// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Virtio memory mapped device driver
 *
 * Copyright 2011-2014, ARM Ltd.
 *
 * This module allows virtio devices to be used over a virtual, memory mapped
 * platform device.
 *
 * The guest device(s) may be instantiated in one of three equivalent ways:
 *
 * 1. Static platform device in board's code, eg.:
 *
 *      static struct platform_device v2m_virtio_device = {
 *              .name = "virtio-mmio",
 *              .id = -1,
 *              .num_resources = 2,
 *              .resource = (struct resource []) {
 *                      {
 *                              .start = 0x1001e000,
 *                              .end = 0x1001e0ff,
 *                              .flags = IORESOURCE_MEM,
 *                      }, {
 *                              .start = 42 + 32,
 *                              .end = 42 + 32,
 *                              .flags = IORESOURCE_IRQ,
 *                      },
 *              }
 *      };
 *
 * 2. Device Tree node, eg.:
 *
 *              virtio_block@1e000 {
 *                      compatible = "virtio,mmio";
 *                      reg = <0x1e000 0x100>;
 *                      interrupts = <42>;
 *              }
 *
 * 3. Kernel module (or command line) parameter. Can be used more than once -
 *    one device will be created for each one. Syntax:
 *
 *              [virtio_mmio.]device=<size>@<baseaddr>:<irq>[:<id>]
 *    where:
 *              <size>     := size (can use standard suffixes like K, M or G)
 *              <baseaddr> := physical base address
 *              <irq>      := interrupt number (as passed to request_irq())
 *              <id>       := (optional) platform device id
 *    eg.:
 *              virtio_mmio.device=0x100@0x100b0000:48 \
 *                              virtio_mmio.device=1K@0x1001e000:74
 *
 * Based on Virtio PCI driver by Anthony Liguori, copyright IBM Corp. 2007
 */

#define pr_fmt(fmt) "virtio-mmio: " fmt

#include <linux/acpi.h>
#include <linux/dma-mapping.h>
#include <linux/highmem.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/slab.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <uapi/linux/virtio_mmio.h>
#include <linux/virtio_ring.h>



/* The alignment to use between consumer and producer parts of vring.
 * Currently hardcoded to the page size. */
#define VIRTIO_MMIO_VRING_ALIGN         PAGE_SIZE



#define to_virtio_mmio_device(_plat_dev) \
        container_of(_plat_dev, struct virtio_mmio_device, vdev)

struct virtio_mmio_device {
        struct virtio_device vdev;
        struct platform_device *pdev;

        void __iomem *base;
        unsigned long version;
};

/* Configuration interface */

static u64 vm_get_features(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        u64 features;

        writel(1, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
        features = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
        features <<= 32;

        writel(0, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
        features |= readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);

        return features;
}

static int vm_finalize_features(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        /* Give virtio_ring a chance to accept features. */
        vring_transport_features(vdev);

        /* Make sure there are no mixed devices */
        if (vm_dev->version == 2 &&
                        !__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
                dev_err(&vdev->dev, "New virtio-mmio devices (version 2) must provide VIRTIO_F_VERSION_1 feature!\n");
                return -EINVAL;
        }

        writel(1, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
        writel((u32)(vdev->features >> 32),
                        vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);

        writel(0, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
        writel((u32)vdev->features,
                        vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);

        return 0;
}

static void vm_get(struct virtio_device *vdev, unsigned int offset,
                   void *buf, unsigned int len)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
        u8 b;
        __le16 w;
        __le32 l;

        if (vm_dev->version == 1) {
                u8 *ptr = buf;
                int i;

                for (i = 0; i < len; i++)
                        ptr[i] = readb(base + offset + i);
                return;
        }

        switch (len) {
        case 1:
                b = readb(base + offset);
                memcpy(buf, &b, sizeof b);
                break;
        case 2:
                w = cpu_to_le16(readw(base + offset));
                memcpy(buf, &w, sizeof w);
                break;
        case 4:
                l = cpu_to_le32(readl(base + offset));
                memcpy(buf, &l, sizeof l);
                break;
        case 8:
                l = cpu_to_le32(readl(base + offset));
                memcpy(buf, &l, sizeof l);
                l = cpu_to_le32(ioread32(base + offset + sizeof l));
                memcpy(buf + sizeof l, &l, sizeof l);
                break;
        default:
                BUG();
        }
}

static void vm_set(struct virtio_device *vdev, unsigned int offset,
                   const void *buf, unsigned int len)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
        u8 b;
        __le16 w;
        __le32 l;

        if (vm_dev->version == 1) {
                const u8 *ptr = buf;
                int i;

                for (i = 0; i < len; i++)
                        writeb(ptr[i], base + offset + i);

                return;
        }

        switch (len) {
        case 1:
                memcpy(&b, buf, sizeof b);
                writeb(b, base + offset);
                break;
        case 2:
                memcpy(&w, buf, sizeof w);
                writew(le16_to_cpu(w), base + offset);
                break;
        case 4:
                memcpy(&l, buf, sizeof l);
                writel(le32_to_cpu(l), base + offset);
                break;
        case 8:
                memcpy(&l, buf, sizeof l);
                writel(le32_to_cpu(l), base + offset);
                memcpy(&l, buf + sizeof l, sizeof l);
                writel(le32_to_cpu(l), base + offset + sizeof l);
                break;
        default:
                BUG();
        }
}

static u32 vm_generation(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        if (vm_dev->version == 1)
                return 0;
        else
                return readl(vm_dev->base + VIRTIO_MMIO_CONFIG_GENERATION);
}

static u8 vm_get_status(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        return readl(vm_dev->base + VIRTIO_MMIO_STATUS) & 0xff;
}

static void vm_set_status(struct virtio_device *vdev, u8 status)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        /* We should never be setting status to 0. */
        BUG_ON(status == 0);

        /*
         * Per memory-barriers.txt, wmb() is not needed to guarantee
         * that the cache coherent memory writes have completed
         * before writing to the MMIO region.
         */
        writel(status, vm_dev->base + VIRTIO_MMIO_STATUS);
}

static void vm_reset(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        /* 0 status means a reset. */
        writel(0, vm_dev->base + VIRTIO_MMIO_STATUS);
}



/* Transport interface */

/* the notify function used when creating a virt queue */
static bool vm_notify(struct virtqueue *vq)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);

        /* We write the queue's selector into the notification register to
         * signal the other end */
        writel(vq->index, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);
        return true;
}

static bool vm_notify_with_data(struct virtqueue *vq)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
        u32 data = vring_notification_data(vq);

        writel(data, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);

        return true;
}

/* Notify all virtqueues on an interrupt. */
static irqreturn_t vm_interrupt(int irq, void *opaque)
{
        struct virtio_mmio_device *vm_dev = opaque;
        struct virtqueue *vq;
        unsigned long status;
        irqreturn_t ret = IRQ_NONE;

        /* Read and acknowledge interrupts */
        status = readl(vm_dev->base + VIRTIO_MMIO_INTERRUPT_STATUS);
        writel(status, vm_dev->base + VIRTIO_MMIO_INTERRUPT_ACK);

        if (unlikely(status & VIRTIO_MMIO_INT_CONFIG)) {
                virtio_config_changed(&vm_dev->vdev);
                ret = IRQ_HANDLED;
        }

        if (likely(status & VIRTIO_MMIO_INT_VRING)) {
                virtio_device_for_each_vq(&vm_dev->vdev, vq)
                        ret |= vring_interrupt(irq, vq);
        }

        return ret;
}



static void vm_del_vq(struct virtqueue *vq)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
        unsigned int index = vq->index;

        /* Select and deactivate the queue */
        writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
        if (vm_dev->version == 1) {
                writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
        } else {
                writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
                WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
        }

        vring_del_virtqueue(vq);
}

static void vm_del_vqs(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        struct virtqueue *vq, *n;

        list_for_each_entry_safe(vq, n, &vdev->vqs, list)
                vm_del_vq(vq);

        free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
}

static void vm_synchronize_cbs(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        synchronize_irq(platform_get_irq(vm_dev->pdev, 0));
}

static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned int index,
                                  void (*callback)(struct virtqueue *vq),
                                  const char *name, bool ctx)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        bool (*notify)(struct virtqueue *vq);
        struct virtqueue *vq;
        unsigned int num;
        int err;

        if (__virtio_test_bit(vdev, VIRTIO_F_NOTIFICATION_DATA))
                notify = vm_notify_with_data;
        else
                notify = vm_notify;

        if (!name)
                return NULL;

        /* Select the queue we're interested in */
        writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);

        /* Queue shouldn't already be set up. */
        if (readl(vm_dev->base + (vm_dev->version == 1 ?
                        VIRTIO_MMIO_QUEUE_PFN : VIRTIO_MMIO_QUEUE_READY))) {
                err = -ENOENT;
                goto error_available;
        }

        num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX);
        if (num == 0) {
                err = -ENOENT;
                goto error_new_virtqueue;
        }

        /* Create the vring */
        vq = vring_create_virtqueue(index, num, VIRTIO_MMIO_VRING_ALIGN, vdev,
                                 true, true, ctx, notify, callback, name);
        if (!vq) {
                err = -ENOMEM;
                goto error_new_virtqueue;
        }

        vq->num_max = num;

        /* Activate the queue */
        writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
        if (vm_dev->version == 1) {
                u64 q_pfn = virtqueue_get_desc_addr(vq) >> PAGE_SHIFT;

                /*
                 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something
                 * that doesn't fit in 32bit, fail the setup rather than
                 * pretending to be successful.
                 */
                if (q_pfn >> 32) {
                        dev_err(&vdev->dev,
                                "platform bug: legacy virtio-mmio must not be used with RAM above 0x%llxGB\n",
                                0x1ULL << (32 + PAGE_SHIFT - 30));
                        err = -E2BIG;
                        goto error_bad_pfn;
                }

                writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
                writel(q_pfn, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
        } else {
                u64 addr;

                addr = virtqueue_get_desc_addr(vq);
                writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
                writel((u32)(addr >> 32),
                                vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);

                addr = virtqueue_get_avail_addr(vq);
                writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
                writel((u32)(addr >> 32),
                                vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);

                addr = virtqueue_get_used_addr(vq);
                writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
                writel((u32)(addr >> 32),
                                vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);

                writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
        }

        return vq;

error_bad_pfn:
        vring_del_virtqueue(vq);
error_new_virtqueue:
        if (vm_dev->version == 1) {
                writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
        } else {
                writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
                WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
        }
error_available:
        return ERR_PTR(err);
}

static int vm_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
                       struct virtqueue *vqs[],
                       struct virtqueue_info vqs_info[],
                       struct irq_affinity *desc)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        int irq = platform_get_irq(vm_dev->pdev, 0);
        int i, err, queue_idx = 0;

        if (irq < 0)
                return irq;

        err = request_irq(irq, vm_interrupt, IRQF_SHARED,
                        dev_name(&vdev->dev), vm_dev);
        if (err)
                return err;

        if (of_property_read_bool(vm_dev->pdev->dev.of_node, "wakeup-source"))
                enable_irq_wake(irq);

        for (i = 0; i < nvqs; ++i) {
                struct virtqueue_info *vqi = &vqs_info[i];

                if (!vqi->name) {
                        vqs[i] = NULL;
                        continue;
                }

                vqs[i] = vm_setup_vq(vdev, queue_idx++, vqi->callback,
                                     vqi->name, vqi->ctx);
                if (IS_ERR(vqs[i])) {
                        vm_del_vqs(vdev);
                        return PTR_ERR(vqs[i]);
                }
        }

        return 0;
}

static const char *vm_bus_name(struct virtio_device *vdev)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        return vm_dev->pdev->name;
}

static bool vm_get_shm_region(struct virtio_device *vdev,
                              struct virtio_shm_region *region, u8 id)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        u64 len, addr;

        /* Select the region we're interested in */
        writel(id, vm_dev->base + VIRTIO_MMIO_SHM_SEL);

        /* Read the region size */
        len = (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_LEN_LOW);
        len |= (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_LEN_HIGH) << 32;

        region->len = len;

        /* Check if region length is -1. If that's the case, the shared memory
         * region does not exist and there is no need to proceed further.
         */
        if (len == ~(u64)0)
                return false;

        /* Read the region base address */
        addr = (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_BASE_LOW);
        addr |= (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_BASE_HIGH) << 32;

        region->addr = addr;

        return true;
}

static const struct virtio_config_ops virtio_mmio_config_ops = {
        .get            = vm_get,
        .set            = vm_set,
        .generation     = vm_generation,
        .get_status     = vm_get_status,
        .set_status     = vm_set_status,
        .reset          = vm_reset,
        .find_vqs       = vm_find_vqs,
        .del_vqs        = vm_del_vqs,
        .get_features   = vm_get_features,
        .finalize_features = vm_finalize_features,
        .bus_name       = vm_bus_name,
        .get_shm_region = vm_get_shm_region,
        .synchronize_cbs = vm_synchronize_cbs,
};

#ifdef CONFIG_PM_SLEEP
static int virtio_mmio_freeze(struct device *dev)
{
        struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);

        return virtio_device_freeze(&vm_dev->vdev);
}

static int virtio_mmio_restore(struct device *dev)
{
        struct virtio_mmio_device *vm_dev = dev_get_drvdata(dev);

        if (vm_dev->version == 1)
                writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);

        return virtio_device_restore(&vm_dev->vdev);
}

static const struct dev_pm_ops virtio_mmio_pm_ops = {
        SET_SYSTEM_SLEEP_PM_OPS(virtio_mmio_freeze, virtio_mmio_restore)
};
#endif

static void virtio_mmio_release_dev(struct device *_d)
{
        struct virtio_device *vdev =
                        container_of(_d, struct virtio_device, dev);
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

        kfree(vm_dev);
}

/* Platform device */

static int virtio_mmio_probe(struct platform_device *pdev)
{
        struct virtio_mmio_device *vm_dev;
        unsigned long magic;
        int rc;

        vm_dev = kzalloc_obj(*vm_dev);
        if (!vm_dev)
                return -ENOMEM;

        vm_dev->vdev.dev.parent = &pdev->dev;
        vm_dev->vdev.dev.release = virtio_mmio_release_dev;
        vm_dev->vdev.config = &virtio_mmio_config_ops;
        vm_dev->pdev = pdev;

        vm_dev->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(vm_dev->base)) {
                rc = PTR_ERR(vm_dev->base);
                goto free_vm_dev;
        }

        /* Check magic value */
        magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE);
        if (magic != ('v' | 'i' << 8 | 'r' << 16 | 't' << 24)) {
                dev_warn(&pdev->dev, "Wrong magic value 0x%08lx!\n", magic);
                rc = -ENODEV;
                goto free_vm_dev;
        }

        /* Check device version */
        vm_dev->version = readl(vm_dev->base + VIRTIO_MMIO_VERSION);
        if (vm_dev->version < 1 || vm_dev->version > 2) {
                dev_err(&pdev->dev, "Version %ld not supported!\n",
                                vm_dev->version);
                rc = -ENXIO;
                goto free_vm_dev;
        }

        vm_dev->vdev.id.device = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_ID);
        if (vm_dev->vdev.id.device == 0) {
                /*
                 * virtio-mmio device with an ID 0 is a (dummy) placeholder
                 * with no function. End probing now with no error reported.
                 */
                rc = -ENODEV;
                goto free_vm_dev;
        }
        vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);

        if (vm_dev->version == 1) {
                writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);

                rc = dma_set_mask(&pdev->dev, DMA_BIT_MASK(64));
                /*
                 * In the legacy case, ensure our coherently-allocated virtio
                 * ring will be at an address expressable as a 32-bit PFN.
                 */
                if (!rc)
                        dma_set_coherent_mask(&pdev->dev,
                                              DMA_BIT_MASK(32 + PAGE_SHIFT));
        } else {
                rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
        }
        if (rc)
                rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
        if (rc)
                dev_warn(&pdev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");

        platform_set_drvdata(pdev, vm_dev);

        rc = register_virtio_device(&vm_dev->vdev);
        if (rc)
                put_device(&vm_dev->vdev.dev);

        return rc;

free_vm_dev:
        kfree(vm_dev);
        return rc;
}

static void virtio_mmio_remove(struct platform_device *pdev)
{
        struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
        unregister_virtio_device(&vm_dev->vdev);
}



/* Devices list parameter */

#if defined(CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES)

static struct device *vm_cmdline_parent;

static int vm_cmdline_parent_registered;
static int vm_cmdline_id;

static int vm_cmdline_set(const char *device,
                const struct kernel_param *kp)
{
        struct resource resources[2] = {};
        char *str;
        long long base, size;
        unsigned int irq;
        int processed, consumed = 0;
        struct platform_device *pdev;

        /* Consume "size" part of the command line parameter */
        size = memparse(device, &str);

        /* Get "@<base>:<irq>[:<id>]" chunks */
        processed = sscanf(str, "@%lli:%u%n:%d%n",
                        &base, &irq, &consumed,
                        &vm_cmdline_id, &consumed);

        /*
         * sscanf() must process at least 2 chunks; also there
         * must be no extra characters after the last chunk, so
         * str[consumed] must be '\0'
         */
        if (processed < 2 || str[consumed] || irq == 0)
                return -EINVAL;

        resources[0].flags = IORESOURCE_MEM;
        resources[0].start = base;
        resources[0].end = base + size - 1;

        resources[1].flags = IORESOURCE_IRQ;
        resources[1].start = resources[1].end = irq;

        if (!vm_cmdline_parent_registered) {
                vm_cmdline_parent = __root_device_register("virtio-mmio-cmdline", NULL);
                if (IS_ERR(vm_cmdline_parent)) {
                        pr_err("Failed to register parent device!\n");
                        return PTR_ERR(vm_cmdline_parent);
                }
                vm_cmdline_parent_registered = 1;
        }

        pr_info("Registering device virtio-mmio.%d at 0x%llx-0x%llx, IRQ %d.\n",
                       vm_cmdline_id,
                       (unsigned long long)resources[0].start,
                       (unsigned long long)resources[0].end,
                       (int)resources[1].start);

        pdev = platform_device_register_resndata(vm_cmdline_parent,
                        "virtio-mmio", vm_cmdline_id++,
                        resources, ARRAY_SIZE(resources), NULL, 0);

        return PTR_ERR_OR_ZERO(pdev);
}

static int vm_cmdline_get_device(struct device *dev, void *data)
{
        char *buffer = data;
        unsigned int len = strlen(buffer);
        struct platform_device *pdev = to_platform_device(dev);

        snprintf(buffer + len, PAGE_SIZE - len, "0x%llx@0x%llx:%llu:%d\n",
                        pdev->resource[0].end - pdev->resource[0].start + 1ULL,
                        (unsigned long long)pdev->resource[0].start,
                        (unsigned long long)pdev->resource[1].start,
                        pdev->id);
        return 0;
}

static int vm_cmdline_get(char *buffer, const struct kernel_param *kp)
{
        buffer[0] = '\0';

        if (vm_cmdline_parent_registered) {
                device_for_each_child(vm_cmdline_parent, buffer,
                                vm_cmdline_get_device);
        }

        return strlen(buffer) + 1;
}

static const struct kernel_param_ops vm_cmdline_param_ops = {
        .set = vm_cmdline_set,
        .get = vm_cmdline_get,
};

device_param_cb(device, &vm_cmdline_param_ops, NULL, S_IRUSR);

static int vm_unregister_cmdline_device(struct device *dev,
                void *data)
{
        platform_device_unregister(to_platform_device(dev));

        return 0;
}

static void vm_unregister_cmdline_devices(void)
{
        if (vm_cmdline_parent_registered) {
                device_for_each_child(vm_cmdline_parent, NULL,
                                vm_unregister_cmdline_device);
                root_device_unregister(vm_cmdline_parent);
                vm_cmdline_parent_registered = 0;
        }
}

#else

static void vm_unregister_cmdline_devices(void)
{
}

#endif

/* Platform driver */

static const struct of_device_id virtio_mmio_match[] = {
        { .compatible = "virtio,mmio", },
        {},
};
MODULE_DEVICE_TABLE(of, virtio_mmio_match);

#ifdef CONFIG_ACPI
static const struct acpi_device_id virtio_mmio_acpi_match[] = {
        { "LNRO0005", },
        { }
};
MODULE_DEVICE_TABLE(acpi, virtio_mmio_acpi_match);
#endif

static struct platform_driver virtio_mmio_driver = {
        .probe          = virtio_mmio_probe,
        .remove         = virtio_mmio_remove,
        .driver         = {
                .name   = "virtio-mmio",
                .of_match_table = virtio_mmio_match,
                .acpi_match_table = ACPI_PTR(virtio_mmio_acpi_match),
#ifdef CONFIG_PM_SLEEP
                .pm     = &virtio_mmio_pm_ops,
#endif
        },
};

static int __init virtio_mmio_init(void)
{
        return platform_driver_register(&virtio_mmio_driver);
}

static void __exit virtio_mmio_exit(void)
{
        platform_driver_unregister(&virtio_mmio_driver);
        vm_unregister_cmdline_devices();
}

module_init(virtio_mmio_init);
module_exit(virtio_mmio_exit);

MODULE_AUTHOR("Pawel Moll <pawel.moll@arm.com>");
MODULE_DESCRIPTION("Platform bus driver for memory mapped virtio devices");
MODULE_LICENSE("GPL");