/*
 * Blackfin On-Chip Watchdog Driver
 *  Supports BF53[123]/BF53[467]/BF54[2489]/BF561
 *
 * Originally based on softdog.c
 * Copyright 2006-2007 Analog Devices Inc.
 * Copyright 2006-2007 Michele d'Amico
 * Copyright 1996 Alan Cox <alan@redhat.com>
 *
 * Enter bugs at http://blackfin.uclinux.org/
 *
 * Licensed under the GPL-2 or later.
 */

#include <linux/platform_device.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <asm/blackfin.h>
#include <asm/uaccess.h>

#define stamp(fmt, args...) pr_debug("%s:%i: " fmt "\n", __func__, __LINE__, ## args)
#define stampit() stamp("here i am")

#define WATCHDOG_NAME "bfin-wdt"
#define PFX WATCHDOG_NAME ": "

/* The BF561 has two watchdogs (one per core), but since Linux
 * only runs on core A, we'll just work with that one.
 */
#ifdef BF561_FAMILY
# define bfin_read_WDOG_CTL()    bfin_read_WDOGA_CTL()
# define bfin_read_WDOG_CNT()    bfin_read_WDOGA_CNT()
# define bfin_read_WDOG_STAT()   bfin_read_WDOGA_STAT()
# define bfin_write_WDOG_CTL(x)  bfin_write_WDOGA_CTL(x)
# define bfin_write_WDOG_CNT(x)  bfin_write_WDOGA_CNT(x)
# define bfin_write_WDOG_STAT(x) bfin_write_WDOGA_STAT(x)
#endif

/* Bit in SWRST that indicates boot caused by watchdog */
#define SWRST_RESET_WDOG 0x4000

/* Bit in WDOG_CTL that indicates watchdog has expired (WDR0) */
#define WDOG_EXPIRED 0x8000

/* Masks for WDEV field in WDOG_CTL register */
#define ICTL_RESET   0x0
#define ICTL_NMI     0x2
#define ICTL_GPI     0x4
#define ICTL_NONE    0x6
#define ICTL_MASK    0x6

/* Masks for WDEN field in WDOG_CTL register */
#define WDEN_MASK    0x0FF0
#define WDEN_ENABLE  0x0000
#define WDEN_DISABLE 0x0AD0

/* some defaults */
#define WATCHDOG_TIMEOUT 20

static unsigned int timeout = WATCHDOG_TIMEOUT;
static int nowayout = WATCHDOG_NOWAYOUT;
static struct watchdog_info bfin_wdt_info;
static unsigned long open_check;
static char expect_close;
static DEFINE_SPINLOCK(bfin_wdt_spinlock);

/**
 *      bfin_wdt_keepalive - Keep the Userspace Watchdog Alive
 *
 *      The Userspace watchdog got a KeepAlive: schedule the next timeout.
 */
static int bfin_wdt_keepalive(void)
{
        stampit();
        bfin_write_WDOG_STAT(0);
        return 0;
}

/**
 *      bfin_wdt_stop - Stop the Watchdog
 *
 *      Stops the on-chip watchdog.
 */
static int bfin_wdt_stop(void)
{
        stampit();
        bfin_write_WDOG_CTL(WDEN_DISABLE);
        return 0;
}

/**
 *      bfin_wdt_start - Start the Watchdog
 *
 *      Starts the on-chip watchdog.  Automatically loads WDOG_CNT
 *      into WDOG_STAT for us.
 */
static int bfin_wdt_start(void)
{
        stampit();
        bfin_write_WDOG_CTL(WDEN_ENABLE | ICTL_RESET);
        return 0;
}

/**
 *      bfin_wdt_running - Check Watchdog status
 *
 *      See if the watchdog is running.
 */
static int bfin_wdt_running(void)
{
        stampit();
        return ((bfin_read_WDOG_CTL() & WDEN_MASK) != WDEN_DISABLE);
}

/**
 *      bfin_wdt_set_timeout - Set the Userspace Watchdog timeout
 *      @t: new timeout value (in seconds)
 *
 *      Translate the specified timeout in seconds into System Clock
 *      terms which is what the on-chip Watchdog requires.
 */
static int bfin_wdt_set_timeout(unsigned long t)
{
        u32 cnt;
        unsigned long flags;

        stampit();

        cnt = t * get_sclk();
        if (cnt < get_sclk()) {
                printk(KERN_WARNING PFX "timeout value is too large\n");
                return -EINVAL;
        }

        spin_lock_irqsave(&bfin_wdt_spinlock, flags);
        {
                int run = bfin_wdt_running();
                bfin_wdt_stop();
                bfin_write_WDOG_CNT(cnt);
                if (run) bfin_wdt_start();
        }
        spin_unlock_irqrestore(&bfin_wdt_spinlock, flags);

        timeout = t;

        return 0;
}

/**
 *      bfin_wdt_open - Open the Device
 *      @inode: inode of device
 *      @file: file handle of device
 *
 *      Watchdog device is opened and started.
 */
static int bfin_wdt_open(struct inode *inode, struct file *file)
{
        stampit();

        if (test_and_set_bit(0, &open_check))
                return -EBUSY;

        if (nowayout)
                __module_get(THIS_MODULE);

        bfin_wdt_keepalive();
        bfin_wdt_start();

        return nonseekable_open(inode, file);
}

/**
 *      bfin_wdt_close - Close the Device
 *      @inode: inode of device
 *      @file: file handle of device
 *
 *      Watchdog device is closed and stopped.
 */
static int bfin_wdt_release(struct inode *inode, struct file *file)
{
        stampit();

        if (expect_close == 42) {
                bfin_wdt_stop();
        } else {
                printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
                bfin_wdt_keepalive();
        }

        expect_close = 0;
        clear_bit(0, &open_check);

        return 0;
}

/**
 *      bfin_wdt_write - Write to Device
 *      @file: file handle of device
 *      @buf: buffer to write
 *      @count: length of buffer
 *      @ppos: offset
 *
 *      Pings the watchdog on write.
 */
static ssize_t bfin_wdt_write(struct file *file, const char __user *data,
                              size_t len, loff_t *ppos)
{
        stampit();

        if (len) {
                if (!nowayout) {
                        size_t i;

                        /* In case it was set long ago */
                        expect_close = 0;

                        for (i = 0; i != len; i++) {
                                char c;
                                if (get_user(c, data + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        expect_close = 42;
                        }
                }
                bfin_wdt_keepalive();
        }

        return len;
}

/**
 *      bfin_wdt_ioctl - Query Device
 *      @inode: inode of device
 *      @file: file handle of device
 *      @cmd: watchdog command
 *      @arg: argument
 *
 *      Query basic information from the device or ping it, as outlined by the
 *      watchdog API.
 */
static int bfin_wdt_ioctl(struct inode *inode, struct file *file,
                          unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;

        stampit();

        switch (cmd) {
                default:
                        return -ENOTTY;

                case WDIOC_GETSUPPORT:
                        if (copy_to_user(argp, &bfin_wdt_info, sizeof(bfin_wdt_info)))
                                return -EFAULT;
                        else
                                return 0;

                case WDIOC_GETSTATUS:
                case WDIOC_GETBOOTSTATUS:
                        return put_user(!!(_bfin_swrst & SWRST_RESET_WDOG), p);

                case WDIOC_KEEPALIVE:
                        bfin_wdt_keepalive();
                        return 0;

                case WDIOC_SETTIMEOUT: {
                        int new_timeout;

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

                        if (bfin_wdt_set_timeout(new_timeout))
                                return -EINVAL;
                }
                        /* Fall */
                case WDIOC_GETTIMEOUT:
                        return put_user(timeout, p);

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

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

                        spin_lock_irqsave(&bfin_wdt_spinlock, flags);

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

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

                        spin_unlock_irqrestore(&bfin_wdt_spinlock, flags);

                        return ret;
                }
        }
}

/**
 *      bfin_wdt_notify_sys - Notifier Handler
 *      @this: notifier block
 *      @code: notifier event
 *      @unused: unused
 *
 *      Handles specific events, such as turning off the watchdog during a
 *      shutdown event.
 */
static int bfin_wdt_notify_sys(struct notifier_block *this, unsigned long code,
                               void *unused)
{
        stampit();

        if (code == SYS_DOWN || code == SYS_HALT)
                bfin_wdt_stop();

        return NOTIFY_DONE;
}

#ifdef CONFIG_PM
static int state_before_suspend;

/**
 *      bfin_wdt_suspend - suspend the watchdog
 *      @pdev: device being suspended
 *      @state: requested suspend state
 *
 *      Remember if the watchdog was running and stop it.
 *      TODO: is this even right?  Doesn't seem to be any
 *            standard in the watchdog world ...
 */
static int bfin_wdt_suspend(struct platform_device *pdev, pm_message_t state)
{
        stampit();

        state_before_suspend = bfin_wdt_running();
        bfin_wdt_stop();

        return 0;
}

/**
 *      bfin_wdt_resume - resume the watchdog
 *      @pdev: device being resumed
 *
 *      If the watchdog was running, turn it back on.
 */
static int bfin_wdt_resume(struct platform_device *pdev)
{
        stampit();

        if (state_before_suspend) {
                bfin_wdt_set_timeout(timeout);
                bfin_wdt_start();
        }

        return 0;
}
#else
# define bfin_wdt_suspend NULL
# define bfin_wdt_resume NULL
#endif

static struct platform_device bfin_wdt_device = {
        .name          = WATCHDOG_NAME,
        .id            = -1,
};

static struct platform_driver bfin_wdt_driver = {
        .driver    = {
                .name  = WATCHDOG_NAME,
                .owner = THIS_MODULE,
        },
        .suspend   = bfin_wdt_suspend,
        .resume    = bfin_wdt_resume,
};

static struct file_operations bfin_wdt_fops = {
        .owner    = THIS_MODULE,
        .llseek   = no_llseek,
        .write    = bfin_wdt_write,
        .ioctl    = bfin_wdt_ioctl,
        .open     = bfin_wdt_open,
        .release  = bfin_wdt_release,
};

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

static struct watchdog_info bfin_wdt_info = {
        .identity = "Blackfin Watchdog",
        .options  = WDIOF_SETTIMEOUT |
                    WDIOF_KEEPALIVEPING |
                    WDIOF_MAGICCLOSE,
};

static struct notifier_block bfin_wdt_notifier = {
        .notifier_call = bfin_wdt_notify_sys,
};

/**
 *      bfin_wdt_init - Initialize module
 *
 *      Registers the device and notifier handler. Actual device
 *      initialization is handled by bfin_wdt_open().
 */
static int __init bfin_wdt_init(void)
{
        int ret;

        stampit();

        /* Check that the timeout value is within range */
        if (bfin_wdt_set_timeout(timeout))
                return -EINVAL;

        /* Since this is an on-chip device and needs no board-specific
         * resources, we'll handle all the platform device stuff here.
         */
        ret = platform_device_register(&bfin_wdt_device);
        if (ret)
                return ret;

        ret = platform_driver_probe(&bfin_wdt_driver, NULL);
        if (ret)
                return ret;

        ret = register_reboot_notifier(&bfin_wdt_notifier);
        if (ret) {
                printk(KERN_ERR PFX "cannot register reboot notifier (err=%d)\n", ret);
                return ret;
        }

        ret = misc_register(&bfin_wdt_miscdev);
        if (ret) {
                printk(KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, ret);
                unregister_reboot_notifier(&bfin_wdt_notifier);
                return ret;
        }

        printk(KERN_INFO PFX "initialized: timeout=%d sec (nowayout=%d)\n",
               timeout, nowayout);

        return 0;
}

/**
 *      bfin_wdt_exit - Deinitialize module
 *
 *      Unregisters the device and notifier handler. Actual device
 *      deinitialization is handled by bfin_wdt_close().
 */
static void __exit bfin_wdt_exit(void)
{
        misc_deregister(&bfin_wdt_miscdev);
        unregister_reboot_notifier(&bfin_wdt_notifier);
}

module_init(bfin_wdt_init);
module_exit(bfin_wdt_exit);

MODULE_AUTHOR("Michele d'Amico, Mike Frysinger <vapier@gentoo.org>");
MODULE_DESCRIPTION("Blackfin Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

module_param(timeout, uint, 0);
MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. (1<=timeout<=((2^32)/SCLK), default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");

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