// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      IT8712F "Smart Guardian" Watchdog support
 *
 *      Copyright (c) 2006-2007 Jorge Boncompte - DTI2 <jorge@dti2.net>
 *
 *      Based on info and code taken from:
 *
 *      drivers/char/watchdog/scx200_wdt.c
 *      drivers/hwmon/it87.c
 *      IT8712F EC-LPC I/O Preliminary Specification 0.8.2
 *      IT8712F EC-LPC I/O Preliminary Specification 0.9.3
 *
 *      The author(s) of this software shall not be held liable for damages
 *      of any nature resulting due to the use of this software. This
 *      software is provided AS-IS with no warranties.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

#define NAME "it8712f_wdt"

MODULE_AUTHOR("Jorge Boncompte - DTI2 <jorge@dti2.net>");
MODULE_DESCRIPTION("IT8712F Watchdog Driver");
MODULE_LICENSE("GPL");

static int max_units = 255;
static int margin = 60;         /* in seconds */
module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");

static unsigned long wdt_open;
static unsigned expect_close;
static unsigned char revision;

/* Dog Food address - We use the game port address */
static unsigned short address;

#define REG             0x2e    /* The register to read/write */
#define VAL             0x2f    /* The value to read/write */

#define LDN             0x07    /* Register: Logical device select */
#define DEVID           0x20    /* Register: Device ID */
#define DEVREV          0x22    /* Register: Device Revision */
#define ACT_REG         0x30    /* LDN Register: Activation */
#define BASE_REG        0x60    /* LDN Register: Base address */

#define IT8712F_DEVID   0x8712

#define LDN_GPIO        0x07    /* GPIO and Watch Dog Timer */
#define LDN_GAME        0x09    /* Game Port */

#define WDT_CONTROL     0x71    /* WDT Register: Control */
#define WDT_CONFIG      0x72    /* WDT Register: Configuration */
#define WDT_TIMEOUT     0x73    /* WDT Register: Timeout Value */

#define WDT_RESET_GAME  0x10    /* Reset timer on read or write to game port */
#define WDT_RESET_KBD   0x20    /* Reset timer on keyboard interrupt */
#define WDT_RESET_MOUSE 0x40    /* Reset timer on mouse interrupt */
#define WDT_RESET_CIR   0x80    /* Reset timer on consumer IR interrupt */

#define WDT_UNIT_SEC    0x80    /* If 0 in MINUTES */

#define WDT_OUT_PWROK   0x10    /* Pulse PWROK on timeout */
#define WDT_OUT_KRST    0x40    /* Pulse reset on timeout */

static int wdt_control_reg = WDT_RESET_GAME;
module_param(wdt_control_reg, int, 0);
MODULE_PARM_DESC(wdt_control_reg, "Value to write to watchdog control "
                "register. The default WDT_RESET_GAME resets the timer on "
                "game port reads that this driver generates. You can also "
                "use KBD, MOUSE or CIR if you have some external way to "
                "generate those interrupts.");

static int superio_inb(int reg)
{
        outb(reg, REG);
        return inb(VAL);
}

static void superio_outb(int val, int reg)
{
        outb(reg, REG);
        outb(val, VAL);
}

static int superio_inw(int reg)
{
        int val;
        outb(reg++, REG);
        val = inb(VAL) << 8;
        outb(reg, REG);
        val |= inb(VAL);
        return val;
}

static inline void superio_select(int ldn)
{
        outb(LDN, REG);
        outb(ldn, VAL);
}

static inline int superio_enter(void)
{
        /*
         * Try to reserve REG and REG + 1 for exclusive access.
         */
        if (!request_muxed_region(REG, 2, NAME))
                return -EBUSY;

        outb(0x87, REG);
        outb(0x01, REG);
        outb(0x55, REG);
        outb(0x55, REG);
        return 0;
}

static inline void superio_exit(void)
{
        outb(0x02, REG);
        outb(0x02, VAL);
        release_region(REG, 2);
}

static inline void it8712f_wdt_ping(void)
{
        if (wdt_control_reg & WDT_RESET_GAME)
                inb(address);
}

static void it8712f_wdt_update_margin(void)
{
        int config = WDT_OUT_KRST | WDT_OUT_PWROK;
        int units = margin;

        /* Switch to minutes precision if the configured margin
         * value does not fit within the register width.
         */
        if (units <= max_units) {
                config |= WDT_UNIT_SEC; /* else UNIT is MINUTES */
                pr_info("timer margin %d seconds\n", units);
        } else {
                units /= 60;
                pr_info("timer margin %d minutes\n", units);
        }
        superio_outb(config, WDT_CONFIG);

        if (revision >= 0x08)
                superio_outb(units >> 8, WDT_TIMEOUT + 1);
        superio_outb(units, WDT_TIMEOUT);
}

static int it8712f_wdt_get_status(void)
{
        if (superio_inb(WDT_CONTROL) & 0x01)
                return WDIOF_CARDRESET;
        else
                return 0;
}

static int it8712f_wdt_enable(void)
{
        int ret = superio_enter();
        if (ret)
                return ret;

        pr_debug("enabling watchdog timer\n");
        superio_select(LDN_GPIO);

        superio_outb(wdt_control_reg, WDT_CONTROL);

        it8712f_wdt_update_margin();

        superio_exit();

        it8712f_wdt_ping();

        return 0;
}

static int it8712f_wdt_disable(void)
{
        int ret = superio_enter();
        if (ret)
                return ret;

        pr_debug("disabling watchdog timer\n");
        superio_select(LDN_GPIO);

        superio_outb(0, WDT_CONFIG);
        superio_outb(0, WDT_CONTROL);
        if (revision >= 0x08)
                superio_outb(0, WDT_TIMEOUT + 1);
        superio_outb(0, WDT_TIMEOUT);

        superio_exit();
        return 0;
}

static int it8712f_wdt_notify(struct notifier_block *this,
                    unsigned long code, void *unused)
{
        if (code == SYS_HALT || code == SYS_POWER_OFF)
                if (!nowayout)
                        it8712f_wdt_disable();

        return NOTIFY_DONE;
}

static struct notifier_block it8712f_wdt_notifier = {
        .notifier_call = it8712f_wdt_notify,
};

static ssize_t it8712f_wdt_write(struct file *file, const char __user *data,
                                        size_t len, loff_t *ppos)
{
        /* check for a magic close character */
        if (len) {
                size_t i;

                it8712f_wdt_ping();

                expect_close = 0;
                for (i = 0; i < len; ++i) {
                        char c;
                        if (get_user(c, data + i))
                                return -EFAULT;
                        if (c == 'V')
                                expect_close = 42;
                }
        }

        return len;
}

static long it8712f_wdt_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        static const struct watchdog_info ident = {
                .identity = "IT8712F Watchdog",
                .firmware_version = 1,
                .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
                                                WDIOF_MAGICCLOSE,
        };
        int value;
        int ret;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &ident, sizeof(ident)))
                        return -EFAULT;
                return 0;
        case WDIOC_GETSTATUS:
                ret = superio_enter();
                if (ret)
                        return ret;
                superio_select(LDN_GPIO);

                value = it8712f_wdt_get_status();

                superio_exit();

                return put_user(value, p);
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);
        case WDIOC_KEEPALIVE:
                it8712f_wdt_ping();
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(value, p))
                        return -EFAULT;
                if (value < 1)
                        return -EINVAL;
                if (value > (max_units * 60))
                        return -EINVAL;
                margin = value;
                ret = superio_enter();
                if (ret)
                        return ret;
                superio_select(LDN_GPIO);

                it8712f_wdt_update_margin();

                superio_exit();
                it8712f_wdt_ping();
                fallthrough;
        case WDIOC_GETTIMEOUT:
                if (put_user(margin, p))
                        return -EFAULT;
                return 0;
        default:
                return -ENOTTY;
        }
}

static int it8712f_wdt_open(struct inode *inode, struct file *file)
{
        int ret;
        /* only allow one at a time */
        if (test_and_set_bit(0, &wdt_open))
                return -EBUSY;

        ret = it8712f_wdt_enable();
        if (ret)
                return ret;
        return stream_open(inode, file);
}

static int it8712f_wdt_release(struct inode *inode, struct file *file)
{
        if (expect_close != 42) {
                pr_warn("watchdog device closed unexpectedly, will not disable the watchdog timer\n");
        } else if (!nowayout) {
                if (it8712f_wdt_disable())
                        pr_warn("Watchdog disable failed\n");
        }
        expect_close = 0;
        clear_bit(0, &wdt_open);

        return 0;
}

static const struct file_operations it8712f_wdt_fops = {
        .owner = THIS_MODULE,
        .write = it8712f_wdt_write,
        .unlocked_ioctl = it8712f_wdt_ioctl,
        .compat_ioctl = compat_ptr_ioctl,
        .open = it8712f_wdt_open,
        .release = it8712f_wdt_release,
};

static struct miscdevice it8712f_wdt_miscdev = {
        .minor = WATCHDOG_MINOR,
        .name = "watchdog",
        .fops = &it8712f_wdt_fops,
};

static int __init it8712f_wdt_find(unsigned short *address)
{
        int err = -ENODEV;
        int chip_type;
        int ret = superio_enter();
        if (ret)
                return ret;

        chip_type = superio_inw(DEVID);
        if (chip_type != IT8712F_DEVID)
                goto exit;

        superio_select(LDN_GAME);
        superio_outb(1, ACT_REG);
        if (!(superio_inb(ACT_REG) & 0x01)) {
                pr_err("Device not activated, skipping\n");
                goto exit;
        }

        *address = superio_inw(BASE_REG);
        if (*address == 0) {
                pr_err("Base address not set, skipping\n");
                goto exit;
        }

        err = 0;
        revision = superio_inb(DEVREV) & 0x0f;

        /* Later revisions have 16-bit values per datasheet 0.9.1 */
        if (revision >= 0x08)
                max_units = 65535;

        if (margin > (max_units * 60))
                margin = (max_units * 60);

        pr_info("Found IT%04xF chip revision %d - using DogFood address 0x%x\n",
                chip_type, revision, *address);

exit:
        superio_exit();
        return err;
}

static int __init it8712f_wdt_init(void)
{
        int err = 0;

        if (it8712f_wdt_find(&address))
                return -ENODEV;

        if (!request_region(address, 1, "IT8712F Watchdog")) {
                pr_warn("watchdog I/O region busy\n");
                return -EBUSY;
        }

        err = it8712f_wdt_disable();
        if (err) {
                pr_err("unable to disable watchdog timer\n");
                goto out;
        }

        err = register_reboot_notifier(&it8712f_wdt_notifier);
        if (err) {
                pr_err("unable to register reboot notifier\n");
                goto out;
        }

        err = misc_register(&it8712f_wdt_miscdev);
        if (err) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, err);
                goto reboot_out;
        }

        return 0;


reboot_out:
        unregister_reboot_notifier(&it8712f_wdt_notifier);
out:
        release_region(address, 1);
        return err;
}

static void __exit it8712f_wdt_exit(void)
{
        misc_deregister(&it8712f_wdt_miscdev);
        unregister_reboot_notifier(&it8712f_wdt_notifier);
        release_region(address, 1);
}

module_init(it8712f_wdt_init);
module_exit(it8712f_wdt_exit);