// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Intel 21285 watchdog driver
 *      Copyright (c) Phil Blundell <pb@nexus.co.uk>, 1998
 *
 *      based on
 *
 *      SoftDog 0.05:   A Software Watchdog Device
 *
 *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 */

#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/mm.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/uaccess.h>
#include <linux/irq.h>
#include <mach/hardware.h>

#include <asm/mach-types.h>
#include <asm/system_info.h>
#include <asm/hardware/dec21285.h>

/*
 * Define this to stop the watchdog actually rebooting the machine.
 */
#undef ONLY_TESTING

static unsigned int soft_margin = 60;           /* in seconds */
static unsigned int reload;
static unsigned long timer_alive;

#ifdef ONLY_TESTING
/*
 *      If the timer expires..
 */
static void watchdog_fire(int irq, void *dev_id)
{
        pr_crit("Would Reboot\n");
        *CSR_TIMER4_CNTL = 0;
        *CSR_TIMER4_CLR = 0;
}
#endif

/*
 *      Refresh the timer.
 */
static void watchdog_ping(void)
{
        *CSR_TIMER4_LOAD = reload;
}

/*
 *      Allow only one person to hold it open
 */
static int watchdog_open(struct inode *inode, struct file *file)
{
        int ret;

        if (*CSR_SA110_CNTL & (1 << 13))
                return -EBUSY;

        if (test_and_set_bit(1, &timer_alive))
                return -EBUSY;

        reload = soft_margin * (mem_fclk_21285 / 256);

        *CSR_TIMER4_CLR = 0;
        watchdog_ping();
        *CSR_TIMER4_CNTL = TIMER_CNTL_ENABLE | TIMER_CNTL_AUTORELOAD
                | TIMER_CNTL_DIV256;

#ifdef ONLY_TESTING
        ret = request_irq(IRQ_TIMER4, watchdog_fire, 0, "watchdog", NULL);
        if (ret) {
                *CSR_TIMER4_CNTL = 0;
                clear_bit(1, &timer_alive);
        }
#else
        /*
         * Setting this bit is irreversible; once enabled, there is
         * no way to disable the watchdog.
         */
        *CSR_SA110_CNTL |= 1 << 13;

        ret = 0;
#endif
        stream_open(inode, file);
        return ret;
}

/*
 *      Shut off the timer.
 *      Note: if we really have enabled the watchdog, there
 *      is no way to turn off.
 */
static int watchdog_release(struct inode *inode, struct file *file)
{
#ifdef ONLY_TESTING
        free_irq(IRQ_TIMER4, NULL);
        clear_bit(1, &timer_alive);
#endif
        return 0;
}

static ssize_t watchdog_write(struct file *file, const char __user *data,
                              size_t len, loff_t *ppos)
{
        /*
         *      Refresh the timer.
         */
        if (len)
                watchdog_ping();

        return len;
}

static const struct watchdog_info ident = {
        .options        = WDIOF_SETTIMEOUT,
        .identity       = "Footbridge Watchdog",
};

static long watchdog_ioctl(struct file *file, unsigned int cmd,
                           unsigned long arg)
{
        int __user *int_arg = (int __user *)arg;
        int new_margin, ret = -ENOTTY;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                ret = 0;
                if (copy_to_user((void __user *)arg, &ident, sizeof(ident)))
                        ret = -EFAULT;
                break;

        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                ret = put_user(0, int_arg);
                break;

        case WDIOC_KEEPALIVE:
                watchdog_ping();
                ret = 0;
                break;

        case WDIOC_SETTIMEOUT:
                ret = get_user(new_margin, int_arg);
                if (ret)
                        break;

                /* Arbitrary, can't find the card's limits */
                if (new_margin < 0 || new_margin > 60) {
                        ret = -EINVAL;
                        break;
                }

                soft_margin = new_margin;
                reload = soft_margin * (mem_fclk_21285 / 256);
                watchdog_ping();
                fallthrough;
        case WDIOC_GETTIMEOUT:
                ret = put_user(soft_margin, int_arg);
                break;
        }
        return ret;
}

static const struct file_operations watchdog_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = watchdog_write,
        .unlocked_ioctl = watchdog_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = watchdog_open,
        .release        = watchdog_release,
};

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

static int __init footbridge_watchdog_init(void)
{
        int retval;

        if (machine_is_netwinder())
                return -ENODEV;

        retval = misc_register(&watchdog_miscdev);
        if (retval < 0)
                return retval;

        pr_info("Footbridge Watchdog Timer: 0.01, timer margin: %d sec\n",
                soft_margin);

        if (machine_is_cats())
                pr_warn("Warning: Watchdog reset may not work on this machine\n");
        return 0;
}

static void __exit footbridge_watchdog_exit(void)
{
        misc_deregister(&watchdog_miscdev);
}

MODULE_AUTHOR("Phil Blundell <pb@nexus.co.uk>");
MODULE_DESCRIPTION("Footbridge watchdog driver");
MODULE_LICENSE("GPL");

module_param(soft_margin, int, 0);
MODULE_PARM_DESC(soft_margin, "Watchdog timeout in seconds");

module_init(footbridge_watchdog_init);
module_exit(footbridge_watchdog_exit);