struct ntb_dev *ndev)
{
        struct ntb_transport_ctx *nt = ndev->ctx;
        struct ntb_transport_qp *qp;
        u64 qp_bitmap_alloc;
        int i;

        ntb_transport_link_cleanup(nt);
        cancel_work_sync(&nt->link_cleanup);
        cancel_delayed_work_sync(&nt->link_work);

        qp_bitmap_alloc = nt->qp_bitmap & ~nt->qp_bitmap_free;

        /* verify that all the qp's are freed */
        for (i = 0; i < nt->qp_count; i++) {
                qp = &nt->qp_vec[i];
                if (qp_bitmap_alloc & BIT_ULL(i))
                        ntb_transport_free_queue(qp);
                debugfs_remove_recursive(qp->debugfs_dir);
        }

        ntb_link_disable(ndev);
        ntb_clear_ctx(ndev);

        ntb_bus_remove(nt);

        for (i = nt->mw_count; i--; ) {
                ntb_free_mw(nt, i);
                iounmap(nt->mw_vec[i].vbase);
        }

        kfree(nt->qp_vec);
        kfree(nt->mw_vec);
        kfree(nt);
}

static void ntb_complete_rxc(struct ntb_transport_qp *qp)
{
        struct ntb_queue_entry *entry;
        void *cb_data;
        unsigned int len;
        unsigned long irqflags;

        spin_lock_irqsave(&qp->ntb_rx_q_lock, irqflags);

        while (!list_empty(&qp->rx_post_q)) {
                entry = list_first_entry(&qp->rx_post_q,
                                         struct ntb_queue_entry, entry);
                if (!(entry->flags & DESC_DONE_FLAG))
                        break;

                entry->rx_hdr->flags = 0;
                iowrite32(entry->rx_index, &qp->rx_info->entry);

                cb_data = entry->cb_data;
                len = entry->len;

                list_move_tail(&entry->entry, &qp->rx_free_q);

                spin_unlock_irqrestore(&qp->ntb_rx_q_lock, irqflags);

                if (qp->rx_handler && qp->client_ready)
                        qp->rx_handler(qp, qp->cb_data, cb_data, len);

                spin_lock_irqsave(&qp->ntb_rx_q_lock, irqflags);
        }

        spin_unlock_irqrestore(&qp->ntb_rx_q_lock, irqflags);
}

static void ntb_rx_copy_callback(void *data,
                                 const struct dmaengine_result *res)
{
        struct ntb_queue_entry *entry = data;

        /* we need to check DMA results if we are using DMA */
        if (res) {
                enum dmaengine_tx_result dma_err = res->result;

                switch (dma_err) {
                case DMA_TRANS_READ_FAILED:
                case DMA_TRANS_WRITE_FAILED:
                        entry->errors++;
                        /* fall through */
                case DMA_TRANS_ABORTED:
                {
                        struct ntb_transport_qp *qp = entry->qp;
                        void *offset = qp->rx_buff + qp->rx_max_frame *
                                        qp->rx_index;

                        ntb_memcpy_rx(entry, offset);
                        qp->rx_memcpy++;
                        return;
                }

                case DMA_TRANS_NOERROR:
                default:
                        break;
                }
        }

        entry->flags |= DESC_DONE_FLAG;

        ntb_complete_rxc(entry->qp);
}

static void ntb_memcpy_rx(struct ntb_queue_entry *entry, void *offset)
{
        void *buf = entry->buf;
        size_t len = entry->len;

        memcpy(buf, offset, len);

        /* Ensure that the data is fully copied out before clearing the flag */
        wmb();

        ntb_rx_copy_callback(entry, NULL);
}

static int ntb_async_rx_submit(struct ntb_queue_entry *entry, void *offset)
{
        struct dma_async_tx_descriptor *txd;
        struct ntb_transport_qp *qp = entry->qp;
        struct dma_chan *chan = qp->rx_dma_chan;
        struct dma_device *device;
        size_t pay_off, buff_off, len;
        struct dmaengine_unmap_data *unmap;
        dma_cookie_t cookie;
        void *buf = entry->buf;

        len = entry->len;
        device = chan->device;
        pay_off = (size_t)offset & ~PAGE_MASK;
        buff_off = (size_t)buf & ~PAGE_MASK;

        if (!is_dma_copy_aligned(device, pay_off, buff_off, len))
                goto err;

        unmap = dmaengine_get_unmap_data(device->dev, 2, GFP_NOWAIT);
        if (!unmap)
                goto err;

        unmap->len = len;
        unmap->addr[0] = dma_map_page(device->dev, virt_to_page(offset),
                                      pay_off, len, DMA_TO_DEVICE);
        if (dma_mapping_error(device->dev, unmap->addr[0]))
                goto err_get_unmap;

        unmap->to_cnt = 1;

        unmap->addr[1] = dma_map_page(device->dev, virt_to_page(buf),
                                      buff_off, len, DMA_FROM_DEVICE);
        if (dma_mapping_error(device->dev, unmap->addr[1]))
                goto err_get_unmap;

        unmap->from_cnt = 1;

        txd = device->device_prep_dma_memcpy(chan, unmap->addr[1],
                                             unmap->addr[0], len,
                                             DMA_PREP_INTERRUPT);
        if (!txd)
                goto err_get_unmap;

        txd->callback_result = ntb_rx_copy_callback;
        txd->callback_param = entry;
        dma_set_unmap(txd, unmap);

        cookie = dmaengine_submit(txd);
        if (dma_submit_error(cookie))
                goto err_set_unmap;

        dmaengine_unmap_put(unmap);

        qp->last_cookie = cookie;

        qp->rx_async++;

        return 0;

err_set_unmap:
        dmaengine_unmap_put(unmap);
err_get_unmap:
        dmaengine_unmap_put(unmap);
err:
        return -ENXIO;
}

static void ntb_async_rx(struct ntb_queue_entry *entry, void *offset)
{
        struct ntb_transport_qp *qp = entry->qp;
        struct dma_chan *chan = qp->rx_dma_chan;
        int res;

        if (!chan)
                goto err;

        if (entry->len < copy_bytes)
                goto err;

        res = ntb_async_rx_submit(entry, offset);
        if (res < 0)
                goto err;

        if (!entry->retries)
                qp->rx_async++;

        return;

err:
        ntb_memcpy_rx(entry, offset);
        qp->rx_memcpy++;
}

static int ntb_process_rxc(struct ntb_transport_qp *qp)
{
        struct ntb_payload_header *hdr;
        struct ntb_queue_entry *entry;
        void *offset;

        offset = qp->rx_buff + qp->rx_max_frame * qp->rx_index;
        hdr = offset + qp->rx_max_frame - sizeof(struct ntb_payload_header);

        dev_dbg(&qp->ndev->pdev->dev, "qp %d: RX ver %u len %d flags %x\n",
                qp->qp_num, hdr->ver, hdr->len, hdr->flags);

        if (!(hdr->flags & DESC_DONE_FLAG)) {
                dev_dbg(&qp->ndev->pdev->dev, "done flag not set\n");
                qp->rx_ring_empty++;
                return -EAGAIN;
        }

        if (hdr->flags & LINK_DOWN_FLAG) {
                dev_dbg(&qp->ndev->pdev->dev, "link down flag set\n");
                ntb_qp_link_down(qp);
                hdr->flags = 0;
                return -EAGAIN;
        }

        if (hdr->ver != (u32)qp->rx_pkts) {
                dev_dbg(&qp->ndev->pdev->dev,
                        "version mismatch, expected %llu - got %u\n",
                        qp->rx_pkts, hdr->ver);
                qp->rx_err_ver++;
                return -EIO;
        }

        entry = ntb_list_mv(&qp->ntb_rx_q_lock, &qp->rx_pend_q, &qp->rx_post_q);
        if (!entry) {
                dev_dbg(&qp->ndev->pdev->dev, "no receive buffer\n");
                qp->rx_err_no_buf++;
                return -EAGAIN;
        }

        entry->rx_hdr = hdr;
        entry->rx_index = qp->rx_index;

        if (hdr->len > entry->len) {
                dev_dbg(&qp->ndev->pdev->dev,
                        "receive buffer overflow! Wanted %d got %d\n",
                        hdr->len, entry->len);
                qp->rx_err_oflow++;

                entry->len = -EIO;
                entry->flags |= DESC_DONE_FLAG;

                ntb_complete_rxc(qp);
        } else {
                dev_dbg(&qp->ndev->pdev->dev,
                        "RX OK index %u ver %u size %d into buf size %d\n",
                        qp->rx_index, hdr->ver, hdr->len, entry->len);

                qp->rx_bytes += hdr->len;
                qp->rx_pkts++;

                entry->len = hdr->len;

                ntb_async_rx(entry, offset);
        }

        qp->rx_index++;
        qp->rx_index %= qp->rx_max_entry;

        return 0;
}

static void ntb_transport_rxc_db(unsigned long data)
{
        struct ntb_transport_qp *qp = (void *)data;
        int rc, i;

        dev_dbg(&qp->ndev->pdev->dev, "%s: doorbell %d received\n",
                __func__, qp->qp_num);

        /* Limit the number of packets processed in a single interrupt to
         * provide fairness to others
         */
        for (i = 0; i < qp->rx_max_entry; i++) {
                rc = ntb_process_rxc(qp);
                if (rc)
                        break;
        }

        if (i && qp->rx_dma_chan)
                dma_async_issue_pending(qp->rx_dma_chan);

        if (i == qp->rx_max_entry) {
                /* there is more work to do */
                if (qp->active)
                        tasklet_schedule(&qp->rxc_db_work);
        } else if (ntb_db_read(qp->ndev) & BIT_ULL(qp->qp_num)) {
                /* the doorbell bit is set: clear it */
                ntb_db_clear(qp->ndev, BIT_ULL(qp->qp_num));
                /* ntb_db_read ensures ntb_db_clear write is committed */
                ntb_db_read(qp->ndev);

                /* an interrupt may have arrived between finishing
                 * ntb_process_rxc and clearing the doorbell bit:
                 * there might be some more work to do.
                 */
                if (qp->active)
                        tasklet_schedule(&qp->rxc_db_work);
        }
}

static void ntb_tx_copy_callback(void *data,
                                 const struct dmaengine_result *res)
{
        struct ntb_queue_entry *entry = data;
        struct ntb_transport_qp *qp = entry->qp;
        struct ntb_payload_header __iomem *hdr = entry->tx_hdr;

        /* we need to check DMA results if we are using DMA */
        if (res) {
                enum dmaengine_tx_result dma_err = res->result;

                switch (dma_err) {
                case DMA_TRANS_READ_FAILED:
                case DMA_TRANS_WRITE_FAILED:
                        entry->errors++;
                        /* fall through */
                case DMA_TRANS_ABORTED:
                {
                        void __iomem *offset =
                                qp->tx_mw + qp->tx_max_frame *
                                entry->tx_index;

                        /* resubmit via CPU */
                        ntb_memcpy_tx(entry, offset);
                        qp->tx_memcpy++;
                        return;
                }

                case DMA_TRANS_NOERROR:
                default:
                        break;
                }
        }

        iowrite32(entry->flags | DESC_DONE_FLAG, &hdr->flags);

        if (qp->use_msi)
                ntb_msi_peer_trigger(qp->ndev, PIDX, &qp->peer_msi_desc);
        else
                ntb_peer_db_set(qp->ndev, BIT_ULL(qp->qp_num));

        /* The entry length can only be zero if the packet is intended to be a
         * "link down" or similar.  Since no payload is being sent in these
         * cases, there is nothing to add to the completion queue.
         */
        if (entry->len > 0) {
                qp->tx_bytes += entry->len;

                if (qp->tx_handler)
                        qp->tx_handler(qp, qp->cb_data, entry->cb_data,
                                       entry->len);
        }

        ntb_list_add(&qp->ntb_tx_free_q_lock, &entry->entry, &qp->tx_free_q);
}

static void ntb_memcpy_tx(struct ntb_queue_entry *entry, void __iomem *offset)
{
#ifdef ARCH_HAS_NOCACHE_UACCESS
        /*
         * Using non-temporal mov to improve performance on non-cached
         * writes, even though we aren't actually copying from user space.
         */
        __copy_from_user_inatomic_nocache(offset, entry->buf, entry->len);
#else
        memcpy_toio(offset, entry->buf, entry->len);
#endif

        /* Ensure that the data is fully copied out before setting the flags */
        wmb();

        ntb_tx_copy_callback(entry, NULL);
}

static int ntb_async_tx_submit(struct ntb_transport_qp *qp,
                               struct ntb_queue_entry *entry)
{
        struct dma_async_tx_descriptor *txd;
        struct dma_chan *chan = qp->tx_dma_chan;
        struct dma_device *device;
        size_t len = entry->len;
        void *buf = entry->buf;
        size_t dest_off, buff_off;
        struct dmaengine_unmap_data *unmap;
        dma_addr_t dest;
        dma_cookie_t cookie;

        device = chan->device;
        dest = qp->tx_mw_dma_addr + qp->tx_max_frame * entry->tx_index;
        buff_off = (size_t)buf & ~PAGE_MASK;
        dest_off = (size_t)dest & ~PAGE_MASK;

        if (!is_dma_copy_aligned(device, buff_off, dest_off, len))
                goto err;

        unmap = dmaengine_get_unmap_data(device->dev, 1, GFP_NOWAIT);
        if (!unmap)
                goto err;

        unmap->len = len;
        unmap->addr[0] = dma_map_page(device->dev, virt_to_page(buf),
                                      buff_off, len, DMA_TO_DEVICE);
        if (dma_mapping_error(device->dev, unmap->addr[0]))
                goto err_get_unmap;

        unmap->to_cnt = 1;

        txd = device->device_prep_dma_memcpy(chan, dest, unmap->addr[0], len,
                                             DMA_PREP_INTERRUPT);
        if (!txd)
                goto err_get_unmap;

        txd->callback_result = ntb_tx_copy_callback;
        txd->callback_param = entry;
        dma_set_unmap(txd, unmap);

        cookie = dmaengine_submit(txd);
        if (dma_submit_error(cookie))
                goto err_set_unmap;

        dmaengine_unmap_put(unmap);

        dma_async_issue_pending(chan);

        return 0;
err_set_unmap:
        dmaengine_unmap_put(unmap);
err_get_unmap:
        dmaengine_unmap_put(unmap);
err:
        return -ENXIO;
}

static void ntb_async_tx(struct ntb_transport_qp *qp,
                         struct ntb_queue_entry *entry)
{
        struct ntb_payload_header __iomem *hdr;
        struct dma_chan *chan = qp->tx_dma_chan;
        void __iomem *offset;
        int res;

        entry->tx_index = qp->tx_index;
        offset = qp->tx_mw + qp->tx_max_frame * entry->tx_index;
        hdr = offset + qp->tx_max_frame - sizeof(struct ntb_payload_header);
        entry->tx_hdr = hdr;

        iowrite32(entry->len, &hdr->len);
        iowrite32((u32)qp->tx_pkts, &hdr->ver);

        if (!chan)
                goto err;

        if (entry->len < copy_bytes)
                goto err;

        res = ntb_async_tx_submit(qp, entry);
        if (res < 0)
                goto err;

        if (!entry->retries)
                qp->tx_async++;

        return;

err:
        ntb_memcpy_tx(entry, offset);
        qp->tx_memcpy++;
}

static int ntb_process_tx(struct ntb_transport_qp *qp,
                          struct ntb_queue_entry *entry)
{
        if (qp->tx_index == qp->remote_rx_info->entry) {
                qp->tx_ring_full++;
                return -EAGAIN;
        }

        if (entry->len > qp->tx_max_frame - sizeof(struct ntb_payload_header)) {
                if (qp->tx_handler)
                        qp->tx_handler(qp, qp->cb_data, NULL, -EIO);

                ntb_list_add(&qp->ntb_tx_free_q_lock, &entry->entry,
                             &qp->tx_free_q);
                return 0;
        }

        ntb_async_tx(qp, entry);

        qp->tx_index++;
        qp->tx_index %= qp->tx_max_entry;

        qp->tx_pkts++;

        return 0;
}

static void ntb_send_link_down(struct ntb_transport_qp *qp)
{
        struct pci_dev *pdev = qp->ndev->pdev;
        struct ntb_queue_entry *entry;
        int i, rc;

        if (!qp->link_is_up)
                return;

        dev_info(&pdev->dev, "qp %d: Send Link Down\n", qp->qp_num);

        for (i = 0; i < NTB_LINK_DOWN_TIMEOUT; i++) {
                entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q);
                if (entry)
                        break;
                msleep(100);
        }

        if (!entry)
                return;

        entry->cb_data = NULL;
        entry->buf = NULL;
        entry->len = 0;
        entry->flags = LINK_DOWN_FLAG;

        rc = ntb_process_tx(qp, entry);
        if (rc)
                dev_err(&pdev->dev, "ntb: QP%d unable to send linkdown msg\n",
                        qp->qp_num);

        ntb_qp_link_down_reset(qp);
}

static bool ntb_dma_filter_fn(struct dma_chan *chan, void *node)
{
        return dev_to_node(&chan->dev->device) == (int)(unsigned long)node;
}

/**
 * ntb_transport_create_queue - Create a new NTB transport layer queue
 * @rx_handler: receive callback function
 * @tx_handler: transmit callback function
 * @event_handler: event callback function
 *
 * Create a new NTB transport layer queue and provide the queue with a callback
 * routine for both transmit and receive.  The receive callback routine will be
 * used to pass up data when the transport has received it on the queue.   The
 * transmit callback routine will be called when the transport has completed the
 * transmission of the data on the queue and the data is ready to be freed.
 *
 * RETURNS: pointer to newly created ntb_queue, NULL on error.
 */
struct ntb_transport_qp *
ntb_transport_create_queue(void *data, struct device *client_dev,
                           const struct ntb_queue_handlers *handlers)
{
        struct ntb_dev *ndev;
        struct pci_dev *pdev;
        struct ntb_transport_ctx *nt;
        struct ntb_queue_entry *entry;
        struct ntb_transport_qp *qp;
        u64 qp_bit;
        unsigned int free_queue;
        dma_cap_mask_t dma_mask;
        int node;
        int i;

        ndev = dev_ntb(client_dev->parent);
        pdev = ndev->pdev;
        nt = ndev->ctx;

        node = dev_to_node(&ndev->dev);

        free_queue = ffs(nt->qp_bitmap_free);
        if (!free_queue)
                goto err;

        /* decrement free_queue to make it zero based */
        free_queue--;

        qp = &nt->qp_vec[free_queue];
        qp_bit = BIT_ULL(qp->qp_num);

        nt->qp_bitmap_free &= ~qp_bit;

        qp->cb_data = data;
        qp->rx_handler = handlers->rx_handler;
        qp->tx_handler = handlers->tx_handler;
        qp->event_handler = handlers->event_handler;

        dma_cap_zero(dma_mask);
        dma_cap_set(DMA_MEMCPY, dma_mask);

        if (use_dma) {
                qp->tx_dma_chan =
                        dma_request_channel(dma_mask, ntb_dma_filter_fn,
                                            (void *)(unsigned long)node);
                if (!qp->tx_dma_chan)
                        dev_info(&pdev->dev, "Unable to allocate TX DMA channel\n");

                qp->rx_dma_chan =
                        dma_request_channel(dma_mask, ntb_dma_filter_fn,
                                            (void *)(unsigned long)node);
                if (!qp->rx_dma_chan)
                        dev_info(&pdev->dev, "Unable to allocate RX DMA channel\n");
        } else {
                qp->tx_dma_chan = NULL;
                qp->rx_dma_chan = NULL;
        }

        qp->tx_mw_dma_addr = 0;
        if (qp->tx_dma_chan) {
                qp->tx_mw_dma_addr =
                        dma_map_resource(qp->tx_dma_chan->device->dev,
                                         qp->tx_mw_phys, qp->tx_mw_size,
                                         DMA_FROM_DEVICE, 0);
                if (dma_mapping_error(qp->tx_dma_chan->device->dev,
                                      qp->tx_mw_dma_addr)) {
                        qp->tx_mw_dma_addr = 0;
                        goto err1;
                }
        }

        dev_dbg(&pdev->dev, "Using %s memcpy for TX\n",
                qp->tx_dma_chan ? "DMA" : "CPU");

        dev_dbg(&pdev->dev, "Using %s memcpy for RX\n",
                qp->rx_dma_chan ? "DMA" : "CPU");

        for (i = 0; i < NTB_QP_DEF_NUM_ENTRIES; i++) {
                entry = kzalloc_node(sizeof(*entry), GFP_KERNEL, node);
                if (!entry)
                        goto err1;

                entry->qp = qp;
                ntb_list_add(&qp->ntb_rx_q_lock, &entry->entry,
                             &qp->rx_free_q);
        }
        qp->rx_alloc_entry = NTB_QP_DEF_NUM_ENTRIES;

        for (i = 0; i < qp->tx_max_entry; i++) {
                entry = kzalloc_node(sizeof(*entry), GFP_KERNEL, node);
                if (!entry)
                        goto err2;

                entry->qp = qp;
                ntb_list_add(&qp->ntb_tx_free_q_lock, &entry->entry,
                             &qp->tx_free_q);
        }

        ntb_db_clear(qp->ndev, qp_bit);
        ntb_db_clear_mask(qp->ndev, qp_bit);

        dev_info(&pdev->dev, "NTB Transport QP %d created\n", qp->qp_num);

        return qp;

err2:
        while ((entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q)))
                kfree(entry);
err1:
        qp->rx_alloc_entry = 0;
        while ((entry = ntb_list_rm(&qp->ntb_rx_q_lock, &qp->rx_free_q)))
                kfree(entry);
        if (qp->tx_mw_dma_addr)
                dma_unmap_resource(qp->tx_dma_chan->device->dev,
                                   qp->tx_mw_dma_addr, qp->tx_mw_size,
                                   DMA_FROM_DEVICE, 0);
        if (qp->tx_dma_chan)
                dma_release_channel(qp->tx_dma_chan);
        if (qp->rx_dma_chan)
                dma_release_channel(qp->rx_dma_chan);
        nt->qp_bitmap_free |= qp_bit;
err:
        return NULL;
}
EXPORT_SYMBOL_GPL(ntb_transport_create_queue);

/**
 * ntb_transport_free_queue - Frees NTB transport queue
 * @qp: NTB queue to be freed
 *
 * Frees NTB transport queue
 */
void ntb_transport_free_queue(struct ntb_transport_qp *qp)
{
        struct pci_dev *pdev;
        struct ntb_queue_entry *entry;
        u64 qp_bit;

        if (!qp)
                return;

        pdev = qp->ndev->pdev;

        qp->active = false;

        if (qp->tx_dma_chan) {
                struct dma_chan *chan = qp->tx_dma_chan;
                /* Putting the dma_chan to NULL will force any new traffic to be
                 * processed by the CPU instead of the DAM engine
                 */
                qp->tx_dma_chan = NULL;

                /* Try to be nice and wait for any queued DMA engine
                 * transactions to process before smashing it with a rock
                 */
                dma_sync_wait(chan, qp->last_cookie);
                dmaengine_terminate_all(chan);

                dma_unmap_resource(chan->device->dev,
                                   qp->tx_mw_dma_addr, qp->tx_mw_size,
                                   DMA_FROM_DEVICE, 0);

                dma_release_channel(chan);
        }

        if (qp->rx_dma_chan) {
                struct dma_chan *chan = qp->rx_dma_chan;
                /* Putting the dma_chan to NULL will force any new traffic to be
                 * processed by the CPU instead of the DAM engine
                 */
                qp->rx_dma_chan = NULL;

                /* Try to be nice and wait for any queued DMA engine
                 * transactions to process before smashing it with a rock
                 */
                dma_sync_wait(chan, qp->last_cookie);
                dmaengine_terminate_all(chan);
                dma_release_channel(chan);
        }

        qp_bit = BIT_ULL(qp->qp_num);

        ntb_db_set_mask(qp->ndev, qp_bit);
        tasklet_kill(&qp->rxc_db_work);

        cancel_delayed_work_sync(&qp->link_work);

        qp->cb_data = NULL;
        qp->rx_handler = NULL;
        qp->tx_handler = NULL;
        qp->event_handler = NULL;

        while ((entry = ntb_list_rm(&qp->ntb_rx_q_lock, &qp->rx_free_q)))
                kfree(entry);

        while ((entry = ntb_list_rm(&qp->ntb_rx_q_lock, &qp->rx_pend_q))) {
                dev_warn(&pdev->dev, "Freeing item from non-empty rx_pend_q\n");
                kfree(entry);
        }

        while ((entry = ntb_list_rm(&qp->ntb_rx_q_lock, &qp->rx_post_q))) {
                dev_warn(&pdev->dev, "Freeing item from non-empty rx_post_q\n");
                kfree(entry);
        }

        while ((entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q)))
                kfree(entry);

        qp->transport->qp_bitmap_free |= qp_bit;

        dev_info(&pdev->dev, "NTB Transport QP %d freed\n", qp->qp_num);
}
EXPORT_SYMBOL_GPL(ntb_transport_free_queue);

/**
 * ntb_transport_rx_remove - Dequeues enqueued rx packet
 * @qp: NTB queue to be freed
 * @len: pointer to variable to write enqueued buffers length
 *
 * Dequeues unused buffers from receive queue.  Should only be used during
 * shutdown of qp.
 *
 * RETURNS: NULL error value on error, or void* for success.
 */
void *ntb_transport_rx_remove(struct ntb_transport_qp *qp, unsigned int *len)
{
        struct ntb_queue_entry *entry;
        void *buf;

        if (!qp || qp->client_ready)
                return NULL;

        entry = ntb_list_rm(&qp->ntb_rx_q_lock, &qp->rx_pend_q);
        if (!entry)
                return NULL;

        buf = entry->cb_data;
        *len = entry->len;

        ntb_list_add(&qp->ntb_rx_q_lock, &entry->entry, &qp->rx_free_q);

        return buf;
}
EXPORT_SYMBOL_GPL(ntb_transport_rx_remove);

/**
 * ntb_transport_rx_enqueue - Enqueue a new NTB queue entry
 * @qp: NTB transport layer queue the entry is to be enqueued on
 * @cb: per buffer pointer for callback function to use
 * @data: pointer to data buffer that incoming packets will be copied into
 * @len: length of the data buffer
 *
 * Enqueue a new receive buffer onto the transport queue into which a NTB
 * payload can be received into.
 *
 * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
 */
int ntb_transport_rx_enqueue(struct ntb_transport_qp *qp, void *cb, void *data,
                             unsigned int len)
{
        struct ntb_queue_entry *entry;

        if (!qp)
                return -EINVAL;

        entry = ntb_list_rm(&qp->ntb_rx_q_lock, &qp->rx_free_q);
        if (!entry)
                return -ENOMEM;

        entry->cb_data = cb;
        entry->buf = data;
        entry->len = len;
        entry->flags = 0;
        entry->retries = 0;
        entry->errors = 0;
        entry->rx_index = 0;

        ntb_list_add(&qp->ntb_rx_q_lock, &entry->entry, &qp->rx_pend_q);

        if (qp->active)
                tasklet_schedule(&qp->rxc_db_work);

        return 0;
}
EXPORT_SYMBOL_GPL(ntb_transport_rx_enqueue);

/**
 * ntb_transport_tx_enqueue - Enqueue a new NTB queue entry
 * @qp: NTB transport layer queue the entry is to be enqueued on
 * @cb: per buffer pointer for callback function to use
 * @data: pointer to data buffer that will be sent
 * @len: length of the data buffer
 *
 * Enqueue a new transmit buffer onto the transport queue from which a NTB
 * payload will be transmitted.  This assumes that a lock is being held to
 * serialize access to the qp.
 *
 * RETURNS: An appropriate -ERRNO error value on error, or zero for success.
 */
int ntb_transport_tx_enqueue(struct ntb_transport_qp *qp, void *cb, void *data,
                             unsigned int len)
{
        struct ntb_queue_entry *entry;
        int rc;

        if (!qp || !qp->link_is_up || !len)
                return -EINVAL;

        entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q);
        if (!entry) {
                qp->tx_err_no_buf++;
                return -EBUSY;
        }

        entry->cb_data = cb;
        entry->buf = data;
        entry->len = len;
        entry->flags = 0;
        entry->errors = 0;
        entry->retries = 0;
        entry->tx_index = 0;

        rc = ntb_process_tx(qp, entry);
        if (rc)
                ntb_list_add(&qp->ntb_tx_free_q_lock, &entry->entry,
                             &qp->tx_free_q);

        return rc;
}
EXPORT_SYMBOL_GPL(ntb_transport_tx_enqueue);

/**
 * ntb_transport_link_up - Notify NTB transport of client readiness to use queue
 * @qp: NTB transport layer queue to be enabled
 *
 * Notify NTB transport layer of client readiness to use queue
 */
void ntb_transport_link_up(struct ntb_transport_qp *qp)
{
        if (!qp)
                return;

        qp->client_ready = true;

        if (qp->transport->link_is_up)
                schedule_delayed_work(&qp->link_work, 0);
}
EXPORT_SYMBOL_GPL(ntb_transport_link_up);

/**
 * ntb_transport_link_down - Notify NTB transport to no longer enqueue data
 * @qp: NTB transport layer queue to be disabled
 *
 * Notify NTB transport layer of client's desire to no longer receive data on
 * transport queue specified.  It is the client's responsibility to ensure all
 * entries on queue are purged or otherwise handled appropriately.
 */
void ntb_transport_link_down(struct ntb_transport_qp *qp)
{
        int val;

        if (!qp)
                return;

        qp->client_ready = false;

        val = ntb_spad_read(qp->ndev, QP_LINKS);

        ntb_peer_spad_write(qp->ndev, PIDX, QP_LINKS, val & ~BIT(qp->qp_num));

        if (qp->link_is_up)
                ntb_send_link_down(qp);
        else
                cancel_delayed_work_sync(&qp->link_work);
}
EXPORT_SYMBOL_GPL(ntb_transport_link_down);

/**
 * ntb_transport_link_query - Query transport link state
 * @qp: NTB transport layer queue to be queried
 *
 * Query connectivity to the remote system of the NTB transport queue
 *
 * RETURNS: true for link up or false for link down
 */
bool ntb_transport_link_query(struct ntb_transport_qp *qp)
{
        if (!qp)
                return false;

        return qp->link_is_up;
}
EXPORT_SYMBOL_GPL(ntb_transport_link_query);

/**
 * ntb_transport_qp_num - Query the qp number
 * @qp: NTB transport layer queue to be queried
 *
 * Query qp number of the NTB transport queue
 *
 * RETURNS: a zero based number specifying the qp number
 */
unsigned char ntb_transport_qp_num(struct ntb_transport_qp *qp)
{
        if (!qp)
                return 0;

        return qp->qp_num;
}
EXPORT_SYMBOL_GPL(ntb_transport_qp_num);

/**
 * ntb_transport_max_size - Query the max payload size of a qp
 * @qp: NTB transport layer queue to be queried
 *
 * Query the maximum payload size permissible on the given qp
 *
 * RETURNS: the max payload size of a qp
 */
unsigned int ntb_transport_max_size(struct ntb_transport_qp *qp)
{
        unsigned int max_size;
        unsigned int copy_align;
        struct dma_chan *rx_chan, *tx_chan;

        if (!qp)
                return 0;

        rx_chan = qp->rx_dma_chan;
        tx_chan = qp->tx_dma_chan;

        copy_align = max(rx_chan ? rx_chan->device->copy_align : 0,
                         tx_chan ? tx_chan->device->copy_align : 0);

        /* If DMA engine usage is possible, try to find the max size for that */
        max_size = qp->tx_max_frame - sizeof(struct ntb_payload_header);
        max_size = round_down(max_size, 1 << copy_align);

        return max_size;
}
EXPORT_SYMBOL_GPL(ntb_transport_max_size);

unsigned int ntb_transport_tx_free_entry(struct ntb_transport_qp *qp)
{
        unsigned int head = qp->tx_index;
        unsigned int tail = qp->remote_rx_info->entry;

        return tail > head ? tail - head : qp->tx_max_entry + tail - head;
}
EXPORT_SYMBOL_GPL(ntb_transport_tx_free_entry);

static void ntb_transport_doorbell_callback(void *data, int vector)
{
        struct ntb_transport_ctx *nt = data;
        struct ntb_transport_qp *qp;
        u64 db_bits;
        unsigned int qp_num;

        if (ntb_db_read(nt->ndev) & nt->msi_db_mask) {
                ntb_transport_msi_peer_desc_changed(nt);
                ntb_db_clear(nt->ndev, nt->msi_db_mask);
        }

        db_bits = (nt->qp_bitmap & ~nt->qp_bitmap_free &
                   ntb_db_vector_mask(nt->ndev, vector));

        while (db_bits) {
                qp_num = __ffs(db_bits);
                qp = &nt->qp_vec[qp_num];

                if (qp->active)
                        tasklet_schedule(&qp->rxc_db_work);

                db_bits &= ~BIT_ULL(qp_num);
        }
}

static const struct ntb_ctx_ops ntb_transport_ops = {
        .link_event = ntb_transport_event_callback,
        .db_event = ntb_transport_doorbell_callback,
};

static struct ntb_client ntb_transport_client = {
        .ops = {
                .probe = ntb_transport_probe,
                .remove = ntb_transport_free,
        },
};

static int __init ntb_transport_init(void)
{
        int rc;

        pr_info("%s, version %s\n", NTB_TRANSPORT_DESC, NTB_TRANSPORT_VER);

        if (debugfs_initialized())
                nt_debugfs_dir = debugfs_create_dir(KBUILD_MODNAME, NULL);

        rc = bus_register(&ntb_transport_bus);
        if (rc)
                goto err_bus;

        rc = ntb_register_client(&ntb_transport_client);
        if (rc)
                goto err_client;

        return 0;

err_client:
        bus_unregister(&ntb_transport_bus);
err_bus:
        debugfs_remove_recursive(nt_debugfs_dir);
        return rc;
}
module_init(ntb_transport_init);

static void __exit ntb_transport_exit(void)
{
        ntb_unregister_client(&ntb_transport_client);
        bus_unregister(&ntb_transport_bus);
        debugfs_remove_recursive(nt_debugfs_dir);
}
module_exit(ntb_transport_exit);