#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/errno.h>
#include <linux/poll.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/miscdevice.h>
#include <linux/timer.h>
#include <linux/jiffies.h>
#include <linux/bt-host.h>

#define DEVICE_NAME	"bt-host"

#define BT_IO_BASE	0xe4
#define BT_IRQ		10

#define BT_CR0		0x0
#define   BT_CR0_IO_BASE		16
#define   BT_CR0_IRQ			12
#define   BT_CR0_EN_CLR_SLV_RDP		0x8
#define   BT_CR0_EN_CLR_SLV_WRP		0x4
#define   BT_CR0_ENABLE_IBT		0x1
#define BT_CR1		0x4
#define   BT_CR1_IRQ_H2B	0x01
#define   BT_CR1_IRQ_HBUSY	0x40
#define BT_CR2		0x8
#define   BT_CR2_IRQ_H2B	0x01
#define   BT_CR2_IRQ_HBUSY	0x40
#define BT_CR3		0xc
#define BT_CTRL		0x10
#define   BT_CTRL_B_BUSY		0x80
#define   BT_CTRL_H_BUSY		0x40
#define   BT_CTRL_OEM0			0x20
#define   BT_CTRL_SMS_ATN		0x10
#define   BT_CTRL_B2H_ATN		0x08
#define   BT_CTRL_H2B_ATN		0x04
#define   BT_CTRL_CLR_RD_PTR		0x02
#define   BT_CTRL_CLR_WR_PTR		0x01
#define BT_BMC2HOST	0x14
#define BT_INTMASK	0x18
#define   BT_INTMASK_B2H_IRQEN		0x01
#define   BT_INTMASK_B2H_IRQ		0x02
#define   BT_INTMASK_BMC_HWRST		0x80

struct bt_host {
	struct device		dev;
	struct miscdevice	miscdev;
	void			*base;
	int			open_count;
	int			irq;
	wait_queue_head_t	queue;
	struct timer_list	poll_timer;
};

static u8 bt_inb(struct bt_host *bt_host, int reg)
{
	return ioread8(bt_host->base + reg);
}

static void bt_outb(struct bt_host *bt_host, u8 data, int reg)
{
	iowrite8(data, bt_host->base + reg);
}

static void clr_rd_ptr(struct bt_host *bt_host)
{
	bt_outb(bt_host, BT_CTRL_CLR_RD_PTR, BT_CTRL);
}

static void clr_wr_ptr(struct bt_host *bt_host)
{
	bt_outb(bt_host, BT_CTRL_CLR_WR_PTR, BT_CTRL);
}

static void clr_h2b_atn(struct bt_host *bt_host)
{
	bt_outb(bt_host, BT_CTRL_H2B_ATN, BT_CTRL);
}

static void set_b_busy(struct bt_host *bt_host)
{
	if (!(bt_inb(bt_host, BT_CTRL) & BT_CTRL_B_BUSY))
		bt_outb(bt_host, BT_CTRL_B_BUSY, BT_CTRL);
}

static void clr_b_busy(struct bt_host *bt_host)
{
	if (bt_inb(bt_host, BT_CTRL) & BT_CTRL_B_BUSY)
		bt_outb(bt_host, BT_CTRL_B_BUSY, BT_CTRL);
}

static void set_b2h_atn(struct bt_host *bt_host)
{
	bt_outb(bt_host, BT_CTRL_B2H_ATN, BT_CTRL);
}

static u8 bt_read(struct bt_host *bt_host)
{
	return bt_inb(bt_host, BT_BMC2HOST);
}

static void bt_write(struct bt_host *bt_host, u8 c)
{
	bt_outb(bt_host, c, BT_BMC2HOST);
}

static void set_sms_atn(struct bt_host *bt_host)
{
	bt_outb(bt_host, BT_CTRL_SMS_ATN, BT_CTRL);
}

static struct bt_host *file_bt_host(struct file *file)
{
	return container_of(file->private_data, struct bt_host, miscdev);
}

static int bt_host_open(struct inode *inode, struct file *file)
{
	struct bt_host *bt_host = file_bt_host(file);

	clr_b_busy(bt_host);

	return 0;
}

static ssize_t bt_host_read(struct file *file, char __user *buf,
				size_t count, loff_t *ppos)
{
	struct bt_host *bt_host = file_bt_host(file);
	char __user *p = buf;
	u8 len;

	if (!access_ok(VERIFY_WRITE, buf, count))
		return -EFAULT;

	WARN_ON(*ppos);

	if (wait_event_interruptible(bt_host->queue,
				bt_inb(bt_host, BT_CTRL) & BT_CTRL_H2B_ATN))
		return -ERESTARTSYS;

	set_b_busy(bt_host);
	clr_h2b_atn(bt_host);
	clr_rd_ptr(bt_host);

	len = bt_read(bt_host);
	__put_user(len, p++);

	/* We pass the length back as well */
	if (len + 1 > count)
		len = count - 1;

	while(len) {
		if (__put_user(bt_read(bt_host), p))
			return -EFAULT;
		len--; p++;
	}

	clr_b_busy(bt_host);

	return p - buf;
}

static ssize_t bt_host_write(struct file *file, const char __user *buf,
				size_t count, loff_t *ppos)
{
	struct bt_host *bt_host = file_bt_host(file);
	const char __user *p = buf;
	u8 c;

	if (!access_ok(VERIFY_READ, buf, count))
		return -EFAULT;

	WARN_ON(*ppos);

	/* There's no interrupt for clearing host busy so we have to
	 * poll */
	if (wait_event_interruptible(bt_host->queue,
				!(bt_inb(bt_host, BT_CTRL) &
					(BT_CTRL_H_BUSY | BT_CTRL_B2H_ATN))))
		return -ERESTARTSYS;

	clr_wr_ptr(bt_host);

	while (count) {
		if (__get_user(c, p))
			return -EFAULT;

		bt_write(bt_host, c);
		count--; p++;
	}

	set_b2h_atn(bt_host);

	return p - buf;
}

static long bt_host_ioctl(struct file *file, unsigned int cmd,
		unsigned long param)
{
	struct bt_host *bt_host = file_bt_host(file);
	switch (cmd) {
	case BT_HOST_IOCTL_SMS_ATN:
		set_sms_atn(bt_host);
		return 0;
	}
	return -EINVAL;
}

static int bt_host_release(struct inode *inode, struct file *file)
{
	struct bt_host *bt_host = file_bt_host(file);
	set_b_busy(bt_host);
	return 0;
}

static unsigned int bt_host_poll(struct file *file, poll_table *wait)
{
	struct bt_host *bt_host = file_bt_host(file);
	unsigned int mask = 0;
	uint8_t ctrl;

	poll_wait(file, &bt_host->queue, wait);

	ctrl = bt_inb(bt_host, BT_CTRL);

	if (ctrl & BT_CTRL_H2B_ATN)
		mask |= POLLIN;

	if (!(ctrl & (BT_CTRL_H_BUSY | BT_CTRL_B2H_ATN)))
		mask |= POLLOUT;

	return mask;
}

static const struct file_operations bt_host_fops = {
	.owner		= THIS_MODULE,
	.open		= bt_host_open,
	.read		= bt_host_read,
	.write		= bt_host_write,
	.release	= bt_host_release,
	.poll		= bt_host_poll,
	.unlocked_ioctl	= bt_host_ioctl,
};

static void poll_timer(unsigned long data)
{
	struct bt_host *bt_host = (void *)data;
	bt_host->poll_timer.expires += msecs_to_jiffies(500);
	wake_up(&bt_host->queue);
	add_timer(&bt_host->poll_timer);
}

irqreturn_t bt_host_irq(int irq, void *arg)
{
	struct bt_host *bt_host = arg;
	uint32_t reg;

	reg = ioread32(bt_host->base + BT_CR2);
	reg &= BT_CR2_IRQ_H2B | BT_CR2_IRQ_HBUSY;
	if (!reg)
		return IRQ_NONE;

	/* ack pending IRQs */
	iowrite32(reg, bt_host->base + BT_CR2);

	wake_up(&bt_host->queue);
	return IRQ_HANDLED;
}

static int bt_host_config_irq(struct bt_host *bt_host,
		struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	uint32_t reg;
	int rc;

	bt_host->irq = irq_of_parse_and_map(dev->of_node, 0);
	if (!bt_host->irq)
		return -ENODEV;

	rc = devm_request_irq(dev, bt_host->irq, bt_host_irq, IRQF_SHARED,
			DEVICE_NAME, bt_host);
	if (rc < 0) {
		dev_warn(dev, "Unable to request IRQ %d\n", bt_host->irq);
		bt_host->irq = 0;
		return rc;
	}

	/* Configure IRQs on the host clearing the H2B and HBUSY bits;
	 * H2B will be asserted when the host has data for us; HBUSY
	 * will be cleared (along with B2H) when we can write the next
	 * message to the BT buffer */
	reg = ioread32(bt_host->base + BT_CR1);
	reg |= BT_CR1_IRQ_H2B | BT_CR1_IRQ_HBUSY;
	iowrite32(reg, bt_host->base + BT_CR1);

	return 0;
}

static int bt_host_probe(struct platform_device *pdev)
{
	struct bt_host *bt_host;
	struct device *dev;
	struct resource *res;
	int rc;

	if (!pdev || !pdev->dev.of_node)
		return -ENODEV;

	dev = &pdev->dev;
	dev_info(dev, "Found bt host device\n");

	bt_host = devm_kzalloc(dev, sizeof(*bt_host), GFP_KERNEL);
	if (!bt_host)
		return -ENOMEM;

	dev_set_drvdata(&pdev->dev, bt_host);

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		dev_err(dev, "Unable to find resources\n");
		rc = -ENXIO;
		goto out_free;
	}

	bt_host->base = devm_ioremap_resource(&pdev->dev, res);
	if (!bt_host->base) {
		rc = -ENOMEM;
		goto out_free;
	}

	init_waitqueue_head(&bt_host->queue);

	bt_host->miscdev.minor	= MISC_DYNAMIC_MINOR,
	bt_host->miscdev.name	= DEVICE_NAME,
	bt_host->miscdev.fops	= &bt_host_fops,
	bt_host->miscdev.parent = dev;
	rc = misc_register(&bt_host->miscdev);
	if (rc) {
		dev_err(dev, "Unable to register device\n");
		goto out_unmap;
	}

	bt_host_config_irq(bt_host, pdev);

	if (bt_host->irq) {
		dev_info(dev, "Using IRQ %d\n", bt_host->irq);
	} else {
		dev_info(dev, "No IRQ; using timer\n");
		init_timer(&bt_host->poll_timer);
		bt_host->poll_timer.function = poll_timer;
		bt_host->poll_timer.data = (unsigned long)bt_host;
		bt_host->poll_timer.expires = jiffies + msecs_to_jiffies(10);
		add_timer(&bt_host->poll_timer);
	}

	iowrite32((BT_IO_BASE << BT_CR0_IO_BASE) |
		  (BT_IRQ << BT_CR0_IRQ) |
		  BT_CR0_EN_CLR_SLV_RDP |
		  BT_CR0_EN_CLR_SLV_WRP |
		  BT_CR0_ENABLE_IBT,
		  bt_host->base + BT_CR0);

	clr_b_busy(bt_host);

	return 0;

out_unmap:
	devm_iounmap(&pdev->dev, bt_host->base);

out_free:
	devm_kfree(dev, bt_host);
	return rc;

}

static int bt_host_remove(struct platform_device *pdev)
{
	struct bt_host *bt_host = dev_get_drvdata(&pdev->dev);
	misc_deregister(&bt_host->miscdev);
	if (!bt_host->irq)
		del_timer_sync(&bt_host->poll_timer);
	devm_iounmap(&pdev->dev, bt_host->base);
	devm_kfree(&pdev->dev, bt_host);
	bt_host = NULL;

	return 0;
}

static const struct of_device_id bt_host_match[] = {
	{ .compatible = "aspeed,bt-host" },
	{ },
};

static struct platform_driver bt_host_driver = {
	.driver = {
		.name		= DEVICE_NAME,
		.owner		= THIS_MODULE,
		.of_match_table = bt_host_match,
	},
	.probe = bt_host_probe,
	.remove = bt_host_remove,
};

module_platform_driver(bt_host_driver);

MODULE_DEVICE_TABLE(of, bt_host_match);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alistair Popple <alistair@popple.id.au>");
MODULE_DESCRIPTION("Linux device interface to the BT interface");