/*
 * txx9wdt: A Hardware Watchdog Driver for TXx9 SoCs
 *
 * Copyright (C) 2007 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <asm/txx9tmr.h>

#define TIMER_MARGIN	60		/* Default is 60 seconds */

static int timeout = TIMER_MARGIN;	/* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
	"Watchdog timeout in seconds. "
	"(0<timeout<((2^" __MODULE_STRING(TXX9_TIMER_BITS) ")/(IMCLK/256)), "
	"default=" __MODULE_STRING(TIMER_MARGIN) ")");

static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout,
	"Watchdog cannot be stopped once started "
	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

#define WD_TIMER_CCD	7	/* 1/256 */
#define WD_TIMER_CLK	(clk_get_rate(txx9_imclk) / (2 << WD_TIMER_CCD))
#define WD_MAX_TIMEOUT	((0xffffffff >> (32 - TXX9_TIMER_BITS)) / WD_TIMER_CLK)

static unsigned long txx9wdt_alive;
static int expect_close;
static struct txx9_tmr_reg __iomem *txx9wdt_reg;
static struct clk *txx9_imclk;
static DECLARE_LOCK(txx9_lock);

static void txx9wdt_ping(void)
{
	spin_lock(&txx9_lock);
	__raw_writel(TXx9_TMWTMR_TWIE | TXx9_TMWTMR_TWC, &txx9wdt_reg->wtmr);
	spin_unlock(&txx9_lock);
}

static void txx9wdt_start(void)
{
	spin_lock(&txx9_lock);
	__raw_writel(WD_TIMER_CLK * timeout, &txx9wdt_reg->cpra);
	__raw_writel(WD_TIMER_CCD, &txx9wdt_reg->ccdr);
	__raw_writel(0, &txx9wdt_reg->tisr);	/* clear pending interrupt */
	__raw_writel(TXx9_TMTCR_TCE | TXx9_TMTCR_CCDE | TXx9_TMTCR_TMODE_WDOG,
		     &txx9wdt_reg->tcr);
	__raw_writel(TXx9_TMWTMR_TWIE | TXx9_TMWTMR_TWC, &txx9wdt_reg->wtmr);
	spin_unlock(&txx9_lock);
}

static void txx9wdt_stop(void)
{
	spin_lock(&txx9_lock);
	__raw_writel(TXx9_TMWTMR_WDIS, &txx9wdt_reg->wtmr);
	__raw_writel(__raw_readl(&txx9wdt_reg->tcr) & ~TXx9_TMTCR_TCE,
		     &txx9wdt_reg->tcr);
	spin_unlock(&txx9_lock);
}

static int txx9wdt_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(0, &txx9wdt_alive))
		return -EBUSY;

	if (__raw_readl(&txx9wdt_reg->tcr) & TXx9_TMTCR_TCE) {
		clear_bit(0, &txx9wdt_alive);
		return -EBUSY;
	}

	if (nowayout)
		__module_get(THIS_MODULE);

	txx9wdt_start();
	return nonseekable_open(inode, file);
}

static int txx9wdt_release(struct inode *inode, struct file *file)
{
	if (expect_close)
		txx9wdt_stop();
	else {
		printk(KERN_CRIT "txx9wdt: "
		       "Unexpected close, not stopping watchdog!\n");
		txx9wdt_ping();
	}
	clear_bit(0, &txx9wdt_alive);
	expect_close = 0;
	return 0;
}

static ssize_t txx9wdt_write(struct file *file, const char __user *data,
			     size_t len, loff_t *ppos)
{
	if (len) {
		if (!nowayout) {
			size_t i;

			expect_close = 0;
			for (i = 0; i != len; i++) {
				char c;
				if (get_user(c, data + i))
					return -EFAULT;
				if (c == 'V')
					expect_close = 1;
			}
		}
		txx9wdt_ping();
	}
	return len;
}

static long txx9wdt_ioctl(struct file *file, unsigned int cmd,
							unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	int new_timeout;
	static const struct watchdog_info ident = {
		.options =		WDIOF_SETTIMEOUT |
					WDIOF_KEEPALIVEPING |
					WDIOF_MAGICCLOSE,
		.firmware_version =	0,
		.identity =		"Hardware Watchdog for TXx9",
	};

	switch (cmd) {
	default:
		return -ENOTTY;
	case WDIOC_GETSUPPORT:
		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
	case WDIOC_GETSTATUS:
	case WDIOC_GETBOOTSTATUS:
		return put_user(0, p);
	case WDIOC_KEEPALIVE:
		txx9wdt_ping();
		return 0;
	case WDIOC_SETTIMEOUT:
		if (get_user(new_timeout, p))
			return -EFAULT;
		if (new_timeout < 1 || new_timeout > WD_MAX_TIMEOUT)
			return -EINVAL;
		timeout = new_timeout;
		txx9wdt_stop();
		txx9wdt_start();
		/* Fall */
	case WDIOC_GETTIMEOUT:
		return put_user(timeout, p);
	}
}

static int txx9wdt_notify_sys(struct notifier_block *this, unsigned long code,
	void *unused)
{
	if (code == SYS_DOWN || code == SYS_HALT)
		txx9wdt_stop();
	return NOTIFY_DONE;
}

static const struct file_operations txx9wdt_fops = {
	.owner		=	THIS_MODULE,
	.llseek		=	no_llseek,
	.write		=	txx9wdt_write,
	.unlocked_ioctl =	txx9wdt_ioctl,
	.open		=	txx9wdt_open,
	.release	=	txx9wdt_release,
};

static struct miscdevice txx9wdt_miscdev = {
	.minor	=	WATCHDOG_MINOR,
	.name	=	"watchdog",
	.fops	=	&txx9wdt_fops,
};

static struct notifier_block txx9wdt_notifier = {
	.notifier_call = txx9wdt_notify_sys
};

static int __init txx9wdt_probe(struct platform_device *dev)
{
	struct resource *res;
	int ret;

	txx9_imclk = clk_get(NULL, "imbus_clk");
	if (IS_ERR(txx9_imclk)) {
		ret = PTR_ERR(txx9_imclk);
		txx9_imclk = NULL;
		goto exit;
	}
	ret = clk_enable(txx9_imclk);
	if (ret) {
		clk_put(txx9_imclk);
		txx9_imclk = NULL;
		goto exit;
	}

	res = platform_get_resource(dev, IORESOURCE_MEM, 0);
	if (!res)
		goto exit_busy;
	if (!devm_request_mem_region(&dev->dev,
				     res->start, res->end - res->start + 1,
				     "txx9wdt"))
		goto exit_busy;
	txx9wdt_reg = devm_ioremap(&dev->dev,
				   res->start, res->end - res->start + 1);
	if (!txx9wdt_reg)
		goto exit_busy;

	ret = register_reboot_notifier(&txx9wdt_notifier);
	if (ret)
		goto exit;

	ret = misc_register(&txx9wdt_miscdev);
	if (ret) {
		unregister_reboot_notifier(&txx9wdt_notifier);
		goto exit;
	}

	printk(KERN_INFO "Hardware Watchdog Timer for TXx9: "
	       "timeout=%d sec (max %ld) (nowayout= %d)\n",
	       timeout, WD_MAX_TIMEOUT, nowayout);

	return 0;
exit_busy:
	ret = -EBUSY;
exit:
	if (txx9_imclk) {
		clk_disable(txx9_imclk);
		clk_put(txx9_imclk);
	}
	return ret;
}

static int __exit txx9wdt_remove(struct platform_device *dev)
{
	misc_deregister(&txx9wdt_miscdev);
	unregister_reboot_notifier(&txx9wdt_notifier);
	clk_disable(txx9_imclk);
	clk_put(txx9_imclk);
	return 0;
}

static struct platform_driver txx9wdt_driver = {
	.remove = __exit_p(txx9wdt_remove),
	.driver = {
		.name = "txx9wdt",
		.owner = THIS_MODULE,
	},
};

static int __init watchdog_init(void)
{
	return platform_driver_probe(&txx9wdt_driver, txx9wdt_probe);
}

static void __exit watchdog_exit(void)
{
	platform_driver_unregister(&txx9wdt_driver);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_DESCRIPTION("TXx9 Watchdog Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS("platform:txx9wdt");