// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      W83977F Watchdog Timer Driver for Winbond W83977F I/O Chip
 *
 *      (c) Copyright 2005  Jose Goncalves <jose.goncalves@inov.pt>
 *
 *      Based on w83877f_wdt.c by Scott Jennings,
 *           and wdt977.c by Woody Suwalski
 *
 *                      -----------------------
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/watchdog.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/uaccess.h>
#include <linux/io.h>


#define WATCHDOG_VERSION  "1.00"
#define WATCHDOG_NAME     "W83977F WDT"

#define IO_INDEX_PORT     0x3F0
#define IO_DATA_PORT      (IO_INDEX_PORT+1)

#define UNLOCK_DATA       0x87
#define LOCK_DATA         0xAA
#define DEVICE_REGISTER   0x07

#define DEFAULT_TIMEOUT   45            /* default timeout in seconds */

static  int timeout = DEFAULT_TIMEOUT;
static  int timeoutW;                   /* timeout in watchdog counter units */
static  unsigned long timer_alive;
static  int testmode;
static  char expect_close;
static  DEFINE_SPINLOCK(spinlock);

module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
                "Watchdog timeout in seconds (15..7635), default="
                                __MODULE_STRING(DEFAULT_TIMEOUT) ")");
module_param(testmode, int, 0);
MODULE_PARM_DESC(testmode, "Watchdog testmode (1 = no reboot), default=0");

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) ")");

/*
 * Start the watchdog
 */

static int wdt_start(void)
{
        unsigned long flags;

        spin_lock_irqsave(&spinlock, flags);

        /* Unlock the SuperIO chip */
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);

        /*
         * Select device Aux2 (device=8) to set watchdog regs F2, F3 and F4.
         * F2 has the timeout in watchdog counter units.
         * F3 is set to enable watchdog LED blink at timeout.
         * F4 is used to just clear the TIMEOUT'ed state (bit 0).
         */
        outb_p(DEVICE_REGISTER, IO_INDEX_PORT);
        outb_p(0x08, IO_DATA_PORT);
        outb_p(0xF2, IO_INDEX_PORT);
        outb_p(timeoutW, IO_DATA_PORT);
        outb_p(0xF3, IO_INDEX_PORT);
        outb_p(0x08, IO_DATA_PORT);
        outb_p(0xF4, IO_INDEX_PORT);
        outb_p(0x00, IO_DATA_PORT);

        /* Set device Aux2 active */
        outb_p(0x30, IO_INDEX_PORT);
        outb_p(0x01, IO_DATA_PORT);

        /*
         * Select device Aux1 (dev=7) to set GP16 as the watchdog output
         * (in reg E6) and GP13 as the watchdog LED output (in reg E3).
         * Map GP16 at pin 119.
         * In test mode watch the bit 0 on F4 to indicate "triggered" or
         * check watchdog LED on SBC.
         */
        outb_p(DEVICE_REGISTER, IO_INDEX_PORT);
        outb_p(0x07, IO_DATA_PORT);
        if (!testmode) {
                unsigned pin_map;

                outb_p(0xE6, IO_INDEX_PORT);
                outb_p(0x0A, IO_DATA_PORT);
                outb_p(0x2C, IO_INDEX_PORT);
                pin_map = inb_p(IO_DATA_PORT);
                pin_map |= 0x10;
                pin_map &= ~(0x20);
                outb_p(0x2C, IO_INDEX_PORT);
                outb_p(pin_map, IO_DATA_PORT);
        }
        outb_p(0xE3, IO_INDEX_PORT);
        outb_p(0x08, IO_DATA_PORT);

        /* Set device Aux1 active */
        outb_p(0x30, IO_INDEX_PORT);
        outb_p(0x01, IO_DATA_PORT);

        /* Lock the SuperIO chip */
        outb_p(LOCK_DATA, IO_INDEX_PORT);

        spin_unlock_irqrestore(&spinlock, flags);

        pr_info("activated\n");

        return 0;
}

/*
 * Stop the watchdog
 */

static int wdt_stop(void)
{
        unsigned long flags;

        spin_lock_irqsave(&spinlock, flags);

        /* Unlock the SuperIO chip */
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);

        /*
         * Select device Aux2 (device=8) to set watchdog regs F2, F3 and F4.
         * F2 is reset to its default value (watchdog timer disabled).
         * F3 is reset to its default state.
         * F4 clears the TIMEOUT'ed state (bit 0) - back to default.
         */
        outb_p(DEVICE_REGISTER, IO_INDEX_PORT);
        outb_p(0x08, IO_DATA_PORT);
        outb_p(0xF2, IO_INDEX_PORT);
        outb_p(0xFF, IO_DATA_PORT);
        outb_p(0xF3, IO_INDEX_PORT);
        outb_p(0x00, IO_DATA_PORT);
        outb_p(0xF4, IO_INDEX_PORT);
        outb_p(0x00, IO_DATA_PORT);
        outb_p(0xF2, IO_INDEX_PORT);
        outb_p(0x00, IO_DATA_PORT);

        /*
         * Select device Aux1 (dev=7) to set GP16 (in reg E6) and
         * Gp13 (in reg E3) as inputs.
         */
        outb_p(DEVICE_REGISTER, IO_INDEX_PORT);
        outb_p(0x07, IO_DATA_PORT);
        if (!testmode) {
                outb_p(0xE6, IO_INDEX_PORT);
                outb_p(0x01, IO_DATA_PORT);
        }
        outb_p(0xE3, IO_INDEX_PORT);
        outb_p(0x01, IO_DATA_PORT);

        /* Lock the SuperIO chip */
        outb_p(LOCK_DATA, IO_INDEX_PORT);

        spin_unlock_irqrestore(&spinlock, flags);

        pr_info("shutdown\n");

        return 0;
}

/*
 * Send a keepalive ping to the watchdog
 * This is done by simply re-writing the timeout to reg. 0xF2
 */

static int wdt_keepalive(void)
{
        unsigned long flags;

        spin_lock_irqsave(&spinlock, flags);

        /* Unlock the SuperIO chip */
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);

        /* Select device Aux2 (device=8) to kick watchdog reg F2 */
        outb_p(DEVICE_REGISTER, IO_INDEX_PORT);
        outb_p(0x08, IO_DATA_PORT);
        outb_p(0xF2, IO_INDEX_PORT);
        outb_p(timeoutW, IO_DATA_PORT);

        /* Lock the SuperIO chip */
        outb_p(LOCK_DATA, IO_INDEX_PORT);

        spin_unlock_irqrestore(&spinlock, flags);

        return 0;
}

/*
 * Set the watchdog timeout value
 */

static int wdt_set_timeout(int t)
{
        unsigned int tmrval;

        /*
         * Convert seconds to watchdog counter time units, rounding up.
         * On PCM-5335 watchdog units are 30 seconds/step with 15 sec startup
         * value. This information is supplied in the PCM-5335 manual and was
         * checked by me on a real board. This is a bit strange because W83977f
         * datasheet says counter unit is in minutes!
         */
        if (t < 15)
                return -EINVAL;

        tmrval = ((t + 15) + 29) / 30;

        if (tmrval > 255)
                return -EINVAL;

        /*
         * timeout is the timeout in seconds,
         * timeoutW is the timeout in watchdog counter units.
         */
        timeoutW = tmrval;
        timeout = (timeoutW * 30) - 15;
        return 0;
}

/*
 * Get the watchdog status
 */

static int wdt_get_status(int *status)
{
        int new_status;
        unsigned long flags;

        spin_lock_irqsave(&spinlock, flags);

        /* Unlock the SuperIO chip */
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);
        outb_p(UNLOCK_DATA, IO_INDEX_PORT);

        /* Select device Aux2 (device=8) to read watchdog reg F4 */
        outb_p(DEVICE_REGISTER, IO_INDEX_PORT);
        outb_p(0x08, IO_DATA_PORT);
        outb_p(0xF4, IO_INDEX_PORT);
        new_status = inb_p(IO_DATA_PORT);

        /* Lock the SuperIO chip */
        outb_p(LOCK_DATA, IO_INDEX_PORT);

        spin_unlock_irqrestore(&spinlock, flags);

        *status = 0;
        if (new_status & 1)
                *status |= WDIOF_CARDRESET;

        return 0;
}


/*
 *      /dev/watchdog handling
 */

static int wdt_open(struct inode *inode, struct file *file)
{
        /* If the watchdog is alive we don't need to start it again */
        if (test_and_set_bit(0, &timer_alive))
                return -EBUSY;

        if (nowayout)
                __module_get(THIS_MODULE);

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

static int wdt_release(struct inode *inode, struct file *file)
{
        /*
         * Shut off the timer.
         * Lock it in if it's a module and we set nowayout
         */
        if (expect_close == 42) {
                wdt_stop();
                clear_bit(0, &timer_alive);
        } else {
                wdt_keepalive();
                pr_crit("unexpected close, not stopping watchdog!\n");
        }
        expect_close = 0;
        return 0;
}

/*
 *      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 don't define content meaning.
 */

static ssize_t wdt_write(struct file *file, const char __user *buf,
                            size_t count, loff_t *ppos)
{
        /* See if we got the magic character 'V' and reload the timer */
        if (count) {
                if (!nowayout) {
                        size_t ofs;

                        /* note: just in case someone wrote the
                           magic character long ago */
                        expect_close = 0;

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

                /* someone wrote to us, we should restart timer */
                wdt_keepalive();
        }
        return count;
}

/*
 *      wdt_ioctl:
 *      @inode: inode of the device
 *      @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.
 */

static const struct watchdog_info ident = {
        .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
        .firmware_version =     1,
        .identity = WATCHDOG_NAME,
};

static long wdt_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        int status;
        int new_options, retval = -EINVAL;
        int new_timeout;
        union {
                struct watchdog_info __user *ident;
                int __user *i;
        } uarg;

        uarg.i = (int __user *)arg;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(uarg.ident, &ident,
                                                sizeof(ident)) ? -EFAULT : 0;

        case WDIOC_GETSTATUS:
                wdt_get_status(&status);
                return put_user(status, uarg.i);

        case WDIOC_GETBOOTSTATUS:
                return put_user(0, uarg.i);

        case WDIOC_SETOPTIONS:
                if (get_user(new_options, uarg.i))
                        return -EFAULT;

                if (new_options & WDIOS_DISABLECARD) {
                        wdt_stop();
                        retval = 0;
                }

                if (new_options & WDIOS_ENABLECARD) {
                        wdt_start();
                        retval = 0;
                }

                return retval;

        case WDIOC_KEEPALIVE:
                wdt_keepalive();
                return 0;

        case WDIOC_SETTIMEOUT:
                if (get_user(new_timeout, uarg.i))
                        return -EFAULT;

                if (wdt_set_timeout(new_timeout))
                        return -EINVAL;

                wdt_keepalive();
                fallthrough;

        case WDIOC_GETTIMEOUT:
                return put_user(timeout, uarg.i);

        default:
                return -ENOTTY;

        }
}

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;
}

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 struct notifier_block wdt_notifier = {
        .notifier_call = wdt_notify_sys,
};

static int __init w83977f_wdt_init(void)
{
        int rc;

        pr_info("driver v%s\n", WATCHDOG_VERSION);

        /*
         * Check that the timeout value is within it's range;
         * if not reset to the default
         */
        if (wdt_set_timeout(timeout)) {
                wdt_set_timeout(DEFAULT_TIMEOUT);
                pr_info("timeout value must be 15 <= timeout <= 7635, using %d\n",
                        DEFAULT_TIMEOUT);
        }

        if (!request_region(IO_INDEX_PORT, 2, WATCHDOG_NAME)) {
                pr_err("I/O address 0x%04x already in use\n", IO_INDEX_PORT);
                rc = -EIO;
                goto err_out;
        }

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

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

        pr_info("initialized. timeout=%d sec (nowayout=%d testmode=%d)\n",
                timeout, nowayout, testmode);

        return 0;

err_out_reboot:
        unregister_reboot_notifier(&wdt_notifier);
err_out_region:
        release_region(IO_INDEX_PORT, 2);
err_out:
        return rc;
}

static void __exit w83977f_wdt_exit(void)
{
        wdt_stop();
        misc_deregister(&wdt_miscdev);
        unregister_reboot_notifier(&wdt_notifier);
        release_region(IO_INDEX_PORT, 2);
}

module_init(w83977f_wdt_init);
module_exit(w83977f_wdt_exit);

MODULE_AUTHOR("Jose Goncalves <jose.goncalves@inov.pt>");
MODULE_DESCRIPTION("Driver for watchdog timer in W83977F I/O chip");
MODULE_LICENSE("GPL");