/*
 * Virtio memory mapped device driver
 *
 * Copyright 2011, 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
 *
 *
 *
 * Registers layout (all 32-bit wide):
 *
 * offset d. name             description
 * ------ -- ---------------- -----------------
 *
 * 0x000  R  MagicValue       Magic value "virt"
 * 0x004  R  Version          Device version (current max. 1)
 * 0x008  R  DeviceID         Virtio device ID
 * 0x00c  R  VendorID         Virtio vendor ID
 *
 * 0x010  R  HostFeatures     Features supported by the host
 * 0x014  W  HostFeaturesSel  Set of host features to access via HostFeatures
 *
 * 0x020  W  GuestFeatures    Features activated by the guest
 * 0x024  W  GuestFeaturesSel Set of activated features to set via GuestFeatures
 * 0x028  W  GuestPageSize    Size of guest's memory page in bytes
 *
 * 0x030  W  QueueSel         Queue selector
 * 0x034  R  QueueNumMax      Maximum size of the currently selected queue
 * 0x038  W  QueueNum         Queue size for the currently selected queue
 * 0x03c  W  QueueAlign       Used Ring alignment for the current queue
 * 0x040  RW QueuePFN         PFN for the currently selected queue
 *
 * 0x050  W  QueueNotify      Queue notifier
 * 0x060  R  InterruptStatus  Interrupt status register
 * 0x064  W  InterruptACK     Interrupt acknowledge register
 * 0x070  RW Status           Device status register
 *
 * 0x100+ RW                  Device-specific configuration space
 *
 * Based on Virtio PCI driver by Anthony Liguori, copyright IBM Corp. 2007
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 */

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

#include <linux/highmem.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <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;

        /* a list of queues so we can dispatch IRQs */
        spinlock_t lock;
        struct list_head virtqueues;
};

struct virtio_mmio_vq_info {
        /* the actual virtqueue */
        struct virtqueue *vq;

        /* the number of entries in the queue */
        unsigned int num;

        /* the virtual address of the ring queue */
        void *queue;

        /* the list node for the virtqueues list */
        struct list_head node;
};



/* Configuration interface */

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

        /* TODO: Features > 32 bits */
        writel(0, vm_dev->base + VIRTIO_MMIO_HOST_FEATURES_SEL);

        return readl(vm_dev->base + VIRTIO_MMIO_HOST_FEATURES);
}

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

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

        for (i = 0; i < ARRAY_SIZE(vdev->features); i++) {
                writel(i, vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES_SEL);
                writel(vdev->features[i],
                                vm_dev->base + VIRTIO_MMIO_GUEST_FEATURES);
        }
}

static void vm_get(struct virtio_device *vdev, unsigned offset,
                   void *buf, unsigned len)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        u8 *ptr = buf;
        int i;

        for (i = 0; i < len; i++)
                ptr[i] = readb(vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
}

static void vm_set(struct virtio_device *vdev, unsigned offset,
                   const void *buf, unsigned len)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        const u8 *ptr = buf;
        int i;

        for (i = 0; i < len; i++)
                writeb(ptr[i], vm_dev->base + VIRTIO_MMIO_CONFIG + offset + i);
}

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);

        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 void 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);
}

/* Notify all virtqueues on an interrupt. */
static irqreturn_t vm_interrupt(int irq, void *opaque)
{
        struct virtio_mmio_device *vm_dev = opaque;
        struct virtio_mmio_vq_info *info;
        struct virtio_driver *vdrv = container_of(vm_dev->vdev.dev.driver,
                        struct virtio_driver, driver);
        unsigned long status;
        unsigned long flags;
        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)
                        && vdrv && vdrv->config_changed) {
                vdrv->config_changed(&vm_dev->vdev);
                ret = IRQ_HANDLED;
        }

        if (likely(status & VIRTIO_MMIO_INT_VRING)) {
                spin_lock_irqsave(&vm_dev->lock, flags);
                list_for_each_entry(info, &vm_dev->virtqueues, node)
                        ret |= vring_interrupt(irq, info->vq);
                spin_unlock_irqrestore(&vm_dev->lock, flags);
        }

        return ret;
}



static void vm_del_vq(struct virtqueue *vq)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
        struct virtio_mmio_vq_info *info = vq->priv;
        unsigned long flags, size;
        unsigned int index = vq->index;

        spin_lock_irqsave(&vm_dev->lock, flags);
        list_del(&info->node);
        spin_unlock_irqrestore(&vm_dev->lock, flags);

        vring_del_virtqueue(vq);

        /* Select and deactivate the queue */
        writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
        writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);

        size = PAGE_ALIGN(vring_size(info->num, VIRTIO_MMIO_VRING_ALIGN));
        free_pages_exact(info->queue, size);
        kfree(info);
}

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 struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
                                  void (*callback)(struct virtqueue *vq),
                                  const char *name)
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        struct virtio_mmio_vq_info *info;
        struct virtqueue *vq;
        unsigned long flags, size;
        int err;

        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 + VIRTIO_MMIO_QUEUE_PFN)) {
                err = -ENOENT;
                goto error_available;
        }

        /* Allocate and fill out our active queue description */
        info = kmalloc(sizeof(*info), GFP_KERNEL);
        if (!info) {
                err = -ENOMEM;
                goto error_kmalloc;
        }

        /* Allocate pages for the queue - start with a queue as big as
         * possible (limited by maximum size allowed by device), drop down
         * to a minimal size, just big enough to fit descriptor table
         * and two rings (which makes it "alignment_size * 2")
         */
        info->num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX);

        /* If the device reports a 0 entry queue, we won't be able to
         * use it to perform I/O, and vring_new_virtqueue() can't create
         * empty queues anyway, so don't bother to set up the device.
         */
        if (info->num == 0) {
                err = -ENOENT;
                goto error_alloc_pages;
        }

        while (1) {
                size = PAGE_ALIGN(vring_size(info->num,
                                VIRTIO_MMIO_VRING_ALIGN));
                /* Did the last iter shrink the queue below minimum size? */
                if (size < VIRTIO_MMIO_VRING_ALIGN * 2) {
                        err = -ENOMEM;
                        goto error_alloc_pages;
                }

                info->queue = alloc_pages_exact(size, GFP_KERNEL | __GFP_ZERO);
                if (info->queue)
                        break;

                info->num /= 2;
        }

        /* Activate the queue */
        writel(info->num, vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
        writel(VIRTIO_MMIO_VRING_ALIGN,
                        vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
        writel(virt_to_phys(info->queue) >> PAGE_SHIFT,
                        vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);

        /* Create the vring */
        vq = vring_new_virtqueue(index, info->num, VIRTIO_MMIO_VRING_ALIGN, vdev,
                                 true, info->queue, vm_notify, callback, name);
        if (!vq) {
                err = -ENOMEM;
                goto error_new_virtqueue;
        }

        vq->priv = info;
        info->vq = vq;

        spin_lock_irqsave(&vm_dev->lock, flags);
        list_add(&info->node, &vm_dev->virtqueues);
        spin_unlock_irqrestore(&vm_dev->lock, flags);

        return vq;

error_new_virtqueue:
        writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
        free_pages_exact(info->queue, size);
error_alloc_pages:
        kfree(info);
error_kmalloc:
error_available:
        return ERR_PTR(err);
}

static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
                       struct virtqueue *vqs[],
                       vq_callback_t *callbacks[],
                       const char *names[])
{
        struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
        unsigned int irq = platform_get_irq(vm_dev->pdev, 0);
        int i, err;

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

        for (i = 0; i < nvqs; ++i) {
                vqs[i] = vm_setup_vq(vdev, i, callbacks[i], names[i]);
                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 const struct virtio_config_ops virtio_mmio_config_ops = {
        .get            = vm_get,
        .set            = vm_set,
        .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,
};



/* Platform device */

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

        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!mem)
                return -EINVAL;

        if (!devm_request_mem_region(&pdev->dev, mem->start,
                        resource_size(mem), pdev->name))
                return -EBUSY;

        vm_dev = devm_kzalloc(&pdev->dev, sizeof(*vm_dev), GFP_KERNEL);
        if (!vm_dev)
                return  -ENOMEM;

        vm_dev->vdev.dev.parent = &pdev->dev;
        vm_dev->vdev.config = &virtio_mmio_config_ops;
        vm_dev->pdev = pdev;
        INIT_LIST_HEAD(&vm_dev->virtqueues);
        spin_lock_init(&vm_dev->lock);

        vm_dev->base = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
        if (vm_dev->base == NULL)
                return -EFAULT;

        /* Check magic value */
        magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE);
        if (memcmp(&magic, "virt", 4) != 0) {
                dev_warn(&pdev->dev, "Wrong magic value 0x%08lx!\n", magic);
                return -ENODEV;
        }

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

        vm_dev->vdev.id.device = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_ID);
        vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);

        writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);

        platform_set_drvdata(pdev, vm_dev);

        return register_virtio_device(&vm_dev->vdev);
}

static int virtio_mmio_remove(struct platform_device *pdev)
{
        struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);

        unregister_virtio_device(&vm_dev->vdev);

        return 0;
}



/* Devices list parameter */

#if defined(CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES)

static struct device vm_cmdline_parent = {
        .init_name = "virtio-mmio-cmdline",
};

static int vm_cmdline_parent_registered;
static int vm_cmdline_id;

static int vm_cmdline_set(const char *device,
                const struct kernel_param *kp)
{
        int err;
        struct resource resources[2] = {};
        char *str;
        long long int 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 processes 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])
                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) {
                err = device_register(&vm_cmdline_parent);
                if (err) {
                        pr_err("Failed to register parent device!\n");
                        return err;
                }
                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);
        if (IS_ERR(pdev))
                return PTR_ERR(pdev);

        return 0;
}

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';
        device_for_each_child(&vm_cmdline_parent, buffer,
                        vm_cmdline_get_device);
        return strlen(buffer) + 1;
}

static 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);
                device_unregister(&vm_cmdline_parent);
                vm_cmdline_parent_registered = 0;
        }
}

#else

static void vm_unregister_cmdline_devices(void)
{
}

#endif

/* Platform driver */

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

static struct platform_driver virtio_mmio_driver = {
        .probe          = virtio_mmio_probe,
        .remove         = virtio_mmio_remove,
        .driver         = {
                .name   = "virtio-mmio",
                .owner  = THIS_MODULE,
                .of_match_table = virtio_mmio_match,
        },
};

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");