// SPDX-License-Identifier: GPL-2.0
/*
 * Greybus connections
 *
 * Copyright 2014 Google Inc.
 * Copyright 2014 Linaro Ltd.
 */

#include <linux/workqueue.h>
#include <linux/greybus.h>

#include "greybus_trace.h"

#define GB_CONNECTION_CPORT_QUIESCE_TIMEOUT     1000

static void gb_connection_kref_release(struct kref *kref);

static DEFINE_SPINLOCK(gb_connections_lock);
static DEFINE_MUTEX(gb_connection_mutex);

/* Caller holds gb_connection_mutex. */
static bool gb_connection_cport_in_use(struct gb_interface *intf, u16 cport_id)
{
        struct gb_host_device *hd = intf->hd;
        struct gb_connection *connection;

        list_for_each_entry(connection, &hd->connections, hd_links) {
                if (connection->intf == intf &&
                    connection->intf_cport_id == cport_id)
                        return true;
        }

        return false;
}

static void gb_connection_get(struct gb_connection *connection)
{
        kref_get(&connection->kref);

        trace_gb_connection_get(connection);
}

static void gb_connection_put(struct gb_connection *connection)
{
        trace_gb_connection_put(connection);

        kref_put(&connection->kref, gb_connection_kref_release);
}

/*
 * Returns a reference-counted pointer to the connection if found.
 */
static struct gb_connection *
gb_connection_hd_find(struct gb_host_device *hd, u16 cport_id)
{
        struct gb_connection *connection;
        unsigned long flags;

        spin_lock_irqsave(&gb_connections_lock, flags);
        list_for_each_entry(connection, &hd->connections, hd_links)
                if (connection->hd_cport_id == cport_id) {
                        gb_connection_get(connection);
                        goto found;
                }
        connection = NULL;
found:
        spin_unlock_irqrestore(&gb_connections_lock, flags);

        return connection;
}

/*
 * Callback from the host driver to let us know that data has been
 * received on the bundle.
 */
void greybus_data_rcvd(struct gb_host_device *hd, u16 cport_id,
                       u8 *data, size_t length)
{
        struct gb_connection *connection;

        trace_gb_hd_in(hd);

        connection = gb_connection_hd_find(hd, cport_id);
        if (!connection) {
                dev_err(&hd->dev,
                        "nonexistent connection (%zu bytes dropped)\n", length);
                return;
        }
        gb_connection_recv(connection, data, length);
        gb_connection_put(connection);
}
EXPORT_SYMBOL_GPL(greybus_data_rcvd);

static void gb_connection_kref_release(struct kref *kref)
{
        struct gb_connection *connection;

        connection = container_of(kref, struct gb_connection, kref);

        trace_gb_connection_release(connection);

        kfree(connection);
}

static void gb_connection_init_name(struct gb_connection *connection)
{
        u16 hd_cport_id = connection->hd_cport_id;
        u16 cport_id = 0;
        u8 intf_id = 0;

        if (connection->intf) {
                intf_id = connection->intf->interface_id;
                cport_id = connection->intf_cport_id;
        }

        snprintf(connection->name, sizeof(connection->name),
                 "%u/%u:%u", hd_cport_id, intf_id, cport_id);
}

/*
 * _gb_connection_create() - create a Greybus connection
 * @hd:                 host device of the connection
 * @hd_cport_id:        host-device cport id, or -1 for dynamic allocation
 * @intf:               remote interface, or NULL for static connections
 * @bundle:             remote-interface bundle (may be NULL)
 * @cport_id:           remote-interface cport id, or 0 for static connections
 * @handler:            request handler (may be NULL)
 * @flags:              connection flags
 *
 * Create a Greybus connection, representing the bidirectional link
 * between a CPort on a (local) Greybus host device and a CPort on
 * another Greybus interface.
 *
 * A connection also maintains the state of operations sent over the
 * connection.
 *
 * Serialised against concurrent create and destroy using the
 * gb_connection_mutex.
 *
 * Return: A pointer to the new connection if successful, or an ERR_PTR
 * otherwise.
 */
static struct gb_connection *
_gb_connection_create(struct gb_host_device *hd, int hd_cport_id,
                      struct gb_interface *intf,
                      struct gb_bundle *bundle, int cport_id,
                      gb_request_handler_t handler,
                      unsigned long flags)
{
        struct gb_connection *connection;
        int ret;

        mutex_lock(&gb_connection_mutex);

        if (intf && gb_connection_cport_in_use(intf, cport_id)) {
                dev_err(&intf->dev, "cport %u already in use\n", cport_id);
                ret = -EBUSY;
                goto err_unlock;
        }

        ret = gb_hd_cport_allocate(hd, hd_cport_id, flags);
        if (ret < 0) {
                dev_err(&hd->dev, "failed to allocate cport: %d\n", ret);
                goto err_unlock;
        }
        hd_cport_id = ret;

        connection = kzalloc(sizeof(*connection), GFP_KERNEL);
        if (!connection) {
                ret = -ENOMEM;
                goto err_hd_cport_release;
        }

        connection->hd_cport_id = hd_cport_id;
        connection->intf_cport_id = cport_id;
        connection->hd = hd;
        connection->intf = intf;
        connection->bundle = bundle;
        connection->handler = handler;
        connection->flags = flags;
        if (intf && (intf->quirks & GB_INTERFACE_QUIRK_NO_CPORT_FEATURES))
                connection->flags |= GB_CONNECTION_FLAG_NO_FLOWCTRL;
        connection->state = GB_CONNECTION_STATE_DISABLED;

        atomic_set(&connection->op_cycle, 0);
        mutex_init(&connection->mutex);
        spin_lock_init(&connection->lock);
        INIT_LIST_HEAD(&connection->operations);

        connection->wq = alloc_workqueue("%s:%d", WQ_UNBOUND, 1,
                                         dev_name(&hd->dev), hd_cport_id);
        if (!connection->wq) {
                ret = -ENOMEM;
                goto err_free_connection;
        }

        kref_init(&connection->kref);

        gb_connection_init_name(connection);

        spin_lock_irq(&gb_connections_lock);
        list_add(&connection->hd_links, &hd->connections);

        if (bundle)
                list_add(&connection->bundle_links, &bundle->connections);
        else
                INIT_LIST_HEAD(&connection->bundle_links);

        spin_unlock_irq(&gb_connections_lock);

        mutex_unlock(&gb_connection_mutex);

        trace_gb_connection_create(connection);

        return connection;

err_free_connection:
        kfree(connection);
err_hd_cport_release:
        gb_hd_cport_release(hd, hd_cport_id);
err_unlock:
        mutex_unlock(&gb_connection_mutex);

        return ERR_PTR(ret);
}

struct gb_connection *
gb_connection_create_static(struct gb_host_device *hd, u16 hd_cport_id,
                            gb_request_handler_t handler)
{
        return _gb_connection_create(hd, hd_cport_id, NULL, NULL, 0, handler,
                                     GB_CONNECTION_FLAG_HIGH_PRIO);
}

struct gb_connection *
gb_connection_create_control(struct gb_interface *intf)
{
        return _gb_connection_create(intf->hd, -1, intf, NULL, 0, NULL,
                                     GB_CONNECTION_FLAG_CONTROL |
                                     GB_CONNECTION_FLAG_HIGH_PRIO);
}

struct gb_connection *
gb_connection_create(struct gb_bundle *bundle, u16 cport_id,
                     gb_request_handler_t handler)
{
        struct gb_interface *intf = bundle->intf;

        return _gb_connection_create(intf->hd, -1, intf, bundle, cport_id,
                                     handler, 0);
}
EXPORT_SYMBOL_GPL(gb_connection_create);

struct gb_connection *
gb_connection_create_flags(struct gb_bundle *bundle, u16 cport_id,
                           gb_request_handler_t handler,
                           unsigned long flags)
{
        struct gb_interface *intf = bundle->intf;

        if (WARN_ON_ONCE(flags & GB_CONNECTION_FLAG_CORE_MASK))
                flags &= ~GB_CONNECTION_FLAG_CORE_MASK;

        return _gb_connection_create(intf->hd, -1, intf, bundle, cport_id,
                                     handler, flags);
}
EXPORT_SYMBOL_GPL(gb_connection_create_flags);

struct gb_connection *
gb_connection_create_offloaded(struct gb_bundle *bundle, u16 cport_id,
                               unsigned long flags)
{
        flags |= GB_CONNECTION_FLAG_OFFLOADED;

        return gb_connection_create_flags(bundle, cport_id, NULL, flags);
}
EXPORT_SYMBOL_GPL(gb_connection_create_offloaded);

static int gb_connection_hd_cport_enable(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        int ret;

        if (!hd->driver->cport_enable)
                return 0;

        ret = hd->driver->cport_enable(hd, connection->hd_cport_id,
                                       connection->flags);
        if (ret) {
                dev_err(&hd->dev, "%s: failed to enable host cport: %d\n",
                        connection->name, ret);
                return ret;
        }

        return 0;
}

static void gb_connection_hd_cport_disable(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        int ret;

        if (!hd->driver->cport_disable)
                return;

        ret = hd->driver->cport_disable(hd, connection->hd_cport_id);
        if (ret) {
                dev_err(&hd->dev, "%s: failed to disable host cport: %d\n",
                        connection->name, ret);
        }
}

static int gb_connection_hd_cport_connected(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        int ret;

        if (!hd->driver->cport_connected)
                return 0;

        ret = hd->driver->cport_connected(hd, connection->hd_cport_id);
        if (ret) {
                dev_err(&hd->dev, "%s: failed to set connected state: %d\n",
                        connection->name, ret);
                return ret;
        }

        return 0;
}

static int gb_connection_hd_cport_flush(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        int ret;

        if (!hd->driver->cport_flush)
                return 0;

        ret = hd->driver->cport_flush(hd, connection->hd_cport_id);
        if (ret) {
                dev_err(&hd->dev, "%s: failed to flush host cport: %d\n",
                        connection->name, ret);
                return ret;
        }

        return 0;
}

static int gb_connection_hd_cport_quiesce(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        size_t peer_space;
        int ret;

        if (!hd->driver->cport_quiesce)
                return 0;

        peer_space = sizeof(struct gb_operation_msg_hdr) +
                        sizeof(struct gb_cport_shutdown_request);

        if (connection->mode_switch)
                peer_space += sizeof(struct gb_operation_msg_hdr);

        if (!hd->driver->cport_quiesce)
                return 0;

        ret = hd->driver->cport_quiesce(hd, connection->hd_cport_id,
                                        peer_space,
                                        GB_CONNECTION_CPORT_QUIESCE_TIMEOUT);
        if (ret) {
                dev_err(&hd->dev, "%s: failed to quiesce host cport: %d\n",
                        connection->name, ret);
                return ret;
        }

        return 0;
}

static int gb_connection_hd_cport_clear(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        int ret;

        if (!hd->driver->cport_clear)
                return 0;

        ret = hd->driver->cport_clear(hd, connection->hd_cport_id);
        if (ret) {
                dev_err(&hd->dev, "%s: failed to clear host cport: %d\n",
                        connection->name, ret);
                return ret;
        }

        return 0;
}

/*
 * Request the SVC to create a connection from AP's cport to interface's
 * cport.
 */
static int
gb_connection_svc_connection_create(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        struct gb_interface *intf;
        u8 cport_flags;
        int ret;

        if (gb_connection_is_static(connection))
                return 0;

        intf = connection->intf;

        /*
         * Enable either E2EFC or CSD, unless no flow control is requested.
         */
        cport_flags = GB_SVC_CPORT_FLAG_CSV_N;
        if (gb_connection_flow_control_disabled(connection)) {
                cport_flags |= GB_SVC_CPORT_FLAG_CSD_N;
        } else if (gb_connection_e2efc_enabled(connection)) {
                cport_flags |= GB_SVC_CPORT_FLAG_CSD_N |
                                GB_SVC_CPORT_FLAG_E2EFC;
        }

        ret = gb_svc_connection_create(hd->svc,
                                       hd->svc->ap_intf_id,
                                       connection->hd_cport_id,
                                       intf->interface_id,
                                       connection->intf_cport_id,
                                       cport_flags);
        if (ret) {
                dev_err(&connection->hd->dev,
                        "%s: failed to create svc connection: %d\n",
                        connection->name, ret);
                return ret;
        }

        return 0;
}

static void
gb_connection_svc_connection_destroy(struct gb_connection *connection)
{
        if (gb_connection_is_static(connection))
                return;

        gb_svc_connection_destroy(connection->hd->svc,
                                  connection->hd->svc->ap_intf_id,
                                  connection->hd_cport_id,
                                  connection->intf->interface_id,
                                  connection->intf_cport_id);
}

/* Inform Interface about active CPorts */
static int gb_connection_control_connected(struct gb_connection *connection)
{
        struct gb_control *control;
        u16 cport_id = connection->intf_cport_id;
        int ret;

        if (gb_connection_is_static(connection))
                return 0;

        if (gb_connection_is_control(connection))
                return 0;

        control = connection->intf->control;

        ret = gb_control_connected_operation(control, cport_id);
        if (ret) {
                dev_err(&connection->bundle->dev,
                        "failed to connect cport: %d\n", ret);
                return ret;
        }

        return 0;
}

static void
gb_connection_control_disconnecting(struct gb_connection *connection)
{
        struct gb_control *control;
        u16 cport_id = connection->intf_cport_id;
        int ret;

        if (gb_connection_is_static(connection))
                return;

        control = connection->intf->control;

        ret = gb_control_disconnecting_operation(control, cport_id);
        if (ret) {
                dev_err(&connection->hd->dev,
                        "%s: failed to send disconnecting: %d\n",
                        connection->name, ret);
        }
}

static void
gb_connection_control_disconnected(struct gb_connection *connection)
{
        struct gb_control *control;
        u16 cport_id = connection->intf_cport_id;
        int ret;

        if (gb_connection_is_static(connection))
                return;

        control = connection->intf->control;

        if (gb_connection_is_control(connection)) {
                if (connection->mode_switch) {
                        ret = gb_control_mode_switch_operation(control);
                        if (ret) {
                                /*
                                 * Allow mode switch to time out waiting for
                                 * mailbox event.
                                 */
                                return;
                        }
                }

                return;
        }

        ret = gb_control_disconnected_operation(control, cport_id);
        if (ret) {
                dev_warn(&connection->bundle->dev,
                         "failed to disconnect cport: %d\n", ret);
        }
}

static int gb_connection_shutdown_operation(struct gb_connection *connection,
                                            u8 phase)
{
        struct gb_cport_shutdown_request *req;
        struct gb_operation *operation;
        int ret;

        operation = gb_operation_create_core(connection,
                                             GB_REQUEST_TYPE_CPORT_SHUTDOWN,
                                             sizeof(*req), 0, 0,
                                             GFP_KERNEL);
        if (!operation)
                return -ENOMEM;

        req = operation->request->payload;
        req->phase = phase;

        ret = gb_operation_request_send_sync(operation);

        gb_operation_put(operation);

        return ret;
}

static int gb_connection_cport_shutdown(struct gb_connection *connection,
                                        u8 phase)
{
        struct gb_host_device *hd = connection->hd;
        const struct gb_hd_driver *drv = hd->driver;
        int ret;

        if (gb_connection_is_static(connection))
                return 0;

        if (gb_connection_is_offloaded(connection)) {
                if (!drv->cport_shutdown)
                        return 0;

                ret = drv->cport_shutdown(hd, connection->hd_cport_id, phase,
                                          GB_OPERATION_TIMEOUT_DEFAULT);
        } else {
                ret = gb_connection_shutdown_operation(connection, phase);
        }

        if (ret) {
                dev_err(&hd->dev, "%s: failed to send cport shutdown (phase %d): %d\n",
                        connection->name, phase, ret);
                return ret;
        }

        return 0;
}

static int
gb_connection_cport_shutdown_phase_1(struct gb_connection *connection)
{
        return gb_connection_cport_shutdown(connection, 1);
}

static int
gb_connection_cport_shutdown_phase_2(struct gb_connection *connection)
{
        return gb_connection_cport_shutdown(connection, 2);
}

/*
 * Cancel all active operations on a connection.
 *
 * Locking: Called with connection lock held and state set to DISABLED or
 * DISCONNECTING.
 */
static void gb_connection_cancel_operations(struct gb_connection *connection,
                                            int errno)
        __must_hold(&connection->lock)
{
        struct gb_operation *operation;

        while (!list_empty(&connection->operations)) {
                operation = list_last_entry(&connection->operations,
                                            struct gb_operation, links);
                gb_operation_get(operation);
                spin_unlock_irq(&connection->lock);

                if (gb_operation_is_incoming(operation))
                        gb_operation_cancel_incoming(operation, errno);
                else
                        gb_operation_cancel(operation, errno);

                gb_operation_put(operation);

                spin_lock_irq(&connection->lock);
        }
}

/*
 * Cancel all active incoming operations on a connection.
 *
 * Locking: Called with connection lock held and state set to ENABLED_TX.
 */
static void
gb_connection_flush_incoming_operations(struct gb_connection *connection,
                                        int errno)
        __must_hold(&connection->lock)
{
        struct gb_operation *operation;
        bool incoming;

        while (!list_empty(&connection->operations)) {
                incoming = false;
                list_for_each_entry(operation, &connection->operations,
                                    links) {
                        if (gb_operation_is_incoming(operation)) {
                                gb_operation_get(operation);
                                incoming = true;
                                break;
                        }
                }

                if (!incoming)
                        break;

                spin_unlock_irq(&connection->lock);

                /* FIXME: flush, not cancel? */
                gb_operation_cancel_incoming(operation, errno);
                gb_operation_put(operation);

                spin_lock_irq(&connection->lock);
        }
}

/*
 * _gb_connection_enable() - enable a connection
 * @connection:         connection to enable
 * @rx:                 whether to enable incoming requests
 *
 * Connection-enable helper for DISABLED->ENABLED, DISABLED->ENABLED_TX, and
 * ENABLED_TX->ENABLED state transitions.
 *
 * Locking: Caller holds connection->mutex.
 */
static int _gb_connection_enable(struct gb_connection *connection, bool rx)
{
        int ret;

        /* Handle ENABLED_TX -> ENABLED transitions. */
        if (connection->state == GB_CONNECTION_STATE_ENABLED_TX) {
                if (!(connection->handler && rx))
                        return 0;

                spin_lock_irq(&connection->lock);
                connection->state = GB_CONNECTION_STATE_ENABLED;
                spin_unlock_irq(&connection->lock);

                return 0;
        }

        ret = gb_connection_hd_cport_enable(connection);
        if (ret)
                return ret;

        ret = gb_connection_svc_connection_create(connection);
        if (ret)
                goto err_hd_cport_clear;

        ret = gb_connection_hd_cport_connected(connection);
        if (ret)
                goto err_svc_connection_destroy;

        spin_lock_irq(&connection->lock);
        if (connection->handler && rx)
                connection->state = GB_CONNECTION_STATE_ENABLED;
        else
                connection->state = GB_CONNECTION_STATE_ENABLED_TX;
        spin_unlock_irq(&connection->lock);

        ret = gb_connection_control_connected(connection);
        if (ret)
                goto err_control_disconnecting;

        return 0;

err_control_disconnecting:
        spin_lock_irq(&connection->lock);
        connection->state = GB_CONNECTION_STATE_DISCONNECTING;
        gb_connection_cancel_operations(connection, -ESHUTDOWN);
        spin_unlock_irq(&connection->lock);

        /* Transmit queue should already be empty. */
        gb_connection_hd_cport_flush(connection);

        gb_connection_control_disconnecting(connection);
        gb_connection_cport_shutdown_phase_1(connection);
        gb_connection_hd_cport_quiesce(connection);
        gb_connection_cport_shutdown_phase_2(connection);
        gb_connection_control_disconnected(connection);
        connection->state = GB_CONNECTION_STATE_DISABLED;
err_svc_connection_destroy:
        gb_connection_svc_connection_destroy(connection);
err_hd_cport_clear:
        gb_connection_hd_cport_clear(connection);

        gb_connection_hd_cport_disable(connection);

        return ret;
}

int gb_connection_enable(struct gb_connection *connection)
{
        int ret = 0;

        mutex_lock(&connection->mutex);

        if (connection->state == GB_CONNECTION_STATE_ENABLED)
                goto out_unlock;

        ret = _gb_connection_enable(connection, true);
        if (!ret)
                trace_gb_connection_enable(connection);

out_unlock:
        mutex_unlock(&connection->mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(gb_connection_enable);

int gb_connection_enable_tx(struct gb_connection *connection)
{
        int ret = 0;

        mutex_lock(&connection->mutex);

        if (connection->state == GB_CONNECTION_STATE_ENABLED) {
                ret = -EINVAL;
                goto out_unlock;
        }

        if (connection->state == GB_CONNECTION_STATE_ENABLED_TX)
                goto out_unlock;

        ret = _gb_connection_enable(connection, false);
        if (!ret)
                trace_gb_connection_enable(connection);

out_unlock:
        mutex_unlock(&connection->mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(gb_connection_enable_tx);

void gb_connection_disable_rx(struct gb_connection *connection)
{
        mutex_lock(&connection->mutex);

        spin_lock_irq(&connection->lock);
        if (connection->state != GB_CONNECTION_STATE_ENABLED) {
                spin_unlock_irq(&connection->lock);
                goto out_unlock;
        }
        connection->state = GB_CONNECTION_STATE_ENABLED_TX;
        gb_connection_flush_incoming_operations(connection, -ESHUTDOWN);
        spin_unlock_irq(&connection->lock);

        trace_gb_connection_disable(connection);

out_unlock:
        mutex_unlock(&connection->mutex);
}
EXPORT_SYMBOL_GPL(gb_connection_disable_rx);

void gb_connection_mode_switch_prepare(struct gb_connection *connection)
{
        connection->mode_switch = true;
}

void gb_connection_mode_switch_complete(struct gb_connection *connection)
{
        gb_connection_svc_connection_destroy(connection);
        gb_connection_hd_cport_clear(connection);

        gb_connection_hd_cport_disable(connection);

        connection->mode_switch = false;
}

void gb_connection_disable(struct gb_connection *connection)
{
        mutex_lock(&connection->mutex);

        if (connection->state == GB_CONNECTION_STATE_DISABLED)
                goto out_unlock;

        trace_gb_connection_disable(connection);

        spin_lock_irq(&connection->lock);
        connection->state = GB_CONNECTION_STATE_DISCONNECTING;
        gb_connection_cancel_operations(connection, -ESHUTDOWN);
        spin_unlock_irq(&connection->lock);

        gb_connection_hd_cport_flush(connection);

        gb_connection_control_disconnecting(connection);
        gb_connection_cport_shutdown_phase_1(connection);
        gb_connection_hd_cport_quiesce(connection);
        gb_connection_cport_shutdown_phase_2(connection);
        gb_connection_control_disconnected(connection);

        connection->state = GB_CONNECTION_STATE_DISABLED;

        /* control-connection tear down is deferred when mode switching */
        if (!connection->mode_switch) {
                gb_connection_svc_connection_destroy(connection);
                gb_connection_hd_cport_clear(connection);

                gb_connection_hd_cport_disable(connection);
        }

out_unlock:
        mutex_unlock(&connection->mutex);
}
EXPORT_SYMBOL_GPL(gb_connection_disable);

/* Disable a connection without communicating with the remote end. */
void gb_connection_disable_forced(struct gb_connection *connection)
{
        mutex_lock(&connection->mutex);

        if (connection->state == GB_CONNECTION_STATE_DISABLED)
                goto out_unlock;

        trace_gb_connection_disable(connection);

        spin_lock_irq(&connection->lock);
        connection->state = GB_CONNECTION_STATE_DISABLED;
        gb_connection_cancel_operations(connection, -ESHUTDOWN);
        spin_unlock_irq(&connection->lock);

        gb_connection_hd_cport_flush(connection);

        gb_connection_svc_connection_destroy(connection);
        gb_connection_hd_cport_clear(connection);

        gb_connection_hd_cport_disable(connection);
out_unlock:
        mutex_unlock(&connection->mutex);
}
EXPORT_SYMBOL_GPL(gb_connection_disable_forced);

/* Caller must have disabled the connection before destroying it. */
void gb_connection_destroy(struct gb_connection *connection)
{
        if (!connection)
                return;

        if (WARN_ON(connection->state != GB_CONNECTION_STATE_DISABLED))
                gb_connection_disable(connection);

        mutex_lock(&gb_connection_mutex);

        spin_lock_irq(&gb_connections_lock);
        list_del(&connection->bundle_links);
        list_del(&connection->hd_links);
        spin_unlock_irq(&gb_connections_lock);

        destroy_workqueue(connection->wq);

        gb_hd_cport_release(connection->hd, connection->hd_cport_id);
        connection->hd_cport_id = CPORT_ID_BAD;

        mutex_unlock(&gb_connection_mutex);

        gb_connection_put(connection);
}
EXPORT_SYMBOL_GPL(gb_connection_destroy);

void gb_connection_latency_tag_enable(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        int ret;

        if (!hd->driver->latency_tag_enable)
                return;

        ret = hd->driver->latency_tag_enable(hd, connection->hd_cport_id);
        if (ret) {
                dev_err(&connection->hd->dev,
                        "%s: failed to enable latency tag: %d\n",
                        connection->name, ret);
        }
}
EXPORT_SYMBOL_GPL(gb_connection_latency_tag_enable);

void gb_connection_latency_tag_disable(struct gb_connection *connection)
{
        struct gb_host_device *hd = connection->hd;
        int ret;

        if (!hd->driver->latency_tag_disable)
                return;

        ret = hd->driver->latency_tag_disable(hd, connection->hd_cport_id);
        if (ret) {
                dev_err(&connection->hd->dev,
                        "%s: failed to disable latency tag: %d\n",
                        connection->name, ret);
        }
}
EXPORT_SYMBOL_GPL(gb_connection_latency_tag_disable);