mv64x60_wdt.c

Go to the documentation of this file.

/*
 * mv64x60_wdt.c - MV64X60 (Marvell Discovery) watchdog userspace interface
 *
 * Author: James Chapman <[email protected]>
 *
 * Platform-specific setup code should configure the dog to generate
 * interrupt or reset as required.  This code only enables/disables
 * and services the watchdog.
 *
 * Derived from mpc8xx_wdt.c, with the following copyright.
 *
 * 2002 (c) Florian Schirmer <[email protected]> This file is licensed under
 * the terms of the GNU General Public License version 2. This program
 * is licensed "as is" without any warranty of any kind, whether express
 * or implied.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/watchdog.h>
#include <linux/platform_device.h>
#include <linux/mv643xx.h>
#include <linux/uaccess.h>
#include <linux/io.h>

#define MV64x60_WDT_WDC_OFFSET  0

/*
 * The watchdog configuration register contains a pair of 2-bit fields,
 *   1.  a reload field, bits 27-26, which triggers a reload of
 *       the countdown register, and
 *   2.  an enable field, bits 25-24, which toggles between
 *       enabling and disabling the watchdog timer.
 * Bit 31 is a read-only field which indicates whether the
 * watchdog timer is currently enabled.
 *
 * The low 24 bits contain the timer reload value.
 */
#define MV64x60_WDC_ENABLE_SHIFT    24
#define MV64x60_WDC_SERVICE_SHIFT   26
#define MV64x60_WDC_ENABLED_SHIFT   31

#define MV64x60_WDC_ENABLED_TRUE    1
#define MV64x60_WDC_ENABLED_FALSE   0

/* Flags bits */
#define MV64x60_WDOG_FLAG_OPENED    0

static unsigned long wdt_flags;
static int wdt_status;
static void __iomem *mv64x60_wdt_regs;
static int mv64x60_wdt_timeout;
static int mv64x60_wdt_count;
static unsigned int bus_clk;
static char expect_close;
static DEFINE_SPINLOCK(mv64x60_wdt_spinlock);

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 int mv64x60_wdt_toggle_wdc(int enabled_predicate, int field_shift)
{
    u32 data;
    u32 enabled;
    int ret = 0;

    spin_lock(&mv64x60_wdt_spinlock);
    data = readl(mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
    enabled = (data >> MV64x60_WDC_ENABLED_SHIFT) & 1;

    /* only toggle the requested field if enabled state matches predicate */
    if ((enabled ^ enabled_predicate) == 0) {
        /* We write a 1, then a 2 -- to the appropriate field */
        data = (1 << field_shift) | mv64x60_wdt_count;
        writel(data, mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);

        data = (2 << field_shift) | mv64x60_wdt_count;
        writel(data, mv64x60_wdt_regs + MV64x60_WDT_WDC_OFFSET);
        ret = 1;
    }
    spin_unlock(&mv64x60_wdt_spinlock);

    return ret;
}

static void mv64x60_wdt_service(void)
{
    mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_TRUE,
                   MV64x60_WDC_SERVICE_SHIFT);
}

static void mv64x60_wdt_handler_enable(void)
{
    if (mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_FALSE,
                   MV64x60_WDC_ENABLE_SHIFT)) {
        mv64x60_wdt_service();
        pr_notice("watchdog activated\n");
    }
}

static void mv64x60_wdt_handler_disable(void)
{
    if (mv64x60_wdt_toggle_wdc(MV64x60_WDC_ENABLED_TRUE,
                   MV64x60_WDC_ENABLE_SHIFT))
        pr_notice("watchdog deactivated\n");
}

static void mv64x60_wdt_set_timeout(unsigned int timeout)
{
    /* maximum bus cycle count is 0xFFFFFFFF */
    if (timeout > 0xFFFFFFFF / bus_clk)
        timeout = 0xFFFFFFFF / bus_clk;

    mv64x60_wdt_count = timeout * bus_clk >> 8;
    mv64x60_wdt_timeout = timeout;
}

static int mv64x60_wdt_open(struct inode *inode, struct file *file)
{
    if (test_and_set_bit(MV64x60_WDOG_FLAG_OPENED, &wdt_flags))
        return -EBUSY;

    if (nowayout)
        __module_get(THIS_MODULE);

    mv64x60_wdt_handler_enable();

    return nonseekable_open(inode, file);
}

static int mv64x60_wdt_release(struct inode *inode, struct file *file)
{
    if (expect_close == 42)
        mv64x60_wdt_handler_disable();
    else {
        pr_crit("unexpected close, not stopping timer!\n");
        mv64x60_wdt_service();
    }
    expect_close = 0;

    clear_bit(MV64x60_WDOG_FLAG_OPENED, &wdt_flags);

    return 0;
}

static ssize_t mv64x60_wdt_write(struct file *file, const char __user *data,
                 size_t len, loff_t *ppos)
{
    if (len) {
        if (!nowayout) {
            size_t i;

            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;
            }
        }
        mv64x60_wdt_service();
    }

    return len;
}

static long mv64x60_wdt_ioctl(struct file *file,
                    unsigned int cmd, unsigned long arg)
{
    int timeout;
    int options;
    void __user *argp = (void __user *)arg;
    static const struct watchdog_info info = {
        .options =  WDIOF_SETTIMEOUT    |
                WDIOF_MAGICCLOSE    |
                WDIOF_KEEPALIVEPING,
        .firmware_version = 0,
        .identity = "MV64x60 watchdog",
    };

    switch (cmd) {
    case WDIOC_GETSUPPORT:
        if (copy_to_user(argp, &info, sizeof(info)))
            return -EFAULT;
        break;

    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        if (put_user(wdt_status, (int __user *)argp))
            return -EFAULT;
        wdt_status &= ~WDIOF_KEEPALIVEPING;
        break;

    case WDIOC_GETTEMP:
        return -EOPNOTSUPP;

    case WDIOC_SETOPTIONS:
        if (get_user(options, (int __user *)argp))
            return -EFAULT;

        if (options & WDIOS_DISABLECARD)
            mv64x60_wdt_handler_disable();

        if (options & WDIOS_ENABLECARD)
            mv64x60_wdt_handler_enable();
        break;

    case WDIOC_KEEPALIVE:
        mv64x60_wdt_service();
        wdt_status |= WDIOF_KEEPALIVEPING;
        break;

    case WDIOC_SETTIMEOUT:
        if (get_user(timeout, (int __user *)argp))
            return -EFAULT;
        mv64x60_wdt_set_timeout(timeout);
        /* Fall through */

    case WDIOC_GETTIMEOUT:
        if (put_user(mv64x60_wdt_timeout, (int __user *)argp))
            return -EFAULT;
        break;

    default:
        return -ENOTTY;
    }

    return 0;
}

static const struct file_operations mv64x60_wdt_fops = {
    .owner = THIS_MODULE,
    .llseek = no_llseek,
    .write = mv64x60_wdt_write,
    .unlocked_ioctl = mv64x60_wdt_ioctl,
    .open = mv64x60_wdt_open,
    .release = mv64x60_wdt_release,
};

static struct miscdevice mv64x60_wdt_miscdev = {
    .minor = WATCHDOG_MINOR,
    .name = "watchdog",
    .fops = &mv64x60_wdt_fops,
};

static int __devinit mv64x60_wdt_probe(struct platform_device *dev)
{
    struct mv64x60_wdt_pdata *pdata = dev->dev.platform_data;
    struct resource *r;
    int timeout = 10;

    bus_clk = 133;          /* in MHz */
    if (pdata) {
        timeout = pdata->timeout;
        bus_clk = pdata->bus_clk;
    }

    /* Since bus_clk is truncated MHz, actual frequency could be
     * up to 1MHz higher.  Round up, since it's better to time out
     * too late than too soon.
     */
    bus_clk++;
    bus_clk *= 1000000;     /* convert to Hz */

    r = platform_get_resource(dev, IORESOURCE_MEM, 0);
    if (!r)
        return -ENODEV;

    mv64x60_wdt_regs = ioremap(r->start, resource_size(r));
    if (mv64x60_wdt_regs == NULL)
        return -ENOMEM;

    mv64x60_wdt_set_timeout(timeout);

    mv64x60_wdt_handler_disable();  /* in case timer was already running */

    return misc_register(&mv64x60_wdt_miscdev);
}

static int __devexit mv64x60_wdt_remove(struct platform_device *dev)
{
    misc_deregister(&mv64x60_wdt_miscdev);

    mv64x60_wdt_handler_disable();

    iounmap(mv64x60_wdt_regs);

    return 0;
}

static struct platform_driver mv64x60_wdt_driver = {
    .probe = mv64x60_wdt_probe,
    .remove = __devexit_p(mv64x60_wdt_remove),
    .driver = {
        .owner = THIS_MODULE,
        .name = MV64x60_WDT_NAME,
    },
};

static int __init mv64x60_wdt_init(void)
{
    pr_info("MV64x60 watchdog driver\n");

    return platform_driver_register(&mv64x60_wdt_driver);
}

static void __exit mv64x60_wdt_exit(void)
{
    platform_driver_unregister(&mv64x60_wdt_driver);
}

module_init(mv64x60_wdt_init);
module_exit(mv64x60_wdt_exit);

MODULE_AUTHOR("James Chapman <[email protected]>");
MODULE_DESCRIPTION("MV64x60 watchdog driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
MODULE_ALIAS("platform:" MV64x60_WDT_NAME);