mpcore_wdt.c

Go to the documentation of this file.

/*
 *  Watchdog driver for the mpcore watchdog timer
 *
 *  (c) Copyright 2004 ARM Limited
 *
 *  Based on the SoftDog driver:
 *  (c) Copyright 1996 Alan Cox <[email protected]>,
 *                      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 <[email protected]>
 *
 */

#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);