/*
 *      Watchdog driver for the mpcore watchdog timer
 *
 *      (c) Copyright 2004 ARM Limited
 *
 *      Based on the SoftDog driver:
 *      (c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 *
 *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *      warranty for any of this software. This material is provided
 *      "AS-IS" and at no charge.
 *
 *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.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/reboot.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/platform_device.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/io.h>

#include <asm/smp_twd.h>

struct mpcore_wdt {
        unsigned long   timer_alive;
        struct device   *dev;
        void __iomem    *base;
        int             irq;
        unsigned int    perturb;
        char            expect_close;
};

static struct platform_device *mpcore_wdt_pdev;
static DEFINE_SPINLOCK(wdt_lock);

#define TIMER_MARGIN    60
static int mpcore_margin = TIMER_MARGIN;
module_param(mpcore_margin, int, 0);
MODULE_PARM_DESC(mpcore_margin,
        "MPcore timer margin in seconds. (0 < mpcore_margin < 65536, default="
                                __MODULE_STRING(TIMER_MARGIN) ")");

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) ")");

#define ONLY_TESTING    0
static int mpcore_noboot = ONLY_TESTING;
module_param(mpcore_noboot, int, 0);
MODULE_PARM_DESC(mpcore_noboot, "MPcore watchdog action, "
        "set to 1 to ignore reboots, 0 to reboot (default="
                                        __MODULE_STRING(ONLY_TESTING) ")");

/*
 *      This is the interrupt handler.  Note that we only use this
 *      in testing mode, so don't actually do a reboot here.
 */
static irqreturn_t mpcore_wdt_fire(int irq, void *arg)
{
        struct mpcore_wdt *wdt = arg;

        /* Check it really was our interrupt */
        if (readl(wdt->base + TWD_WDOG_INTSTAT)) {
                dev_printk(KERN_CRIT, wdt->dev,
                                        "Triggered - Reboot ignored.\n");
                /* Clear the interrupt on the watchdog */
                writel(1, wdt->base + TWD_WDOG_INTSTAT);
                return IRQ_HANDLED;
        }
        return IRQ_NONE;
}

/*
 *      mpcore_wdt_keepalive - reload the timer
 *
 *      Note that the spec says a DIFFERENT value must be written to the reload
 *      register each time.  The "perturb" variable deals with this by adding 1
 *      to the count every other time the function is called.
 */
static void mpcore_wdt_keepalive(struct mpcore_wdt *wdt)
{
        unsigned long count;

        spin_lock(&wdt_lock);
        /* Assume prescale is set to 256 */
        count =  __raw_readl(wdt->base + TWD_WDOG_COUNTER);
        count = (0xFFFFFFFFU - count) * (HZ / 5);
        count = (count / 256) * mpcore_margin;

        /* Reload the counter */
        writel(count + wdt->perturb, wdt->base + TWD_WDOG_LOAD);
        wdt->perturb = wdt->perturb ? 0 : 1;
        spin_unlock(&wdt_lock);
}

static void mpcore_wdt_stop(struct mpcore_wdt *wdt)
{
        spin_lock(&wdt_lock);
        writel(0x12345678, wdt->base + TWD_WDOG_DISABLE);
        writel(0x87654321, wdt->base + TWD_WDOG_DISABLE);
        writel(0x0, wdt->base + TWD_WDOG_CONTROL);
        spin_unlock(&wdt_lock);
}

static void mpcore_wdt_start(struct mpcore_wdt *wdt)
{
        dev_printk(KERN_INFO, wdt->dev, "enabling watchdog.\n");

        /* This loads the count register but does NOT start the count yet */
        mpcore_wdt_keepalive(wdt);

        if (mpcore_noboot) {
                /* Enable watchdog - prescale=256, watchdog mode=0, enable=1 */
                writel(0x0000FF01, wdt->base + TWD_WDOG_CONTROL);
        } else {
                /* Enable watchdog - prescale=256, watchdog mode=1, enable=1 */
                writel(0x0000FF09, wdt->base + TWD_WDOG_CONTROL);
        }
}

static int mpcore_wdt_set_heartbeat(int t)
{
        if (t < 0x0001 || t > 0xFFFF)
                return -EINVAL;

        mpcore_margin = t;
        return 0;
}

/*
 *      /dev/watchdog handling
 */
static int mpcore_wdt_open(struct inode *inode, struct file *file)
{
        struct mpcore_wdt *wdt = platform_get_drvdata(mpcore_wdt_pdev);

        if (test_and_set_bit(0, &wdt->timer_alive))
                return -EBUSY;

        if (nowayout)
                __module_get(THIS_MODULE);

        file->private_data = wdt;

        /*
         *      Activate timer
         */
        mpcore_wdt_start(wdt);

        return nonseekable_open(inode, file);
}

static int mpcore_wdt_release(struct inode *inode, struct file *file)
{
        struct mpcore_wdt *wdt = file->private_data;

        /*
         *      Shut off the timer.
         *      Lock it in if it's a module and we set nowayout
         */
        if (wdt->expect_close == 42)
                mpcore_wdt_stop(wdt);
        else {
                dev_printk(KERN_CRIT, wdt->dev,
                                "unexpected close, not stopping watchdog!\n");
                mpcore_wdt_keepalive(wdt);
        }
        clear_bit(0, &wdt->timer_alive);
        wdt->expect_close = 0;
        return 0;
}

static ssize_t mpcore_wdt_write(struct file *file, const char *data,
                                                size_t len, loff_t *ppos)
{
        struct mpcore_wdt *wdt = file->private_data;

        /*
         *      Refresh the timer.
         */
        if (len) {
                if (!nowayout) {
                        size_t i;

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

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

                                if (get_user(c, data + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        wdt->expect_close = 42;
                        }
                }
                mpcore_wdt_keepalive(wdt);
        }
        return len;
}

static const struct watchdog_info ident = {
        .options                = WDIOF_SETTIMEOUT |
                                  WDIOF_KEEPALIVEPING |
                                  WDIOF_MAGICCLOSE,
        .identity               = "MPcore Watchdog",
};

static long mpcore_wdt_ioctl(struct file *file, unsigned int cmd,
                                                        unsigned long arg)
{
        struct mpcore_wdt *wdt = file->private_data;
        int ret;
        union {
                struct watchdog_info ident;
                int i;
        } uarg;

        if (_IOC_DIR(cmd) && _IOC_SIZE(cmd) > sizeof(uarg))
                return -ENOTTY;

        if (_IOC_DIR(cmd) & _IOC_WRITE) {
                ret = copy_from_user(&uarg, (void __user *)arg, _IOC_SIZE(cmd));
                if (ret)
                        return -EFAULT;
        }

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                uarg.ident = ident;
                ret = 0;
                break;

        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                uarg.i = 0;
                ret = 0;
                break;

        case WDIOC_SETOPTIONS:
                ret = -EINVAL;
                if (uarg.i & WDIOS_DISABLECARD) {
                        mpcore_wdt_stop(wdt);
                        ret = 0;
                }
                if (uarg.i & WDIOS_ENABLECARD) {
                        mpcore_wdt_start(wdt);
                        ret = 0;
                }
                break;

        case WDIOC_KEEPALIVE:
                mpcore_wdt_keepalive(wdt);
                ret = 0;
                break;

        case WDIOC_SETTIMEOUT:
                ret = mpcore_wdt_set_heartbeat(uarg.i);
                if (ret)
                        break;

                mpcore_wdt_keepalive(wdt);
                /* Fall */
        case WDIOC_GETTIMEOUT:
                uarg.i = mpcore_margin;
                ret = 0;
                break;

        default:
                return -ENOTTY;
        }

        if (ret == 0 && _IOC_DIR(cmd) & _IOC_READ) {
                ret = copy_to_user((void __user *)arg, &uarg, _IOC_SIZE(cmd));
                if (ret)
                        ret = -EFAULT;
        }
        return ret;
}

/*
 *      System shutdown handler.  Turn off the watchdog if we're
 *      restarting or halting the system.
 */
static void mpcore_wdt_shutdown(struct platform_device *pdev)
{
        struct mpcore_wdt *wdt = platform_get_drvdata(pdev);

        if (system_state == SYSTEM_RESTART || system_state == SYSTEM_HALT)
                mpcore_wdt_stop(wdt);
}

/*
 *      Kernel Interfaces
 */
static const struct file_operations mpcore_wdt_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = mpcore_wdt_write,
        .unlocked_ioctl = mpcore_wdt_ioctl,
        .open           = mpcore_wdt_open,
        .release        = mpcore_wdt_release,
};

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

static int __devinit mpcore_wdt_probe(struct platform_device *pdev)
{
        struct mpcore_wdt *wdt;
        struct resource *res;
        int ret;

        /* We only accept one device, and it must have an id of -1 */
        if (pdev->id != -1)
                return -ENODEV;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENODEV;

        wdt = devm_kzalloc(&pdev->dev, sizeof(struct mpcore_wdt), GFP_KERNEL);
        if (!wdt)
                return -ENOMEM;

        wdt->dev = &pdev->dev;
        wdt->irq = platform_get_irq(pdev, 0);
        if (wdt->irq >= 0) {
                ret = devm_request_irq(wdt->dev, wdt->irq, mpcore_wdt_fire, 0,
                                "mpcore_wdt", wdt);
                if (ret) {
                        dev_printk(KERN_ERR, wdt->dev,
                                        "cannot register IRQ%d for watchdog\n",
                                        wdt->irq);
                        return ret;
                }
        }

        wdt->base = devm_ioremap(wdt->dev, res->start, resource_size(res));
        if (!wdt->base)
                return -ENOMEM;

        mpcore_wdt_miscdev.parent = &pdev->dev;
        ret = misc_register(&mpcore_wdt_miscdev);
        if (ret) {
                dev_printk(KERN_ERR, wdt->dev,
                        "cannot register miscdev on minor=%d (err=%d)\n",
                                                        WATCHDOG_MINOR, ret);
                return ret;
        }

        mpcore_wdt_stop(wdt);
        platform_set_drvdata(pdev, wdt);
        mpcore_wdt_pdev = pdev;

        return 0;
}

static int __devexit mpcore_wdt_remove(struct platform_device *pdev)
{
        platform_set_drvdata(pdev, NULL);

        misc_deregister(&mpcore_wdt_miscdev);

        mpcore_wdt_pdev = NULL;

        return 0;
}

#ifdef CONFIG_PM
static int mpcore_wdt_suspend(struct platform_device *pdev, pm_message_t msg)
{
        struct mpcore_wdt *wdt = platform_get_drvdata(pdev);
        mpcore_wdt_stop(wdt);           /* Turn the WDT off */
        return 0;
}

static int mpcore_wdt_resume(struct platform_device *pdev)
{
        struct mpcore_wdt *wdt = platform_get_drvdata(pdev);
        /* re-activate timer */
        if (test_bit(0, &wdt->timer_alive))
                mpcore_wdt_start(wdt);
        return 0;
}
#else
#define mpcore_wdt_suspend      NULL
#define mpcore_wdt_resume       NULL
#endif

/* work with hotplug and coldplug */
MODULE_ALIAS("platform:mpcore_wdt");

static struct platform_driver mpcore_wdt_driver = {
        .probe          = mpcore_wdt_probe,
        .remove         = __devexit_p(mpcore_wdt_remove),
        .suspend        = mpcore_wdt_suspend,
        .resume         = mpcore_wdt_resume,
        .shutdown       = mpcore_wdt_shutdown,
        .driver         = {
                .owner  = THIS_MODULE,
                .name   = "mpcore_wdt",
        },
};

static int __init mpcore_wdt_init(void)
{
        /*
         * Check that the margin value is within it's range;
         * if not reset to the default
         */
        if (mpcore_wdt_set_heartbeat(mpcore_margin)) {
                mpcore_wdt_set_heartbeat(TIMER_MARGIN);
                pr_info("mpcore_margin value must be 0 < mpcore_margin < 65536, using %d\n",
                        TIMER_MARGIN);
        }

        pr_info("MPcore Watchdog Timer: 0.1. mpcore_noboot=%d mpcore_margin=%d sec (nowayout= %d)\n",
                mpcore_noboot, mpcore_margin, nowayout);

        return platform_driver_register(&mpcore_wdt_driver);
}

static void __exit mpcore_wdt_exit(void)
{
        platform_driver_unregister(&mpcore_wdt_driver);
}

module_init(mpcore_wdt_init);
module_exit(mpcore_wdt_exit);

MODULE_AUTHOR("ARM Limited");
MODULE_DESCRIPTION("MPcore Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);