// SPDX-License-Identifier: GPL-2.0+
/*
 *      SBC8360 Watchdog driver
 *
 *      (c) Copyright 2005 Webcon, Inc.
 *
 *      Based on ib700wdt.c, which is based on advantechwdt.c which is based
 *      on acquirewdt.c which is based on wdt.c.
 *
 *      (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/delay.h>
#include <linux/notifier.h>
#include <linux/fs.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/moduleparam.h>
#include <linux/io.h>
#include <linux/uaccess.h>


static unsigned long sbc8360_is_open;
static char expect_close;

/*
 *
 * Watchdog Timer Configuration
 *
 * The function of the watchdog timer is to reset the system automatically
 * and is defined at I/O port 0120H and 0121H.  To enable the watchdog timer
 * and allow the system to reset, write appropriate values from the table
 * below to I/O port 0120H and 0121H.  To disable the timer, write a zero
 * value to I/O port 0121H for the system to stop the watchdog function.
 *
 * The following describes how the timer should be programmed (according to
 * the vendor documentation)
 *
 * Enabling Watchdog:
 * MOV AX,000AH (enable, phase I)
 * MOV DX,0120H
 * OUT DX,AX
 * MOV AX,000BH (enable, phase II)
 * MOV DX,0120H
 * OUT DX,AX
 * MOV AX,000nH (set multiplier n, from 1-4)
 * MOV DX,0120H
 * OUT DX,AX
 * MOV AX,000mH (set base timer m, from 0-F)
 * MOV DX,0121H
 * OUT DX,AX
 *
 * Reset timer:
 * MOV AX,000mH (same as set base timer, above)
 * MOV DX,0121H
 * OUT DX,AX
 *
 * Disabling Watchdog:
 * MOV AX,0000H (a zero value)
 * MOV DX,0120H
 * OUT DX,AX
 *
 * Watchdog timeout configuration values:
 *              N
 *      M |     1       2       3       4
 *      --|----------------------------------
 *      0 |     0.5s    5s      50s     100s
 *      1 |     1s      10s     100s    200s
 *      2 |     1.5s    15s     150s    300s
 *      3 |     2s      20s     200s    400s
 *      4 |     2.5s    25s     250s    500s
 *      5 |     3s      30s     300s    600s
 *      6 |     3.5s    35s     350s    700s
 *      7 |     4s      40s     400s    800s
 *      8 |     4.5s    45s     450s    900s
 *      9 |     5s      50s     500s    1000s
 *      A |     5.5s    55s     550s    1100s
 *      B |     6s      60s     600s    1200s
 *      C |     6.5s    65s     650s    1300s
 *      D |     7s      70s     700s    1400s
 *      E |     7.5s    75s     750s    1500s
 *      F |     8s      80s     800s    1600s
 *
 * Another way to say the same things is:
 *  For N=1, Timeout = (M+1) * 0.5s
 *  For N=2, Timeout = (M+1) * 5s
 *  For N=3, Timeout = (M+1) * 50s
 *  For N=4, Timeout = (M+1) * 100s
 *
 */

static int wd_times[64][2] = {
        {0, 1},                 /* 0  = 0.5s */
        {1, 1},                 /* 1  = 1s   */
        {2, 1},                 /* 2  = 1.5s */
        {3, 1},                 /* 3  = 2s   */
        {4, 1},                 /* 4  = 2.5s */
        {5, 1},                 /* 5  = 3s   */
        {6, 1},                 /* 6  = 3.5s */
        {7, 1},                 /* 7  = 4s   */
        {8, 1},                 /* 8  = 4.5s */
        {9, 1},                 /* 9  = 5s   */
        {0xA, 1},               /* 10 = 5.5s */
        {0xB, 1},               /* 11 = 6s   */
        {0xC, 1},               /* 12 = 6.5s */
        {0xD, 1},               /* 13 = 7s   */
        {0xE, 1},               /* 14 = 7.5s */
        {0xF, 1},               /* 15 = 8s   */
        {0, 2},                 /* 16 = 5s  */
        {1, 2},                 /* 17 = 10s */
        {2, 2},                 /* 18 = 15s */
        {3, 2},                 /* 19 = 20s */
        {4, 2},                 /* 20 = 25s */
        {5, 2},                 /* 21 = 30s */
        {6, 2},                 /* 22 = 35s */
        {7, 2},                 /* 23 = 40s */
        {8, 2},                 /* 24 = 45s */
        {9, 2},                 /* 25 = 50s */
        {0xA, 2},               /* 26 = 55s */
        {0xB, 2},               /* 27 = 60s */
        {0xC, 2},               /* 28 = 65s */
        {0xD, 2},               /* 29 = 70s */
        {0xE, 2},               /* 30 = 75s */
        {0xF, 2},               /* 31 = 80s */
        {0, 3},                 /* 32 = 50s  */
        {1, 3},                 /* 33 = 100s */
        {2, 3},                 /* 34 = 150s */
        {3, 3},                 /* 35 = 200s */
        {4, 3},                 /* 36 = 250s */
        {5, 3},                 /* 37 = 300s */
        {6, 3},                 /* 38 = 350s */
        {7, 3},                 /* 39 = 400s */
        {8, 3},                 /* 40 = 450s */
        {9, 3},                 /* 41 = 500s */
        {0xA, 3},               /* 42 = 550s */
        {0xB, 3},               /* 43 = 600s */
        {0xC, 3},               /* 44 = 650s */
        {0xD, 3},               /* 45 = 700s */
        {0xE, 3},               /* 46 = 750s */
        {0xF, 3},               /* 47 = 800s */
        {0, 4},                 /* 48 = 100s */
        {1, 4},                 /* 49 = 200s */
        {2, 4},                 /* 50 = 300s */
        {3, 4},                 /* 51 = 400s */
        {4, 4},                 /* 52 = 500s */
        {5, 4},                 /* 53 = 600s */
        {6, 4},                 /* 54 = 700s */
        {7, 4},                 /* 55 = 800s */
        {8, 4},                 /* 56 = 900s */
        {9, 4},                 /* 57 = 1000s */
        {0xA, 4},               /* 58 = 1100s */
        {0xB, 4},               /* 59 = 1200s */
        {0xC, 4},               /* 60 = 1300s */
        {0xD, 4},               /* 61 = 1400s */
        {0xE, 4},               /* 62 = 1500s */
        {0xF, 4}                /* 63 = 1600s */
};

#define SBC8360_ENABLE 0x120
#define SBC8360_BASETIME 0x121

static int timeout = 27;
static int wd_margin = 0xB;
static int wd_multiplier = 2;
static bool nowayout = WATCHDOG_NOWAYOUT;

module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "Index into timeout table (0-63) (default=27 (60s))");
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
                 "Watchdog cannot be stopped once started (default="
                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

/*
 *      Kernel methods.
 */

/* Activate and pre-configure watchdog */
static void sbc8360_activate(void)
{
        /* Enable the watchdog */
        outb(0x0A, SBC8360_ENABLE);
        msleep_interruptible(100);
        outb(0x0B, SBC8360_ENABLE);
        msleep_interruptible(100);
        /* Set timeout multiplier */
        outb(wd_multiplier, SBC8360_ENABLE);
        msleep_interruptible(100);
        /* Nothing happens until first sbc8360_ping() */
}

/* Kernel pings watchdog */
static void sbc8360_ping(void)
{
        /* Write the base timer register */
        outb(wd_margin, SBC8360_BASETIME);
}

/* stop watchdog */
static void sbc8360_stop(void)
{
        /* De-activate the watchdog */
        outb(0, SBC8360_ENABLE);
}

/* Userspace pings kernel driver, or requests clean close */
static ssize_t sbc8360_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;
                        }
                }
                sbc8360_ping();
        }
        return count;
}

static int sbc8360_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &sbc8360_is_open))
                return -EBUSY;
        if (nowayout)
                __module_get(THIS_MODULE);

        /* Activate and ping once to start the countdown */
        sbc8360_activate();
        sbc8360_ping();
        return stream_open(inode, file);
}

static int sbc8360_close(struct inode *inode, struct file *file)
{
        if (expect_close == 42)
                sbc8360_stop();
        else
                pr_crit("SBC8360 device closed unexpectedly.  SBC8360 will not stop!\n");

        clear_bit(0, &sbc8360_is_open);
        expect_close = 0;
        return 0;
}

/*
 *      Notifier for system down
 */

static int sbc8360_notify_sys(struct notifier_block *this, unsigned long code,
                              void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                sbc8360_stop(); /* Disable the SBC8360 Watchdog */

        return NOTIFY_DONE;
}

/*
 *      Kernel Interfaces
 */

static const struct file_operations sbc8360_fops = {
        .owner = THIS_MODULE,
        .write = sbc8360_write,
        .open = sbc8360_open,
        .release = sbc8360_close,
};

static struct miscdevice sbc8360_miscdev = {
        .minor = WATCHDOG_MINOR,
        .name = "watchdog",
        .fops = &sbc8360_fops,
};

/*
 *      The SBC8360 needs to learn about soft shutdowns in order to
 *      turn the timebomb registers off.
 */

static struct notifier_block sbc8360_notifier = {
        .notifier_call = sbc8360_notify_sys,
};

static int __init sbc8360_init(void)
{
        int res;
        unsigned long int mseconds = 60000;

        if (timeout < 0 || timeout > 63) {
                pr_err("Invalid timeout index (must be 0-63)\n");
                res = -EINVAL;
                goto out;
        }

        if (!request_region(SBC8360_ENABLE, 1, "SBC8360")) {
                pr_err("ENABLE method I/O %X is not available\n",
                       SBC8360_ENABLE);
                res = -EIO;
                goto out;
        }
        if (!request_region(SBC8360_BASETIME, 1, "SBC8360")) {
                pr_err("BASETIME method I/O %X is not available\n",
                       SBC8360_BASETIME);
                res = -EIO;
                goto out_nobasetimereg;
        }

        res = register_reboot_notifier(&sbc8360_notifier);
        if (res) {
                pr_err("Failed to register reboot notifier\n");
                goto out_noreboot;
        }

        res = misc_register(&sbc8360_miscdev);
        if (res) {
                pr_err("failed to register misc device\n");
                goto out_nomisc;
        }

        wd_margin = wd_times[timeout][0];
        wd_multiplier = wd_times[timeout][1];

        if (wd_multiplier == 1)
                mseconds = (wd_margin + 1) * 500;
        else if (wd_multiplier == 2)
                mseconds = (wd_margin + 1) * 5000;
        else if (wd_multiplier == 3)
                mseconds = (wd_margin + 1) * 50000;
        else if (wd_multiplier == 4)
                mseconds = (wd_margin + 1) * 100000;

        /* My kingdom for the ability to print "0.5 seconds" in the kernel! */
        pr_info("Timeout set at %ld ms\n", mseconds);

        return 0;

out_nomisc:
        unregister_reboot_notifier(&sbc8360_notifier);
out_noreboot:
        release_region(SBC8360_BASETIME, 1);
out_nobasetimereg:
        release_region(SBC8360_ENABLE, 1);
out:
        return res;
}

static void __exit sbc8360_exit(void)
{
        misc_deregister(&sbc8360_miscdev);
        unregister_reboot_notifier(&sbc8360_notifier);
        release_region(SBC8360_ENABLE, 1);
        release_region(SBC8360_BASETIME, 1);
}

module_init(sbc8360_init);
module_exit(sbc8360_exit);

MODULE_AUTHOR("Ian E. Morgan <imorgan@webcon.ca>");
MODULE_DESCRIPTION("SBC8360 watchdog driver");
MODULE_LICENSE("GPL");
MODULE_VERSION("1.01");

/* end of sbc8360.c */