// SPDX-License-Identifier: GPL-2.0+
/*
 *      Advantech Single Board Computer WDT driver
 *
 *      (c) Copyright 2000-2001 Marek Michalkiewicz <marekm@linux.org.pl>
 *
 *      Based on acquirewdt.c which is based on wdt.c.
 *      Original copyright messages:
 *
 *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 *
 *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *      warranty for any of this software. This material is provided
 *      "AS-IS" and at no charge.
 *
 *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 *      14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
 *          Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
 *
 *      16-Oct-2002 Rob Radez <rob@osinvestor.com>
 *          Clean up ioctls, clean up init + exit, add expect close support,
 *          add wdt_start and wdt_stop as parameters.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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/ioport.h>
#include <linux/platform_device.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/uaccess.h>


#define DRV_NAME "advantechwdt"
#define WATCHDOG_NAME "Advantech WDT"
#define WATCHDOG_TIMEOUT 60             /* 60 sec default timeout */

/* the watchdog platform device */
static struct platform_device *advwdt_platform_device;
static unsigned long advwdt_is_open;
static char adv_expect_close;

/*
 *      You must set these - there is no sane way to probe for this board.
 *
 *      To enable or restart, write the timeout value in seconds (1 to 63)
 *      to I/O port wdt_start.  To disable, read I/O port wdt_stop.
 *      Both are 0x443 for most boards (tested on a PCA-6276VE-00B1), but
 *      check your manual (at least the PCA-6159 seems to be different -
 *      the manual says wdt_stop is 0x43, not 0x443).
 *      (0x43 is also a write-only control register for the 8254 timer!)
 */

static int wdt_stop = 0x443;
module_param(wdt_stop, int, 0);
MODULE_PARM_DESC(wdt_stop, "Advantech WDT 'stop' io port (default 0x443)");

static int wdt_start = 0x443;
module_param(wdt_start, int, 0);
MODULE_PARM_DESC(wdt_start, "Advantech WDT 'start' io port (default 0x443)");

static int timeout = WATCHDOG_TIMEOUT;  /* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
        "Watchdog timeout in seconds. 1<= timeout <=63, default="
                __MODULE_STRING(WATCHDOG_TIMEOUT) ".");

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) ")");

/*
 *      Watchdog Operations
 */

static void advwdt_ping(void)
{
        /* Write a watchdog value */
        outb_p(timeout, wdt_start);
}

static void advwdt_disable(void)
{
        inb_p(wdt_stop);
}

static int advwdt_set_heartbeat(int t)
{
        if (t < 1 || t > 63)
                return -EINVAL;
        timeout = t;
        return 0;
}

/*
 *      /dev/watchdog handling
 */

static ssize_t advwdt_write(struct file *file, const char __user *buf,
                                                size_t count, loff_t *ppos)
{
        if (count) {
                if (!nowayout) {
                        size_t i;

                        adv_expect_close = 0;

                        for (i = 0; i != count; i++) {
                                char c;
                                if (get_user(c, buf + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        adv_expect_close = 42;
                        }
                }
                advwdt_ping();
        }
        return count;
}

static long advwdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        int new_timeout;
        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 = WATCHDOG_NAME,
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &ident, sizeof(ident)))
                        return -EFAULT;
                break;

        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);

        case WDIOC_SETOPTIONS:
        {
                int options, retval = -EINVAL;

                if (get_user(options, p))
                        return -EFAULT;
                if (options & WDIOS_DISABLECARD) {
                        advwdt_disable();
                        retval = 0;
                }
                if (options & WDIOS_ENABLECARD) {
                        advwdt_ping();
                        retval = 0;
                }
                return retval;
        }
        case WDIOC_KEEPALIVE:
                advwdt_ping();
                break;

        case WDIOC_SETTIMEOUT:
                if (get_user(new_timeout, p))
                        return -EFAULT;
                if (advwdt_set_heartbeat(new_timeout))
                        return -EINVAL;
                advwdt_ping();
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(timeout, p);
        default:
                return -ENOTTY;
        }
        return 0;
}

static int advwdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &advwdt_is_open))
                return -EBUSY;
        /*
         *      Activate
         */

        advwdt_ping();
        return stream_open(inode, file);
}

static int advwdt_close(struct inode *inode, struct file *file)
{
        if (adv_expect_close == 42) {
                advwdt_disable();
        } else {
                pr_crit("Unexpected close, not stopping watchdog!\n");
                advwdt_ping();
        }
        clear_bit(0, &advwdt_is_open);
        adv_expect_close = 0;
        return 0;
}

/*
 *      Kernel Interfaces
 */

static const struct file_operations advwdt_fops = {
        .owner          = THIS_MODULE,
        .write          = advwdt_write,
        .unlocked_ioctl = advwdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = advwdt_open,
        .release        = advwdt_close,
};

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

/*
 *      Init & exit routines
 */

static int __init advwdt_probe(struct platform_device *dev)
{
        int ret;

        if (wdt_stop != wdt_start) {
                if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {
                        pr_err("I/O address 0x%04x already in use\n",
                               wdt_stop);
                        ret = -EIO;
                        goto out;
                }
        }

        if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
                pr_err("I/O address 0x%04x already in use\n", wdt_start);
                ret = -EIO;
                goto unreg_stop;
        }

        /* Check that the heartbeat value is within it's range ;
         * if not reset to the default */
        if (advwdt_set_heartbeat(timeout)) {
                advwdt_set_heartbeat(WATCHDOG_TIMEOUT);
                pr_info("timeout value must be 1<=x<=63, using %d\n", timeout);
        }

        ret = misc_register(&advwdt_miscdev);
        if (ret != 0) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, ret);
                goto unreg_regions;
        }
        pr_info("initialized. timeout=%d sec (nowayout=%d)\n",
                timeout, nowayout);
out:
        return ret;
unreg_regions:
        release_region(wdt_start, 1);
unreg_stop:
        if (wdt_stop != wdt_start)
                release_region(wdt_stop, 1);
        goto out;
}

static void advwdt_remove(struct platform_device *dev)
{
        misc_deregister(&advwdt_miscdev);
        release_region(wdt_start, 1);
        if (wdt_stop != wdt_start)
                release_region(wdt_stop, 1);
}

static void advwdt_shutdown(struct platform_device *dev)
{
        /* Turn the WDT off if we have a soft shutdown */
        advwdt_disable();
}

static struct platform_driver advwdt_driver = {
        .remove         = advwdt_remove,
        .shutdown       = advwdt_shutdown,
        .driver         = {
                .name   = DRV_NAME,
        },
};

static int __init advwdt_init(void)
{
        int err;

        pr_info("WDT driver for Advantech single board computer initialising\n");

        advwdt_platform_device = platform_device_register_simple(DRV_NAME,
                                                                -1, NULL, 0);
        if (IS_ERR(advwdt_platform_device))
                return PTR_ERR(advwdt_platform_device);

        err = platform_driver_probe(&advwdt_driver, advwdt_probe);
        if (err)
                goto unreg_platform_device;

        return 0;

unreg_platform_device:
        platform_device_unregister(advwdt_platform_device);
        return err;
}

static void __exit advwdt_exit(void)
{
        platform_device_unregister(advwdt_platform_device);
        platform_driver_unregister(&advwdt_driver);
        pr_info("Watchdog Module Unloaded\n");
}

module_init(advwdt_init);
module_exit(advwdt_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marek Michalkiewicz <marekm@linux.org.pl>");
MODULE_DESCRIPTION("Advantech Single Board Computer WDT driver");