/*
 *  Copyright (C) 2010, Paul Cercueil <paul@crapouillou.net>
 *  JZ4740 Watchdog driver
 *
 *  This program is free software; you can redistribute it and/or modify it
 *  under  the terms of the GNU General  Public License as published by the
 *  Free Software Foundation;  either version 2 of the License, or (at your
 *  option) any later version.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/init.h>
#include <linux/bitops.h>
#include <linux/platform_device.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/device.h>
#include <linux/clk.h>
#include <linux/slab.h>

#include <asm/mach-jz4740/timer.h>

#define JZ_REG_WDT_TIMER_DATA     0x0
#define JZ_REG_WDT_COUNTER_ENABLE 0x4
#define JZ_REG_WDT_TIMER_COUNTER  0x8
#define JZ_REG_WDT_TIMER_CONTROL  0xC

#define JZ_WDT_CLOCK_PCLK 0x1
#define JZ_WDT_CLOCK_RTC  0x2
#define JZ_WDT_CLOCK_EXT  0x4

#define WDT_IN_USE        0
#define WDT_OK_TO_CLOSE   1

#define JZ_WDT_CLOCK_DIV_SHIFT   3

#define JZ_WDT_CLOCK_DIV_1    (0 << JZ_WDT_CLOCK_DIV_SHIFT)
#define JZ_WDT_CLOCK_DIV_4    (1 << JZ_WDT_CLOCK_DIV_SHIFT)
#define JZ_WDT_CLOCK_DIV_16   (2 << JZ_WDT_CLOCK_DIV_SHIFT)
#define JZ_WDT_CLOCK_DIV_64   (3 << JZ_WDT_CLOCK_DIV_SHIFT)
#define JZ_WDT_CLOCK_DIV_256  (4 << JZ_WDT_CLOCK_DIV_SHIFT)
#define JZ_WDT_CLOCK_DIV_1024 (5 << JZ_WDT_CLOCK_DIV_SHIFT)

#define DEFAULT_HEARTBEAT 5
#define MAX_HEARTBEAT     2048

static struct {
	void __iomem *base;
	struct resource	*mem;
	struct clk *rtc_clk;
	unsigned long status;
} jz4740_wdt;

static int heartbeat = DEFAULT_HEARTBEAT;


static void jz4740_wdt_service(void)
{
	writew(0x0, jz4740_wdt.base + JZ_REG_WDT_TIMER_COUNTER);
}

static void jz4740_wdt_set_heartbeat(int new_heartbeat)
{
	unsigned int rtc_clk_rate;
	unsigned int timeout_value;
	unsigned short clock_div = JZ_WDT_CLOCK_DIV_1;

	heartbeat = new_heartbeat;

	rtc_clk_rate = clk_get_rate(jz4740_wdt.rtc_clk);

	timeout_value = rtc_clk_rate * heartbeat;
	while (timeout_value > 0xffff) {
		if (clock_div == JZ_WDT_CLOCK_DIV_1024) {
			/* Requested timeout too high;
			* use highest possible value. */
			timeout_value = 0xffff;
			break;
		}
		timeout_value >>= 2;
		clock_div += (1 << JZ_WDT_CLOCK_DIV_SHIFT);
	}

	writeb(0x0, jz4740_wdt.base + JZ_REG_WDT_COUNTER_ENABLE);
	writew(clock_div, jz4740_wdt.base + JZ_REG_WDT_TIMER_CONTROL);

	writew((u16)timeout_value, jz4740_wdt.base + JZ_REG_WDT_TIMER_DATA);
	writew(0x0, jz4740_wdt.base + JZ_REG_WDT_TIMER_COUNTER);
	writew(clock_div | JZ_WDT_CLOCK_RTC,
		jz4740_wdt.base + JZ_REG_WDT_TIMER_CONTROL);

	writeb(0x1, jz4740_wdt.base + JZ_REG_WDT_COUNTER_ENABLE);
}

static void jz4740_wdt_enable(void)
{
	jz4740_timer_enable_watchdog();
	jz4740_wdt_set_heartbeat(heartbeat);
}

static void jz4740_wdt_disable(void)
{
	jz4740_timer_disable_watchdog();
	writeb(0x0, jz4740_wdt.base + JZ_REG_WDT_COUNTER_ENABLE);
}

static int jz4740_wdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(WDT_IN_USE, &jz4740_wdt.status))
		return -EBUSY;

	jz4740_wdt_enable();

	return nonseekable_open(inode, file);
}

static ssize_t jz4740_wdt_write(struct file *file, const char *data,
		size_t len, loff_t *ppos)
{
	if (len) {
		size_t i;

		clear_bit(WDT_OK_TO_CLOSE, &jz4740_wdt.status);
		for (i = 0; i != len; i++) {
			char c;

			if (get_user(c, data + i))
				return -EFAULT;

			if (c == 'V')
				set_bit(WDT_OK_TO_CLOSE, &jz4740_wdt.status);
		}
		jz4740_wdt_service();
	}

	return len;
}

static const struct watchdog_info ident = {
	.options = WDIOF_KEEPALIVEPING,
	.identity = "jz4740 Watchdog",
};

static long jz4740_wdt_ioctl(struct file *file,
					unsigned int cmd, unsigned long arg)
{
	int ret = -ENOTTY;
	int heartbeat_seconds;

	switch (cmd) {
	case WDIOC_GETSUPPORT:
		ret = copy_to_user((struct watchdog_info *)arg, &ident,
				sizeof(ident)) ? -EFAULT : 0;
		break;

	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		ret = put_user(0, (int *)arg);
		break;

	case WDIOC_KEEPALIVE:
		jz4740_wdt_service();
		return 0;

	case WDIOC_SETTIMEOUT:
		if (get_user(heartbeat_seconds, (int __user *)arg))
			return -EFAULT;

		jz4740_wdt_set_heartbeat(heartbeat_seconds);
		return 0;

	case WDIOC_GETTIMEOUT:
		return put_user(heartbeat, (int *)arg);

	default:
		break;
	}

	return ret;
}

static int jz4740_wdt_release(struct inode *inode, struct file *file)
{
	jz4740_wdt_service();

	if (test_and_clear_bit(WDT_OK_TO_CLOSE, &jz4740_wdt.status))
		jz4740_wdt_disable();

	clear_bit(WDT_IN_USE, &jz4740_wdt.status);
	return 0;
}

static const struct file_operations jz4740_wdt_fops = {
	.owner = THIS_MODULE,
	.llseek = no_llseek,
	.write = jz4740_wdt_write,
	.unlocked_ioctl = jz4740_wdt_ioctl,
	.open = jz4740_wdt_open,
	.release = jz4740_wdt_release,
};

static struct miscdevice jz4740_wdt_miscdev = {
	.minor = WATCHDOG_MINOR,
	.name = "watchdog",
	.fops = &jz4740_wdt_fops,
};

static int __devinit jz4740_wdt_probe(struct platform_device *pdev)
{
	int ret = 0, size;
	struct resource *res;
	struct device *dev = &pdev->dev;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (res == NULL) {
		dev_err(dev, "failed to get memory region resource\n");
		return -ENXIO;
	}

	size = resource_size(res);
	jz4740_wdt.mem = request_mem_region(res->start, size, pdev->name);
	if (jz4740_wdt.mem == NULL) {
		dev_err(dev, "failed to get memory region\n");
		return -EBUSY;
	}

	jz4740_wdt.base = ioremap_nocache(res->start, size);
	if (jz4740_wdt.base == NULL) {
		dev_err(dev, "failed to map memory region\n");
		ret = -EBUSY;
		goto err_release_region;
	}

	jz4740_wdt.rtc_clk = clk_get(NULL, "rtc");
	if (IS_ERR(jz4740_wdt.rtc_clk)) {
		dev_err(dev, "cannot find RTC clock\n");
		ret = PTR_ERR(jz4740_wdt.rtc_clk);
		goto err_iounmap;
	}

	ret = misc_register(&jz4740_wdt_miscdev);
	if (ret < 0) {
		dev_err(dev, "cannot register misc device\n");
		goto err_disable_clk;
	}

	return 0;

err_disable_clk:
	clk_put(jz4740_wdt.rtc_clk);
err_iounmap:
	iounmap(jz4740_wdt.base);
err_release_region:
	release_mem_region(jz4740_wdt.mem->start,
			resource_size(jz4740_wdt.mem));
	return ret;
}


static int __devexit jz4740_wdt_remove(struct platform_device *pdev)
{
	jz4740_wdt_disable();
	misc_deregister(&jz4740_wdt_miscdev);
	clk_put(jz4740_wdt.rtc_clk);

	iounmap(jz4740_wdt.base);
	jz4740_wdt.base = NULL;

	release_mem_region(jz4740_wdt.mem->start,
				resource_size(jz4740_wdt.mem));
	jz4740_wdt.mem = NULL;

	return 0;
}


static struct platform_driver jz4740_wdt_driver = {
	.probe = jz4740_wdt_probe,
	.remove = __devexit_p(jz4740_wdt_remove),
	.driver = {
		.name = "jz4740-wdt",
		.owner	= THIS_MODULE,
	},
};


static int __init jz4740_wdt_init(void)
{
	return platform_driver_register(&jz4740_wdt_driver);
}
module_init(jz4740_wdt_init);

static void __exit jz4740_wdt_exit(void)
{
	platform_driver_unregister(&jz4740_wdt_driver);
}
module_exit(jz4740_wdt_exit);

MODULE_AUTHOR("Paul Cercueil <paul@crapouillou.net>");
MODULE_DESCRIPTION("jz4740 Watchdog Driver");

module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat,
		"Watchdog heartbeat period in seconds from 1 to "
		__MODULE_STRING(MAX_HEARTBEAT) ", default "
		__MODULE_STRING(DEFAULT_HEARTBEAT));

MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS("platform:jz4740-wdt");