// SPDX-License-Identifier: GPL-2.0-or-later
/* Watchdog timer for machines with the CS5535/CS5536 companion chip
 *
 * Copyright (C) 2006-2007, Advanced Micro Devices, Inc.
 * Copyright (C) 2009  Andres Salomon <dilinger@collabora.co.uk>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/uaccess.h>

#include <linux/cs5535.h>

#define GEODEWDT_HZ 500
#define GEODEWDT_SCALE 6
#define GEODEWDT_MAX_SECONDS 131

#define WDT_FLAGS_OPEN 1
#define WDT_FLAGS_ORPHAN 2

#define DRV_NAME "geodewdt"
#define WATCHDOG_NAME "Geode GX/LX WDT"
#define WATCHDOG_TIMEOUT 60

static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
        "Watchdog timeout in seconds. 1<= timeout <=131, default="
                                __MODULE_STRING(WATCHDOG_TIMEOUT) ".");

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) ")");

static struct platform_device *geodewdt_platform_device;
static unsigned long wdt_flags;
static struct cs5535_mfgpt_timer *wdt_timer;
static int safe_close;

static void geodewdt_ping(void)
{
        /* Stop the counter */
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);

        /* Reset the counter */
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);

        /* Enable the counter */
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
}

static void geodewdt_disable(void)
{
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);
}

static int geodewdt_set_heartbeat(int val)
{
        if (val < 1 || val > GEODEWDT_MAX_SECONDS)
                return -EINVAL;

        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_CMP2, val * GEODEWDT_HZ);
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);
        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);

        timeout = val;
        return 0;
}

static int geodewdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(WDT_FLAGS_OPEN, &wdt_flags))
                return -EBUSY;

        if (!test_and_clear_bit(WDT_FLAGS_ORPHAN, &wdt_flags))
                __module_get(THIS_MODULE);

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

static int geodewdt_release(struct inode *inode, struct file *file)
{
        if (safe_close) {
                geodewdt_disable();
                module_put(THIS_MODULE);
        } else {
                pr_crit("Unexpected close - watchdog is not stopping\n");
                geodewdt_ping();

                set_bit(WDT_FLAGS_ORPHAN, &wdt_flags);
        }

        clear_bit(WDT_FLAGS_OPEN, &wdt_flags);
        safe_close = 0;
        return 0;
}

static ssize_t geodewdt_write(struct file *file, const char __user *data,
                                size_t len, loff_t *ppos)
{
        if (len) {
                if (!nowayout) {
                        size_t i;
                        safe_close = 0;

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

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

                                if (c == 'V')
                                        safe_close = 1;
                        }
                }

                geodewdt_ping();
        }
        return len;
}

static long geodewdt_ioctl(struct file *file, unsigned int cmd,
                                unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        int interval;

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

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, &ident,
                                    sizeof(ident)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);

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

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

                if (options & WDIOS_DISABLECARD) {
                        geodewdt_disable();
                        ret = 0;
                }

                if (options & WDIOS_ENABLECARD) {
                        geodewdt_ping();
                        ret = 0;
                }

                return ret;
        }
        case WDIOC_KEEPALIVE:
                geodewdt_ping();
                return 0;

        case WDIOC_SETTIMEOUT:
                if (get_user(interval, p))
                        return -EFAULT;

                if (geodewdt_set_heartbeat(interval))
                        return -EINVAL;
                fallthrough;
        case WDIOC_GETTIMEOUT:
                return put_user(timeout, p);

        default:
                return -ENOTTY;
        }

        return 0;
}

static const struct file_operations geodewdt_fops = {
        .owner          = THIS_MODULE,
        .write          = geodewdt_write,
        .unlocked_ioctl = geodewdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = geodewdt_open,
        .release        = geodewdt_release,
};

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

static int __init geodewdt_probe(struct platform_device *dev)
{
        int ret;

        wdt_timer = cs5535_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING);
        if (!wdt_timer) {
                pr_err("No timers were available\n");
                return -ENODEV;
        }

        /* Set up the timer */

        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP,
                          GEODEWDT_SCALE | (3 << 8));

        /* Set up comparator 2 to reset when the event fires */
        cs5535_mfgpt_toggle_event(wdt_timer, MFGPT_CMP2, MFGPT_EVENT_RESET, 1);

        /* Set up the initial timeout */

        cs5535_mfgpt_write(wdt_timer, MFGPT_REG_CMP2,
                timeout * GEODEWDT_HZ);

        ret = misc_register(&geodewdt_miscdev);

        return ret;
}

static void geodewdt_remove(struct platform_device *dev)
{
        misc_deregister(&geodewdt_miscdev);
}

static void geodewdt_shutdown(struct platform_device *dev)
{
        geodewdt_disable();
}

static struct platform_driver geodewdt_driver = {
        .remove         = geodewdt_remove,
        .shutdown       = geodewdt_shutdown,
        .driver         = {
                .name   = DRV_NAME,
        },
};

static int __init geodewdt_init(void)
{
        int ret;

        geodewdt_platform_device = platform_device_register_simple(DRV_NAME,
                                                                -1, NULL, 0);
        if (IS_ERR(geodewdt_platform_device))
                return PTR_ERR(geodewdt_platform_device);

        ret = platform_driver_probe(&geodewdt_driver, geodewdt_probe);
        if (ret)
                goto err;

        return 0;
err:
        platform_device_unregister(geodewdt_platform_device);
        return ret;
}

static void __exit geodewdt_exit(void)
{
        platform_device_unregister(geodewdt_platform_device);
        platform_driver_unregister(&geodewdt_driver);
}

module_init(geodewdt_init);
module_exit(geodewdt_exit);

MODULE_AUTHOR("Advanced Micro Devices, Inc");
MODULE_DESCRIPTION("Geode GX/LX Watchdog Driver");
MODULE_LICENSE("GPL");