// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2018-2020, The Linux Foundation. All rights reserved.*/

#include <linux/kernel.h>
#include <linux/mhi.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/poll.h>

#define MHI_DEVICE_NAME "mhi"
#define MHI_UCI_DRIVER_NAME "mhi_uci"
#define MHI_MAX_UCI_MINORS 128

static DEFINE_IDR(uci_idr);
static DEFINE_MUTEX(uci_drv_lock);
static struct class *uci_dev_class;
static int uci_dev_major;

struct uci_buf {
	struct list_head node;
	void *data;
	size_t len;
	size_t consumed;
};

struct uci_dev {
	unsigned int minor;
	size_t mtu;

	struct mhi_device *mhi_dev;
	struct mutex mhi_dev_lock;

	wait_queue_head_t ul_wq;
	wait_queue_head_t dl_wq;

	spinlock_t dl_queue_lock;
	struct list_head dl_queue;

	struct mutex write_lock;

	unsigned long flags;
#define UCI_DEV_DL_CAP		0
#define UCI_DEV_UL_CAP		1
#define UCI_DEV_CONNECTED	2

	struct kref ref_count;
};

static void mhi_uci_dev_release(struct kref *ref)
{
	struct uci_dev *udev = container_of(ref, struct uci_dev, ref_count);
	struct uci_buf *buf_itr, *tmp;

	/* Release non consumed buffers */
	list_for_each_entry_safe(buf_itr, tmp, &udev->dl_queue, node) {
		list_del(&buf_itr->node);
		kfree(buf_itr->data);
	}

	mutex_destroy(&udev->mhi_dev_lock);
	mutex_destroy(&udev->write_lock);

	kfree(udev);
}

static int mhi_uci_queue_inbound(struct uci_dev *udev)
{
	struct mhi_device *mhi_dev = udev->mhi_dev;
	struct device *dev = &mhi_dev->dev;
	int nr_desc, i, ret = -EIO;
	struct uci_buf *ubuf;
	void *buf;

	/*
	 * skip queuing without error if dl channel is not supported. This
	 * allows open to succeed for udev, supporting ul only channel.
	 */
	if (!udev->mhi_dev->dl_chan)
		return 0;

	nr_desc = mhi_get_free_desc_count(mhi_dev, DMA_FROM_DEVICE);

	for (i = 0; i < nr_desc; i++) {
		buf = kmalloc(udev->mtu + sizeof(*ubuf), GFP_KERNEL);
		if (!buf)
			return -ENOMEM;

		/* save uci_buf info at the end of buf */
		ubuf = buf + udev->mtu;
		ubuf->data = buf;

		dev_dbg(dev, "Allocated buf %d of %d size %zu\n", i + 1, nr_desc, udev->mtu);

		ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, ubuf->data, udev->mtu, MHI_EOT);
		if (ret) {
			kfree(buf);
			dev_err(dev, "Failed to queue buffer %d\n", i);
			return ret;
		}
	}

	return ret;
}

static int mhi_uci_open(struct inode *inode, struct file *filp)
{
	unsigned int minor = iminor(inode);
	struct uci_dev *udev = NULL;
	int ret;

	/* Retrieve corresponding uci_dev and get a reference */
	mutex_lock(&uci_drv_lock);
	udev = idr_find(&uci_idr, minor);
	if (!udev) {
		mutex_unlock(&uci_drv_lock);
		return -ENODEV;
	}
	kref_get(&udev->ref_count);
	mutex_unlock(&uci_drv_lock);

	/* Start MHI channel(s) and fill RX queue */
	mutex_lock(&udev->mhi_dev_lock);
	ret = mhi_prepare_for_transfer(udev->mhi_dev);
	if (!ret)
		ret = mhi_uci_queue_inbound(udev);
	mutex_unlock(&udev->mhi_dev_lock);

	if (ret)
		return ret;

	filp->private_data = udev;

	/* stream-like non-seekable file descriptor */
	stream_open(inode, filp);

	return 0;
}

static int mhi_uci_release(struct inode *inode, struct file *file)
{
	struct uci_dev *udev = file->private_data;

	/* Stop the channels, if it is not already destroyed */
	mutex_lock(&udev->mhi_dev_lock);
	if (udev->mhi_dev)
		mhi_unprepare_from_transfer(udev->mhi_dev);
	mutex_unlock(&udev->mhi_dev_lock);

	file->private_data = NULL;

	kref_put(&udev->ref_count, mhi_uci_dev_release);

	return 0;
}

static __poll_t mhi_uci_poll(struct file *file, poll_table *wait)
{
	struct uci_dev *udev = file->private_data;
	__poll_t mask = 0;

	poll_wait(file, &udev->ul_wq, wait);
	poll_wait(file, &udev->dl_wq, wait);

	/* Any buffer in the DL queue ? */
	spin_lock_bh(&udev->dl_queue_lock);
	if (!list_empty(&udev->dl_queue))
		mask |= EPOLLIN | EPOLLRDNORM;
	spin_unlock_bh(&udev->dl_queue_lock);

	/* If MHI queue is not full, write is possible */
	mutex_lock(&udev->mhi_dev_lock);
	if (!udev->mhi_dev)
		mask = EPOLLERR;
	else if (!mhi_queue_is_full(udev->mhi_dev, DMA_TO_DEVICE))
		mask |= EPOLLOUT | EPOLLWRNORM;
	mutex_unlock(&udev->mhi_dev_lock);

	return mask;
}

static ssize_t mhi_uci_write(struct file *file, const char __user *buf,
			     size_t count, loff_t *offp)
{
	struct uci_dev *udev = file->private_data;
	size_t bytes_xfered = 0;
	void *kbuf = NULL;
	int ret;

	if (!test_bit(UCI_DEV_UL_CAP, &udev->flags))
		return -EOPNOTSUPP;

	if (!buf || !count)
		return -EINVAL;

	/* Serialize MHI queueing */
	if (mutex_lock_interruptible(&udev->write_lock))
		return -EINTR;

	while (count) {
		size_t xfer_size;

		/* Wait for available transfer descriptor */
		ret = wait_event_interruptible(udev->ul_wq,
					       !test_bit(UCI_DEV_CONNECTED, &udev->flags) ||
					       !mhi_queue_is_full(udev->mhi_dev, DMA_TO_DEVICE));
		if (ret)
			break;

		if (!test_bit(UCI_DEV_CONNECTED, &udev->flags)) {
			ret = -EPIPE;
			break;
		}

		xfer_size = min_t(size_t, count, udev->mtu);
		kbuf = kmalloc(xfer_size, GFP_KERNEL);
		if (!kbuf) {
			ret = -ENOMEM;
			break;
		}

		ret = copy_from_user(kbuf, buf, xfer_size);
		if (ret)
			break;

		/* Add buffer to MHI queue */
		ret = mhi_queue_buf(udev->mhi_dev, DMA_TO_DEVICE, kbuf, xfer_size, MHI_EOT);
		if (ret)
			break;

		bytes_xfered += xfer_size;
		count -= xfer_size;
		buf += xfer_size;
		kbuf = NULL;
	}

	mutex_unlock(&udev->write_lock);

	if (kbuf) /* aborted buffer queueing */
		kfree(kbuf);

	return ret ? ret : bytes_xfered;
}

static int mhi_uci_recycle_ubuf(struct uci_dev *udev, struct uci_buf *ubuf)
{
	int ret;

	mutex_lock(&udev->mhi_dev_lock);

	if (!udev->mhi_dev) {
		ret = -ENODEV;
		goto exit_unlock;
	}

	ret = mhi_queue_buf(udev->mhi_dev, DMA_FROM_DEVICE, ubuf->data,
			    udev->mtu, MHI_EOT);

exit_unlock:
	mutex_unlock(&udev->mhi_dev_lock);

	return ret;
}

static ssize_t mhi_uci_read(struct file *file, char __user *buf, size_t count,
			    loff_t *ppos)
{
	struct uci_dev *udev = file->private_data;
	bool recycle_buf = false;
	struct uci_buf *ubuf;
	size_t copy_len;
	char *copy_ptr;
	int ret = 0;

	if (!test_bit(UCI_DEV_DL_CAP, &udev->flags))
		return -EOPNOTSUPP;

	if (!buf)
		return -EINVAL;

	spin_lock_irq(&udev->dl_queue_lock);

	ret = wait_event_interruptible_lock_irq(udev->dl_wq,
						!list_empty(&udev->dl_queue) ||
						!test_bit(UCI_DEV_CONNECTED, &udev->flags),
						udev->dl_queue_lock);
	if (ret) {
		goto err_unlock;
	} else if (!test_bit(UCI_DEV_CONNECTED, &udev->flags)) {
		ret = -EPIPE;
		goto err_unlock;
	}

	ubuf = list_first_entry_or_null(&udev->dl_queue, struct uci_buf, node);
	if (!ubuf) {
		ret = -EIO;
		goto err_unlock;
	}

	/* Consume the buffer */
	copy_len = min_t(size_t, count, ubuf->len - ubuf->consumed);
	copy_ptr = ubuf->data + ubuf->consumed;
	ubuf->consumed += copy_len;

	/* Remove buffer from the DL queue if entirely consumed */
	if (ubuf->consumed == ubuf->len) {
		list_del(&ubuf->node);
		recycle_buf = true;
	}

	spin_unlock_irq(&udev->dl_queue_lock);

	ret = copy_to_user(buf, copy_ptr, copy_len);
	if (ret)
		return -EFAULT;

	if (recycle_buf) {
		/* Give the buffer back to MHI queue */
		ret = mhi_uci_recycle_ubuf(udev, ubuf);
		if (ret) /* unable to recycle, release */
			kfree(ubuf->data);
	}

	return copy_len;

err_unlock:
	spin_unlock_irq(&udev->dl_queue_lock);

	return ret;
}

static const struct file_operations mhidev_fops = {
	.owner = THIS_MODULE,
	.open = mhi_uci_open,
	.release = mhi_uci_release,
	.read = mhi_uci_read,
	.write = mhi_uci_write,
	.poll = mhi_uci_poll,
};

static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev,
			   struct mhi_result *mhi_result)
{
	struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev);
	struct device *dev = &mhi_dev->dev;

	dev_dbg(dev, "%s: status: %d xfer_len: %zu\n", __func__,
		mhi_result->transaction_status, mhi_result->bytes_xferd);

	kfree(mhi_result->buf_addr);

	if (!mhi_result->transaction_status)
		wake_up_interruptible(&udev->ul_wq);
}

static void mhi_dl_xfer_cb(struct mhi_device *mhi_dev,
			   struct mhi_result *mhi_result)
{
	struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev);
	struct uci_buf *ubuf;

	dev_dbg(&mhi_dev->dev, "%s: status: %d receive_len: %zu\n", __func__,
		mhi_result->transaction_status, mhi_result->bytes_xferd);

	if (mhi_result->transaction_status &&
	    mhi_result->transaction_status != -EOVERFLOW) {
		kfree(mhi_result->buf_addr);
		return;
	}

	/* ubuf is placed at the end of the buffer (cf mhi_uci_queue_inbound) */
	ubuf = mhi_result->buf_addr + udev->mtu;

	/* paranoia, should never happen */
	if (WARN_ON(mhi_result->buf_addr != ubuf->data)) {
		kfree(mhi_result->buf_addr);
		return;
	}

	ubuf->data = mhi_result->buf_addr;
	ubuf->len = mhi_result->bytes_xferd;
	ubuf->consumed = 0;

	spin_lock_bh(&udev->dl_queue_lock);
	list_add_tail(&ubuf->node, &udev->dl_queue);
	spin_unlock_bh(&udev->dl_queue_lock);

	wake_up_interruptible(&udev->dl_wq);
}

static int mhi_uci_probe(struct mhi_device *mhi_dev,
			 const struct mhi_device_id *id)
{
	struct uci_dev *udev;
	struct device *dev;
	int index, err;

	/* Create UCI data context */
	udev = kzalloc(sizeof(*udev), GFP_KERNEL);
	if (!udev)
		return -ENOMEM;

	/* Retrieve index */
	mutex_lock(&uci_drv_lock);
	index = idr_alloc(&uci_idr, udev, 0, MHI_MAX_UCI_MINORS, GFP_KERNEL);
	mutex_unlock(&uci_drv_lock);
	if (index < 0) {
		err = index;
		goto err_free_udev;
	}

	/* Init UCI data */
	kref_init(&udev->ref_count);
	mutex_init(&udev->mhi_dev_lock);
	mutex_init(&udev->write_lock);
	init_waitqueue_head(&udev->ul_wq);
	init_waitqueue_head(&udev->dl_wq);
	spin_lock_init(&udev->dl_queue_lock);
	INIT_LIST_HEAD(&udev->dl_queue);
	udev->mhi_dev = mhi_dev;
	udev->minor = index;
	udev->mtu = min_t(size_t, id->driver_data, MHI_MAX_MTU);
	set_bit(UCI_DEV_CONNECTED, &udev->flags);

	if (mhi_dev->dl_chan)
		set_bit(UCI_DEV_DL_CAP, &udev->flags);
	if (mhi_dev->ul_chan)
		set_bit(UCI_DEV_UL_CAP, &udev->flags);

	dev_set_drvdata(&mhi_dev->dev, udev);

	/* Creates a new device and registers it with sysfs */
	dev = device_create(uci_dev_class, &mhi_dev->dev,
			    MKDEV(uci_dev_major, index), udev,
			    dev_name(&mhi_dev->dev));
	if (IS_ERR(dev)) {
		err = PTR_ERR(dev);
		goto err_free_idr;
	}

	dev_dbg(&mhi_dev->dev, "probed uci dev: %s\n", id->chan);

	return 0;

err_free_idr:
	mutex_lock(&uci_drv_lock);
	idr_remove(&uci_idr, udev->minor);
	mutex_unlock(&uci_drv_lock);
err_free_udev:
	kfree(udev);
	dev_set_drvdata(&mhi_dev->dev, NULL);

	return err;
};

static void mhi_uci_remove(struct mhi_device *mhi_dev)
{
	struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev);

	dev_set_drvdata(&mhi_dev->dev, NULL);

	mutex_lock(&uci_drv_lock);
	idr_remove(&uci_idr, udev->minor);
	mutex_unlock(&uci_drv_lock);

	clear_bit(UCI_DEV_CONNECTED, &udev->flags);
	device_destroy(uci_dev_class, MKDEV(uci_dev_major, udev->minor));

	/* Unlink mhi_dev from uci_dev */
	mutex_lock(&udev->mhi_dev_lock);
	udev->mhi_dev = NULL;
	mutex_unlock(&udev->mhi_dev_lock);

	/* wake up any blocked user */
	wake_up_interruptible(&udev->dl_wq);
	wake_up_interruptible(&udev->ul_wq);

	kref_put(&udev->ref_count, mhi_uci_dev_release);
}

/* .driver_data stores max mtu */
static const struct mhi_device_id mhi_uci_match_table[] = {
	{ .chan = "QMI", .driver_data = 0x1000},
	{ .chan = "MBIM", .driver_data = 0x1000},
	{ .chan = "DUN", .driver_data = 0x1000},
	{},
};
MODULE_DEVICE_TABLE(mhi, mhi_uci_match_table);

static struct mhi_driver mhi_uci_driver = {
	.id_table = mhi_uci_match_table,
	.remove = mhi_uci_remove,
	.probe = mhi_uci_probe,
	.ul_xfer_cb = mhi_ul_xfer_cb,
	.dl_xfer_cb = mhi_dl_xfer_cb,
	.driver = {
		.name = MHI_UCI_DRIVER_NAME,
	},
};

static int __init mhi_uci_init(void)
{
	int ret;

	ret = register_chrdev(0, MHI_UCI_DRIVER_NAME, &mhidev_fops);
	if (ret < 0)
		return ret;

	uci_dev_major = ret;
	uci_dev_class = class_create(THIS_MODULE, MHI_UCI_DRIVER_NAME);
	if (IS_ERR(uci_dev_class)) {
		unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME);
		return PTR_ERR(uci_dev_class);
	}

	ret = mhi_driver_register(&mhi_uci_driver);
	if (ret) {
		class_destroy(uci_dev_class);
		unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME);
	}

	return ret;
}

static void __exit mhi_uci_exit(void)
{
	mhi_driver_unregister(&mhi_uci_driver);
	class_destroy(uci_dev_class);
	unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME);
	idr_destroy(&uci_idr);
}

module_init(mhi_uci_init);
module_exit(mhi_uci_exit);

MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MHI UCI Driver");