// SPDX-License-Identifier: GPL-2.0+
/*
 *      IB700 Single Board Computer WDT driver
 *
 *      (c) Copyright 2001 Charles Howes <chowes@vsol.net>
 *
 *      Based on advantechwdt.c which is based on acquirewdt.c which
 *      is based on wdt.c.
 *
 *      (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
 *           Added timeout module option to override default
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/ioport.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/io.h>
#include <linux/uaccess.h>


static struct platform_device *ibwdt_platform_device;
static unsigned long ibwdt_is_open;
static DEFINE_SPINLOCK(ibwdt_lock);
static char expect_close;

/* Module information */
#define DRV_NAME "ib700wdt"

/*
 *
 * Watchdog Timer Configuration
 *
 * The function of the watchdog timer is to reset the system
 * automatically and is defined at I/O port 0443H.  To enable the
 * watchdog timer and allow the system to reset, write I/O port 0443H.
 * To disable the timer, write I/O port 0441H for the system to stop the
 * watchdog function.  The timer has a tolerance of 20% for its
 * intervals.
 *
 * The following describes how the timer should be programmed.
 *
 * Enabling Watchdog:
 * MOV AX,000FH (Choose the values from 0 to F)
 * MOV DX,0443H
 * OUT DX,AX
 *
 * Disabling Watchdog:
 * MOV AX,000FH (Any value is fine.)
 * MOV DX,0441H
 * OUT DX,AX
 *
 * Watchdog timer control table:
 * Level   Value  Time/sec | Level Value Time/sec
 *   1       F       0     |   9     7      16
 *   2       E       2     |   10    6      18
 *   3       D       4     |   11    5      20
 *   4       C       6     |   12    4      22
 *   5       B       8     |   13    3      24
 *   6       A       10    |   14    2      26
 *   7       9       12    |   15    1      28
 *   8       8       14    |   16    0      30
 *
 */

#define WDT_STOP 0x441
#define WDT_START 0x443

/* Default timeout */
#define WATCHDOG_TIMEOUT 30             /* 30 seconds +/- 20% */
static int timeout = WATCHDOG_TIMEOUT;  /* in seconds */
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
        "Watchdog timeout in seconds. 0<= timeout <=30, 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 ibwdt_ping(void)
{
        int wd_margin = 15 - ((timeout + 1) / 2);

        spin_lock(&ibwdt_lock);

        /* Write a watchdog value */
        outb_p(wd_margin, WDT_START);

        spin_unlock(&ibwdt_lock);
}

static void ibwdt_disable(void)
{
        spin_lock(&ibwdt_lock);
        outb_p(0, WDT_STOP);
        spin_unlock(&ibwdt_lock);
}

static int ibwdt_set_heartbeat(int t)
{
        if (t < 0 || t > 30)
                return -EINVAL;

        timeout = t;
        return 0;
}

/*
 *      /dev/watchdog handling
 */

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

                        /* In case it was set long ago */
                        expect_close = 0;

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

static long ibwdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        int new_margin;
        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 = "IB700 WDT",
        };

        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) {
                        ibwdt_disable();
                        retval = 0;
                }
                if (options & WDIOS_ENABLECARD) {
                        ibwdt_ping();
                        retval = 0;
                }
                return retval;
        }
        case WDIOC_KEEPALIVE:
                ibwdt_ping();
                break;

        case WDIOC_SETTIMEOUT:
                if (get_user(new_margin, p))
                        return -EFAULT;
                if (ibwdt_set_heartbeat(new_margin))
                        return -EINVAL;
                ibwdt_ping();
                fallthrough;

        case WDIOC_GETTIMEOUT:
                return put_user(timeout, p);

        default:
                return -ENOTTY;
        }
        return 0;
}

static int ibwdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &ibwdt_is_open))
                return -EBUSY;
        if (nowayout)
                __module_get(THIS_MODULE);

        /* Activate */
        ibwdt_ping();
        return stream_open(inode, file);
}

static int ibwdt_close(struct inode *inode, struct file *file)
{
        if (expect_close == 42) {
                ibwdt_disable();
        } else {
                pr_crit("WDT device closed unexpectedly.  WDT will not stop!\n");
                ibwdt_ping();
        }
        clear_bit(0, &ibwdt_is_open);
        expect_close = 0;
        return 0;
}

/*
 *      Kernel Interfaces
 */

static const struct file_operations ibwdt_fops = {
        .owner          = THIS_MODULE,
        .write          = ibwdt_write,
        .unlocked_ioctl = ibwdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = ibwdt_open,
        .release        = ibwdt_close,
};

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

/*
 *      Init & exit routines
 */

static int __init ibwdt_probe(struct platform_device *dev)
{
        int res;

#if WDT_START != WDT_STOP
        if (!request_region(WDT_STOP, 1, "IB700 WDT")) {
                pr_err("STOP method I/O %X is not available\n", WDT_STOP);
                res = -EIO;
                goto out_nostopreg;
        }
#endif

        if (!request_region(WDT_START, 1, "IB700 WDT")) {
                pr_err("START method I/O %X is not available\n", WDT_START);
                res = -EIO;
                goto out_nostartreg;
        }

        /* Check that the heartbeat value is within it's range ;
         * if not reset to the default */
        if (ibwdt_set_heartbeat(timeout)) {
                ibwdt_set_heartbeat(WATCHDOG_TIMEOUT);
                pr_info("timeout value must be 0<=x<=30, using %d\n", timeout);
        }

        res = misc_register(&ibwdt_miscdev);
        if (res) {
                pr_err("failed to register misc device\n");
                goto out_nomisc;
        }
        return 0;

out_nomisc:
        release_region(WDT_START, 1);
out_nostartreg:
#if WDT_START != WDT_STOP
        release_region(WDT_STOP, 1);
#endif
out_nostopreg:
        return res;
}

static void ibwdt_remove(struct platform_device *dev)
{
        misc_deregister(&ibwdt_miscdev);
        release_region(WDT_START, 1);
#if WDT_START != WDT_STOP
        release_region(WDT_STOP, 1);
#endif
}

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

static struct platform_driver ibwdt_driver = {
        .remove         = ibwdt_remove,
        .shutdown       = ibwdt_shutdown,
        .driver         = {
                .name   = DRV_NAME,
        },
};

static int __init ibwdt_init(void)
{
        int err;

        pr_info("WDT driver for IB700 single board computer initialising\n");

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

        err = platform_driver_probe(&ibwdt_driver, ibwdt_probe);
        if (err)
                goto unreg_platform_device;

        return 0;

unreg_platform_device:
        platform_device_unregister(ibwdt_platform_device);
        return err;
}

static void __exit ibwdt_exit(void)
{
        platform_device_unregister(ibwdt_platform_device);
        platform_driver_unregister(&ibwdt_driver);
        pr_info("Watchdog Module Unloaded\n");
}

module_init(ibwdt_init);
module_exit(ibwdt_exit);

MODULE_AUTHOR("Charles Howes <chowes@vsol.net>");
MODULE_DESCRIPTION("IB700 SBC watchdog driver");
MODULE_LICENSE("GPL");

/* end of ib700wdt.c */