// SPDX-License-Identifier: GPL-2.0-only
/*
 * Watchdog driver for SBC-FITPC2 board
 *
 * Author: Denis Turischev <denis@compulab.co.il>
 *
 * Adapted from the IXP2000 watchdog driver by Deepak Saxena.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME " WATCHDOG: " fmt

#include <linux/module.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/ioport.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/dmi.h>
#include <linux/io.h>
#include <linux/uaccess.h>


static bool nowayout = WATCHDOG_NOWAYOUT;
static unsigned int margin = 60;        /* (secs) Default is 1 minute */
static unsigned long wdt_status;
static DEFINE_MUTEX(wdt_lock);

#define WDT_IN_USE              0
#define WDT_OK_TO_CLOSE         1

#define COMMAND_PORT            0x4c
#define DATA_PORT               0x48

#define IFACE_ON_COMMAND        1
#define REBOOT_COMMAND          2

#define WATCHDOG_NAME           "SBC-FITPC2 Watchdog"

static void wdt_send_data(unsigned char command, unsigned char data)
{
        outb(data, DATA_PORT);
        msleep(200);
        outb(command, COMMAND_PORT);
        msleep(100);
}

static void wdt_enable(void)
{
        mutex_lock(&wdt_lock);
        wdt_send_data(IFACE_ON_COMMAND, 1);
        wdt_send_data(REBOOT_COMMAND, margin);
        mutex_unlock(&wdt_lock);
}

static void wdt_disable(void)
{
        mutex_lock(&wdt_lock);
        wdt_send_data(IFACE_ON_COMMAND, 0);
        wdt_send_data(REBOOT_COMMAND, 0);
        mutex_unlock(&wdt_lock);
}

static int fitpc2_wdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(WDT_IN_USE, &wdt_status))
                return -EBUSY;

        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

        wdt_enable();

        return stream_open(inode, file);
}

static ssize_t fitpc2_wdt_write(struct file *file, const char __user *data,
                                                size_t len, loff_t *ppos)
{
        size_t i;

        if (!len)
                return 0;

        if (nowayout) {
                len = 0;
                goto out;
        }

        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

        for (i = 0; i != len; i++) {
                char c;

                if (get_user(c, data + i))
                        return -EFAULT;

                if (c == 'V')
                        set_bit(WDT_OK_TO_CLOSE, &wdt_status);
        }

out:
        wdt_enable();

        return len;
}


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


static long fitpc2_wdt_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        int ret = -ENOTTY;
        int time;

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

        case WDIOC_GETSTATUS:
                ret = put_user(0, (int __user *)arg);
                break;

        case WDIOC_GETBOOTSTATUS:
                ret = put_user(0, (int __user *)arg);
                break;

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

        case WDIOC_SETTIMEOUT:
                ret = get_user(time, (int __user *)arg);
                if (ret)
                        break;

                if (time < 31 || time > 255) {
                        ret = -EINVAL;
                        break;
                }

                margin = time;
                wdt_enable();
                fallthrough;

        case WDIOC_GETTIMEOUT:
                ret = put_user(margin, (int __user *)arg);
                break;
        }

        return ret;
}

static int fitpc2_wdt_release(struct inode *inode, struct file *file)
{
        if (test_bit(WDT_OK_TO_CLOSE, &wdt_status)) {
                wdt_disable();
                pr_info("Device disabled\n");
        } else {
                pr_warn("Device closed unexpectedly - timer will not stop\n");
                wdt_enable();
        }

        clear_bit(WDT_IN_USE, &wdt_status);
        clear_bit(WDT_OK_TO_CLOSE, &wdt_status);

        return 0;
}


static const struct file_operations fitpc2_wdt_fops = {
        .owner          = THIS_MODULE,
        .write          = fitpc2_wdt_write,
        .unlocked_ioctl = fitpc2_wdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = fitpc2_wdt_open,
        .release        = fitpc2_wdt_release,
};

static struct miscdevice fitpc2_wdt_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &fitpc2_wdt_fops,
};

static int __init fitpc2_wdt_init(void)
{
        int err;
        const char *brd_name;

        brd_name = dmi_get_system_info(DMI_BOARD_NAME);

        if (!brd_name || !strstr(brd_name, "SBC-FITPC2"))
                return -ENODEV;

        pr_info("%s found\n", brd_name);

        if (!request_region(COMMAND_PORT, 1, WATCHDOG_NAME)) {
                pr_err("I/O address 0x%04x already in use\n", COMMAND_PORT);
                return -EIO;
        }

        if (!request_region(DATA_PORT, 1, WATCHDOG_NAME)) {
                pr_err("I/O address 0x%04x already in use\n", DATA_PORT);
                err = -EIO;
                goto err_data_port;
        }

        if (margin < 31 || margin > 255) {
                pr_err("margin must be in range 31 - 255 seconds, you tried to set %d\n",
                       margin);
                err = -EINVAL;
                goto err_margin;
        }

        err = misc_register(&fitpc2_wdt_miscdev);
        if (err) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, err);
                goto err_margin;
        }

        return 0;

err_margin:
        release_region(DATA_PORT, 1);
err_data_port:
        release_region(COMMAND_PORT, 1);

        return err;
}

static void __exit fitpc2_wdt_exit(void)
{
        misc_deregister(&fitpc2_wdt_miscdev);
        release_region(DATA_PORT, 1);
        release_region(COMMAND_PORT, 1);
}

module_init(fitpc2_wdt_init);
module_exit(fitpc2_wdt_exit);

MODULE_AUTHOR("Denis Turischev <denis@compulab.co.il>");
MODULE_DESCRIPTION("SBC-FITPC2 Watchdog");

module_param(margin, int, 0);
MODULE_PARM_DESC(margin, "Watchdog margin in seconds (default 60s)");

module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");

MODULE_LICENSE("GPL");