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/*

 *      ALi M7101 PMU Computer Watchdog Timer driver for Linux 2.4.x

 *

 *      Based on w83877f_wdt.c by Scott Jennings <management@oro.net>

 *      and the Cobalt kernel WDT timer driver by Tim Hockin

 *                                            <thockin@cobaltnet.com>

 *

 *      (c)2002 Steve Hill <steve@navaho.co.uk>

 *

 *  Theory of operation:

 *  A Watchdog Timer (WDT) is a hardware circuit that can

 *  reset the computer system in case of a software fault.

 *  You probably knew that already.

 *

 *  Usually a userspace daemon will notify the kernel WDT driver

 *  via the /proc/watchdog special device file that userspace is

 *  still alive, at regular intervals.  When such a notification

 *  occurs, the driver will usually tell the hardware watchdog

 *  that everything is in order, and that the watchdog should wait

 *  for yet another little while to reset the system.

 *  If userspace fails (RAM error, kernel bug, whatever), the

 *  notifications cease to occur, and the hardware watchdog will

 *  reset the system (causing a reboot) after the timeout occurs.

 *

 *  This WDT driver is different from most other Linux WDT

 *  drivers in that the driver will ping the watchdog by itself,

 *  because this particular WDT has a very short timeout (1.6

 *  seconds) and it would be insane to count on any userspace

 *  daemon always getting scheduled within that time frame.

 */

#include <linux/module.h>

#include <linux/version.h>

#include <linux/types.h>

#include <linux/errno.h>

#include <linux/kernel.h>

#include <linux/timer.h>

#include <linux/sched.h>

#include <linux/miscdevice.h>

#include <linux/watchdog.h>

#include <linux/slab.h>

#include <linux/ioport.h>

#include <linux/fcntl.h>

#include <linux/smp_lock.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#include <asm/system.h>

#include <linux/notifier.h>

#include <linux/reboot.h>

#include <linux/init.h>

#include <linux/pci.h>

#define OUR_NAME "alim7101_wdt"

#define WDT_ENABLE 0x9C

#define WDT_DISABLE 0x8C

#define ALI_7101_WDT    0x92

#define ALI_WDT_ARM     0x01

/*

 * We're going to use a 1 second timeout.

 * If we reset the watchdog every ~250ms we should be safe.  */

#define WDT_INTERVAL (HZ/4+1)

/*

 * We must not require too good response from the userspace daemon.

 * Here we require the userspace daemon to send us a heartbeat

 * char to /dev/watchdog every 30 seconds.

 */

#define WDT_HEARTBEAT (HZ * 30)

static void wdt_timer_ping(unsigned long);

static struct timer_list timer;

static unsigned long next_heartbeat;

static unsigned long wdt_is_open;

static int wdt_expect_close;

static struct pci_dev *alim7101_pmu;

#ifdef CONFIG_WATCHDOG_NOWAYOUT

static int nowayout = 1;

#else

static int nowayout = 0;

#endif

MODULE_PARM(nowayout,"i");

MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");

/*

 *      Whack the dog

 */

static void wdt_timer_ping(unsigned long data)

{

        /* If we got a heartbeat pulse within the WDT_US_INTERVAL

         * we agree to ping the WDT

         */

        char    tmp;

        if(time_before(jiffies, next_heartbeat))

        {

                /* Ping the WDT (this is actually a disarm/arm sequence) */

                pci_read_config_byte(alim7101_pmu, 0x92, &tmp);

                pci_write_config_byte(alim7101_pmu, ALI_7101_WDT, (tmp & ~ALI_WDT_ARM));

                pci_write_config_byte(alim7101_pmu, ALI_7101_WDT, (tmp | ALI_WDT_ARM));

        } else {

                printk(OUR_NAME ": Heartbeat lost! Will not ping the watchdog\n");

        }

        /* Re-set the timer interval */

        timer.expires = jiffies + WDT_INTERVAL;

        add_timer(&timer);

}

/*

 * Utility routines

 */

static void wdt_change(int writeval)

{

        char    tmp;

        pci_read_config_byte(alim7101_pmu, 0x92, &tmp);

        if (writeval == WDT_ENABLE)

                pci_write_config_byte(alim7101_pmu, ALI_7101_WDT, (tmp | ALI_WDT_ARM));

        else

                pci_write_config_byte(alim7101_pmu, ALI_7101_WDT, (tmp & ~ALI_WDT_ARM));

}

static void wdt_startup(void)

{

        next_heartbeat = jiffies + WDT_HEARTBEAT;

        /* We must enable before we kick off the timer in case the timer

           occurs as we ping it */

        wdt_change(WDT_ENABLE);

        /* Start the timer */

        timer.expires = jiffies + WDT_INTERVAL;

        add_timer(&timer);

        printk(OUR_NAME ": Watchdog timer is now enabled.\n");

}

static void wdt_turnoff(void)

{

        /* Stop the timer */

        del_timer_sync(&timer);

        wdt_change(WDT_DISABLE);

        printk(OUR_NAME ": Watchdog timer is now disabled...\n");

}

/*

 * /dev/watchdog handling

 */

static ssize_t fop_write(struct file * file, const char * buf, size_t count, loff_t * ppos)

{

        /* We can't seek */

        if(ppos != &file->f_pos)

                return -ESPIPE;

        /* See if we got the magic character */

        if(count)

        {

                if (!nowayout) {

                        size_t ofs;

                        /* note: just in case someone wrote the magic character

                         * five months ago... */

                        wdt_expect_close = 0;

                        /* now scan */

                        for(ofs = 0; ofs != count; ofs++)

                        {

                                char c;

                                if(get_user(c, buf+ofs))

                                        return -EFAULT;

                                if(c == 'V')

                                        wdt_expect_close = 1;

                        }

                }

                /* someone wrote to us, we should restart timer */

                next_heartbeat = jiffies + WDT_HEARTBEAT;

                return 1;

        };

        return 0;

}

static ssize_t fop_read(struct file * file, char * buf, size_t count, loff_t * ppos)

{

        /* No can do */

        return -EINVAL;

}

static int fop_open(struct inode * inode, struct file * file)

{

        /* Just in case we're already talking to someone... */

        if(test_and_set_bit(0, &wdt_is_open))

                return -EBUSY;

        /* Good, fire up the show */

        wdt_startup();

        return 0;

}

static int fop_close(struct inode * inode, struct file * file)

{

        if ((wdt_expect_close) || (! nowayout))

                wdt_turnoff();

        else {

                printk(OUR_NAME ": device file closed unexpectedly. Will not stop the WDT!\n");

        }

        clear_bit(0, &wdt_is_open);

        return 0;

}

static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)

{

        static struct watchdog_info ident=

        {

                WDIOF_MAGICCLOSE,

                1,

                "ALiM7101"

        };

        switch(cmd)

        {

                case WDIOC_GETSUPPORT:

                        return copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident))?-EFAULT:0;

                case WDIOC_KEEPALIVE:

                        next_heartbeat = jiffies + WDT_HEARTBEAT;

                        return 0;

                default:

                        return -ENOTTY;

        }

}

static struct file_operations wdt_fops = {

        owner:          THIS_MODULE,

        llseek:         no_llseek,

        read:           fop_read,

        write:          fop_write,

        open:           fop_open,

        release:        fop_close,

        ioctl:          fop_ioctl

};

static struct miscdevice wdt_miscdev = {

        WATCHDOG_MINOR,

        "watchdog",

        &wdt_fops

};

/*

 *      Notifier for system down

 */

static int wdt_notify_sys(struct notifier_block *this, unsigned long code, void *unused)

{

        if (code==SYS_DOWN || code==SYS_HALT) wdt_turnoff();

        if (code==SYS_RESTART) {

                /*

                 * Cobalt devices have no way of rebooting themselves other than

                 * getting the watchdog to pull reset, so we restart the watchdog on

                 * reboot with no heartbeat

                 */

                wdt_change(WDT_ENABLE);

                printk(OUR_NAME ": Watchdog timer is now enabled with no heartbeat - should reboot in ~1 second.\n");

        };

        return NOTIFY_DONE;

}

/*

 *      The WDT needs to learn about soft shutdowns in order to

 *      turn the timebomb registers off.

 */

static struct notifier_block wdt_notifier=

{

        wdt_notify_sys,

        0,

};

static void __exit alim7101_wdt_unload(void)

{

        wdt_turnoff();

        /* Deregister */

        misc_deregister(&wdt_miscdev);

        unregister_reboot_notifier(&wdt_notifier);

}

static int __init alim7101_wdt_init(void)

{

        int rc = -EBUSY;

        struct pci_dev *ali1543_south;

        char tmp;

        printk(KERN_INFO OUR_NAME ": Steve Hill <steve@navaho.co.uk>.\n");

        alim7101_pmu = pci_find_device(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M7101,NULL);

        if (!alim7101_pmu) {

                printk(KERN_INFO OUR_NAME ": ALi M7101 PMU not present - WDT not set\n");

                return -EBUSY;

        };

        /* Set the WDT in the PMU to 1 second */

        pci_write_config_byte(alim7101_pmu, ALI_7101_WDT, 0x02);

        ali1543_south = pci_find_device(PCI_VENDOR_ID_AL, PCI_DEVICE_ID_AL_M1533, NULL);

        if (!ali1543_south) {

                printk(KERN_INFO OUR_NAME ": ALi 1543 South-Bridge not present - WDT not set\n");

                return -EBUSY;

        };

        pci_read_config_byte(ali1543_south, 0x5e, &tmp);

        if ((tmp & 0x1e) != 0x12) {

                printk(KERN_INFO OUR_NAME ": ALi 1543 South-Bridge does not have the correct revision number (???1001?) - WDT not set\n");

                return -EBUSY;

        };

        init_timer(&timer);

        timer.function = wdt_timer_ping;

        timer.data = 1;

        rc = misc_register(&wdt_miscdev);

        if (rc)

                return rc;

        rc = register_reboot_notifier(&wdt_notifier);

        if (rc) {

                misc_deregister(&wdt_miscdev);

                return rc;

        };

        printk(KERN_INFO OUR_NAME ": WDT driver for ALi M7101 initialised.\n");

        return 0;

}

module_init(alim7101_wdt_init);

module_exit(alim7101_wdt_unload);

EXPORT_NO_SYMBOLS;

MODULE_AUTHOR("Steve Hill");

MODULE_LICENSE("GPL");