/*
 * Blackfin On-Chip Watchdog Driver
 *
 * Originally based on softdog.c
 * Copyright 2006-2010 Analog Devices Inc.
 * Copyright 2006-2007 Michele d'Amico
 * Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 * Enter bugs at http://blackfin.uclinux.org/
 *
 * Licensed under the GPL-2 or later.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#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/init.h>
#include <linux/interrupt.h>
#include <linux/uaccess.h>
#include <asm/blackfin.h>
#include <asm/bfin_watchdog.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"

/* 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

/* some defaults */
#define WATCHDOG_TIMEOUT 20

static unsigned int timeout = WATCHDOG_TIMEOUT;
static bool nowayout = WATCHDOG_NOWAYOUT;
static const 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, max_t, sclk;
        unsigned long flags;

        sclk = get_sclk();
        max_t = -1 / sclk;
        cnt = t * sclk;
        stamp("maxtimeout=%us newtimeout=%lus (cnt=%#x)", max_t, t, cnt);

        if (t > max_t) {
                pr_warn("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 {
                pr_crit("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
 *      @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 long bfin_wdt_ioctl(struct file *file,
                                unsigned int cmd, unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        int __user *p = argp;

        stampit();

        switch (cmd) {
        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_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;
        }
        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);
        default:
                return -ENOTTY;
        }
}

#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 const struct file_operations bfin_wdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = bfin_wdt_write,
        .unlocked_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 const struct watchdog_info bfin_wdt_info = {
        .identity = "Blackfin Watchdog",
        .options  = WDIOF_SETTIMEOUT |
                    WDIOF_KEEPALIVEPING |
                    WDIOF_MAGICCLOSE,
};

/**
 *      bfin_wdt_probe - Initialize module
 *
 *      Registers the misc device.  Actual device
 *      initialization is handled by bfin_wdt_open().
 */
static int bfin_wdt_probe(struct platform_device *pdev)
{
        int ret;

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

        pr_info("initialized: timeout=%d sec (nowayout=%d)\n",
                timeout, nowayout);

        return 0;
}

/**
 *      bfin_wdt_remove - Initialize module
 *
 *      Unregisters the misc device.  Actual device
 *      deinitialization is handled by bfin_wdt_close().
 */
static int bfin_wdt_remove(struct platform_device *pdev)
{
        misc_deregister(&bfin_wdt_miscdev);
        return 0;
}

/**
 *      bfin_wdt_shutdown - Soft Shutdown Handler
 *
 *      Handles the soft shutdown event.
 */
static void bfin_wdt_shutdown(struct platform_device *pdev)
{
        stampit();

        bfin_wdt_stop();
}

static struct platform_device *bfin_wdt_device;

static struct platform_driver bfin_wdt_driver = {
        .probe     = bfin_wdt_probe,
        .remove    = bfin_wdt_remove,
        .shutdown  = bfin_wdt_shutdown,
        .suspend   = bfin_wdt_suspend,
        .resume    = bfin_wdt_resume,
        .driver    = {
                .name  = WATCHDOG_NAME,
                .owner = THIS_MODULE,
        },
};

/**
 *      bfin_wdt_init - Initialize module
 *
 *      Checks the module params and registers the platform device & driver.
 *      Real work is in the platform probe function.
 */
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_driver_register(&bfin_wdt_driver);
        if (ret) {
                pr_err("unable to register driver\n");
                return ret;
        }

        bfin_wdt_device = platform_device_register_simple(WATCHDOG_NAME,
                                                                -1, NULL, 0);
        if (IS_ERR(bfin_wdt_device)) {
                pr_err("unable to register device\n");
                platform_driver_unregister(&bfin_wdt_driver);
                return PTR_ERR(bfin_wdt_device);
        }

        return 0;
}

/**
 *      bfin_wdt_exit - Deinitialize module
 *
 *      Back out the platform device & driver steps.  Real work is in the
 *      platform remove function.
 */
static void __exit bfin_wdt_exit(void)
{
        platform_device_unregister(bfin_wdt_device);
        platform_driver_unregister(&bfin_wdt_driver);
}

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