at91sam9_wdt.c

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/*
 * Watchdog driver for Atmel AT91SAM9x processors.
 *
 * Copyright (C) 2008 Renaud CERRATO [email protected]
 *
 * 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.
 */

/*
 * The Watchdog Timer Mode Register can be only written to once. If the
 * timeout need to be set from Linux, be sure that the bootstrap or the
 * bootloader doesn't write to this register.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/io.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 <linux/jiffies.h>
#include <linux/timer.h>
#include <linux/bitops.h>
#include <linux/uaccess.h>

#include "at91sam9_wdt.h"

#define DRV_NAME "AT91SAM9 Watchdog"

#define wdt_read(field) \
    __raw_readl(at91wdt_private.base + field)
#define wdt_write(field, val) \
    __raw_writel((val), at91wdt_private.base + field)

/* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
 * use this to convert a watchdog
 * value from/to milliseconds.
 */
#define ms_to_ticks(t)  (((t << 8) / 1000) - 1)
#define ticks_to_ms(t)  (((t + 1) * 1000) >> 8)

/* Hardware timeout in seconds */
#define WDT_HW_TIMEOUT 2

/* Timer heartbeat (500ms) */
#define WDT_TIMEOUT (HZ/2)

/* User land timeout */
#define WDT_HEARTBEAT 15
static int heartbeat = WDT_HEARTBEAT;
module_param(heartbeat, int, 0);
MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
    "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");

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) ")");

static void at91_ping(unsigned long data);

static struct {
    void __iomem *base;
    unsigned long next_heartbeat;   /* the next_heartbeat for the timer */
    unsigned long open;
    char expect_close;
    struct timer_list timer;    /* The timer that pings the watchdog */
} at91wdt_private;

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


/*
 * Reload the watchdog timer.  (ie, pat the watchdog)
 */
static inline void at91_wdt_reset(void)
{
    wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
}

/*
 * Timer tick
 */
static void at91_ping(unsigned long data)
{
    if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
            (!nowayout && !at91wdt_private.open)) {
        at91_wdt_reset();
        mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
    } else
        pr_crit("I will reset your machine !\n");
}

/*
 * Watchdog device is opened, and watchdog starts running.
 */
static int at91_wdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(0, &at91wdt_private.open))
        return -EBUSY;

    at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
    mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);

    return nonseekable_open(inode, file);
}

/*
 * Close the watchdog device.
 */
static int at91_wdt_close(struct inode *inode, struct file *file)
{
    clear_bit(0, &at91wdt_private.open);

    /* stop internal ping */
    if (!at91wdt_private.expect_close)
        del_timer(&at91wdt_private.timer);

    at91wdt_private.expect_close = 0;
    return 0;
}

/*
 * Set the watchdog time interval in 1/256Hz (write-once)
 * Counter is 12 bit.
 */
static int at91_wdt_settimeout(unsigned int timeout)
{
    unsigned int reg;
    unsigned int mr;

    /* Check if disabled */
    mr = wdt_read(AT91_WDT_MR);
    if (mr & AT91_WDT_WDDIS) {
        pr_err("sorry, watchdog is disabled\n");
        return -EIO;
    }

    /*
     * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
     *
     * Since WDV is a 12-bit counter, the maximum period is
     * 4096 / 256 = 16 seconds.
     */
    reg = AT91_WDT_WDRSTEN  /* causes watchdog reset */
        /* | AT91_WDT_WDRPROC   causes processor reset only */
        | AT91_WDT_WDDBGHLT /* disabled in debug mode */
        | AT91_WDT_WDD      /* restart at any time */
        | (timeout & AT91_WDT_WDV);  /* timer value */
    wdt_write(AT91_WDT_MR, reg);

    return 0;
}

static const struct watchdog_info at91_wdt_info = {
    .identity   = DRV_NAME,
    .options    = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
                        WDIOF_MAGICCLOSE,
};

/*
 * Handle commands from user-space.
 */
static long at91_wdt_ioctl(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_GETSUPPORT:
        return copy_to_user(argp, &at91_wdt_info,
                    sizeof(at91_wdt_info)) ? -EFAULT : 0;

    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, p);

    case WDIOC_KEEPALIVE:
        at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
        return 0;

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

        heartbeat = new_value;
        at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;

        return put_user(new_value, p);  /* return current value */

    case WDIOC_GETTIMEOUT:
        return put_user(heartbeat, p);
    }
    return -ENOTTY;
}

/*
 * Pat the watchdog whenever device is written to.
 */
static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
                                loff_t *ppos)
{
    if (!len)
        return 0;

    /* Scan for magic character */
    if (!nowayout) {
        size_t i;

        at91wdt_private.expect_close = 0;

        for (i = 0; i < len; i++) {
            char c;
            if (get_user(c, data + i))
                return -EFAULT;
            if (c == 'V') {
                at91wdt_private.expect_close = 42;
                break;
            }
        }
    }

    at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;

    return len;
}

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

static const struct file_operations at91wdt_fops = {
    .owner          = THIS_MODULE,
    .llseek         = no_llseek,
    .unlocked_ioctl = at91_wdt_ioctl,
    .open           = at91_wdt_open,
    .release        = at91_wdt_close,
    .write          = at91_wdt_write,
};

static struct miscdevice at91wdt_miscdev = {
    .minor      = WATCHDOG_MINOR,
    .name       = "watchdog",
    .fops       = &at91wdt_fops,
};

static int __init at91wdt_probe(struct platform_device *pdev)
{
    struct resource *r;
    int res;

    if (at91wdt_miscdev.parent)
        return -EBUSY;
    at91wdt_miscdev.parent = &pdev->dev;

    r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!r)
        return -ENODEV;
    at91wdt_private.base = ioremap(r->start, resource_size(r));
    if (!at91wdt_private.base) {
        dev_err(&pdev->dev, "failed to map registers, aborting.\n");
        return -ENOMEM;
    }

    /* Set watchdog */
    res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
    if (res)
        return res;

    res = misc_register(&at91wdt_miscdev);
    if (res)
        return res;

    at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
    setup_timer(&at91wdt_private.timer, at91_ping, 0);
    mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);

    pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
        heartbeat, nowayout);

    return 0;
}

static int __exit at91wdt_remove(struct platform_device *pdev)
{
    int res;

    res = misc_deregister(&at91wdt_miscdev);
    if (!res)
        at91wdt_miscdev.parent = NULL;

    return res;
}

static struct platform_driver at91wdt_driver = {
    .remove     = __exit_p(at91wdt_remove),
    .driver     = {
        .name   = "at91_wdt",
        .owner  = THIS_MODULE,
    },
};

static int __init at91sam_wdt_init(void)
{
    return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
}

static void __exit at91sam_wdt_exit(void)
{
    platform_driver_unregister(&at91wdt_driver);
}

module_init(at91sam_wdt_init);
module_exit(at91sam_wdt_exit);

MODULE_AUTHOR("Renaud CERRATO <[email protected]>");
MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);