// SPDX-License-Identifier: GPL-2.0+
/*
 *      Industrial Computer Source WDT501 driver
 *
 *      (c) Copyright 1996-1997 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>
 *
 *      Release 0.10.
 *
 *      Fixes
 *              Dave Gregorich  :       Modularisation and minor bugs
 *              Alan Cox        :       Added the watchdog ioctl() stuff
 *              Alan Cox        :       Fixed the reboot problem (as noted by
 *                                      Matt Crocker).
 *              Alan Cox        :       Added wdt= boot option
 *              Alan Cox        :       Cleaned up copy/user stuff
 *              Tim Hockin      :       Added insmod parameters, comment
 *                                      cleanup, parameterized timeout
 *              Tigran Aivazian :       Restructured wdt_init() to handle
 *                                      failures
 *              Joel Becker     :       Added WDIOC_GET/SETTIMEOUT
 *              Matt Domsch     :       Added nowayout module option
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/interrupt.h>
#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/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#include "wd501p.h"

static unsigned long wdt_is_open;
static char expect_close;

/*
 *      Module parameters
 */

#define WD_TIMO 60                      /* Default heartbeat = 60 seconds */

static int heartbeat = WD_TIMO;
static int wd_heartbeat;
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat,
        "Watchdog heartbeat in seconds. (0 < heartbeat < 65536, default="
                                __MODULE_STRING(WD_TIMO) ")");

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) ")");

/* You must set these - there is no sane way to probe for this board. */
static int io = 0x240;
static int irq = 11;

static DEFINE_SPINLOCK(wdt_lock);

module_param_hw(io, int, ioport, 0);
MODULE_PARM_DESC(io, "WDT io port (default=0x240)");
module_param_hw(irq, int, irq, 0);
MODULE_PARM_DESC(irq, "WDT irq (default=11)");

/* Support for the Fan Tachometer on the WDT501-P */
static int tachometer;
module_param(tachometer, int, 0);
MODULE_PARM_DESC(tachometer,
                "WDT501-P Fan Tachometer support (0=disable, default=0)");

static int type = 500;
module_param(type, int, 0);
MODULE_PARM_DESC(type,
                "WDT501-P Card type (500 or 501, default=500)");

/*
 *      Programming support
 */

static void wdt_ctr_mode(int ctr, int mode)
{
        ctr <<= 6;
        ctr |= 0x30;
        ctr |= (mode << 1);
        outb_p(ctr, WDT_CR);
}

static void wdt_ctr_load(int ctr, int val)
{
        outb_p(val&0xFF, WDT_COUNT0+ctr);
        outb_p(val>>8, WDT_COUNT0+ctr);
}

/**
 *      wdt_start:
 *
 *      Start the watchdog driver.
 */

static int wdt_start(void)
{
        unsigned long flags;
        spin_lock_irqsave(&wdt_lock, flags);
        inb_p(WDT_DC);                  /* Disable watchdog */
        wdt_ctr_mode(0, 3);             /* Program CTR0 for Mode 3:
                                                Square Wave Generator */
        wdt_ctr_mode(1, 2);             /* Program CTR1 for Mode 2:
                                                Rate Generator */
        wdt_ctr_mode(2, 0);             /* Program CTR2 for Mode 0:
                                                Pulse on Terminal Count */
        wdt_ctr_load(0, 8948);          /* Count at 100Hz */
        wdt_ctr_load(1, wd_heartbeat);  /* Heartbeat */
        wdt_ctr_load(2, 65535);         /* Length of reset pulse */
        outb_p(0, WDT_DC);              /* Enable watchdog */
        spin_unlock_irqrestore(&wdt_lock, flags);
        return 0;
}

/**
 *      wdt_stop:
 *
 *      Stop the watchdog driver.
 */

static int wdt_stop(void)
{
        unsigned long flags;
        spin_lock_irqsave(&wdt_lock, flags);
        /* Turn the card off */
        inb_p(WDT_DC);                  /* Disable watchdog */
        wdt_ctr_load(2, 0);             /* 0 length reset pulses now */
        spin_unlock_irqrestore(&wdt_lock, flags);
        return 0;
}

/**
 *      wdt_ping:
 *
 *      Reload counter one with the watchdog heartbeat. We don't bother
 *      reloading the cascade counter.
 */

static void wdt_ping(void)
{
        unsigned long flags;
        spin_lock_irqsave(&wdt_lock, flags);
        /* Write a watchdog value */
        inb_p(WDT_DC);                  /* Disable watchdog */
        wdt_ctr_mode(1, 2);             /* Re-Program CTR1 for Mode 2:
                                                        Rate Generator */
        wdt_ctr_load(1, wd_heartbeat);  /* Heartbeat */
        outb_p(0, WDT_DC);              /* Enable watchdog */
        spin_unlock_irqrestore(&wdt_lock, flags);
}

/**
 *      wdt_set_heartbeat:
 *      @t:             the new heartbeat value that needs to be set.
 *
 *      Set a new heartbeat value for the watchdog device. If the heartbeat
 *      value is incorrect we keep the old value and return -EINVAL. If
 *      successful we return 0.
 */

static int wdt_set_heartbeat(int t)
{
        if (t < 1 || t > 65535)
                return -EINVAL;

        heartbeat = t;
        wd_heartbeat = t * 100;
        return 0;
}

/**
 *      wdt_get_status:
 *
 *      Extract the status information from a WDT watchdog device. There are
 *      several board variants so we have to know which bits are valid. Some
 *      bits default to one and some to zero in order to be maximally painful.
 *
 *      we then map the bits onto the status ioctl flags.
 */

static int wdt_get_status(void)
{
        unsigned char new_status;
        int status = 0;
        unsigned long flags;

        spin_lock_irqsave(&wdt_lock, flags);
        new_status = inb_p(WDT_SR);
        spin_unlock_irqrestore(&wdt_lock, flags);

        if (new_status & WDC_SR_ISOI0)
                status |= WDIOF_EXTERN1;
        if (new_status & WDC_SR_ISII1)
                status |= WDIOF_EXTERN2;
        if (type == 501) {
                if (!(new_status & WDC_SR_TGOOD))
                        status |= WDIOF_OVERHEAT;
                if (!(new_status & WDC_SR_PSUOVER))
                        status |= WDIOF_POWEROVER;
                if (!(new_status & WDC_SR_PSUUNDR))
                        status |= WDIOF_POWERUNDER;
                if (tachometer) {
                        if (!(new_status & WDC_SR_FANGOOD))
                                status |= WDIOF_FANFAULT;
                }
        }
        return status;
}

/**
 *      wdt_get_temperature:
 *
 *      Reports the temperature in degrees Fahrenheit. The API is in
 *      farenheit. It was designed by an imperial measurement luddite.
 */

static int wdt_get_temperature(void)
{
        unsigned short c;
        unsigned long flags;

        spin_lock_irqsave(&wdt_lock, flags);
        c = inb_p(WDT_RT);
        spin_unlock_irqrestore(&wdt_lock, flags);
        return (c * 11 / 15) + 7;
}

static void wdt_decode_501(int status)
{
        if (!(status & WDC_SR_TGOOD))
                pr_crit("Overheat alarm (%d)\n", inb_p(WDT_RT));
        if (!(status & WDC_SR_PSUOVER))
                pr_crit("PSU over voltage\n");
        if (!(status & WDC_SR_PSUUNDR))
                pr_crit("PSU under voltage\n");
}

/**
 *      wdt_interrupt:
 *      @irq:           Interrupt number
 *      @dev_id:        Unused as we don't allow multiple devices.
 *
 *      Handle an interrupt from the board. These are raised when the status
 *      map changes in what the board considers an interesting way. That means
 *      a failure condition occurring.
 */

static irqreturn_t wdt_interrupt(int irq, void *dev_id)
{
        /*
         *      Read the status register see what is up and
         *      then printk it.
         */
        unsigned char status;

        spin_lock(&wdt_lock);
        status = inb_p(WDT_SR);

        pr_crit("WDT status %d\n", status);

        if (type == 501) {
                wdt_decode_501(status);
                if (tachometer) {
                        if (!(status & WDC_SR_FANGOOD))
                                pr_crit("Possible fan fault\n");
                }
        }
        if (!(status & WDC_SR_WCCR)) {
#ifdef SOFTWARE_REBOOT
#ifdef ONLY_TESTING
                pr_crit("Would Reboot\n");
#else
                pr_crit("Initiating system reboot\n");
                emergency_restart();
#endif
#else
                pr_crit("Reset in 5ms\n");
#endif
        }
        spin_unlock(&wdt_lock);
        return IRQ_HANDLED;
}


/**
 *      wdt_write:
 *      @file: file handle to the watchdog
 *      @buf: buffer to write (unused as data does not matter here
 *      @count: count of bytes
 *      @ppos: pointer to the position to write. No seeks allowed
 *
 *      A write to a watchdog device is defined as a keepalive signal. Any
 *      write of data will do, as we we don't define content meaning.
 */

static ssize_t wdt_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;
                        }
                }
                wdt_ping();
        }
        return count;
}

/**
 *      wdt_ioctl:
 *      @file: file handle to the device
 *      @cmd: watchdog command
 *      @arg: argument pointer
 *
 *      The watchdog API defines a common set of functions for all watchdogs
 *      according to their available features. We only actually usefully support
 *      querying capabilities and current status.
 */

static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        int new_heartbeat;
        int status;

        struct watchdog_info ident = {
                .options =              WDIOF_SETTIMEOUT|
                                        WDIOF_MAGICCLOSE|
                                        WDIOF_KEEPALIVEPING,
                .firmware_version =     1,
                .identity =             "WDT500/501",
        };

        /* Add options according to the card we have */
        ident.options |= (WDIOF_EXTERN1|WDIOF_EXTERN2);
        if (type == 501) {
                ident.options |= (WDIOF_OVERHEAT|WDIOF_POWERUNDER|
                                                        WDIOF_POWEROVER);
                if (tachometer)
                        ident.options |= WDIOF_FANFAULT;
        }

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
                status = wdt_get_status();
                return put_user(status, p);
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);
        case WDIOC_KEEPALIVE:
                wdt_ping();
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(new_heartbeat, p))
                        return -EFAULT;
                if (wdt_set_heartbeat(new_heartbeat))
                        return -EINVAL;
                wdt_ping();
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(heartbeat, p);
        default:
                return -ENOTTY;
        }
}

/**
 *      wdt_open:
 *      @inode: inode of device
 *      @file: file handle to device
 *
 *      The watchdog device has been opened. The watchdog device is single
 *      open and on opening we load the counters. Counter zero is a 100Hz
 *      cascade, into counter 1 which downcounts to reboot. When the counter
 *      triggers counter 2 downcounts the length of the reset pulse which
 *      set set to be as long as possible.
 */

static int wdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &wdt_is_open))
                return -EBUSY;
        /*
         *      Activate
         */
        wdt_start();
        return stream_open(inode, file);
}

/**
 *      wdt_release:
 *      @inode: inode to board
 *      @file: file handle to board
 *
 *      The watchdog has a configurable API. There is a religious dispute
 *      between people who want their watchdog to be able to shut down and
 *      those who want to be sure if the watchdog manager dies the machine
 *      reboots. In the former case we disable the counters, in the latter
 *      case you have to open it again very soon.
 */

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

/**
 *      wdt_temp_read:
 *      @file: file handle to the watchdog board
 *      @buf: buffer to write 1 byte into
 *      @count: length of buffer
 *      @ptr: offset (no seek allowed)
 *
 *      Temp_read reports the temperature in degrees Fahrenheit. The API is in
 *      farenheit. It was designed by an imperial measurement luddite.
 */

static ssize_t wdt_temp_read(struct file *file, char __user *buf,
                                                size_t count, loff_t *ptr)
{
        int temperature = wdt_get_temperature();

        if (copy_to_user(buf, &temperature, 1))
                return -EFAULT;

        return 1;
}

/**
 *      wdt_temp_open:
 *      @inode: inode of device
 *      @file: file handle to device
 *
 *      The temperature device has been opened.
 */

static int wdt_temp_open(struct inode *inode, struct file *file)
{
        return stream_open(inode, file);
}

/**
 *      wdt_temp_release:
 *      @inode: inode to board
 *      @file: file handle to board
 *
 *      The temperature device has been closed.
 */

static int wdt_temp_release(struct inode *inode, struct file *file)
{
        return 0;
}

/**
 *      wdt_notify_sys:
 *      @this: our notifier block
 *      @code: the event being reported
 *      @unused: unused
 *
 *      Our notifier is called on system shutdowns. We want to turn the card
 *      off at reboot otherwise the machine will reboot again during memory
 *      test or worse yet during the following fsck. This would suck, in fact
 *      trust me - if it happens it does suck.
 */

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

/*
 *      Kernel Interfaces
 */


static const struct file_operations wdt_fops = {
        .owner          = THIS_MODULE,
        .write          = wdt_write,
        .unlocked_ioctl = wdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = wdt_open,
        .release        = wdt_release,
};

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

static const struct file_operations wdt_temp_fops = {
        .owner          = THIS_MODULE,
        .read           = wdt_temp_read,
        .open           = wdt_temp_open,
        .release        = wdt_temp_release,
};

static struct miscdevice temp_miscdev = {
        .minor  = TEMP_MINOR,
        .name   = "temperature",
        .fops   = &wdt_temp_fops,
};

/*
 *      The WDT card 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,
};

/**
 *      wdt_exit:
 *
 *      Unload the watchdog. You cannot do this with any file handles open.
 *      If your watchdog is set to continue ticking on close and you unload
 *      it, well it keeps ticking. We won't get the interrupt but the board
 *      will not touch PC memory so all is fine. You just have to load a new
 *      module in 60 seconds or reboot.
 */

static void __exit wdt_exit(void)
{
        misc_deregister(&wdt_miscdev);
        if (type == 501)
                misc_deregister(&temp_miscdev);
        unregister_reboot_notifier(&wdt_notifier);
        free_irq(irq, NULL);
        release_region(io, 8);
}

/**
 *      wdt_init:
 *
 *      Set up the WDT watchdog board. All we have to do is grab the
 *      resources we require and bitch if anyone beat us to them.
 *      The open() function will actually kick the board off.
 */

static int __init wdt_init(void)
{
        int ret;

        if (type != 500 && type != 501) {
                pr_err("unknown card type '%d'\n", type);
                return -ENODEV;
        }

        /* Check that the heartbeat value is within it's range;
           if not reset to the default */
        if (wdt_set_heartbeat(heartbeat)) {
                wdt_set_heartbeat(WD_TIMO);
                pr_info("heartbeat value must be 0 < heartbeat < 65536, using %d\n",
                        WD_TIMO);
        }

        if (!request_region(io, 8, "wdt501p")) {
                pr_err("I/O address 0x%04x already in use\n", io);
                ret = -EBUSY;
                goto out;
        }

        ret = request_irq(irq, wdt_interrupt, 0, "wdt501p", NULL);
        if (ret) {
                pr_err("IRQ %d is not free\n", irq);
                goto outreg;
        }

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

        if (type == 501) {
                ret = misc_register(&temp_miscdev);
                if (ret) {
                        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                               TEMP_MINOR, ret);
                        goto outrbt;
                }
        }

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

        pr_info("WDT500/501-P driver 0.10 at 0x%04x (Interrupt %d). heartbeat=%d sec (nowayout=%d)\n",
                io, irq, heartbeat, nowayout);
        if (type == 501)
                pr_info("Fan Tachometer is %s\n",
                        tachometer ? "Enabled" : "Disabled");
        return 0;

outmisc:
        if (type == 501)
                misc_deregister(&temp_miscdev);
outrbt:
        unregister_reboot_notifier(&wdt_notifier);
outirq:
        free_irq(irq, NULL);
outreg:
        release_region(io, 8);
out:
        return ret;
}

module_init(wdt_init);
module_exit(wdt_exit);

MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("Driver for ISA ICS watchdog cards (WDT500/501)");
MODULE_LICENSE("GPL");