// SPDX-License-Identifier: GPL-2.0+
/*
 *	Watchdog driver for the SA11x0/PXA2xx
 *
 *	(c) Copyright 2000 Oleg Drokin <green@crimea.edu>
 *	    Based on SoftDog driver by Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 *	Neither Oleg Drokin nor iXcelerator.com admit liability nor provide
 *	warranty for any of this software. This material is provided
 *	"AS-IS" and at no charge.
 *
 *	(c) Copyright 2000           Oleg Drokin <green@crimea.edu>
 *
 *	27/11/2000 Initial release
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

#define REG_OSMR0  	0x0000  /* OS timer Match Reg. 0 */
#define REG_OSMR1  	0x0004  /* OS timer Match Reg. 1 */
#define REG_OSMR2  	0x0008  /* OS timer Match Reg. 2 */
#define REG_OSMR3  	0x000c  /* OS timer Match Reg. 3 */
#define REG_OSCR   	0x0010  /* OS timer Counter Reg. */
#define REG_OSSR   	0x0014  /* OS timer Status Reg. */
#define REG_OWER   	0x0018  /* OS timer Watch-dog Enable Reg. */
#define REG_OIER  	0x001C  /* OS timer Interrupt Enable Reg. */

#define OSSR_M3		(1 << 3)	/* Match status channel 3 */
#define OSSR_M2		(1 << 2)	/* Match status channel 2 */
#define OSSR_M1		(1 << 1)	/* Match status channel 1 */
#define OSSR_M0		(1 << 0)	/* Match status channel 0 */

#define OWER_WME	(1 << 0)	/* Watchdog Match Enable */

#define OIER_E3		(1 << 3)	/* Interrupt enable channel 3 */
#define OIER_E2		(1 << 2)	/* Interrupt enable channel 2 */
#define OIER_E1		(1 << 1)	/* Interrupt enable channel 1 */
#define OIER_E0		(1 << 0)	/* Interrupt enable channel 0 */

static unsigned long oscr_freq;
static unsigned long sa1100wdt_users;
static unsigned int pre_margin;
static int boot_status;
static void __iomem *reg_base;

static inline void sa1100_wr(u32 val, u32 offset)
{
	writel_relaxed(val, reg_base + offset);
}

static inline u32 sa1100_rd(u32 offset)
{
	return readl_relaxed(reg_base + offset);
}

/*
 *	Allow only one person to hold it open
 */
static int sa1100dog_open(struct inode *inode, struct file *file)
{
	if (test_and_set_bit(1, &sa1100wdt_users))
		return -EBUSY;

	/* Activate SA1100 Watchdog timer */
	sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
	sa1100_wr(OSSR_M3, REG_OSSR);
	sa1100_wr(OWER_WME, REG_OWER);
	sa1100_wr(sa1100_rd(REG_OIER) | OIER_E3, REG_OIER);
	return stream_open(inode, file);
}

/*
 * The watchdog cannot be disabled.
 *
 * Previous comments suggested that turning off the interrupt by
 * clearing REG_OIER[E3] would prevent the watchdog timing out but this
 * does not appear to be true (at least on the PXA255).
 */
static int sa1100dog_release(struct inode *inode, struct file *file)
{
	pr_crit("Device closed - timer will not stop\n");
	clear_bit(1, &sa1100wdt_users);
	return 0;
}

static ssize_t sa1100dog_write(struct file *file, const char __user *data,
						size_t len, loff_t *ppos)
{
	if (len)
		/* Refresh OSMR3 timer. */
		sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
	return len;
}

static const struct watchdog_info ident = {
	.options	= WDIOF_CARDRESET | WDIOF_SETTIMEOUT
				| WDIOF_KEEPALIVEPING,
	.identity	= "SA1100/PXA255 Watchdog",
	.firmware_version	= 1,
};

static long sa1100dog_ioctl(struct file *file, unsigned int cmd,
							unsigned long arg)
{
	int ret = -ENOTTY;
	int time;
	void __user *argp = (void __user *)arg;
	int __user *p = argp;

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

	case WDIOC_GETSTATUS:
		ret = put_user(0, p);
		break;

	case WDIOC_GETBOOTSTATUS:
		ret = put_user(boot_status, p);
		break;

	case WDIOC_KEEPALIVE:
		sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
		ret = 0;
		break;

	case WDIOC_SETTIMEOUT:
		ret = get_user(time, p);
		if (ret)
			break;

		if (time <= 0 || (oscr_freq * (long long)time >= 0xffffffff)) {
			ret = -EINVAL;
			break;
		}

		pre_margin = oscr_freq * time;
		sa1100_wr(sa1100_rd(REG_OSCR) + pre_margin, REG_OSMR3);
		fallthrough;

	case WDIOC_GETTIMEOUT:
		ret = put_user(pre_margin / oscr_freq, p);
		break;
	}
	return ret;
}

static const struct file_operations sa1100dog_fops = {
	.owner		= THIS_MODULE,
	.llseek		= no_llseek,
	.write		= sa1100dog_write,
	.unlocked_ioctl	= sa1100dog_ioctl,
	.compat_ioctl	= compat_ptr_ioctl,
	.open		= sa1100dog_open,
	.release	= sa1100dog_release,
};

static struct miscdevice sa1100dog_miscdev = {
	.minor		= WATCHDOG_MINOR,
	.name		= "watchdog",
	.fops		= &sa1100dog_fops,
};

static int margin = 60;		/* (secs) Default is 1 minute */
static struct clk *clk;

static int sa1100dog_probe(struct platform_device *pdev)
{
	int ret;
	int *platform_data;
	struct resource *res;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
		return -ENXIO;
	reg_base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
	ret = PTR_ERR_OR_ZERO(reg_base);
	if (ret)
		return ret;

	clk = clk_get(NULL, "OSTIMER0");
	if (IS_ERR(clk)) {
		pr_err("SA1100/PXA2xx Watchdog Timer: clock not found: %d\n",
		       (int) PTR_ERR(clk));
		return PTR_ERR(clk);
	}

	ret = clk_prepare_enable(clk);
	if (ret) {
		pr_err("SA1100/PXA2xx Watchdog Timer: clock failed to prepare+enable: %d\n",
		       ret);
		goto err;
	}

	oscr_freq = clk_get_rate(clk);

	platform_data = pdev->dev.platform_data;
	if (platform_data && *platform_data)
		boot_status = WDIOF_CARDRESET;
	pre_margin = oscr_freq * margin;

	ret = misc_register(&sa1100dog_miscdev);
	if (ret == 0) {
		pr_info("SA1100/PXA2xx Watchdog Timer: timer margin %d sec\n",
			margin);
		return 0;
	}

	clk_disable_unprepare(clk);
err:
	clk_put(clk);
	return ret;
}

static int sa1100dog_remove(struct platform_device *pdev)
{
	misc_deregister(&sa1100dog_miscdev);
	clk_disable_unprepare(clk);
	clk_put(clk);

	return 0;
}

static struct platform_driver sa1100dog_driver = {
	.driver.name = "sa1100_wdt",
	.probe	  = sa1100dog_probe,
	.remove	  = sa1100dog_remove,
};
module_platform_driver(sa1100dog_driver);

MODULE_AUTHOR("Oleg Drokin <green@crimea.edu>");
MODULE_DESCRIPTION("SA1100/PXA2xx Watchdog");

module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds (default 60s)");

MODULE_LICENSE("GPL");