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

static bool region_idle;
module_param_named(region_idle, region_idle, bool, 0644);

static int dax_hmem_probe(struct platform_device *pdev)
{
        unsigned long flags = IORESOURCE_DAX_KMEM;
        struct device *dev = &pdev->dev;
        struct dax_region *dax_region;
        struct memregion_info *mri;
        struct dev_dax_data data;

        /*
         * @region_idle == true indicates that an administrative agent
         * wants to manipulate the range partitioning before the devices
         * are created, so do not send them to the dax_kmem driver by
         * default.
         */
        if (region_idle)
                flags = 0;

        mri = dev->platform_data;
        dax_region = alloc_dax_region(dev, pdev->id, &mri->range,
                                      mri->target_node, PMD_SIZE, flags);
        if (!dax_region)
                return -ENOMEM;

        data = (struct dev_dax_data) {
                .dax_region = dax_region,
                .id = -1,
                .size = region_idle ? 0 : range_len(&mri->range),
                .memmap_on_memory = false,
        };

        return PTR_ERR_OR_ZERO(devm_create_dev_dax(&data));
}

static struct platform_driver dax_hmem_driver = {
        .probe = dax_hmem_probe,
        .driver = {
                .name = "hmem",
        },
};

static void release_memregion(void *data)
{
        memregion_free((long) data);
}

static void release_hmem(void *pdev)
{
        platform_device_unregister(pdev);
}

static struct workqueue_struct *dax_hmem_wq;

void dax_hmem_flush_work(void)
{
        flush_workqueue(dax_hmem_wq);
}
EXPORT_SYMBOL_FOR_MODULES(dax_hmem_flush_work, "dax_cxl");

static int __hmem_register_device(struct device *host, int target_nid,
                                  const struct resource *res)
{
        struct platform_device *pdev;
        struct memregion_info info;
        long id;
        int rc;

        rc = region_intersects_soft_reserve(res->start, resource_size(res));
        if (rc != REGION_INTERSECTS)
                return 0;

        /* TODO: Add Soft-Reserved memory back to iomem */

        id = memregion_alloc(GFP_KERNEL);
        if (id < 0) {
                dev_err(host, "memregion allocation failure for %pr\n", res);
                return -ENOMEM;
        }
        rc = devm_add_action_or_reset(host, release_memregion, (void *) id);
        if (rc)
                return rc;

        pdev = platform_device_alloc("hmem", id);
        if (!pdev) {
                dev_err(host, "device allocation failure for %pr\n", res);
                return -ENOMEM;
        }

        pdev->dev.parent = host;
        pdev->dev.numa_node = numa_map_to_online_node(target_nid);
        info = (struct memregion_info) {
                .target_node = target_nid,
                .range = {
                        .start = res->start,
                        .end = res->end,
                },
        };
        rc = platform_device_add_data(pdev, &info, sizeof(info));
        if (rc < 0) {
                dev_err(host, "memregion_info allocation failure for %pr\n",
                       res);
                goto out_put;
        }

        rc = platform_device_add(pdev);
        if (rc < 0) {
                dev_err(host, "%s add failed for %pr\n", dev_name(&pdev->dev),
                        res);
                goto out_put;
        }

        return devm_add_action_or_reset(host, release_hmem, pdev);

out_put:
        platform_device_put(pdev);
        return rc;
}

static int hmem_register_cxl_device(struct device *host, int target_nid,
                                    const struct resource *res)
{
        if (region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
                              IORES_DESC_CXL) == REGION_DISJOINT)
                return 0;

        if (cxl_region_contains_resource(res)) {
                dev_dbg(host, "CXL claims resource, dropping: %pr\n", res);
                return 0;
        }

        dev_dbg(host, "CXL did not claim resource, registering: %pr\n", res);
        return __hmem_register_device(host, target_nid, res);
}

static void process_defer_work(struct work_struct *w)
{
        struct hmem_platform_device *hpdev = container_of(w, typeof(*hpdev), work);
        struct device *dev = &hpdev->pdev.dev;

        /* Relies on cxl_acpi and cxl_pci having had a chance to load */
        wait_for_device_probe();

        guard(device)(dev);
        if (!dev->driver)
                goto out;

        if (!hpdev->did_probe) {
                hpdev->did_probe = true;
                walk_hmem_resources(dev, hmem_register_cxl_device);
        }
out:
        put_device(dev);
}

static int hmem_register_device(struct device *host, int target_nid,
                                const struct resource *res)
{
        struct platform_device *pdev = to_platform_device(host);
        struct hmem_platform_device *hpdev = to_hmem_platform_device(pdev);

        if (IS_ENABLED(CONFIG_DEV_DAX_CXL) &&
            region_intersects(res->start, resource_size(res), IORESOURCE_MEM,
                              IORES_DESC_CXL) != REGION_DISJOINT) {
                if (!hpdev->did_probe) {
                        dev_dbg(host, "await CXL initial probe: %pr\n", res);
                        hpdev->work.func = process_defer_work;
                        get_device(host);
                        if (!queue_work(dax_hmem_wq, &hpdev->work))
                                put_device(host);
                        return 0;
                }
                dev_dbg(host, "deferring range to CXL: %pr\n", res);
                return 0;
        }

        return __hmem_register_device(host, target_nid, res);
}

static int dax_hmem_platform_probe(struct platform_device *pdev)
{
        struct hmem_platform_device *hpdev = to_hmem_platform_device(pdev);

        /* queue is only flushed on module unload, fail rebind with pending work */
        if (work_pending(&hpdev->work))
                return -EBUSY;

        return walk_hmem_resources(&pdev->dev, hmem_register_device);
}

static struct platform_driver dax_hmem_platform_driver = {
        .probe = dax_hmem_platform_probe,
        .driver = {
                .name = "hmem_platform",
        },
};

static __init int dax_hmem_init(void)
{
        int rc;

        /*
         * Ensure that cxl_acpi and cxl_pci have a chance to kick off
         * CXL topology discovery at least once before scanning the
         * iomem resource tree for IORES_DESC_CXL resources.
         */
        if (IS_ENABLED(CONFIG_DEV_DAX_CXL)) {
                request_module("cxl_acpi");
                request_module("cxl_pci");
        }

        dax_hmem_wq = alloc_ordered_workqueue("dax_hmem_wq", 0);
        if (!dax_hmem_wq)
                return -ENOMEM;

        rc = platform_driver_register(&dax_hmem_platform_driver);
        if (rc)
                goto err_platform_driver;

        rc = platform_driver_register(&dax_hmem_driver);
        if (rc)
                goto err_driver;

        return 0;

err_driver:
        platform_driver_unregister(&dax_hmem_platform_driver);
err_platform_driver:
        destroy_workqueue(dax_hmem_wq);

        return rc;
}

static __exit void dax_hmem_exit(void)
{
        platform_driver_unregister(&dax_hmem_driver);
        platform_driver_unregister(&dax_hmem_platform_driver);
        destroy_workqueue(dax_hmem_wq);
}

module_init(dax_hmem_init);
module_exit(dax_hmem_exit);

MODULE_ALIAS("platform:hmem*");
MODULE_ALIAS("platform:hmem_platform*");
MODULE_DESCRIPTION("HMEM DAX: direct access to 'specific purpose' memory");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Intel Corporation");