// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      SMsC 37B787 Watchdog Timer driver for Linux 2.6.x.x
 *
 *      Based on acquirewdt.c by Alan Cox <alan@lxorguk.ukuu.org.uk>
 *      and some other existing drivers
 *
 *      The authors do NOT admit liability nor provide warranty for
 *      any of this software. This material is provided "AS-IS" in
 *      the hope that it may be useful for others.
 *
 *      (C) Copyright 2003-2006  Sven Anders <anders@anduras.de>
 *
 *  History:
 *      2003 - Created version 1.0 for Linux 2.4.x.
 *      2006 - Ported to Linux 2.6, added nowayout and MAGICCLOSE
 *             features. Released version 1.1
 *
 *  Theory of operation:
 *
 *      A Watchdog Timer (WDT) is a hardware circuit that can
 *      reset the computer system in case of a software fault.
 *      You probably knew that already.
 *
 *      Usually a userspace daemon will notify the kernel WDT driver
 *      via the /dev/watchdog special device file that userspace is
 *      still alive, at regular intervals.  When such a notification
 *      occurs, the driver will usually tell the hardware watchdog
 *      that everything is in order, and that the watchdog should wait
 *      for yet another little while to reset the system.
 *      If userspace fails (RAM error, kernel bug, whatever), the
 *      notifications cease to occur, and the hardware watchdog will
 *      reset the system (causing a reboot) after the timeout occurs.
 *
 * Create device with:
 *  mknod /dev/watchdog c 10 130
 *
 * For an example userspace keep-alive daemon, see:
 *   Documentation/watchdog/wdt.rst
 */

#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/delay.h>
#include <linux/fs.h>
#include <linux/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/io.h>
#include <linux/uaccess.h>


/* enable support for minutes as units? */
/* (does not always work correctly, so disabled by default!) */
#define SMSC_SUPPORT_MINUTES
#undef SMSC_SUPPORT_MINUTES

#define MAX_TIMEOUT     255

#define UNIT_SECOND     0
#define UNIT_MINUTE     1

#define VERSION         "1.1"

#define IOPORT          0x3F0
#define IOPORT_SIZE     2
#define IODEV_NO        8

static int unit = UNIT_SECOND;  /* timer's unit */
static int timeout = 60;        /* timeout value: default is 60 "units" */
static unsigned long timer_enabled;   /* is the timer enabled? */

static char expect_close;       /* is the close expected? */

static DEFINE_SPINLOCK(io_lock);/* to guard the watchdog from io races */

static bool nowayout = WATCHDOG_NOWAYOUT;

/* -- Low level function ----------------------------------------*/

/* unlock the IO chip */

static inline void open_io_config(void)
{
        outb(0x55, IOPORT);
        mdelay(1);
        outb(0x55, IOPORT);
}

/* lock the IO chip */
static inline void close_io_config(void)
{
        outb(0xAA, IOPORT);
}

/* select the IO device */
static inline void select_io_device(unsigned char devno)
{
        outb(0x07, IOPORT);
        outb(devno, IOPORT+1);
}

/* write to the control register */
static inline void write_io_cr(unsigned char reg, unsigned char data)
{
        outb(reg, IOPORT);
        outb(data, IOPORT+1);
}

/* read from the control register */
static inline char read_io_cr(unsigned char reg)
{
        outb(reg, IOPORT);
        return inb(IOPORT+1);
}

/* -- Medium level functions ------------------------------------*/

static inline void gpio_bit12(unsigned char reg)
{
        /* -- General Purpose I/O Bit 1.2 --
         * Bit 0,   In/Out: 0 = Output, 1 = Input
         * Bit 1,   Polarity: 0 = No Invert, 1 = Invert
         * Bit 2,   Group Enable Intr.: 0 = Disable, 1 = Enable
         * Bit 3/4, Function select: 00 = GPI/O, 01 = WDT, 10 = P17,
         *                           11 = Either Edge Triggered Intr. 2
         * Bit 5/6  (Reserved)
         * Bit 7,   Output Type: 0 = Push Pull Bit, 1 = Open Drain
         */
        write_io_cr(0xE2, reg);
}

static inline void gpio_bit13(unsigned char reg)
{
        /* -- General Purpose I/O Bit 1.3 --
         * Bit 0,  In/Out: 0 = Output, 1 = Input
         * Bit 1,  Polarity: 0 = No Invert, 1 = Invert
         * Bit 2,  Group Enable Intr.: 0 = Disable, 1 = Enable
         * Bit 3,  Function select: 0 = GPI/O, 1 = LED
         * Bit 4-6 (Reserved)
         * Bit 7,  Output Type: 0 = Push Pull Bit, 1 = Open Drain
         */
        write_io_cr(0xE3, reg);
}

static inline void wdt_timer_units(unsigned char new_units)
{
        /* -- Watchdog timer units --
         * Bit 0-6 (Reserved)
         * Bit 7,  WDT Time-out Value Units Select
         *         (0 = Minutes, 1 = Seconds)
         */
        write_io_cr(0xF1, new_units);
}

static inline void wdt_timeout_value(unsigned char new_timeout)
{
        /* -- Watchdog Timer Time-out Value --
         * Bit 0-7 Binary coded units (0=Disabled, 1..255)
         */
        write_io_cr(0xF2, new_timeout);
}

static inline void wdt_timer_conf(unsigned char conf)
{
        /* -- Watchdog timer configuration --
         * Bit 0   Joystick enable: 0* = No Reset, 1 = Reset WDT upon
         *                                                      Gameport I/O
         * Bit 1   Keyboard enable: 0* = No Reset, 1 = Reset WDT upon KBD Intr.
         * Bit 2   Mouse enable: 0* = No Reset, 1 = Reset WDT upon Mouse Intr
         * Bit 3   Reset the timer
         *         (Wrong in SMsC documentation? Given as: PowerLED Timout
         *                                                      Enabled)
         * Bit 4-7 WDT Interrupt Mapping: (0000* = Disabled,
         *            0001=IRQ1, 0010=(Invalid), 0011=IRQ3 to 1111=IRQ15)
         */
        write_io_cr(0xF3, conf);
}

static inline void wdt_timer_ctrl(unsigned char reg)
{
        /* -- Watchdog timer control --
         * Bit 0   Status Bit: 0 = Timer counting, 1 = Timeout occurred
         * Bit 1   Power LED Toggle: 0 = Disable Toggle, 1 = Toggle at 1 Hz
         * Bit 2   Force Timeout: 1 = Forces WD timeout event (self-cleaning)
         * Bit 3   P20 Force Timeout enabled:
         *          0 = P20 activity does not generate the WD timeout event
         *          1 = P20 Allows rising edge of P20, from the keyboard
         *              controller, to force the WD timeout event.
         * Bit 4   (Reserved)
         * -- Soft power management --
         * Bit 5   Stop Counter: 1 = Stop software power down counter
         *            set via register 0xB8, (self-cleaning)
         *            (Upon read: 0 = Counter running, 1 = Counter stopped)
         * Bit 6   Restart Counter: 1 = Restart software power down counter
         *            set via register 0xB8, (self-cleaning)
         * Bit 7   SPOFF: 1 = Force software power down (self-cleaning)
         */
        write_io_cr(0xF4, reg);
}

/* -- Higher level functions ------------------------------------*/

/* initialize watchdog */

static void wb_smsc_wdt_initialize(void)
{
        unsigned char old;

        spin_lock(&io_lock);
        open_io_config();
        select_io_device(IODEV_NO);

        /* enable the watchdog */
        gpio_bit13(0x08);  /* Select pin 80 = LED not GPIO */
        gpio_bit12(0x0A);  /* Set pin 79 = WDT not
                              GPIO/Output/Polarity=Invert */
        /* disable the timeout */
        wdt_timeout_value(0);

        /* reset control register */
        wdt_timer_ctrl(0x00);

        /* reset configuration register */
        wdt_timer_conf(0x00);

        /* read old (timer units) register */
        old = read_io_cr(0xF1) & 0x7F;
        if (unit == UNIT_SECOND)
                old |= 0x80;    /* set to seconds */

        /* set the watchdog timer units */
        wdt_timer_units(old);

        close_io_config();
        spin_unlock(&io_lock);
}

/* shutdown the watchdog */

static void wb_smsc_wdt_shutdown(void)
{
        spin_lock(&io_lock);
        open_io_config();
        select_io_device(IODEV_NO);

        /* disable the watchdog */
        gpio_bit13(0x09);
        gpio_bit12(0x09);

        /* reset watchdog config register */
        wdt_timer_conf(0x00);

        /* reset watchdog control register */
        wdt_timer_ctrl(0x00);

        /* disable timeout */
        wdt_timeout_value(0x00);

        close_io_config();
        spin_unlock(&io_lock);
}

/* set timeout => enable watchdog */

static void wb_smsc_wdt_set_timeout(unsigned char new_timeout)
{
        spin_lock(&io_lock);
        open_io_config();
        select_io_device(IODEV_NO);

        /* set Power LED to blink, if we enable the timeout */
        wdt_timer_ctrl((new_timeout == 0) ? 0x00 : 0x02);

        /* set timeout value */
        wdt_timeout_value(new_timeout);

        close_io_config();
        spin_unlock(&io_lock);
}

/* get timeout */

static unsigned char wb_smsc_wdt_get_timeout(void)
{
        unsigned char set_timeout;

        spin_lock(&io_lock);
        open_io_config();
        select_io_device(IODEV_NO);
        set_timeout = read_io_cr(0xF2);
        close_io_config();
        spin_unlock(&io_lock);

        return set_timeout;
}

/* disable watchdog */

static void wb_smsc_wdt_disable(void)
{
        /* set the timeout to 0 to disable the watchdog */
        wb_smsc_wdt_set_timeout(0);
}

/* enable watchdog by setting the current timeout */

static void wb_smsc_wdt_enable(void)
{
        /* set the current timeout... */
        wb_smsc_wdt_set_timeout(timeout);
}

/* reset the timer */

static void wb_smsc_wdt_reset_timer(void)
{
        spin_lock(&io_lock);
        open_io_config();
        select_io_device(IODEV_NO);

        /* reset the timer */
        wdt_timeout_value(timeout);
        wdt_timer_conf(0x08);

        close_io_config();
        spin_unlock(&io_lock);
}

/* return, if the watchdog is enabled (timeout is set...) */

static int wb_smsc_wdt_status(void)
{
        return (wb_smsc_wdt_get_timeout() == 0) ? 0 : WDIOF_KEEPALIVEPING;
}


/* -- File operations -------------------------------------------*/

/* open => enable watchdog and set initial timeout */

static int wb_smsc_wdt_open(struct inode *inode, struct file *file)
{
        /* /dev/watchdog can only be opened once */

        if (test_and_set_bit(0, &timer_enabled))
                return -EBUSY;

        if (nowayout)
                __module_get(THIS_MODULE);

        /* Reload and activate timer */
        wb_smsc_wdt_enable();

        pr_info("Watchdog enabled. Timeout set to %d %s\n",
                timeout, (unit == UNIT_SECOND) ? "second(s)" : "minute(s)");

        return stream_open(inode, file);
}

/* close => shut off the timer */

static int wb_smsc_wdt_release(struct inode *inode, struct file *file)
{
        /* Shut off the timer. */

        if (expect_close == 42) {
                wb_smsc_wdt_disable();
                pr_info("Watchdog disabled, sleeping again...\n");
        } else {
                pr_crit("Unexpected close, not stopping watchdog!\n");
                wb_smsc_wdt_reset_timer();
        }

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

/* write => update the timer to keep the machine alive */

static ssize_t wb_smsc_wdt_write(struct file *file, const char __user *data,
                                 size_t len, loff_t *ppos)
{
        /* See if we got the magic character 'V' and reload the timer */
        if (len) {
                if (!nowayout) {
                        size_t i;

                        /* reset expect flag */
                        expect_close = 0;

                        /* scan to see whether or not we got the
                           magic character */
                        for (i = 0; i != len; i++) {
                                char c;
                                if (get_user(c, data + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        expect_close = 42;
                        }
                }

                /* someone wrote to us, we should reload the timer */
                wb_smsc_wdt_reset_timer();
        }
        return len;
}

/* ioctl => control interface */

static long wb_smsc_wdt_ioctl(struct file *file,
                                        unsigned int cmd, unsigned long arg)
{
        int new_timeout;

        union {
                struct watchdog_info __user *ident;
                int __user *i;
        } uarg;

        static const struct watchdog_info ident = {
                .options =              WDIOF_KEEPALIVEPING |
                                        WDIOF_SETTIMEOUT |
                                        WDIOF_MAGICCLOSE,
                .firmware_version =     0,
                .identity =             "SMsC 37B787 Watchdog",
        };

        uarg.i = (int __user *)arg;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(uarg.ident, &ident, sizeof(ident))
                                                                ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
                return put_user(wb_smsc_wdt_status(), uarg.i);
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, uarg.i);
        case WDIOC_SETOPTIONS:
        {
                int options, retval = -EINVAL;

                if (get_user(options, uarg.i))
                        return -EFAULT;

                if (options & WDIOS_DISABLECARD) {
                        wb_smsc_wdt_disable();
                        retval = 0;
                }
                if (options & WDIOS_ENABLECARD) {
                        wb_smsc_wdt_enable();
                        retval = 0;
                }
                return retval;
        }
        case WDIOC_KEEPALIVE:
                wb_smsc_wdt_reset_timer();
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(new_timeout, uarg.i))
                        return -EFAULT;
                /* the API states this is given in secs */
                if (unit == UNIT_MINUTE)
                        new_timeout /= 60;
                if (new_timeout < 0 || new_timeout > MAX_TIMEOUT)
                        return -EINVAL;
                timeout = new_timeout;
                wb_smsc_wdt_set_timeout(timeout);
                fallthrough;    /* and return the new timeout */
        case WDIOC_GETTIMEOUT:
                new_timeout = timeout;
                if (unit == UNIT_MINUTE)
                        new_timeout *= 60;
                return put_user(new_timeout, uarg.i);
        default:
                return -ENOTTY;
        }
}

/* -- Notifier funtions -----------------------------------------*/

static int wb_smsc_wdt_notify_sys(struct notifier_block *this,
                                        unsigned long code, void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT) {
                /* set timeout to 0, to avoid possible race-condition */
                timeout = 0;
                wb_smsc_wdt_disable();
        }
        return NOTIFY_DONE;
}

/* -- Module's structures ---------------------------------------*/

static const struct file_operations wb_smsc_wdt_fops = {
        .owner    = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = wb_smsc_wdt_write,
        .unlocked_ioctl = wb_smsc_wdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = wb_smsc_wdt_open,
        .release        = wb_smsc_wdt_release,
};

static struct notifier_block wb_smsc_wdt_notifier = {
        .notifier_call  = wb_smsc_wdt_notify_sys,
};

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

/* -- Module init functions -------------------------------------*/

/* module's "constructor" */

static int __init wb_smsc_wdt_init(void)
{
        int ret;

        pr_info("SMsC 37B787 watchdog component driver "
                VERSION " initialising...\n");

        if (!request_region(IOPORT, IOPORT_SIZE, "SMsC 37B787 watchdog")) {
                pr_err("Unable to register IO port %#x\n", IOPORT);
                ret = -EBUSY;
                goto out_pnp;
        }

        /* set new maximum, if it's too big */
        if (timeout > MAX_TIMEOUT)
                timeout = MAX_TIMEOUT;

        /* init the watchdog timer */
        wb_smsc_wdt_initialize();

        ret = register_reboot_notifier(&wb_smsc_wdt_notifier);
        if (ret) {
                pr_err("Unable to register reboot notifier err = %d\n", ret);
                goto out_io;
        }

        ret = misc_register(&wb_smsc_wdt_miscdev);
        if (ret) {
                pr_err("Unable to register miscdev on minor %d\n",
                       WATCHDOG_MINOR);
                goto out_rbt;
        }

        /* output info */
        pr_info("Timeout set to %d %s\n",
                timeout, (unit == UNIT_SECOND) ? "second(s)" : "minute(s)");
        pr_info("Watchdog initialized and sleeping (nowayout=%d)...\n",
                nowayout);
out_clean:
        return ret;

out_rbt:
        unregister_reboot_notifier(&wb_smsc_wdt_notifier);

out_io:
        release_region(IOPORT, IOPORT_SIZE);

out_pnp:
        goto out_clean;
}

/* module's "destructor" */

static void __exit wb_smsc_wdt_exit(void)
{
        /* Stop the timer before we leave */
        if (!nowayout) {
                wb_smsc_wdt_shutdown();
                pr_info("Watchdog disabled\n");
        }

        misc_deregister(&wb_smsc_wdt_miscdev);
        unregister_reboot_notifier(&wb_smsc_wdt_notifier);
        release_region(IOPORT, IOPORT_SIZE);

        pr_info("SMsC 37B787 watchdog component driver removed\n");
}

module_init(wb_smsc_wdt_init);
module_exit(wb_smsc_wdt_exit);

MODULE_AUTHOR("Sven Anders <anders@anduras.de>");
MODULE_DESCRIPTION("Driver for SMsC 37B787 watchdog component (Version "
                                                                VERSION ")");
MODULE_LICENSE("GPL");

#ifdef SMSC_SUPPORT_MINUTES
module_param(unit, int, 0);
MODULE_PARM_DESC(unit,
                "set unit to use, 0=seconds or 1=minutes, default is 0");
#endif

module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "range is 1-255 units, default is 60");

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