// SPDX-License-Identifier: GPL-2.0+
/*
 * Watchdog driver for Atmel AT91RM9200 (Thunder)
 *
 *  Copyright (C) 2003 SAN People (Pty) Ltd
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/mfd/syscon.h>
#include <linux/mfd/syscon/atmel-st.h>
#include <linux/miscdevice.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/reboot.h>
#include <linux/regmap.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>

#define WDT_DEFAULT_TIME        5       /* seconds */
#define WDT_MAX_TIME            256     /* seconds */

static int wdt_time = WDT_DEFAULT_TIME;
static bool nowayout = WATCHDOG_NOWAYOUT;
static struct regmap *regmap_st;

module_param(wdt_time, int, 0);
MODULE_PARM_DESC(wdt_time, "Watchdog time in seconds. (default="
                                __MODULE_STRING(WDT_DEFAULT_TIME) ")");

#ifdef CONFIG_WATCHDOG_NOWAYOUT
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
                "Watchdog cannot be stopped once started (default="
                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
#endif


static unsigned long at91wdt_busy;

/* ......................................................................... */

static int at91rm9200_restart(struct notifier_block *this,
                                        unsigned long mode, void *cmd)
{
        /*
         * Perform a hardware reset with the use of the Watchdog timer.
         */
        regmap_write(regmap_st, AT91_ST_WDMR,
                     AT91_ST_RSTEN | AT91_ST_EXTEN | 1);
        regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);

        mdelay(2000);

        pr_emerg("Unable to restart system\n");
        return NOTIFY_DONE;
}

static struct notifier_block at91rm9200_restart_nb = {
        .notifier_call = at91rm9200_restart,
        .priority = 192,
};

/*
 * Disable the watchdog.
 */
static inline void at91_wdt_stop(void)
{
        regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN);
}

/*
 * Enable and reset the watchdog.
 */
static inline void at91_wdt_start(void)
{
        regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN | AT91_ST_RSTEN |
                                (((65536 * wdt_time) >> 8) & AT91_ST_WDV));
        regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
}

/*
 * Reload the watchdog timer.  (ie, pat the watchdog)
 */
static inline void at91_wdt_reload(void)
{
        regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
}

/* ......................................................................... */

/*
 * Watchdog device is opened, and watchdog starts running.
 */
static int at91_wdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &at91wdt_busy))
                return -EBUSY;

        at91_wdt_start();
        return stream_open(inode, file);
}

/*
 * Close the watchdog device.
 * If CONFIG_WATCHDOG_NOWAYOUT is NOT defined then the watchdog is also
 *  disabled.
 */
static int at91_wdt_close(struct inode *inode, struct file *file)
{
        /* Disable the watchdog when file is closed */
        if (!nowayout)
                at91_wdt_stop();

        clear_bit(0, &at91wdt_busy);
        return 0;
}

/*
 * Change the watchdog time interval.
 */
static int at91_wdt_settimeout(int new_time)
{
        /*
         * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
         *
         * Since WDV is a 16-bit counter, the maximum period is
         * 65536 / 256 = 256 seconds.
         */
        if ((new_time <= 0) || (new_time > WDT_MAX_TIME))
                return -EINVAL;

        /* Set new watchdog time. It will be used when
           at91_wdt_start() is called. */
        wdt_time = new_time;
        return 0;
}

static const struct watchdog_info at91_wdt_info = {
        .identity       = "at91 watchdog",
        .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
};

/*
 * Handle commands from user-space.
 */
static long at91_wdt_ioctl(struct file *file,
                                        unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;
        int new_value;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp, &at91_wdt_info,
                                sizeof(at91_wdt_info)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);
        case WDIOC_SETOPTIONS:
                if (get_user(new_value, p))
                        return -EFAULT;
                if (new_value & WDIOS_DISABLECARD)
                        at91_wdt_stop();
                if (new_value & WDIOS_ENABLECARD)
                        at91_wdt_start();
                return 0;
        case WDIOC_KEEPALIVE:
                at91_wdt_reload();      /* pat the watchdog */
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(new_value, p))
                        return -EFAULT;
                if (at91_wdt_settimeout(new_value))
                        return -EINVAL;
                /* Enable new time value */
                at91_wdt_start();
                /* Return current value */
                return put_user(wdt_time, p);
        case WDIOC_GETTIMEOUT:
                return put_user(wdt_time, p);
        default:
                return -ENOTTY;
        }
}

/*
 * Pat the watchdog whenever device is written to.
 */
static ssize_t at91_wdt_write(struct file *file, const char *data,
                                                size_t len, loff_t *ppos)
{
        at91_wdt_reload();              /* pat the watchdog */
        return len;
}

/* ......................................................................... */

static const struct file_operations at91wdt_fops = {
        .owner          = THIS_MODULE,
        .unlocked_ioctl = at91_wdt_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = at91_wdt_open,
        .release        = at91_wdt_close,
        .write          = at91_wdt_write,
};

static struct miscdevice at91wdt_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &at91wdt_fops,
};

static int at91wdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct device *parent;
        int res;

        if (at91wdt_miscdev.parent)
                return -EBUSY;
        at91wdt_miscdev.parent = &pdev->dev;

        parent = dev->parent;
        if (!parent) {
                dev_err(dev, "no parent\n");
                return -ENODEV;
        }

        regmap_st = syscon_node_to_regmap(parent->of_node);
        if (IS_ERR(regmap_st))
                return -ENODEV;

        res = misc_register(&at91wdt_miscdev);
        if (res)
                return res;

        res = register_restart_handler(&at91rm9200_restart_nb);
        if (res)
                dev_warn(dev, "failed to register restart handler\n");

        pr_info("AT91 Watchdog Timer enabled (%d seconds%s)\n",
                wdt_time, nowayout ? ", nowayout" : "");
        return 0;
}

static void at91wdt_remove(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        int res;

        res = unregister_restart_handler(&at91rm9200_restart_nb);
        if (res)
                dev_warn(dev, "failed to unregister restart handler\n");

        misc_deregister(&at91wdt_miscdev);
        at91wdt_miscdev.parent = NULL;
}

static void at91wdt_shutdown(struct platform_device *pdev)
{
        at91_wdt_stop();
}

static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
{
        at91_wdt_stop();
        return 0;
}

static int at91wdt_resume(struct platform_device *pdev)
{
        if (at91wdt_busy)
                at91_wdt_start();
        return 0;
}

static const struct of_device_id at91_wdt_dt_ids[] = {
        { .compatible = "atmel,at91rm9200-wdt" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, at91_wdt_dt_ids);

static struct platform_driver at91wdt_driver = {
        .probe          = at91wdt_probe,
        .remove         = at91wdt_remove,
        .shutdown       = at91wdt_shutdown,
        .suspend        = pm_ptr(at91wdt_suspend),
        .resume         = pm_ptr(at91wdt_resume),
        .driver         = {
                .name   = "atmel_st_watchdog",
                .of_match_table = at91_wdt_dt_ids,
        },
};

static int __init at91_wdt_init(void)
{
        /* Check that the heartbeat value is within range;
           if not reset to the default */
        if (at91_wdt_settimeout(wdt_time)) {
                at91_wdt_settimeout(WDT_DEFAULT_TIME);
                pr_info("wdt_time value must be 1 <= wdt_time <= 256, using %d\n",
                        wdt_time);
        }

        return platform_driver_register(&at91wdt_driver);
}

static void __exit at91_wdt_exit(void)
{
        platform_driver_unregister(&at91wdt_driver);
}

module_init(at91_wdt_init);
module_exit(at91_wdt_exit);

MODULE_AUTHOR("Andrew Victor");
MODULE_DESCRIPTION("Watchdog driver for Atmel AT91RM9200");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:atmel_st_watchdog");