/*
 * Watchdog driver for Kendin/Micrel KS8695.
 *
 * (C) 2007 Andrew Victor
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/bitops.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/platform_device.h>
#include <linux/types.h>
#include <linux/watchdog.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/arch/regs-timer.h>


#define WDT_DEFAULT_TIME        5       /* seconds */
#define WDT_MAX_TIME            171     /* seconds */

static int wdt_time = WDT_DEFAULT_TIME;
static int nowayout = WATCHDOG_NOWAYOUT;

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


static unsigned long ks8695wdt_busy;

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

/*
 * Disable the watchdog.
 */
static void inline ks8695_wdt_stop(void)
{
        unsigned long tmcon;

        /* disable timer0 */
        tmcon = __raw_readl(KS8695_TMR_VA + KS8695_TMCON);
        __raw_writel(tmcon & ~TMCON_T0EN, KS8695_TMR_VA + KS8695_TMCON);
}

/*
 * Enable and reset the watchdog.
 */
static void inline ks8695_wdt_start(void)
{
        unsigned long tmcon;
        unsigned long tval = wdt_time * CLOCK_TICK_RATE;

        /* disable timer0 */
        tmcon = __raw_readl(KS8695_TMR_VA + KS8695_TMCON);
        __raw_writel(tmcon & ~TMCON_T0EN, KS8695_TMR_VA + KS8695_TMCON);

        /* program timer0 */
        __raw_writel(tval | T0TC_WATCHDOG, KS8695_TMR_VA + KS8695_T0TC);

        /* re-enable timer0 */
        tmcon = __raw_readl(KS8695_TMR_VA + KS8695_TMCON);
        __raw_writel(tmcon | TMCON_T0EN, KS8695_TMR_VA + KS8695_TMCON);
}

/*
 * Reload the watchdog timer.  (ie, pat the watchdog)
 */
static void inline ks8695_wdt_reload(void)
{
        unsigned long tmcon;

        /* disable, then re-enable timer0 */
        tmcon = __raw_readl(KS8695_TMR_VA + KS8695_TMCON);
        __raw_writel(tmcon & ~TMCON_T0EN, KS8695_TMR_VA + KS8695_TMCON);
        __raw_writel(tmcon | TMCON_T0EN, KS8695_TMR_VA + KS8695_TMCON);
}

/*
 * Change the watchdog time interval.
 */
static int ks8695_wdt_settimeout(int new_time)
{
        /*
         * All counting occurs at SLOW_CLOCK / 128 = 0.256 Hz
         *
         * Since WDV is a 16-bit counter, the maximum period is
         * 65536 / 0.256 = 256 seconds.
         */
        if ((new_time <= 0) || (new_time > WDT_MAX_TIME))
                return -EINVAL;

        /* Set new watchdog time. It will be used when ks8695_wdt_start() is called. */
        wdt_time = new_time;
        return 0;
}

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

/*
 * Watchdog device is opened, and watchdog starts running.
 */
static int ks8695_wdt_open(struct inode *inode, struct file *file)
{
        if (test_and_set_bit(0, &ks8695wdt_busy))
                return -EBUSY;

        ks8695_wdt_start();
        return nonseekable_open(inode, file);
}

/*
 * Close the watchdog device.
 * If CONFIG_WATCHDOG_NOWAYOUT is NOT defined then the watchdog is also
 *  disabled.
 */
static int ks8695_wdt_close(struct inode *inode, struct file *file)
{
        if (!nowayout)
                ks8695_wdt_stop();      /* Disable the watchdog when file is closed */

        clear_bit(0, &ks8695wdt_busy);
        return 0;
}

static struct watchdog_info ks8695_wdt_info = {
        .identity       = "ks8695 watchdog",
        .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
};

/*
 * Handle commands from user-space.
 */
static int ks8695_wdt_ioctl(struct inode *inode, 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_KEEPALIVE:
                        ks8695_wdt_reload();    /* pat the watchdog */
                        return 0;

                case WDIOC_GETSUPPORT:
                        return copy_to_user(argp, &ks8695_wdt_info, sizeof(ks8695_wdt_info)) ? -EFAULT : 0;

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

                        if (ks8695_wdt_settimeout(new_value))
                                return -EINVAL;

                        /* Enable new time value */
                        ks8695_wdt_start();

                        /* Return current value */
                        return put_user(wdt_time, p);

                case WDIOC_GETTIMEOUT:
                        return put_user(wdt_time, p);

                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)
                                ks8695_wdt_stop();
                        if (new_value & WDIOS_ENABLECARD)
                                ks8695_wdt_start();
                        return 0;

                default:
                        return -ENOTTY;
        }
}

/*
 * Pat the watchdog whenever device is written to.
 */
static ssize_t ks8695_wdt_write(struct file *file, const char *data, size_t len, loff_t *ppos)
{
        ks8695_wdt_reload();            /* pat the watchdog */
        return len;
}

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

static const struct file_operations ks8695wdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .ioctl          = ks8695_wdt_ioctl,
        .open           = ks8695_wdt_open,
        .release        = ks8695_wdt_close,
        .write          = ks8695_wdt_write,
};

static struct miscdevice ks8695wdt_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &ks8695wdt_fops,
};

static int __init ks8695wdt_probe(struct platform_device *pdev)
{
        int res;

        if (ks8695wdt_miscdev.parent)
                return -EBUSY;
        ks8695wdt_miscdev.parent = &pdev->dev;

        res = misc_register(&ks8695wdt_miscdev);
        if (res)
                return res;

        printk("KS8695 Watchdog Timer enabled (%d seconds%s)\n", wdt_time, nowayout ? ", nowayout" : "");
        return 0;
}

static int __exit ks8695wdt_remove(struct platform_device *pdev)
{
        int res;

        res = misc_deregister(&ks8695wdt_miscdev);
        if (!res)
                ks8695wdt_miscdev.parent = NULL;

        return res;
}

static void ks8695wdt_shutdown(struct platform_device *pdev)
{
        ks8695_wdt_stop();
}

#ifdef CONFIG_PM

static int ks8695wdt_suspend(struct platform_device *pdev, pm_message_t message)
{
        ks8695_wdt_stop();
        return 0;
}

static int ks8695wdt_resume(struct platform_device *pdev)
{
        if (ks8695wdt_busy)
                ks8695_wdt_start();
        return 0;
}

#else
#define ks8695wdt_suspend NULL
#define ks8695wdt_resume        NULL
#endif

static struct platform_driver ks8695wdt_driver = {
        .probe          = ks8695wdt_probe,
        .remove         = __exit_p(ks8695wdt_remove),
        .shutdown       = ks8695wdt_shutdown,
        .suspend        = ks8695wdt_suspend,
        .resume         = ks8695wdt_resume,
        .driver         = {
                .name   = "ks8695_wdt",
                .owner  = THIS_MODULE,
        },
};

static int __init ks8695_wdt_init(void)
{
        /* Check that the heartbeat value is within range; if not reset to the default */
        if (ks8695_wdt_settimeout(wdt_time)) {
                ks8695_wdt_settimeout(WDT_DEFAULT_TIME);
                pr_info("ks8695_wdt: wdt_time value must be 1 <= wdt_time <= %i, using %d\n", wdt_time, WDT_MAX_TIME);
        }

        return platform_driver_register(&ks8695wdt_driver);
}

static void __exit ks8695_wdt_exit(void)
{
        platform_driver_unregister(&ks8695wdt_driver);
}

module_init(ks8695_wdt_init);
module_exit(ks8695_wdt_exit);

MODULE_AUTHOR("Andrew Victor");
MODULE_DESCRIPTION("Watchdog driver for KS8695");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);