// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      National Semiconductor PC87307/PC97307 (ala SC1200) WDT driver
 *      (c) Copyright 2002 Zwane Mwaikambo <zwane@commfireservices.com>,
 *                      All Rights Reserved.
 *      Based on wdt.c and wdt977.c by Alan Cox and Woody Suwalski respectively.
 *
 *      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.
 *
 *      Changelog:
 *      20020220 Zwane Mwaikambo        Code based on datasheet, no hardware.
 *      20020221 Zwane Mwaikambo        Cleanups as suggested by Jeff Garzik
 *                                      and Alan Cox.
 *      20020222 Zwane Mwaikambo        Added probing.
 *      20020225 Zwane Mwaikambo        Added ISAPNP support.
 *      20020412 Rob Radez              Broke out start/stop functions
 *               <rob@osinvestor.com>   Return proper status instead of
 *                                      temperature warning
 *                                      Add WDIOC_GETBOOTSTATUS and
 *                                      WDIOC_SETOPTIONS ioctls
 *                                      Fix CONFIG_WATCHDOG_NOWAYOUT
 *      20020530 Joel Becker            Add Matt Domsch's nowayout module
 *                                      option
 *      20030116 Adam Belay             Updated to the latest pnp code
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

#define SC1200_MODULE_VER       "build 20020303"
#define SC1200_MODULE_NAME      "sc1200wdt"

#define MAX_TIMEOUT     255     /* 255 minutes */
#define PMIR            (io)    /* Power Management Index Register */
#define PMDR            (io+1)  /* Power Management Data Register */

/* Data Register indexes */
#define FER1            0x00    /* Function enable register 1 */
#define FER2            0x01    /* Function enable register 2 */
#define PMC1            0x02    /* Power Management Ctrl 1 */
#define PMC2            0x03    /* Power Management Ctrl 2 */
#define PMC3            0x04    /* Power Management Ctrl 3 */
#define WDTO            0x05    /* Watchdog timeout register */
#define WDCF            0x06    /* Watchdog config register */
#define WDST            0x07    /* Watchdog status register */

/* WDCF bitfields - which devices assert WDO */
#define KBC_IRQ         0x01    /* Keyboard Controller */
#define MSE_IRQ         0x02    /* Mouse */
#define UART1_IRQ       0x03    /* Serial0 */
#define UART2_IRQ       0x04    /* Serial1 */
/* 5 -7 are reserved */

static int timeout = 1;
static int io = -1;
static int io_len = 2;          /* for non plug and play */
static unsigned long open_flag;
static char expect_close;
static DEFINE_SPINLOCK(sc1200wdt_lock); /* io port access serialisation */

#if defined CONFIG_PNP
static int isapnp = 1;
static struct pnp_dev *wdt_dev;

module_param(isapnp, int, 0);
MODULE_PARM_DESC(isapnp,
        "When set to 0 driver ISA PnP support will be disabled");
#endif

module_param_hw(io, int, ioport, 0);
MODULE_PARM_DESC(io, "io port");
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout, "range is 0-255 minutes, default is 1");

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) ")");



/* Read from Data Register */
static inline void __sc1200wdt_read_data(unsigned char index,
                                                unsigned char *data)
{
        outb_p(index, PMIR);
        *data = inb(PMDR);
}

static void sc1200wdt_read_data(unsigned char index, unsigned char *data)
{
        spin_lock(&sc1200wdt_lock);
        __sc1200wdt_read_data(index, data);
        spin_unlock(&sc1200wdt_lock);
}

/* Write to Data Register */
static inline void __sc1200wdt_write_data(unsigned char index,
                                                unsigned char data)
{
        outb_p(index, PMIR);
        outb(data, PMDR);
}

static inline void sc1200wdt_write_data(unsigned char index,
                                                unsigned char data)
{
        spin_lock(&sc1200wdt_lock);
        __sc1200wdt_write_data(index, data);
        spin_unlock(&sc1200wdt_lock);
}


static void sc1200wdt_start(void)
{
        unsigned char reg;
        spin_lock(&sc1200wdt_lock);

        __sc1200wdt_read_data(WDCF, &reg);
        /* assert WDO when any of the following interrupts are triggered too */
        reg |= (KBC_IRQ | MSE_IRQ | UART1_IRQ | UART2_IRQ);
        __sc1200wdt_write_data(WDCF, reg);
        /* set the timeout and get the ball rolling */
        __sc1200wdt_write_data(WDTO, timeout);

        spin_unlock(&sc1200wdt_lock);
}

static void sc1200wdt_stop(void)
{
        sc1200wdt_write_data(WDTO, 0);
}

/* This returns the status of the WDO signal, inactive high. */
static inline int sc1200wdt_status(void)
{
        unsigned char ret;

        sc1200wdt_read_data(WDST, &ret);
        /* If the bit is inactive, the watchdog is enabled, so return
         * KEEPALIVEPING which is a bit of a kludge because there's nothing
         * else for enabled/disabled status
         */
        return (ret & 0x01) ? 0 : WDIOF_KEEPALIVEPING;
}

static int sc1200wdt_open(struct inode *inode, struct file *file)
{
        /* allow one at a time */
        if (test_and_set_bit(0, &open_flag))
                return -EBUSY;

        if (timeout > MAX_TIMEOUT)
                timeout = MAX_TIMEOUT;

        sc1200wdt_start();
        pr_info("Watchdog enabled, timeout = %d min(s)", timeout);

        return stream_open(inode, file);
}


static long sc1200wdt_ioctl(struct file *file, unsigned int cmd,
                                                unsigned long arg)
{
        int new_timeout;
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        static const struct watchdog_info ident = {
                .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
                                                        WDIOF_MAGICCLOSE,
                .firmware_version = 0,
                .identity = "PC87307/PC97307",
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                if (copy_to_user(argp, &ident, sizeof(ident)))
                        return -EFAULT;
                return 0;

        case WDIOC_GETSTATUS:
                return put_user(sc1200wdt_status(), p);

        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);

        case WDIOC_SETOPTIONS:
        {
                int options, retval = -EINVAL;

                if (get_user(options, p))
                        return -EFAULT;

                if (options & WDIOS_DISABLECARD) {
                        sc1200wdt_stop();
                        retval = 0;
                }

                if (options & WDIOS_ENABLECARD) {
                        sc1200wdt_start();
                        retval = 0;
                }

                return retval;
        }
        case WDIOC_KEEPALIVE:
                sc1200wdt_write_data(WDTO, timeout);
                return 0;

        case WDIOC_SETTIMEOUT:
                if (get_user(new_timeout, p))
                        return -EFAULT;
                /* the API states this is given in secs */
                new_timeout /= 60;
                if (new_timeout < 0 || new_timeout > MAX_TIMEOUT)
                        return -EINVAL;
                timeout = new_timeout;
                sc1200wdt_write_data(WDTO, timeout);
                fallthrough;    /* and return the new timeout */

        case WDIOC_GETTIMEOUT:
                return put_user(timeout * 60, p);

        default:
                return -ENOTTY;
        }
}


static int sc1200wdt_release(struct inode *inode, struct file *file)
{
        if (expect_close == 42) {
                sc1200wdt_stop();
                pr_info("Watchdog disabled\n");
        } else {
                sc1200wdt_write_data(WDTO, timeout);
                pr_crit("Unexpected close!, timeout = %d min(s)\n", timeout);
        }
        clear_bit(0, &open_flag);
        expect_close = 0;

        return 0;
}


static ssize_t sc1200wdt_write(struct file *file, const char __user *data,
                                                size_t len, loff_t *ppos)
{
        if (len) {
                if (!nowayout) {
                        size_t i;

                        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;
                        }
                }

                sc1200wdt_write_data(WDTO, timeout);
                return len;
        }

        return 0;
}


static int sc1200wdt_notify_sys(struct notifier_block *this,
                                        unsigned long code, void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                sc1200wdt_stop();

        return NOTIFY_DONE;
}


static struct notifier_block sc1200wdt_notifier = {
        .notifier_call =        sc1200wdt_notify_sys,
};

static const struct file_operations sc1200wdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = sc1200wdt_write,
        .unlocked_ioctl = sc1200wdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = sc1200wdt_open,
        .release        = sc1200wdt_release,
};

static struct miscdevice sc1200wdt_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &sc1200wdt_fops,
};


static int __init sc1200wdt_probe(void)
{
        /* The probe works by reading the PMC3 register's default value of 0x0e
         * there is one caveat, if the device disables the parallel port or any
         * of the UARTs we won't be able to detect it.
         * NB. This could be done with accuracy by reading the SID registers,
         * but we don't have access to those io regions.
         */

        unsigned char reg;

        sc1200wdt_read_data(PMC3, &reg);
        reg &= 0x0f;            /* we don't want the UART busy bits */
        return (reg == 0x0e) ? 0 : -ENODEV;
}


#if defined CONFIG_PNP

static const struct pnp_device_id scl200wdt_pnp_devices[] = {
        /* National Semiconductor PC87307/PC97307 watchdog component */
        {.id = "NSC0800", .driver_data = 0},
        {.id = ""},
};

static int scl200wdt_pnp_probe(struct pnp_dev *dev,
                                        const struct pnp_device_id *dev_id)
{
        /* this driver only supports one card at a time */
        if (wdt_dev || !isapnp)
                return -EBUSY;

        wdt_dev = dev;
        io = pnp_port_start(wdt_dev, 0);
        io_len = pnp_port_len(wdt_dev, 0);

        if (!request_region(io, io_len, SC1200_MODULE_NAME)) {
                pr_err("Unable to register IO port %#x\n", io);
                return -EBUSY;
        }

        pr_info("PnP device found at io port %#x/%d\n", io, io_len);
        return 0;
}

static void scl200wdt_pnp_remove(struct pnp_dev *dev)
{
        if (wdt_dev) {
                release_region(io, io_len);
                wdt_dev = NULL;
        }
}

static struct pnp_driver scl200wdt_pnp_driver = {
        .name           = "scl200wdt",
        .id_table       = scl200wdt_pnp_devices,
        .probe          = scl200wdt_pnp_probe,
        .remove         = scl200wdt_pnp_remove,
};

#endif /* CONFIG_PNP */


static int __init sc1200wdt_init(void)
{
        int ret;

        pr_info("%s\n", SC1200_MODULE_VER);

#if defined CONFIG_PNP
        if (isapnp) {
                ret = pnp_register_driver(&scl200wdt_pnp_driver);
                if (ret)
                        goto out_clean;
        }
#endif

        if (io == -1) {
                pr_err("io parameter must be specified\n");
                ret = -EINVAL;
                goto out_pnp;
        }

#if defined CONFIG_PNP
        /* now that the user has specified an IO port and we haven't detected
         * any devices, disable pnp support */
        if (isapnp)
                pnp_unregister_driver(&scl200wdt_pnp_driver);
        isapnp = 0;
#endif

        if (!request_region(io, io_len, SC1200_MODULE_NAME)) {
                pr_err("Unable to register IO port %#x\n", io);
                ret = -EBUSY;
                goto out_pnp;
        }

        ret = sc1200wdt_probe();
        if (ret)
                goto out_io;

        ret = register_reboot_notifier(&sc1200wdt_notifier);
        if (ret) {
                pr_err("Unable to register reboot notifier err = %d\n", ret);
                goto out_io;
        }

        ret = misc_register(&sc1200wdt_miscdev);
        if (ret) {
                pr_err("Unable to register miscdev on minor %d\n",
                       WATCHDOG_MINOR);
                goto out_rbt;
        }

        /* ret = 0 */

out_clean:
        return ret;

out_rbt:
        unregister_reboot_notifier(&sc1200wdt_notifier);

out_io:
        release_region(io, io_len);

out_pnp:
#if defined CONFIG_PNP
        if (isapnp)
                pnp_unregister_driver(&scl200wdt_pnp_driver);
#endif
        goto out_clean;
}


static void __exit sc1200wdt_exit(void)
{
        misc_deregister(&sc1200wdt_miscdev);
        unregister_reboot_notifier(&sc1200wdt_notifier);

#if defined CONFIG_PNP
        if (isapnp)
                pnp_unregister_driver(&scl200wdt_pnp_driver);
        else
#endif
        release_region(io, io_len);
}

module_init(sc1200wdt_init);
module_exit(sc1200wdt_exit);

MODULE_AUTHOR("Zwane Mwaikambo <zwane@commfireservices.com>");
MODULE_DESCRIPTION(
        "Driver for National Semiconductor PC87307/PC97307 watchdog component");
MODULE_LICENSE("GPL");