/*
 * drivers/misc/goldfish_audio.c
 *
 * Copyright (C) 2007 Google, Inc.
 * Copyright (C) 2012 Intel, Inc.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/fs.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/pci.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/sched.h>
#include <linux/dma-mapping.h>
#include <linux/uaccess.h>

MODULE_AUTHOR("Google, Inc.");
MODULE_DESCRIPTION("Android QEMU Audio Driver");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.0");

struct goldfish_audio {
	char __iomem *reg_base;
	int irq;
	spinlock_t lock;
	wait_queue_head_t wait;

	char __iomem *buffer_virt;      /* combined buffer virtual address */
	unsigned long buffer_phys;      /* combined buffer physical address */

	char __iomem *write_buffer1;    /* write buffer 1 virtual address */
	char __iomem *write_buffer2;    /* write buffer 2 virtual address */
	char __iomem *read_buffer;      /* read buffer virtual address */
	int buffer_status;
	int read_supported;         /* true if we have audio input support */
};

/*
 *  We will allocate two read buffers and two write buffers.
 *  Having two read buffers facilitate stereo -> mono conversion.
 *  Having two write buffers facilitate interleaved IO.
 */
#define READ_BUFFER_SIZE        16384
#define WRITE_BUFFER_SIZE       16384
#define COMBINED_BUFFER_SIZE    ((2 * READ_BUFFER_SIZE) + \
					(2 * WRITE_BUFFER_SIZE))

#define AUDIO_READ(data, addr)		(readl(data->reg_base + addr))
#define AUDIO_WRITE(data, addr, x)	(writel(x, data->reg_base + addr))

/*
 *  temporary variable used between goldfish_audio_probe() and
 *  goldfish_audio_open()
 */
static struct goldfish_audio *audio_data;

enum {
	/* audio status register */
	AUDIO_INT_STATUS	= 0x00,
	/* set this to enable IRQ */
	AUDIO_INT_ENABLE	= 0x04,
	/* set these to specify buffer addresses */
	AUDIO_SET_WRITE_BUFFER_1 = 0x08,
	AUDIO_SET_WRITE_BUFFER_2 = 0x0C,
	/* set number of bytes in buffer to write */
	AUDIO_WRITE_BUFFER_1  = 0x10,
	AUDIO_WRITE_BUFFER_2  = 0x14,

	/* true if audio input is supported */
	AUDIO_READ_SUPPORTED = 0x18,
	/* buffer to use for audio input */
	AUDIO_SET_READ_BUFFER = 0x1C,

	/* driver writes number of bytes to read */
	AUDIO_START_READ  = 0x20,

	/* number of bytes available in read buffer */
	AUDIO_READ_BUFFER_AVAILABLE  = 0x24,

	/* AUDIO_INT_STATUS bits */

	/* this bit set when it is safe to write more bytes to the buffer */
	AUDIO_INT_WRITE_BUFFER_1_EMPTY	= 1U << 0,
	AUDIO_INT_WRITE_BUFFER_2_EMPTY	= 1U << 1,
	AUDIO_INT_READ_BUFFER_FULL      = 1U << 2,

	AUDIO_INT_MASK                  = AUDIO_INT_WRITE_BUFFER_1_EMPTY |
					  AUDIO_INT_WRITE_BUFFER_2_EMPTY |
					  AUDIO_INT_READ_BUFFER_FULL,
};


static atomic_t open_count = ATOMIC_INIT(0);


static ssize_t goldfish_audio_read(struct file *fp, char __user *buf,
						size_t count, loff_t *pos)
{
	struct goldfish_audio *data = fp->private_data;
	int length;
	int result = 0;

	if (!data->read_supported)
		return -ENODEV;

	while (count > 0) {
		length = (count > READ_BUFFER_SIZE ? READ_BUFFER_SIZE : count);
		AUDIO_WRITE(data, AUDIO_START_READ, length);

		wait_event_interruptible(data->wait,
			(data->buffer_status & AUDIO_INT_READ_BUFFER_FULL));

		length = AUDIO_READ(data,
						AUDIO_READ_BUFFER_AVAILABLE);

		/* copy data to user space */
		if (copy_to_user(buf, data->read_buffer, length))
			return -EFAULT;

		result += length;
		buf += length;
		count -= length;
	}
	return result;
}

static ssize_t goldfish_audio_write(struct file *fp, const char __user *buf,
						 size_t count, loff_t *pos)
{
	struct goldfish_audio *data = fp->private_data;
	unsigned long irq_flags;
	ssize_t result = 0;
	char __iomem *kbuf;

	while (count > 0) {
		ssize_t copy = count;
		if (copy > WRITE_BUFFER_SIZE)
			copy = WRITE_BUFFER_SIZE;
		wait_event_interruptible(data->wait, (data->buffer_status &
					(AUDIO_INT_WRITE_BUFFER_1_EMPTY |
					AUDIO_INT_WRITE_BUFFER_2_EMPTY)));

		if ((data->buffer_status & AUDIO_INT_WRITE_BUFFER_1_EMPTY) != 0)
			kbuf = data->write_buffer1;
		else
			kbuf = data->write_buffer2;

		/* copy from user space to the appropriate buffer */
		if (copy_from_user(kbuf, buf, copy)) {
			result = -EFAULT;
			break;
		}

		spin_lock_irqsave(&data->lock, irq_flags);
		/*
		 *  clear the buffer empty flag, and signal the emulator
		 *  to start writing the buffer
		 */
		if (kbuf == data->write_buffer1) {
			data->buffer_status &= ~AUDIO_INT_WRITE_BUFFER_1_EMPTY;
			AUDIO_WRITE(data, AUDIO_WRITE_BUFFER_1, copy);
		} else {
			data->buffer_status &= ~AUDIO_INT_WRITE_BUFFER_2_EMPTY;
			AUDIO_WRITE(data, AUDIO_WRITE_BUFFER_2, copy);
		}
		spin_unlock_irqrestore(&data->lock, irq_flags);

		buf += copy;
		result += copy;
		count -= copy;
	}
	return result;
}

static int goldfish_audio_open(struct inode *ip, struct file *fp)
{
	if (!audio_data)
		return -ENODEV;

	if (atomic_inc_return(&open_count) == 1) {
		fp->private_data = audio_data;
		audio_data->buffer_status = (AUDIO_INT_WRITE_BUFFER_1_EMPTY |
					     AUDIO_INT_WRITE_BUFFER_2_EMPTY);
		AUDIO_WRITE(audio_data, AUDIO_INT_ENABLE, AUDIO_INT_MASK);
		return 0;
	} else {
		atomic_dec(&open_count);
		return -EBUSY;
	}
}

static int goldfish_audio_release(struct inode *ip, struct file *fp)
{
	atomic_dec(&open_count);
	/* FIXME: surely this is wrong for the multi-opened case */
	AUDIO_WRITE(audio_data, AUDIO_INT_ENABLE, 0);
	return 0;
}

static long goldfish_audio_ioctl(struct file *fp, unsigned int cmd,
							unsigned long arg)
{
	/* temporary workaround, until we switch to the ALSA API */
	if (cmd == 315)
		return -1;
	else
		return 0;
}

static irqreturn_t goldfish_audio_interrupt(int irq, void *dev_id)
{
	unsigned long irq_flags;
	struct goldfish_audio	*data = dev_id;
	u32 status;

	spin_lock_irqsave(&data->lock, irq_flags);

	/* read buffer status flags */
	status = AUDIO_READ(data, AUDIO_INT_STATUS);
	status &= AUDIO_INT_MASK;
	/*
	 *  if buffers are newly empty, wake up blocked
	 *  goldfish_audio_write() call
	 */
	if (status) {
		data->buffer_status = status;
		wake_up(&data->wait);
	}

	spin_unlock_irqrestore(&data->lock, irq_flags);
	return status ? IRQ_HANDLED : IRQ_NONE;
}

/* file operations for /dev/eac */
static const struct file_operations goldfish_audio_fops = {
	.owner = THIS_MODULE,
	.read = goldfish_audio_read,
	.write = goldfish_audio_write,
	.open = goldfish_audio_open,
	.release = goldfish_audio_release,
	.unlocked_ioctl = goldfish_audio_ioctl,
};

static struct miscdevice goldfish_audio_device = {
	.minor = MISC_DYNAMIC_MINOR,
	.name = "eac",
	.fops = &goldfish_audio_fops,
};

static int goldfish_audio_probe(struct platform_device *pdev)
{
	int ret;
	struct resource *r;
	struct goldfish_audio *data;
	dma_addr_t buf_addr;

	data = kzalloc(sizeof(*data), GFP_KERNEL);
	if (data == NULL) {
		ret = -ENOMEM;
		goto err_data_alloc_failed;
	}
	spin_lock_init(&data->lock);
	init_waitqueue_head(&data->wait);
	platform_set_drvdata(pdev, data);

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (r == NULL) {
		dev_err(&pdev->dev, "platform_get_resource failed\n");
		ret = -ENODEV;
		goto err_no_io_base;
	}
	data->reg_base = ioremap(r->start, PAGE_SIZE);
	if (data->reg_base == NULL) {
		ret = -ENOMEM;
		goto err_no_io_base;
	}

	data->irq = platform_get_irq(pdev, 0);
	if (data->irq < 0) {
		dev_err(&pdev->dev, "platform_get_irq failed\n");
		ret = -ENODEV;
		goto err_no_irq;
	}
	data->buffer_virt = dma_alloc_coherent(&pdev->dev,
				COMBINED_BUFFER_SIZE, &buf_addr, GFP_KERNEL);
	if (data->buffer_virt == 0) {
		ret = -ENOMEM;
		dev_err(&pdev->dev, "allocate buffer failed\n");
		goto err_alloc_write_buffer_failed;
	}
	data->buffer_phys = buf_addr;
	data->write_buffer1 = data->buffer_virt;
	data->write_buffer2 = data->buffer_virt + WRITE_BUFFER_SIZE;
	data->read_buffer = data->buffer_virt + 2 * WRITE_BUFFER_SIZE;

	ret = request_irq(data->irq, goldfish_audio_interrupt,
					IRQF_SHARED, pdev->name, data);
	if (ret) {
		dev_err(&pdev->dev, "request_irq failed\n");
		goto err_request_irq_failed;
	}

	ret = misc_register(&goldfish_audio_device);
	if (ret) {
		dev_err(&pdev->dev,
			"misc_register returned %d in goldfish_audio_init\n",
								ret);
		goto err_misc_register_failed;
	}

	AUDIO_WRITE(data, AUDIO_SET_WRITE_BUFFER_1, buf_addr);
	AUDIO_WRITE(data, AUDIO_SET_WRITE_BUFFER_2,
						buf_addr + WRITE_BUFFER_SIZE);

	data->read_supported = AUDIO_READ(data, AUDIO_READ_SUPPORTED);
	if (data->read_supported)
		AUDIO_WRITE(data, AUDIO_SET_READ_BUFFER,
					buf_addr + 2 * WRITE_BUFFER_SIZE);

	audio_data = data;
	return 0;

err_misc_register_failed:
err_request_irq_failed:
	dma_free_coherent(&pdev->dev, COMBINED_BUFFER_SIZE,
					data->buffer_virt, data->buffer_phys);
err_alloc_write_buffer_failed:
err_no_irq:
	iounmap(data->reg_base);
err_no_io_base:
	kfree(data);
err_data_alloc_failed:
	return ret;
}

static int goldfish_audio_remove(struct platform_device *pdev)
{
	struct goldfish_audio *data = platform_get_drvdata(pdev);

	misc_deregister(&goldfish_audio_device);
	free_irq(data->irq, data);
	dma_free_coherent(&pdev->dev, COMBINED_BUFFER_SIZE,
					data->buffer_virt, data->buffer_phys);
	iounmap(data->reg_base);
	kfree(data);
	audio_data = NULL;
	return 0;
}

static struct platform_driver goldfish_audio_driver = {
	.probe		= goldfish_audio_probe,
	.remove		= goldfish_audio_remove,
	.driver = {
		.name = "goldfish_audio"
	}
};

module_platform_driver(goldfish_audio_driver);