// SPDX-License-Identifier: GPL-2.0-only
/*
 *	ALi M7101 PMU Computer Watchdog Timer driver
 *
 *	Based on w83877f_wdt.c by Scott Jennings <linuxdrivers@oro.net>
 *	and the Cobalt kernel WDT timer driver by Tim Hockin
 *	                                      <thockin@cobaltnet.com>
 *
 *	(c)2002 Steve Hill <steve@navaho.co.uk>
 *
 *  This WDT driver is different from most other Linux WDT
 *  drivers in that the driver will ping the watchdog by itself,
 *  because this particular WDT has a very short timeout (1.6
 *  seconds) and it would be insane to count on any userspace
 *  daemon always getting scheduled within that time frame.
 *
 *  Additions:
 *   Aug 23, 2004 - Added use_gpio module parameter for use on revision a1d PMUs
 *                  found on very old cobalt hardware.
 *                  -- Mike Waychison <michael.waychison@sun.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/io.h>
#include <linux/uaccess.h>


#define WDT_ENABLE 0x9C
#define WDT_DISABLE 0x8C

#define ALI_7101_WDT    0x92
#define ALI_7101_GPIO   0x7D
#define ALI_7101_GPIO_O 0x7E
#define ALI_WDT_ARM     0x01

/*
 * We're going to use a 1 second timeout.
 * If we reset the watchdog every ~250ms we should be safe.  */

#define WDT_INTERVAL (HZ/4+1)

/*
 * We must not require too good response from the userspace daemon.
 * Here we require the userspace daemon to send us a heartbeat
 * char to /dev/watchdog every 30 seconds.
 */

#define WATCHDOG_TIMEOUT 30            /* 30 sec default timeout */
/* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
		"Watchdog timeout in seconds. (1<=timeout<=3600, default="
				__MODULE_STRING(WATCHDOG_TIMEOUT) ")");

static int use_gpio; /* Use the pic (for a1d revision alim7101) */
module_param(use_gpio, int, 0);
MODULE_PARM_DESC(use_gpio,
		"Use the gpio watchdog (required by old cobalt boards).");

static void wdt_timer_ping(struct timer_list *);
static DEFINE_TIMER(timer, wdt_timer_ping);
static unsigned long next_heartbeat;
static unsigned long wdt_is_open;
static char wdt_expect_close;
static struct pci_dev *alim7101_pmu;

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

/*
 *	Whack the dog
 */

static void wdt_timer_ping(struct timer_list *unused)
{
	/* If we got a heartbeat pulse within the WDT_US_INTERVAL
	 * we agree to ping the WDT
	 */
	char tmp;

	if (time_before(jiffies, next_heartbeat)) {
		/* Ping the WDT (this is actually a disarm/arm sequence) */
		pci_read_config_byte(alim7101_pmu, 0x92, &tmp);
		pci_write_config_byte(alim7101_pmu,
					ALI_7101_WDT, (tmp & ~ALI_WDT_ARM));
		pci_write_config_byte(alim7101_pmu,
					ALI_7101_WDT, (tmp | ALI_WDT_ARM));
		if (use_gpio) {
			pci_read_config_byte(alim7101_pmu,
					ALI_7101_GPIO_O, &tmp);
			pci_write_config_byte(alim7101_pmu,
					ALI_7101_GPIO_O, tmp | 0x20);
			pci_write_config_byte(alim7101_pmu,
					ALI_7101_GPIO_O, tmp & ~0x20);
		}
	} else {
		pr_warn("Heartbeat lost! Will not ping the watchdog\n");
	}
	/* Re-set the timer interval */
	mod_timer(&timer, jiffies + WDT_INTERVAL);
}

/*
 * Utility routines
 */

static void wdt_change(int writeval)
{
	char tmp;

	pci_read_config_byte(alim7101_pmu, ALI_7101_WDT, &tmp);
	if (writeval == WDT_ENABLE) {
		pci_write_config_byte(alim7101_pmu,
					ALI_7101_WDT, (tmp | ALI_WDT_ARM));
		if (use_gpio) {
			pci_read_config_byte(alim7101_pmu,
					ALI_7101_GPIO_O, &tmp);
			pci_write_config_byte(alim7101_pmu,
					ALI_7101_GPIO_O, tmp & ~0x20);
		}

	} else {
		pci_write_config_byte(alim7101_pmu,
					ALI_7101_WDT, (tmp & ~ALI_WDT_ARM));
		if (use_gpio) {
			pci_read_config_byte(alim7101_pmu,
					ALI_7101_GPIO_O, &tmp);
			pci_write_config_byte(alim7101_pmu,
					ALI_7101_GPIO_O, tmp | 0x20);
		}
	}
}

static void wdt_startup(void)
{
	next_heartbeat = jiffies + (timeout * HZ);

	/* We must enable before we kick off the timer in case the timer
	   occurs as we ping it */

	wdt_change(WDT_ENABLE);

	/* Start the timer */
	mod_timer(&timer, jiffies + WDT_INTERVAL);

	pr_info("Watchdog timer is now enabled\n");
}

static void wdt_turnoff(void)
{
	/* Stop the timer */
	del_timer_sync(&timer);
	wdt_change(WDT_DISABLE);
	pr_info("Watchdog timer is now disabled...\n");
}

static void wdt_keepalive(void)
{
	/* user land ping */
	next_heartbeat = jiffies + (timeout * HZ);
}

/*
 * /dev/watchdog handling
 */

static ssize_t fop_write(struct file *file, const char __user *buf,
						size_t count, loff_t *ppos)
{
	/* See if we got the magic character 'V' and reload the timer */
	if (count) {
		if (!nowayout) {
			size_t ofs;

			/* note: just in case someone wrote the magic character
			 * five months ago... */
			wdt_expect_close = 0;

			/* now scan */
			for (ofs = 0; ofs != count; ofs++) {
				char c;
				if (get_user(c, buf + ofs))
					return -EFAULT;
				if (c == 'V')
					wdt_expect_close = 42;
			}
		}
		/* someone wrote to us, we should restart timer */
		wdt_keepalive();
	}
	return count;
}

static int fop_open(struct inode *inode, struct file *file)
{
	/* Just in case we're already talking to someone... */
	if (test_and_set_bit(0, &wdt_is_open))
		return -EBUSY;
	/* Good, fire up the show */
	wdt_startup();
	return stream_open(inode, file);
}

static int fop_close(struct inode *inode, struct file *file)
{
	if (wdt_expect_close == 42)
		wdt_turnoff();
	else {
		/* wim: shouldn't there be a: del_timer(&timer); */
		pr_crit("device file closed unexpectedly. Will not stop the WDT!\n");
	}
	clear_bit(0, &wdt_is_open);
	wdt_expect_close = 0;
	return 0;
}

static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	int __user *p = argp;
	static const struct watchdog_info ident = {
		.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
							| WDIOF_MAGICCLOSE,
		.firmware_version = 1,
		.identity = "ALiM7101",
	};

	switch (cmd) {
	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_SETOPTIONS:
	{
		int new_options, retval = -EINVAL;

		if (get_user(new_options, p))
			return -EFAULT;
		if (new_options & WDIOS_DISABLECARD) {
			wdt_turnoff();
			retval = 0;
		}
		if (new_options & WDIOS_ENABLECARD) {
			wdt_startup();
			retval = 0;
		}
		return retval;
	}
	case WDIOC_KEEPALIVE:
		wdt_keepalive();
		return 0;
	case WDIOC_SETTIMEOUT:
	{
		int new_timeout;

		if (get_user(new_timeout, p))
			return -EFAULT;
		/* arbitrary upper limit */
		if (new_timeout < 1 || new_timeout > 3600)
			return -EINVAL;
		timeout = new_timeout;
		wdt_keepalive();
	}
		fallthrough;
	case WDIOC_GETTIMEOUT:
		return put_user(timeout, p);
	default:
		return -ENOTTY;
	}
}

static const struct file_operations wdt_fops = {
	.owner		=	THIS_MODULE,
	.write		=	fop_write,
	.open		=	fop_open,
	.release	=	fop_close,
	.unlocked_ioctl	=	fop_ioctl,
	.compat_ioctl	= 	compat_ptr_ioctl,
};

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

static int wdt_restart_handle(struct notifier_block *this, unsigned long mode,
			      void *cmd)
{
	/*
	 * Cobalt devices have no way of rebooting themselves other
	 * than getting the watchdog to pull reset, so we restart the
	 * watchdog on reboot with no heartbeat.
	 */
	wdt_change(WDT_ENABLE);

	/* loop until the watchdog fires */
	while (true)
		;

	return NOTIFY_DONE;
}

static struct notifier_block wdt_restart_handler = {
	.notifier_call = wdt_restart_handle,
	.priority = 128,
};

/*
 *	Notifier for system down
 */

static int wdt_notify_sys(struct notifier_block *this,
					unsigned long code, void *unused)
{
	if (code == SYS_DOWN || code == SYS_HALT)
		wdt_turnoff();

	return NOTIFY_DONE;
}

/*
 *	The WDT needs to learn about soft shutdowns in order to
 *	turn the timebomb registers off.
 */

static struct notifier_block wdt_notifier = {
	.notifier_call = wdt_notify_sys,
};

static void __exit alim7101_wdt_unload(void)
{
	wdt_turnoff();
	/* Deregister */
	misc_deregister(&wdt_miscdev);
	unregister_reboot_notifier(&wdt_notifier);
	unregister_restart_handler(&wdt_restart_handler);
	pci_dev_put(alim7101_pmu);
}

static int __init alim7101_wdt_init(void)
{
	int rc = -EBUSY;
	struct pci_dev *ali1543_south;
	char tmp;

	pr_info("Steve Hill <steve@navaho.co.uk>\n");
	alim7101_pmu = pci_get_device(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M7101,
		NULL);
	if (!alim7101_pmu) {
		pr_info("ALi M7101 PMU not present - WDT not set\n");
		return -EBUSY;
	}

	/* Set the WDT in the PMU to 1 second */
	pci_write_config_byte(alim7101_pmu, ALI_7101_WDT, 0x02);

	ali1543_south = pci_get_device(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M1533,
		NULL);
	if (!ali1543_south) {
		pr_info("ALi 1543 South-Bridge not present - WDT not set\n");
		goto err_out;
	}
	pci_read_config_byte(ali1543_south, 0x5e, &tmp);
	pci_dev_put(ali1543_south);
	if ((tmp & 0x1e) == 0x00) {
		if (!use_gpio) {
			pr_info("Detected old alim7101 revision 'a1d'.  If this is a cobalt board, set the 'use_gpio' module parameter.\n");
			goto err_out;
		}
		nowayout = 1;
	} else if ((tmp & 0x1e) != 0x12 && (tmp & 0x1e) != 0x00) {
		pr_info("ALi 1543 South-Bridge does not have the correct revision number (???1001?) - WDT not set\n");
		goto err_out;
	}

	if (timeout < 1 || timeout > 3600) {
		/* arbitrary upper limit */
		timeout = WATCHDOG_TIMEOUT;
		pr_info("timeout value must be 1 <= x <= 3600, using %d\n",
			timeout);
	}

	rc = register_reboot_notifier(&wdt_notifier);
	if (rc) {
		pr_err("cannot register reboot notifier (err=%d)\n", rc);
		goto err_out;
	}

	rc = register_restart_handler(&wdt_restart_handler);
	if (rc) {
		pr_err("cannot register restart handler (err=%d)\n", rc);
		goto err_out_reboot;
	}

	rc = misc_register(&wdt_miscdev);
	if (rc) {
		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
		       wdt_miscdev.minor, rc);
		goto err_out_restart;
	}

	if (nowayout)
		__module_get(THIS_MODULE);

	pr_info("WDT driver for ALi M7101 initialised. timeout=%d sec (nowayout=%d)\n",
		timeout, nowayout);
	return 0;

err_out_restart:
	unregister_restart_handler(&wdt_restart_handler);
err_out_reboot:
	unregister_reboot_notifier(&wdt_notifier);
err_out:
	pci_dev_put(alim7101_pmu);
	return rc;
}

module_init(alim7101_wdt_init);
module_exit(alim7101_wdt_unload);

static const struct pci_device_id alim7101_pci_tbl[] __used = {
	{ PCI_DEVICE(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M1533) },
	{ PCI_DEVICE(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M7101) },
	{ }
};

MODULE_DEVICE_TABLE(pci, alim7101_pci_tbl);

MODULE_AUTHOR("Steve Hill");
MODULE_DESCRIPTION("ALi M7101 PMU Computer Watchdog Timer driver");
MODULE_LICENSE("GPL");