NTB: Remove reads across NTB

[deliverable/linux.git] / drivers / ntb / ntb_transport.c

/*
 * 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.
 *
 *   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.
 *
 *   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.
 *
 * Intel PCIe NTB Linux driver
 *
 * Contact Information:
 * Jon Mason <jon.mason@intel.com>
 */
#include <linux/debugfs.h>
#include <linux/delay.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/ntb.h>
#include "ntb_hw.h"

#define NTB_TRANSPORT_VERSION   1

static unsigned int transport_mtu = 0x401E;
module_param(transport_mtu, uint, 0644);
MODULE_PARM_DESC(transport_mtu, "Maximum size of NTB transport packets");

static unsigned char max_num_clients = 2;
module_param(max_num_clients, byte, 0644);
MODULE_PARM_DESC(max_num_clients, "Maximum number of NTB transport clients");

struct ntb_queue_entry {
        /* ntb_queue list reference */
        struct list_head entry;
        /* pointers to data to be transfered */
        void *cb_data;
        void *buf;
        unsigned int len;
        unsigned int flags;
};

struct ntb_rx_info {
        unsigned int entry;
};

struct ntb_transport_qp {
        struct ntb_transport *transport;
        struct ntb_device *ndev;
        void *cb_data;

        bool client_ready;
        bool qp_link;
        u8 qp_num;      /* Only 64 QP's are allowed.  0-63 */

        struct ntb_rx_info *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 *tx_mw;
        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 tasklet_struct rx_work;
        struct list_head rx_pend_q;
        struct list_head rx_free_q;
        spinlock_t ntb_rx_pend_q_lock;
        spinlock_t ntb_rx_free_q_lock;
        void *rx_buff;
        unsigned int rx_index;
        unsigned int rx_max_entry;
        unsigned int rx_max_frame;

        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 tx_bytes;
        u64 tx_pkts;
        u64 tx_ring_full;
};

struct ntb_transport_mw {
        size_t size;
        void *virt_addr;
        dma_addr_t dma_addr;
};

struct ntb_transport_client_dev {
        struct list_head entry;
        struct device dev;
};

struct ntb_transport {
        struct list_head entry;
        struct list_head client_devs;

        struct ntb_device *ndev;
        struct ntb_transport_mw mw[NTB_NUM_MW];
        struct ntb_transport_qp *qps;
        unsigned int max_qps;
        unsigned long qp_bitmap;
        bool transport_link;
        struct delayed_work link_work;
        struct work_struct link_cleanup;
        struct dentry *debugfs_dir;
};

enum {
        DESC_DONE_FLAG = 1 << 0,
        LINK_DOWN_FLAG = 1 << 1,
};

struct ntb_payload_header {
        u64 ver;
        unsigned int len;
        unsigned int flags;
};

enum {
        VERSION = 0,
        MW0_SZ,
        MW1_SZ,
        NUM_QPS,
        QP_LINKS,
        MAX_SPAD,
};

#define QP_TO_MW(qp)            ((qp) % NTB_NUM_MW)
#define NTB_QP_DEF_NUM_ENTRIES  100
#define NTB_LINK_DOWN_TIMEOUT   10

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

static int ntb_client_probe(struct device *dev)
{
        const struct ntb_client *drv = container_of(dev->driver,
                                                    struct ntb_client, driver);
        struct pci_dev *pdev = container_of(dev->parent, struct pci_dev, dev);
        int rc = -EINVAL;

        get_device(dev);
        if (drv && drv->probe)
                rc = drv->probe(pdev);
        if (rc)
                put_device(dev);

        return rc;
}

static int ntb_client_remove(struct device *dev)
{
        const struct ntb_client *drv = container_of(dev->driver,
                                                    struct ntb_client, driver);
        struct pci_dev *pdev = container_of(dev->parent, struct pci_dev, dev);

        if (drv && drv->remove)
                drv->remove(pdev);

        put_device(dev);

        return 0;
}

static struct bus_type ntb_bus_type = {
        .name = "ntb_bus",
        .match = ntb_match_bus,
        .probe = ntb_client_probe,
        .remove = ntb_client_remove,
};

static LIST_HEAD(ntb_transport_list);

static int ntb_bus_init(struct ntb_transport *nt)
{
        if (list_empty(&ntb_transport_list)) {
                int rc = bus_register(&ntb_bus_type);
                if (rc)
                        return rc;
        }

        list_add(&nt->entry, &ntb_transport_list);

        return 0;
}

static void ntb_bus_remove(struct ntb_transport *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);

        if (list_empty(&ntb_transport_list))
                bus_unregister(&ntb_bus_type);
}

static void ntb_client_release(struct device *dev)
{
        struct ntb_transport_client_dev *client_dev;
        client_dev = container_of(dev, struct ntb_transport_client_dev, dev);

        kfree(client_dev);
}

/**
 * ntb_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_unregister_client_dev(char *device_name)
{
        struct ntb_transport_client_dev *client, *cd;
        struct ntb_transport *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_unregister_client_dev);

/**
 * ntb_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_register_client_dev(char *device_name)
{
        struct ntb_transport_client_dev *client_dev;
        struct ntb_transport *nt;
        int rc;

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

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

                client_dev = kzalloc(sizeof(struct ntb_transport_client_dev),
                                     GFP_KERNEL);
                if (!client_dev) {
                        rc = -ENOMEM;
                        goto err;
                }

                dev = &client_dev->dev;

                /* setup and register client devices */
                dev_set_name(dev, "%s", device_name);
                dev->bus = &ntb_bus_type;
                dev->release = ntb_client_release;
                dev->parent = &ntb_query_pdev(nt->ndev)->dev;

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

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

        return 0;

err:
        ntb_unregister_client_dev(device_name);

        return rc;
}
EXPORT_SYMBOL_GPL(ntb_register_client_dev);

/**
 * ntb_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_register_client(struct ntb_client *drv)
{
        drv->driver.bus = &ntb_bus_type;

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

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

/**
 * ntb_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_unregister_client(struct ntb_client *drv)
{
        driver_unregister(&drv->driver);
}
EXPORT_SYMBOL_GPL(ntb_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;

        out_count = 600;

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

        qp = filp->private_data;
        out_offset = 0;
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "NTB QP stats\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_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 - \t%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,
                               "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_ring_full - \t%llu\n", qp->tx_ring_full);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_mw - \t%p\n", qp->tx_mw);
        out_offset += snprintf(buf + out_offset, out_count - out_offset,
                               "tx_index - \t%u\n", qp->tx_index);
        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,
                               "\nQP Link %s\n", (qp->qp_link == NTB_LINK_UP) ?
                               "Up" : "Down");
        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 void ntb_transport_setup_qp_mw(struct ntb_transport *nt,
                                      unsigned int qp_num)
{
        struct ntb_transport_qp *qp = &nt->qps[qp_num];
        unsigned int rx_size, num_qps_mw;
        u8 mw_num = QP_TO_MW(qp_num);
        unsigned int i;

        WARN_ON(nt->mw[mw_num].virt_addr == 0);

        if (nt->max_qps % NTB_NUM_MW && mw_num < nt->max_qps % NTB_NUM_MW)
                num_qps_mw = nt->max_qps / NTB_NUM_MW + 1;
        else
                num_qps_mw = nt->max_qps / NTB_NUM_MW;

        rx_size = (unsigned int) nt->mw[mw_num].size / num_qps_mw;
        qp->remote_rx_info = nt->mw[mw_num].virt_addr +
                             (qp_num / NTB_NUM_MW * rx_size);
        rx_size -= sizeof(struct ntb_rx_info);

        qp->rx_buff = qp->remote_rx_info + sizeof(struct ntb_rx_info);
        qp->rx_max_frame = min(transport_mtu, rx_size);
        qp->rx_max_entry = rx_size / qp->rx_max_frame;
        qp->rx_index = 0;

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

        /* 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;
}

static int ntb_set_mw(struct ntb_transport *nt, int num_mw, unsigned int size)
{
        struct ntb_transport_mw *mw = &nt->mw[num_mw];
        struct pci_dev *pdev = ntb_query_pdev(nt->ndev);

        /* Alloc memory for receiving data.  Must be 4k aligned */
        mw->size = ALIGN(size, 4096);

        mw->virt_addr = dma_alloc_coherent(&pdev->dev, mw->size, &mw->dma_addr,
                                           GFP_KERNEL);
        if (!mw->virt_addr) {
                dev_err(&pdev->dev, "Unable to allocate MW buffer of size %d\n",
                       (int) mw->size);
                return -ENOMEM;
        }

        /* Notify HW the memory location of the receive buffer */
        ntb_set_mw_addr(nt->ndev, num_mw, mw->dma_addr);

        return 0;
}

static void ntb_qp_link_cleanup(struct work_struct *work)
{
        struct ntb_transport_qp *qp = container_of(work,
                                                   struct ntb_transport_qp,
                                                   link_cleanup);
        struct ntb_transport *nt = qp->transport;
        struct pci_dev *pdev = ntb_query_pdev(nt->ndev);

        if (qp->qp_link == NTB_LINK_DOWN) {
                cancel_delayed_work_sync(&qp->link_work);
                return;
        }

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

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

        if (nt->transport_link == NTB_LINK_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 work_struct *work)
{
        struct ntb_transport *nt = container_of(work, struct ntb_transport,
                                                link_cleanup);
        int i;

        if (nt->transport_link == NTB_LINK_DOWN)
                cancel_delayed_work_sync(&nt->link_work);
        else
                nt->transport_link = NTB_LINK_DOWN;

        /* Pass along the info to any clients */
        for (i = 0; i < nt->max_qps; i++)
                if (!test_bit(i, &nt->qp_bitmap))
                        ntb_qp_link_down(&nt->qps[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
         */
        for (i = 0; i < MAX_SPAD; i++)
                ntb_write_local_spad(nt->ndev, i, 0);
}

static void ntb_transport_event_callback(void *data, enum ntb_hw_event event)
{
        struct ntb_transport *nt = data;

        switch (event) {
        case NTB_EVENT_HW_LINK_UP:
                schedule_delayed_work(&nt->link_work, 0);
                break;
        case NTB_EVENT_HW_LINK_DOWN:
                schedule_work(&nt->link_cleanup);
                break;
        default:
                BUG();
        }
}

static void ntb_transport_link_work(struct work_struct *work)
{
        struct ntb_transport *nt = container_of(work, struct ntb_transport,
                                                link_work.work);
        struct ntb_device *ndev = nt->ndev;
        struct pci_dev *pdev = ntb_query_pdev(ndev);
        u32 val;
        int rc, i;

        /* send the local info */
        rc = ntb_write_remote_spad(ndev, VERSION, NTB_TRANSPORT_VERSION);
        if (rc) {
                dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
                        0, VERSION);
                goto out;
        }

        rc = ntb_write_remote_spad(ndev, MW0_SZ, ntb_get_mw_size(ndev, 0));
        if (rc) {
                dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
                        (u32) ntb_get_mw_size(ndev, 0), MW0_SZ);
                goto out;
        }

        rc = ntb_write_remote_spad(ndev, MW1_SZ, ntb_get_mw_size(ndev, 1));
        if (rc) {
                dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
                        (u32) ntb_get_mw_size(ndev, 1), MW1_SZ);
                goto out;
        }

        rc = ntb_write_remote_spad(ndev, NUM_QPS, nt->max_qps);
        if (rc) {
                dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
                        nt->max_qps, NUM_QPS);
                goto out;
        }

        rc = ntb_read_local_spad(nt->ndev, QP_LINKS, &val);
        if (rc) {
                dev_err(&pdev->dev, "Error reading spad %d\n", QP_LINKS);
                goto out;
        }

        rc = ntb_write_remote_spad(ndev, QP_LINKS, val);
        if (rc) {
                dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
                        val, QP_LINKS);
                goto out;
        }

        /* Query the remote side for its info */
        rc = ntb_read_remote_spad(ndev, VERSION, &val);
        if (rc) {
                dev_err(&pdev->dev, "Error reading remote spad %d\n", VERSION);
                goto out;
        }

        if (val != NTB_TRANSPORT_VERSION)
                goto out;
        dev_dbg(&pdev->dev, "Remote version = %d\n", val);

        rc = ntb_read_remote_spad(ndev, NUM_QPS, &val);
        if (rc) {
                dev_err(&pdev->dev, "Error reading remote spad %d\n", NUM_QPS);
                goto out;
        }

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

        rc = ntb_read_remote_spad(ndev, MW0_SZ, &val);
        if (rc) {
                dev_err(&pdev->dev, "Error reading remote spad %d\n", MW0_SZ);
                goto out;
        }

        if (!val)
                goto out;
        dev_dbg(&pdev->dev, "Remote MW0 size = %d\n", val);

        rc = ntb_set_mw(nt, 0, val);
        if (rc)
                goto out;

        rc = ntb_read_remote_spad(ndev, MW1_SZ, &val);
        if (rc) {
                dev_err(&pdev->dev, "Error reading remote spad %d\n", MW1_SZ);
                goto out;
        }

        if (!val)
                goto out;
        dev_dbg(&pdev->dev, "Remote MW1 size = %d\n", val);

        rc = ntb_set_mw(nt, 1, val);
        if (rc)
                goto out;

        nt->transport_link = NTB_LINK_UP;

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

                ntb_transport_setup_qp_mw(nt, i);

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

        return;

out:
        if (ntb_hw_link_status(ndev))
                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 = ntb_query_pdev(qp->ndev);
        struct ntb_transport *nt = qp->transport;
        int rc, val;

        WARN_ON(nt->transport_link != NTB_LINK_UP);

        rc = ntb_read_local_spad(nt->ndev, QP_LINKS, &val);
        if (rc) {
                dev_err(&pdev->dev, "Error reading spad %d\n", QP_LINKS);
                return;
        }

        rc = ntb_write_remote_spad(nt->ndev, QP_LINKS, val | 1 << qp->qp_num);
        if (rc)
                dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
                        val | 1 << qp->qp_num, QP_LINKS);

        /* query remote spad for qp ready bits */
        rc = ntb_read_remote_spad(nt->ndev, QP_LINKS, &val);
        if (rc)
                dev_err(&pdev->dev, "Error reading remote spad %d\n", QP_LINKS);

        dev_dbg(&pdev->dev, "Remote QP link status = %x\n", val);

        /* See if the remote side is up */
        if (1 << qp->qp_num & val) {
                qp->qp_link = NTB_LINK_UP;

                dev_info(&pdev->dev, "qp %d: Link Up\n", qp->qp_num);
                if (qp->event_handler)
                        qp->event_handler(qp->cb_data, NTB_LINK_UP);
        } else if (nt->transport_link == NTB_LINK_UP)
                schedule_delayed_work(&qp->link_work,
                                      msecs_to_jiffies(NTB_LINK_DOWN_TIMEOUT));
}

static void ntb_transport_init_queue(struct ntb_transport *nt,
                                     unsigned int qp_num)
{
        struct ntb_transport_qp *qp;
        unsigned int num_qps_mw, tx_size;
        u8 mw_num = QP_TO_MW(qp_num);

        qp = &nt->qps[qp_num];
        qp->qp_num = qp_num;
        qp->transport = nt;
        qp->ndev = nt->ndev;
        qp->qp_link = NTB_LINK_DOWN;
        qp->client_ready = NTB_LINK_DOWN;
        qp->event_handler = NULL;

        if (nt->max_qps % NTB_NUM_MW && mw_num < nt->max_qps % NTB_NUM_MW)
                num_qps_mw = nt->max_qps / NTB_NUM_MW + 1;
        else
                num_qps_mw = nt->max_qps / NTB_NUM_MW;

        tx_size = (unsigned int) ntb_get_mw_size(qp->ndev, mw_num) / num_qps_mw;
        qp->rx_info = ntb_get_mw_vbase(nt->ndev, mw_num) +
                      (qp_num / NTB_NUM_MW * tx_size);
        tx_size -= sizeof(struct ntb_rx_info);

        qp->tx_mw = qp->rx_info + sizeof(struct ntb_rx_info);
        qp->tx_max_frame = min(transport_mtu, tx_size);
        qp->tx_max_entry = tx_size / qp->tx_max_frame;
        qp->tx_index = 0;

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

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

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

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

        spin_lock_init(&qp->ntb_rx_pend_q_lock);
        spin_lock_init(&qp->ntb_rx_free_q_lock);
        spin_lock_init(&qp->ntb_tx_free_q_lock);

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

int ntb_transport_init(struct pci_dev *pdev)
{
        struct ntb_transport *nt;
        int rc, i;

        nt = kzalloc(sizeof(struct ntb_transport), GFP_KERNEL);
        if (!nt)
                return -ENOMEM;

        if (debugfs_initialized())
                nt->debugfs_dir = debugfs_create_dir(KBUILD_MODNAME, NULL);
        else
                nt->debugfs_dir = NULL;

        nt->ndev = ntb_register_transport(pdev, nt);
        if (!nt->ndev) {
                rc = -EIO;
                goto err;
        }

        nt->max_qps = min(nt->ndev->max_cbs, max_num_clients);

        nt->qps = kcalloc(nt->max_qps, sizeof(struct ntb_transport_qp),
                          GFP_KERNEL);
        if (!nt->qps) {
                rc = -ENOMEM;
                goto err1;
        }

        nt->qp_bitmap = ((u64) 1 << nt->max_qps) - 1;

        for (i = 0; i < nt->max_qps; i++)
                ntb_transport_init_queue(nt, i);

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

        rc = ntb_register_event_callback(nt->ndev,
                                         ntb_transport_event_callback);
        if (rc)
                goto err2;

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

        if (ntb_hw_link_status(nt->ndev))
                schedule_delayed_work(&nt->link_work, 0);

        return 0;

err3:
        ntb_unregister_event_callback(nt->ndev);
err2:
        kfree(nt->qps);
err1:
        ntb_unregister_transport(nt->ndev);
err:
        debugfs_remove_recursive(nt->debugfs_dir);
        kfree(nt);
        return rc;
}

void ntb_transport_free(void *transport)
{
        struct ntb_transport *nt = transport;
        struct pci_dev *pdev;
        int i;

        nt->transport_link = NTB_LINK_DOWN;

        /* verify that all the qp's are freed */
        for (i = 0; i < nt->max_qps; i++)
                if (!test_bit(i, &nt->qp_bitmap))
                        ntb_transport_free_queue(&nt->qps[i]);

        ntb_bus_remove(nt);

        cancel_delayed_work_sync(&nt->link_work);

        debugfs_remove_recursive(nt->debugfs_dir);

        ntb_unregister_event_callback(nt->ndev);

        pdev = ntb_query_pdev(nt->ndev);

        for (i = 0; i < NTB_NUM_MW; i++)
                if (nt->mw[i].virt_addr)
                        dma_free_coherent(&pdev->dev, nt->mw[i].size,
                                          nt->mw[i].virt_addr,
                                          nt->mw[i].dma_addr);

        kfree(nt->qps);
        ntb_unregister_transport(nt->ndev);
        kfree(nt);
}

static void ntb_rx_copy_task(struct ntb_transport_qp *qp,
                             struct ntb_queue_entry *entry, void *offset)
{
        memcpy(entry->buf, offset, entry->len);

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

        ntb_list_add(&qp->ntb_rx_free_q_lock, &entry->entry, &qp->rx_free_q);
}

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);

        entry = ntb_list_rm(&qp->ntb_rx_pend_q_lock, &qp->rx_pend_q);
        if (!entry) {
                dev_dbg(&ntb_query_pdev(qp->ndev)->dev,
                        "no buffer - HDR ver %llu, len %d, flags %x\n",
                        hdr->ver, hdr->len, hdr->flags);
                qp->rx_err_no_buf++;
                return -ENOMEM;
        }

        if (!(hdr->flags & DESC_DONE_FLAG)) {
                ntb_list_add(&qp->ntb_rx_pend_q_lock, &entry->entry,
                             &qp->rx_pend_q);
                qp->rx_ring_empty++;
                return -EAGAIN;
        }

        if (hdr->ver != qp->rx_pkts) {
                dev_dbg(&ntb_query_pdev(qp->ndev)->dev,
                        "qp %d: version mismatch, expected %llu - got %llu\n",
                        qp->qp_num, qp->rx_pkts, hdr->ver);
                ntb_list_add(&qp->ntb_rx_pend_q_lock, &entry->entry,
                             &qp->rx_pend_q);
                qp->rx_err_ver++;
                return -EIO;
        }

        if (hdr->flags & LINK_DOWN_FLAG) {
                ntb_qp_link_down(qp);

                ntb_list_add(&qp->ntb_rx_pend_q_lock, &entry->entry,
                             &qp->rx_pend_q);
                goto out;
        }

        dev_dbg(&ntb_query_pdev(qp->ndev)->dev,
                "rx offset %u, ver %llu - %d payload received, buf size %d\n",
                qp->rx_index, hdr->ver, hdr->len, entry->len);

        if (hdr->len <= entry->len) {
                entry->len = hdr->len;
                ntb_rx_copy_task(qp, entry, offset);
        } else {
                ntb_list_add(&qp->ntb_rx_pend_q_lock, &entry->entry,
                             &qp->rx_pend_q);

                qp->rx_err_oflow++;
                dev_dbg(&ntb_query_pdev(qp->ndev)->dev,
                        "RX overflow! Wanted %d got %d\n",
                        hdr->len, entry->len);
        }

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

out:
        /* Ensure that the data is fully copied out before clearing the flag */
        wmb();
        hdr->flags = 0;
        qp->rx_info->entry = qp->rx_index;

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

        return 0;
}

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

        do {
                rc = ntb_process_rxc(qp);
        } while (!rc);
}

static void ntb_transport_rxc_db(void *data, int db_num)
{
        struct ntb_transport_qp *qp = data;

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

        tasklet_schedule(&qp->rx_work);
}

static void ntb_tx_copy_task(struct ntb_transport_qp *qp,
                             struct ntb_queue_entry *entry,
                             void *offset)
{
        struct ntb_payload_header *hdr;

        memcpy_toio(offset, entry->buf, entry->len);

        hdr = offset + qp->tx_max_frame - sizeof(struct ntb_payload_header);
        hdr->len = entry->len;
        hdr->ver = qp->tx_pkts;

        /* Ensure that the data is fully copied out before setting the flag */
        wmb();
        hdr->flags = entry->flags | DESC_DONE_FLAG;

        ntb_ring_sdb(qp->ndev, 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 int ntb_process_tx(struct ntb_transport_qp *qp,
                          struct ntb_queue_entry *entry)
{
        void *offset;

        offset = qp->tx_mw + qp->tx_max_frame * qp->tx_index;

        dev_dbg(&ntb_query_pdev(qp->ndev)->dev, "%lld - offset %p, tx %u, entry len %d flags %x buff %p\n",
                qp->tx_pkts, offset, qp->tx_index, entry->len, entry->flags,
                entry->buf);
        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->cb_data, qp, NULL, -EIO);

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

        ntb_tx_copy_task(qp, entry, offset);

        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 = ntb_query_pdev(qp->ndev);
        struct ntb_queue_entry *entry;
        int i, rc;

        if (qp->qp_link == NTB_LINK_DOWN)
                return;

        qp->qp_link = NTB_LINK_DOWN;
        dev_info(&pdev->dev, "qp %d: 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_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 pci_dev *pdev,
                           const struct ntb_queue_handlers *handlers)
{
        struct ntb_queue_entry *entry;
        struct ntb_transport_qp *qp;
        struct ntb_transport *nt;
        unsigned int free_queue;
        int rc, i;

        nt = ntb_find_transport(pdev);
        if (!nt)
                goto err;

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

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

        clear_bit(free_queue, &nt->qp_bitmap);

        qp = &nt->qps[free_queue];
        qp->cb_data = data;
        qp->rx_handler = handlers->rx_handler;
        qp->tx_handler = handlers->tx_handler;
        qp->event_handler = handlers->event_handler;

        for (i = 0; i < NTB_QP_DEF_NUM_ENTRIES; i++) {
                entry = kzalloc(sizeof(struct ntb_queue_entry), GFP_ATOMIC);
                if (!entry)
                        goto err1;

                ntb_list_add(&qp->ntb_rx_free_q_lock, &entry->entry,
                             &qp->rx_free_q);
        }

        for (i = 0; i < NTB_QP_DEF_NUM_ENTRIES; i++) {
                entry = kzalloc(sizeof(struct ntb_queue_entry), GFP_ATOMIC);
                if (!entry)
                        goto err2;

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

        tasklet_init(&qp->rx_work, ntb_transport_rx, (unsigned long) qp);

        rc = ntb_register_db_callback(qp->ndev, free_queue, qp,
                                      ntb_transport_rxc_db);
        if (rc)
                goto err3;

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

        return qp;

err3:
        tasklet_disable(&qp->rx_work);
err2:
        while ((entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q)))
                kfree(entry);
err1:
        while ((entry = ntb_list_rm(&qp->ntb_rx_free_q_lock, &qp->rx_free_q)))
                kfree(entry);
        set_bit(free_queue, &nt->qp_bitmap);
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 = ntb_query_pdev(qp->ndev);
        struct ntb_queue_entry *entry;

        if (!qp)
                return;

        cancel_delayed_work_sync(&qp->link_work);

        ntb_unregister_db_callback(qp->ndev, qp->qp_num);
        tasklet_disable(&qp->rx_work);

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

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

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

        set_bit(qp->qp_num, &qp->transport->qp_bitmap);

        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 == NTB_LINK_UP)
                return NULL;

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

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

        ntb_list_add(&qp->ntb_rx_free_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_free_q_lock, &qp->rx_free_q);
        if (!entry)
                return -ENOMEM;

        entry->cb_data = cb;
        entry->buf = data;
        entry->len = len;

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

        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 behing 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->qp_link != NTB_LINK_UP || !len)
                return -EINVAL;

        entry = ntb_list_rm(&qp->ntb_tx_free_q_lock, &qp->tx_free_q);
        if (!entry)
                return -ENOMEM;

        entry->cb_data = cb;
        entry->buf = data;
        entry->len = len;
        entry->flags = 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 = NTB_LINK_UP;

        if (qp->transport->transport_link == NTB_LINK_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 appropraitely.
 */
void ntb_transport_link_down(struct ntb_transport_qp *qp)
{
        struct pci_dev *pdev = ntb_query_pdev(qp->ndev);
        int rc, val;

        if (!qp)
                return;

        qp->client_ready = NTB_LINK_DOWN;

        rc = ntb_read_local_spad(qp->ndev, QP_LINKS, &val);
        if (rc) {
                dev_err(&pdev->dev, "Error reading spad %d\n", QP_LINKS);
                return;
        }

        rc = ntb_write_remote_spad(qp->ndev, QP_LINKS,
                                   val & ~(1 << qp->qp_num));
        if (rc)
                dev_err(&pdev->dev, "Error writing %x to remote spad %d\n",
                        val & ~(1 << qp->qp_num), QP_LINKS);

        if (qp->qp_link == NTB_LINK_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)
{
        return qp->qp_link == NTB_LINK_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)
{
        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)
{
        return qp->tx_max_frame - sizeof(struct ntb_payload_header);
}
EXPORT_SYMBOL_GPL(ntb_transport_max_size);