geodewdt.c

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/* Watchdog timer for machines with the CS5535/CS5536 companion chip
 *
 * Copyright (C) 2006-2007, Advanced Micro Devices, Inc.
 * Copyright (C) 2009  Andres Salomon <[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.
 */

#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/platform_device.h>
#include <linux/reboot.h>
#include <linux/uaccess.h>

#include <linux/cs5535.h>

#define GEODEWDT_HZ 500
#define GEODEWDT_SCALE 6
#define GEODEWDT_MAX_SECONDS 131

#define WDT_FLAGS_OPEN 1
#define WDT_FLAGS_ORPHAN 2

#define DRV_NAME "geodewdt"
#define WATCHDOG_NAME "Geode GX/LX WDT"
#define WATCHDOG_TIMEOUT 60

static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
    "Watchdog timeout in seconds. 1<= timeout <=131, default="
                __MODULE_STRING(WATCHDOG_TIMEOUT) ".");

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 struct platform_device *geodewdt_platform_device;
static unsigned long wdt_flags;
static struct cs5535_mfgpt_timer *wdt_timer;
static int safe_close;

static void geodewdt_ping(void)
{
    /* Stop the counter */
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);

    /* Reset the counter */
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);

    /* Enable the counter */
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);
}

static void geodewdt_disable(void)
{
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);
}

static int geodewdt_set_heartbeat(int val)
{
    if (val < 1 || val > GEODEWDT_MAX_SECONDS)
        return -EINVAL;

    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, 0);
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_CMP2, val * GEODEWDT_HZ);
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_COUNTER, 0);
    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP, MFGPT_SETUP_CNTEN);

    timeout = val;
    return 0;
}

static int geodewdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(WDT_FLAGS_OPEN, &wdt_flags))
        return -EBUSY;

    if (!test_and_clear_bit(WDT_FLAGS_ORPHAN, &wdt_flags))
        __module_get(THIS_MODULE);

    geodewdt_ping();
    return nonseekable_open(inode, file);
}

static int geodewdt_release(struct inode *inode, struct file *file)
{
    if (safe_close) {
        geodewdt_disable();
        module_put(THIS_MODULE);
    } else {
        pr_crit("Unexpected close - watchdog is not stopping\n");
        geodewdt_ping();

        set_bit(WDT_FLAGS_ORPHAN, &wdt_flags);
    }

    clear_bit(WDT_FLAGS_OPEN, &wdt_flags);
    safe_close = 0;
    return 0;
}

static ssize_t geodewdt_write(struct file *file, const char __user *data,
                size_t len, loff_t *ppos)
{
    if (len) {
        if (!nowayout) {
            size_t i;
            safe_close = 0;

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

                if (get_user(c, data + i))
                    return -EFAULT;

                if (c == 'V')
                    safe_close = 1;
            }
        }

        geodewdt_ping();
    }
    return len;
}

static long geodewdt_ioctl(struct file *file, unsigned int cmd,
                unsigned long arg)
{
    void __user *argp = (void __user *)arg;
    int __user *p = argp;
    int interval;

    static const struct watchdog_info ident = {
        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING
        | WDIOF_MAGICCLOSE,
        .firmware_version =     1,
        .identity =             WATCHDOG_NAME,
    };

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        return copy_to_user(argp, &ident,
                    sizeof(ident)) ? -EFAULT : 0;
        break;

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

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

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

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

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

        return ret;
    }
    case WDIOC_KEEPALIVE:
        geodewdt_ping();
        return 0;

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

        if (geodewdt_set_heartbeat(interval))
            return -EINVAL;
    /* Fall through */
    case WDIOC_GETTIMEOUT:
        return put_user(timeout, p);

    default:
        return -ENOTTY;
    }

    return 0;
}

static const struct file_operations geodewdt_fops = {
    .owner          = THIS_MODULE,
    .llseek         = no_llseek,
    .write          = geodewdt_write,
    .unlocked_ioctl = geodewdt_ioctl,
    .open           = geodewdt_open,
    .release        = geodewdt_release,
};

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

static int __devinit geodewdt_probe(struct platform_device *dev)
{
    int ret;

    wdt_timer = cs5535_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING);
    if (!wdt_timer) {
        pr_err("No timers were available\n");
        return -ENODEV;
    }

    /* Set up the timer */

    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_SETUP,
              GEODEWDT_SCALE | (3 << 8));

    /* Set up comparator 2 to reset when the event fires */
    cs5535_mfgpt_toggle_event(wdt_timer, MFGPT_CMP2, MFGPT_EVENT_RESET, 1);

    /* Set up the initial timeout */

    cs5535_mfgpt_write(wdt_timer, MFGPT_REG_CMP2,
        timeout * GEODEWDT_HZ);

    ret = misc_register(&geodewdt_miscdev);

    return ret;
}

static int __devexit geodewdt_remove(struct platform_device *dev)
{
    misc_deregister(&geodewdt_miscdev);
    return 0;
}

static void geodewdt_shutdown(struct platform_device *dev)
{
    geodewdt_disable();
}

static struct platform_driver geodewdt_driver = {
    .probe      = geodewdt_probe,
    .remove     = __devexit_p(geodewdt_remove),
    .shutdown   = geodewdt_shutdown,
    .driver     = {
        .owner  = THIS_MODULE,
        .name   = DRV_NAME,
    },
};

static int __init geodewdt_init(void)
{
    int ret;

    ret = platform_driver_register(&geodewdt_driver);
    if (ret)
        return ret;

    geodewdt_platform_device = platform_device_register_simple(DRV_NAME,
                                -1, NULL, 0);
    if (IS_ERR(geodewdt_platform_device)) {
        ret = PTR_ERR(geodewdt_platform_device);
        goto err;
    }

    return 0;
err:
    platform_driver_unregister(&geodewdt_driver);
    return ret;
}

static void __exit geodewdt_exit(void)
{
    platform_device_unregister(geodewdt_platform_device);
    platform_driver_unregister(&geodewdt_driver);
}

module_init(geodewdt_init);
module_exit(geodewdt_exit);

MODULE_AUTHOR("Advanced Micro Devices, Inc");
MODULE_DESCRIPTION("Geode GX/LX Watchdog Driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);