alim1535_wdt.c

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/*
 *  Watchdog for the 7101 PMU version found in the ALi M1535 chipsets
 *
 *  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/ioport.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pci.h>
#include <linux/uaccess.h>
#include <linux/io.h>

#define WATCHDOG_NAME "ALi_M1535"
#define WATCHDOG_TIMEOUT 60 /* 60 sec default timeout */

/* internal variables */
static unsigned long ali_is_open;
static char ali_expect_release;
static struct pci_dev *ali_pci;
static u32 ali_timeout_bits;        /* stores the computed timeout */
static DEFINE_SPINLOCK(ali_lock);   /* Guards the hardware */

/* module parameters */
static int timeout = WATCHDOG_TIMEOUT;
module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
        "Watchdog timeout in seconds. (0 < timeout < 18000, 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) ")");

/*
 *  ali_start   -   start watchdog countdown
 *
 *  Starts the timer running providing the timer has a counter
 *  configuration set.
 */

static void ali_start(void)
{
    u32 val;

    spin_lock(&ali_lock);

    pci_read_config_dword(ali_pci, 0xCC, &val);
    val &= ~0x3F;   /* Mask count */
    val |= (1 << 25) | ali_timeout_bits;
    pci_write_config_dword(ali_pci, 0xCC, val);

    spin_unlock(&ali_lock);
}

/*
 *  ali_stop    -   stop the timer countdown
 *
 *  Stop the ALi watchdog countdown
 */

static void ali_stop(void)
{
    u32 val;

    spin_lock(&ali_lock);

    pci_read_config_dword(ali_pci, 0xCC, &val);
    val &= ~0x3F;       /* Mask count to zero (disabled) */
    val &= ~(1 << 25);  /* and for safety mask the reset enable */
    pci_write_config_dword(ali_pci, 0xCC, val);

    spin_unlock(&ali_lock);
}

/*
 *  ali_keepalive   -   send a keepalive to the watchdog
 *
 *  Send a keepalive to the timer (actually we restart the timer).
 */

static void ali_keepalive(void)
{
    ali_start();
}

/*
 *  ali_settimer    -   compute the timer reload value
 *  @t: time in seconds
 *
 *  Computes the timeout values needed
 */

static int ali_settimer(int t)
{
    if (t < 0)
        return -EINVAL;
    else if (t < 60)
        ali_timeout_bits = t|(1 << 6);
    else if (t < 3600)
        ali_timeout_bits = (t / 60)|(1 << 7);
    else if (t < 18000)
        ali_timeout_bits = (t / 300)|(1 << 6)|(1 << 7);
    else
        return -EINVAL;

    timeout = t;
    return 0;
}

/*
 *  /dev/watchdog handling
 */

/*
 *  ali_write   -   writes to ALi watchdog
 *  @file: file from VFS
 *  @data: user address of data
 *  @len: length of data
 *  @ppos: pointer to the file offset
 *
 *  Handle a write to the ALi watchdog. Writing to the file pings
 *  the watchdog and resets it. Writing the magic 'V' sequence allows
 *  the next close to turn off the watchdog.
 */

static ssize_t ali_write(struct file *file, const char __user *data,
                        size_t len, loff_t *ppos)
{
    /* See if we got the magic character 'V' and reload the timer */
    if (len) {
        if (!nowayout) {
            size_t i;

            /* note: just in case someone wrote the
               magic character five months ago... */
            ali_expect_release = 0;

            /* scan to see whether or not we got
               the magic character */
            for (i = 0; i != len; i++) {
                char c;
                if (get_user(c, data + i))
                    return -EFAULT;
                if (c == 'V')
                    ali_expect_release = 42;
            }
        }

        /* someone wrote to us, we should reload the timer */
        ali_start();
    }
    return len;
}

/*
 *  ali_ioctl   -   handle watchdog ioctls
 *  @file: VFS file pointer
 *  @cmd: ioctl number
 *  @arg: arguments to the ioctl
 *
 *  Handle the watchdog ioctls supported by the ALi driver. Really
 *  we want an extension to enable irq ack monitoring and the like
 */

static long ali_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
    void __user *argp = (void __user *)arg;
    int __user *p = argp;
    static const struct watchdog_info ident = {
        .options =      WDIOF_KEEPALIVEPING |
                    WDIOF_SETTIMEOUT |
                    WDIOF_MAGICCLOSE,
        .firmware_version = 0,
        .identity =     "ALi M1535 WatchDog Timer",
    };

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

    case WDIOC_GETSTATUS:
    case WDIOC_GETBOOTSTATUS:
        return put_user(0, p);
    case WDIOC_SETOPTIONS:
    {
        int new_options, retval = -EINVAL;

        if (get_user(new_options, p))
            return -EFAULT;
        if (new_options & WDIOS_DISABLECARD) {
            ali_stop();
            retval = 0;
        }
        if (new_options & WDIOS_ENABLECARD) {
            ali_start();
            retval = 0;
        }
        return retval;
    }
    case WDIOC_KEEPALIVE:
        ali_keepalive();
        return 0;
    case WDIOC_SETTIMEOUT:
    {
        int new_timeout;
        if (get_user(new_timeout, p))
            return -EFAULT;
        if (ali_settimer(new_timeout))
            return -EINVAL;
        ali_keepalive();
        /* Fall */
    }
    case WDIOC_GETTIMEOUT:
        return put_user(timeout, p);
    default:
        return -ENOTTY;
    }
}

/*
 *  ali_open    -   handle open of ali watchdog
 *  @inode: inode from VFS
 *  @file: file from VFS
 *
 *  Open the ALi watchdog device. Ensure only one person opens it
 *  at a time. Also start the watchdog running.
 */

static int ali_open(struct inode *inode, struct file *file)
{
    /* /dev/watchdog can only be opened once */
    if (test_and_set_bit(0, &ali_is_open))
        return -EBUSY;

    /* Activate */
    ali_start();
    return nonseekable_open(inode, file);
}

/*
 *  ali_release -   close an ALi watchdog
 *  @inode: inode from VFS
 *  @file: file from VFS
 *
 *  Close the ALi watchdog device. Actual shutdown of the timer
 *  only occurs if the magic sequence has been set.
 */

static int ali_release(struct inode *inode, struct file *file)
{
    /*
     *      Shut off the timer.
     */
    if (ali_expect_release == 42)
        ali_stop();
    else {
        pr_crit("Unexpected close, not stopping watchdog!\n");
        ali_keepalive();
    }
    clear_bit(0, &ali_is_open);
    ali_expect_release = 0;
    return 0;
}

/*
 *  ali_notify_sys  -   System down notifier
 *
 *  Notifier for system down
 */


static int ali_notify_sys(struct notifier_block *this,
                    unsigned long code, void *unused)
{
    if (code == SYS_DOWN || code == SYS_HALT)
        ali_stop();     /* Turn the WDT off */
    return NOTIFY_DONE;
}

/*
 *  Data for PCI driver interface
 *
 *  This data only exists for exporting the supported
 *  PCI ids via MODULE_DEVICE_TABLE.  We do not actually
 *  register a pci_driver, because someone else might one day
 *  want to register another driver on the same PCI id.
 */

static DEFINE_PCI_DEVICE_TABLE(ali_pci_tbl) __used = {
    { PCI_VENDOR_ID_AL, 0x1533, PCI_ANY_ID, PCI_ANY_ID,},
    { PCI_VENDOR_ID_AL, 0x1535, PCI_ANY_ID, PCI_ANY_ID,},
    { 0, },
};
MODULE_DEVICE_TABLE(pci, ali_pci_tbl);

/*
 *  ali_find_watchdog   -   find a 1535 and 7101
 *
 *  Scans the PCI hardware for a 1535 series bridge and matching 7101
 *  watchdog device. This may be overtight but it is better to be safe
 */

static int __init ali_find_watchdog(void)
{
    struct pci_dev *pdev;
    u32 wdog;

    /* Check for a 1533/1535 series bridge */
    pdev = pci_get_device(PCI_VENDOR_ID_AL, 0x1535, NULL);
    if (pdev == NULL)
        pdev = pci_get_device(PCI_VENDOR_ID_AL, 0x1533, NULL);
    if (pdev == NULL)
        return -ENODEV;
    pci_dev_put(pdev);

    /* Check for the a 7101 PMU */
    pdev = pci_get_device(PCI_VENDOR_ID_AL, 0x7101, NULL);
    if (pdev == NULL)
        return -ENODEV;

    if (pci_enable_device(pdev)) {
        pci_dev_put(pdev);
        return -EIO;
    }

    ali_pci = pdev;

    /*
     *  Initialize the timer bits
     */
    pci_read_config_dword(pdev, 0xCC, &wdog);

    /* Timer bits */
    wdog &= ~0x3F;
    /* Issued events */
    wdog &= ~((1 << 27)|(1 << 26)|(1 << 25)|(1 << 24));
    /* No monitor bits */
    wdog &= ~((1 << 16)|(1 << 13)|(1 << 12)|(1 << 11)|(1 << 10)|(1 << 9));

    pci_write_config_dword(pdev, 0xCC, wdog);

    return 0;
}

/*
 *  Kernel Interfaces
 */

static const struct file_operations ali_fops = {
    .owner      =   THIS_MODULE,
    .llseek     =   no_llseek,
    .write      =   ali_write,
    .unlocked_ioctl =   ali_ioctl,
    .open       =   ali_open,
    .release    =   ali_release,
};

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

static struct notifier_block ali_notifier = {
    .notifier_call =    ali_notify_sys,
};

/*
 *  watchdog_init   -   module initialiser
 *
 *  Scan for a suitable watchdog and if so initialize it. Return an error
 *  if we cannot, the error causes the module to unload
 */

static int __init watchdog_init(void)
{
    int ret;

    /* Check whether or not the hardware watchdog is there */
    if (ali_find_watchdog() != 0)
        return -ENODEV;

    /* Check that the timeout value is within it's range;
       if not reset to the default */
    if (timeout < 1 || timeout >= 18000) {
        timeout = WATCHDOG_TIMEOUT;
        pr_info("timeout value must be 0 < timeout < 18000, using %d\n",
            timeout);
    }

    /* Calculate the watchdog's timeout */
    ali_settimer(timeout);

    ret = register_reboot_notifier(&ali_notifier);
    if (ret != 0) {
        pr_err("cannot register reboot notifier (err=%d)\n", ret);
        goto out;
    }

    ret = misc_register(&ali_miscdev);
    if (ret != 0) {
        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
               WATCHDOG_MINOR, ret);
        goto unreg_reboot;
    }

    pr_info("initialized. timeout=%d sec (nowayout=%d)\n",
        timeout, nowayout);

out:
    return ret;
unreg_reboot:
    unregister_reboot_notifier(&ali_notifier);
    goto out;
}

/*
 *  watchdog_exit   -   module de-initialiser
 *
 *  Called while unloading a successfully installed watchdog module.
 */

static void __exit watchdog_exit(void)
{
    /* Stop the timer before we leave */
    ali_stop();

    /* Deregister */
    misc_deregister(&ali_miscdev);
    unregister_reboot_notifier(&ali_notifier);
    pci_dev_put(ali_pci);
}

module_init(watchdog_init);
module_exit(watchdog_exit);

MODULE_AUTHOR("Alan Cox");
MODULE_DESCRIPTION("ALi M1535 PMU Watchdog Timer driver");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);