// SPDX-License-Identifier: GPL-2.0-only
/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
#include <linux/libnvdimm.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/ndctl.h>
#include <linux/async.h>
#include <linux/slab.h>
#include "cxlmem.h"
#include "cxl.h"

/*
 * Ordered workqueue for cxl nvdimm device arrival and departure
 * to coordinate bus rescans when a bridge arrives and trigger remove
 * operations when the bridge is removed.
 */
static struct workqueue_struct *cxl_pmem_wq;

static void unregister_nvdimm(void *nvdimm)
{
        nvdimm_delete(nvdimm);
}

static int match_nvdimm_bridge(struct device *dev, const void *data)
{
        return strcmp(dev_name(dev), "nvdimm-bridge") == 0;
}

static struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(void)
{
        struct device *dev;

        dev = bus_find_device(&cxl_bus_type, NULL, NULL, match_nvdimm_bridge);
        if (!dev)
                return NULL;
        return to_cxl_nvdimm_bridge(dev);
}

static int cxl_nvdimm_probe(struct device *dev)
{
        struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
        struct cxl_nvdimm_bridge *cxl_nvb;
        unsigned long flags = 0;
        struct nvdimm *nvdimm;
        int rc = -ENXIO;

        cxl_nvb = cxl_find_nvdimm_bridge();
        if (!cxl_nvb)
                return -ENXIO;

        device_lock(&cxl_nvb->dev);
        if (!cxl_nvb->nvdimm_bus)
                goto out;

        set_bit(NDD_LABELING, &flags);
        nvdimm = nvdimm_create(cxl_nvb->nvdimm_bus, cxl_nvd, NULL, flags, 0, 0,
                               NULL);
        if (!nvdimm)
                goto out;

        rc = devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
out:
        device_unlock(&cxl_nvb->dev);
        put_device(&cxl_nvb->dev);

        return rc;
}

static struct cxl_driver cxl_nvdimm_driver = {
        .name = "cxl_nvdimm",
        .probe = cxl_nvdimm_probe,
        .id = CXL_DEVICE_NVDIMM,
};

static int cxl_pmem_ctl(struct nvdimm_bus_descriptor *nd_desc,
                        struct nvdimm *nvdimm, unsigned int cmd, void *buf,
                        unsigned int buf_len, int *cmd_rc)
{
        return -ENOTTY;
}

static bool online_nvdimm_bus(struct cxl_nvdimm_bridge *cxl_nvb)
{
        if (cxl_nvb->nvdimm_bus)
                return true;
        cxl_nvb->nvdimm_bus =
                nvdimm_bus_register(&cxl_nvb->dev, &cxl_nvb->nd_desc);
        return cxl_nvb->nvdimm_bus != NULL;
}

static int cxl_nvdimm_release_driver(struct device *dev, void *data)
{
        if (!is_cxl_nvdimm(dev))
                return 0;
        device_release_driver(dev);
        return 0;
}

static void offline_nvdimm_bus(struct nvdimm_bus *nvdimm_bus)
{
        if (!nvdimm_bus)
                return;

        /*
         * Set the state of cxl_nvdimm devices to unbound / idle before
         * nvdimm_bus_unregister() rips the nvdimm objects out from
         * underneath them.
         */
        bus_for_each_dev(&cxl_bus_type, NULL, NULL, cxl_nvdimm_release_driver);
        nvdimm_bus_unregister(nvdimm_bus);
}

static void cxl_nvb_update_state(struct work_struct *work)
{
        struct cxl_nvdimm_bridge *cxl_nvb =
                container_of(work, typeof(*cxl_nvb), state_work);
        struct nvdimm_bus *victim_bus = NULL;
        bool release = false, rescan = false;

        device_lock(&cxl_nvb->dev);
        switch (cxl_nvb->state) {
        case CXL_NVB_ONLINE:
                if (!online_nvdimm_bus(cxl_nvb)) {
                        dev_err(&cxl_nvb->dev,
                                "failed to establish nvdimm bus\n");
                        release = true;
                } else
                        rescan = true;
                break;
        case CXL_NVB_OFFLINE:
        case CXL_NVB_DEAD:
                victim_bus = cxl_nvb->nvdimm_bus;
                cxl_nvb->nvdimm_bus = NULL;
                break;
        default:
                break;
        }
        device_unlock(&cxl_nvb->dev);

        if (release)
                device_release_driver(&cxl_nvb->dev);
        if (rescan) {
                int rc = bus_rescan_devices(&cxl_bus_type);

                dev_dbg(&cxl_nvb->dev, "rescan: %d\n", rc);
        }
        offline_nvdimm_bus(victim_bus);

        put_device(&cxl_nvb->dev);
}

static void cxl_nvdimm_bridge_remove(struct device *dev)
{
        struct cxl_nvdimm_bridge *cxl_nvb = to_cxl_nvdimm_bridge(dev);

        if (cxl_nvb->state == CXL_NVB_ONLINE)
                cxl_nvb->state = CXL_NVB_OFFLINE;
        if (queue_work(cxl_pmem_wq, &cxl_nvb->state_work))
                get_device(&cxl_nvb->dev);
}

static int cxl_nvdimm_bridge_probe(struct device *dev)
{
        struct cxl_nvdimm_bridge *cxl_nvb = to_cxl_nvdimm_bridge(dev);

        if (cxl_nvb->state == CXL_NVB_DEAD)
                return -ENXIO;

        if (cxl_nvb->state == CXL_NVB_NEW) {
                cxl_nvb->nd_desc = (struct nvdimm_bus_descriptor) {
                        .provider_name = "CXL",
                        .module = THIS_MODULE,
                        .ndctl = cxl_pmem_ctl,
                };

                INIT_WORK(&cxl_nvb->state_work, cxl_nvb_update_state);
        }

        cxl_nvb->state = CXL_NVB_ONLINE;
        if (queue_work(cxl_pmem_wq, &cxl_nvb->state_work))
                get_device(&cxl_nvb->dev);

        return 0;
}

static struct cxl_driver cxl_nvdimm_bridge_driver = {
        .name = "cxl_nvdimm_bridge",
        .probe = cxl_nvdimm_bridge_probe,
        .remove = cxl_nvdimm_bridge_remove,
        .id = CXL_DEVICE_NVDIMM_BRIDGE,
};

static __init int cxl_pmem_init(void)
{
        int rc;

        cxl_pmem_wq = alloc_ordered_workqueue("cxl_pmem", 0);
        if (!cxl_pmem_wq)
                return -ENXIO;

        rc = cxl_driver_register(&cxl_nvdimm_bridge_driver);
        if (rc)
                goto err_bridge;

        rc = cxl_driver_register(&cxl_nvdimm_driver);
        if (rc)
                goto err_nvdimm;

        return 0;

err_nvdimm:
        cxl_driver_unregister(&cxl_nvdimm_bridge_driver);
err_bridge:
        destroy_workqueue(cxl_pmem_wq);
        return rc;
}

static __exit void cxl_pmem_exit(void)
{
        cxl_driver_unregister(&cxl_nvdimm_driver);
        cxl_driver_unregister(&cxl_nvdimm_bridge_driver);
        destroy_workqueue(cxl_pmem_wq);
}

MODULE_LICENSE("GPL v2");
module_init(cxl_pmem_init);
module_exit(cxl_pmem_exit);
MODULE_IMPORT_NS(CXL);
MODULE_ALIAS_CXL(CXL_DEVICE_NVDIMM_BRIDGE);
MODULE_ALIAS_CXL(CXL_DEVICE_NVDIMM);