// SPDX-License-Identifier: GPL-2.0
#include <linux/platform_device.h>
#include <linux/memregion.h>
#include <linux/module.h>
#include <linux/dax.h>
#include <linux/mm.h>
#include "../bus.h"

static bool nohmem;
module_param_named(disable, nohmem, bool, 0444);

static bool platform_initialized;
static DEFINE_MUTEX(hmem_resource_lock);
static struct resource hmem_active = {
        .name = "HMEM devices",
        .start = 0,
        .end = -1,
        .flags = IORESOURCE_MEM,
};

int walk_hmem_resources(struct device *host, walk_hmem_fn fn)
{
        struct resource *res;
        int rc = 0;

        mutex_lock(&hmem_resource_lock);
        for (res = hmem_active.child; res; res = res->sibling) {
                rc = fn(host, (int) res->desc, res);
                if (rc)
                        break;
        }
        mutex_unlock(&hmem_resource_lock);
        return rc;
}
EXPORT_SYMBOL_GPL(walk_hmem_resources);

static void hmem_work(struct work_struct *work)
{
        /* place holder until dax_hmem driver attaches */
}

static struct hmem_platform_device hmem_platform = {
        .pdev = {
                .name = "hmem_platform",
                .id = 0,
        },
        .work = __WORK_INITIALIZER(hmem_platform.work, hmem_work),
};

static void __hmem_register_resource(int target_nid, struct resource *res)
{
        struct resource *new;
        int rc;

        new = __request_region(&hmem_active, res->start, resource_size(res), "",
                               0);
        if (!new) {
                pr_debug("hmem range %pr already active\n", res);
                return;
        }

        new->desc = target_nid;

        if (platform_initialized)
                return;

        rc = platform_device_register(&hmem_platform.pdev);
        if (rc) {
                pr_err_once("failed to register device-dax hmem_platform device\n");
                return;
        }

        platform_initialized = true;
}

void hmem_register_resource(int target_nid, struct resource *res)
{
        if (nohmem)
                return;

        mutex_lock(&hmem_resource_lock);
        __hmem_register_resource(target_nid, res);
        mutex_unlock(&hmem_resource_lock);
}

static __init int hmem_register_one(struct resource *res, void *data)
{
        hmem_register_resource(phys_to_target_node(res->start), res);

        return 0;
}

static __init int hmem_init(void)
{
        walk_soft_reserve_res(0, -1, NULL, hmem_register_one);
        return 0;
}

/*
 * As this is a fallback for address ranges unclaimed by the ACPI HMAT
 * parsing it must be at an initcall level greater than hmat_init().
 */
device_initcall(hmem_init);