/*
 * Intel MIC Platform Software Stack (MPSS)
 *
 * Copyright(c) 2014 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * Intel SCIF driver.
 */
#include "scif_main.h"
#include "../bus/scif_bus.h"
#include "scif_peer_bus.h"

static inline struct scif_peer_dev *
dev_to_scif_peer(struct device *dev)
{
        return container_of(dev, struct scif_peer_dev, dev);
}

struct bus_type scif_peer_bus = {
        .name  = "scif_peer_bus",
};

static void scif_peer_release_dev(struct device *d)
{
        struct scif_peer_dev *sdev = dev_to_scif_peer(d);
        struct scif_dev *scifdev = &scif_dev[sdev->dnode];

        scif_cleanup_scifdev(scifdev);
        kfree(sdev);
}

static int scif_peer_initialize_device(struct scif_dev *scifdev)
{
        struct scif_peer_dev *spdev;
        int ret;

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

        spdev->dev.parent = scifdev->sdev->dev.parent;
        spdev->dev.release = scif_peer_release_dev;
        spdev->dnode = scifdev->node;
        spdev->dev.bus = &scif_peer_bus;
        dev_set_name(&spdev->dev, "scif_peer-dev%u", spdev->dnode);

        device_initialize(&spdev->dev);
        get_device(&spdev->dev);
        rcu_assign_pointer(scifdev->spdev, spdev);

        mutex_lock(&scif_info.conflock);
        scif_info.total++;
        scif_info.maxid = max_t(u32, spdev->dnode, scif_info.maxid);
        mutex_unlock(&scif_info.conflock);
        return 0;
err:
        dev_err(&scifdev->sdev->dev,
                "dnode %d: initialize_device rc %d\n", scifdev->node, ret);
        return ret;
}

static int scif_peer_add_device(struct scif_dev *scifdev)
{
        struct scif_peer_dev *spdev = rcu_dereference(scifdev->spdev);
        char pool_name[16];
        int ret;

        ret = device_add(&spdev->dev);
        put_device(&spdev->dev);
        if (ret) {
                dev_err(&scifdev->sdev->dev,
                        "dnode %d: peer device_add failed\n", scifdev->node);
                goto put_spdev;
        }

        scnprintf(pool_name, sizeof(pool_name), "scif-%d", spdev->dnode);
        scifdev->signal_pool = dmam_pool_create(pool_name, &scifdev->sdev->dev,
                                                sizeof(struct scif_status), 1,
                                                0);
        if (!scifdev->signal_pool) {
                dev_err(&scifdev->sdev->dev,
                        "dnode %d: dmam_pool_create failed\n", scifdev->node);
                ret = -ENOMEM;
                goto del_spdev;
        }
        dev_dbg(&spdev->dev, "Added peer dnode %d\n", spdev->dnode);
        return 0;
del_spdev:
        device_del(&spdev->dev);
put_spdev:
        RCU_INIT_POINTER(scifdev->spdev, NULL);
        synchronize_rcu();
        put_device(&spdev->dev);

        mutex_lock(&scif_info.conflock);
        scif_info.total--;
        mutex_unlock(&scif_info.conflock);
        return ret;
}

void scif_add_peer_device(struct work_struct *work)
{
        struct scif_dev *scifdev = container_of(work, struct scif_dev,
                                                peer_add_work);

        scif_peer_add_device(scifdev);
}

/*
 * Peer device registration is split into a device_initialize and a device_add.
 * The reason for doing this is as follows: First, peer device registration
 * itself cannot be done in the message processing thread and must be delegated
 * to another workqueue, otherwise if SCIF client probe, called during peer
 * device registration, calls scif_connect(..), it will block the message
 * processing thread causing a deadlock. Next, device_initialize is done in the
 * "top-half" message processing thread and device_add in the "bottom-half"
 * workqueue. If this is not done, SCIF_CNCT_REQ message processing executing
 * concurrently with SCIF_INIT message processing is unable to get a reference
 * on the peer device, thereby failing the connect request.
 */
void scif_peer_register_device(struct scif_dev *scifdev)
{
        int ret;

        mutex_lock(&scifdev->lock);
        ret = scif_peer_initialize_device(scifdev);
        if (ret)
                goto exit;
        schedule_work(&scifdev->peer_add_work);
exit:
        mutex_unlock(&scifdev->lock);
}

int scif_peer_unregister_device(struct scif_dev *scifdev)
{
        struct scif_peer_dev *spdev;

        mutex_lock(&scifdev->lock);
        /* Flush work to ensure device register is complete */
        flush_work(&scifdev->peer_add_work);

        /*
         * Continue holding scifdev->lock since theoretically unregister_device
         * can be called simultaneously from multiple threads
         */
        spdev = rcu_dereference(scifdev->spdev);
        if (!spdev) {
                mutex_unlock(&scifdev->lock);
                return -ENODEV;
        }

        RCU_INIT_POINTER(scifdev->spdev, NULL);
        synchronize_rcu();
        mutex_unlock(&scifdev->lock);

        dev_dbg(&spdev->dev, "Removing peer dnode %d\n", spdev->dnode);
        device_unregister(&spdev->dev);

        mutex_lock(&scif_info.conflock);
        scif_info.total--;
        mutex_unlock(&scif_info.conflock);
        return 0;
}

int scif_peer_bus_init(void)
{
        return bus_register(&scif_peer_bus);
}

void scif_peer_bus_exit(void)
{
        bus_unregister(&scif_peer_bus);
}