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/*

 *      AMD Elan SC520 processor Watchdog Timer driver

 *

 *      Based on acquirewdt.c by Alan Cox,

 *           and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>

 *

 *      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 authors do NOT admit liability nor provide warranty for

 *      any of this software. This material is provided "AS-IS" in

 *      the hope that it may be useful for others.

 *

 *      (c) Copyright 2001    Scott Jennings <linuxdrivers@oro.net>

 *           9/27 - 2001      [Initial release]

 *

 *      Additional fixes Alan Cox

 *      -       Fixed formatting

 *      -       Removed debug printks

 *      -       Fixed SMP built kernel deadlock

 *      -       Switched to private locks not lock_kernel

 *      -       Used ioremap/writew/readw

 *      -       Added NOWAYOUT support

 *      4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>

 *      -       Change comments

 *      -       Eliminate fop_llseek

 *      -       Change CONFIG_WATCHDOG_NOWAYOUT semantics

 *      -       Add KERN_* tags to printks

 *      -       fix possible wdt_is_open race

 *      -       Report proper capabilities in watchdog_info

 *      -       Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,

 *              GETTIMEOUT, SETOPTIONS} ioctls

 *      09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>

 *      -       cleanup of trailing spaces

 *      -       added extra printk's for startup problems

 *      -       use module_param

 *      -       made timeout (the emulated heartbeat) a module_param

 *      -       made the keepalive ping an internal subroutine

 *      3/27 - 2004 Changes by Sean Young <sean@mess.org>

 *      -       set MMCR_BASE to 0xfffef000

 *      -       CBAR does not need to be read

 *      -       removed debugging printks

 *

 *  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.

 *

 *  This driver uses memory mapped IO, and spinlock.

 */

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/types.h>

#include <linux/timer.h>

#include <linux/miscdevice.h>

#include <linux/watchdog.h>

#include <linux/fs.h>

#include <linux/ioport.h>

#include <linux/notifier.h>

#include <linux/reboot.h>

#include <linux/init.h>

#include <linux/jiffies.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#include <asm/system.h>

#define OUR_NAME "sc520_wdt"

#define PFX OUR_NAME ": "

/*

 * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)

 *

 *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s

 *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s

 *

 * We will program the SC520 watchdog for a timeout of 2.01s.

 * 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 WATCHDOG_TIMEOUT 30             /* 30 sec default timeout */

static int timeout = WATCHDOG_TIMEOUT;  /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */

module_param(timeout, int, 0);

MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. (1<=timeout<=3600, default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");

static int nowayout = WATCHDOG_NOWAYOUT;

module_param(nowayout, int, 0);

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

/*

 * AMD Elan SC520 - Watchdog Timer Registers

 */

#define MMCR_BASE       0xfffef000      /* The default base address */

#define OFFS_WDTMRCTL   0xCB0   /* Watchdog Timer Control Register */

/* WDT Control Register bit definitions */

#define WDT_EXP_SEL_01  0x0001  /* [01] Time-out = 496 us (with 33 Mhz clk). */

#define WDT_EXP_SEL_02  0x0002  /* [02] Time-out = 508 ms (with 33 Mhz clk). */

#define WDT_EXP_SEL_03  0x0004  /* [03] Time-out = 1.02 s (with 33 Mhz clk). */

#define WDT_EXP_SEL_04  0x0008  /* [04] Time-out = 2.03 s (with 33 Mhz clk). */

#define WDT_EXP_SEL_05  0x0010  /* [05] Time-out = 4.07 s (with 33 Mhz clk). */

#define WDT_EXP_SEL_06  0x0020  /* [06] Time-out = 8.13 s (with 33 Mhz clk). */

#define WDT_EXP_SEL_07  0x0040  /* [07] Time-out = 16.27s (with 33 Mhz clk). */

#define WDT_EXP_SEL_08  0x0080  /* [08] Time-out = 32.54s (with 33 Mhz clk). */

#define WDT_IRQ_FLG     0x1000  /* [12] Interrupt Request Flag */

#define WDT_WRST_ENB    0x4000  /* [14] Watchdog Timer Reset Enable */

#define WDT_ENB         0x8000  /* [15] Watchdog Timer Enable */

static __u16 __iomem *wdtmrctl;

static void wdt_timer_ping(unsigned long);

static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);

static unsigned long next_heartbeat;

static unsigned long wdt_is_open;

static char wdt_expect_close;

static DEFINE_SPINLOCK(wdt_spinlock);

/*

 *      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

         */

        if(time_before(jiffies, next_heartbeat))

        {

                /* Ping the WDT */

                spin_lock(&wdt_spinlock);

                writew(0xAAAA, wdtmrctl);

                writew(0x5555, wdtmrctl);

                spin_unlock(&wdt_spinlock);

                /* Re-set the timer interval */

                mod_timer(&timer, jiffies + WDT_INTERVAL);

        } else {

                printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");

        }

}

/*

 *      Utility routines

 */

static void wdt_config(int writeval)

{

        __u16 dummy;

        unsigned long flags;

        /* buy some time (ping) */

        spin_lock_irqsave(&wdt_spinlock, flags);

        dummy=readw(wdtmrctl);  /* ensure write synchronization */

        writew(0xAAAA, wdtmrctl);

        writew(0x5555, wdtmrctl);

        /* unlock WDT = make WDT configuration register writable one time */

        writew(0x3333, wdtmrctl);

        writew(0xCCCC, wdtmrctl);

        /* write WDT configuration register */

        writew(writeval, wdtmrctl);

        spin_unlock_irqrestore(&wdt_spinlock, flags);

}

static int wdt_startup(void)

{

        next_heartbeat = jiffies + (timeout * HZ);

        /* Start the timer */

        mod_timer(&timer, jiffies + WDT_INTERVAL);

        /* Start the watchdog */

        wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);

        printk(KERN_INFO PFX "Watchdog timer is now enabled.\n");

        return 0;

}

static int wdt_turnoff(void)

{

        /* Stop the timer */

        del_timer(&timer);

        /* Stop the watchdog */

        wdt_config(0);

        printk(KERN_INFO PFX "Watchdog timer is now disabled...\n");

        return 0;

}

static int wdt_keepalive(void)

{

        /* user land ping */

        next_heartbeat = jiffies + (timeout * HZ);

        return 0;

}

static int wdt_set_heartbeat(int t)

{

        if ((t < 1) || (t > 3600))      /* arbitrary upper limit */

                return -EINVAL;

        timeout = t;

        return 0;

}

/*

 *      /dev/watchdog handling

 */

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

{

        /* See if we got the magic character 'V' and reload the timer */

        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 = 42;

                        }

                }

                /* Well, anyhow someone wrote to us, we should return that favour */

                wdt_keepalive();

        }

        return count;

}

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;

        if (nowayout)

                __module_get(THIS_MODULE);

        /* Good, fire up the show */

        wdt_startup();

        return nonseekable_open(inode, file);

}

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

{

        if(wdt_expect_close == 42) {

                wdt_turnoff();

        } else {

                printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");

                wdt_keepalive();

        }

        clear_bit(0, &wdt_is_open);

        wdt_expect_close = 0;

        return 0;

}

static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd,

        unsigned long arg)

{

        void __user *argp = (void __user *)arg;

        int __user *p = argp;

        static struct watchdog_info ident = {

                .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,

                .firmware_version = 1,

                .identity = "SC520",

        };

        switch(cmd)

        {

                default:

                        return -ENOTTY;

                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_KEEPALIVE:

                        wdt_keepalive();

                        return 0;

                case WDIOC_SETOPTIONS:

                {

                        int new_options, retval = -EINVAL;

                        if(get_user(new_options, p))

                                return -EFAULT;

                        if(new_options & WDIOS_DISABLECARD) {

                                wdt_turnoff();

                                retval = 0;

                        }

                        if(new_options & WDIOS_ENABLECARD) {

                                wdt_startup();

                                retval = 0;

                        }

                        return retval;

                }

                case WDIOC_SETTIMEOUT:

                {

                        int new_timeout;

                        if(get_user(new_timeout, p))

                                return -EFAULT;

                        if(wdt_set_heartbeat(new_timeout))

                                return -EINVAL;

                        wdt_keepalive();

                        /* Fall through */

                }

                case WDIOC_GETTIMEOUT:

                        return put_user(timeout, p);

        }

}

static const struct file_operations wdt_fops = {

        .owner          = THIS_MODULE,

        .llseek         = no_llseek,

        .write          = fop_write,

        .open           = fop_open,

        .release        = fop_close,

        .ioctl          = fop_ioctl,

};

static struct miscdevice wdt_miscdev = {

        .minor  = WATCHDOG_MINOR,

        .name   = "watchdog",

        .fops   = &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();

        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 = {

        .notifier_call = wdt_notify_sys,

};

static void __exit sc520_wdt_unload(void)

{

        if (!nowayout)

                wdt_turnoff();

        /* Deregister */

        misc_deregister(&wdt_miscdev);

        unregister_reboot_notifier(&wdt_notifier);

        iounmap(wdtmrctl);

}

static int __init sc520_wdt_init(void)

{

        int rc = -EBUSY;

        /* Check that the timeout value is within it's range ; if not reset to the default */

        if (wdt_set_heartbeat(timeout)) {

                wdt_set_heartbeat(WATCHDOG_TIMEOUT);

                printk(KERN_INFO PFX "timeout value must be 1<=timeout<=3600, using %d\n",

                        WATCHDOG_TIMEOUT);

        }

        wdtmrctl = ioremap((unsigned long)(MMCR_BASE + OFFS_WDTMRCTL), 2);

        if (!wdtmrctl) {

                printk(KERN_ERR PFX "Unable to remap memory\n");

                rc = -ENOMEM;

                goto err_out_region2;

        }

        rc = register_reboot_notifier(&wdt_notifier);

        if (rc) {

                printk(KERN_ERR PFX "cannot register reboot notifier (err=%d)\n",

                        rc);

                goto err_out_ioremap;

        }

        rc = misc_register(&wdt_miscdev);

        if (rc) {

                printk(KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",

                        WATCHDOG_MINOR, rc);

                goto err_out_notifier;

        }

        printk(KERN_INFO PFX "WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",

                timeout,nowayout);

        return 0;

err_out_notifier:

        unregister_reboot_notifier(&wdt_notifier);

err_out_ioremap:

        iounmap(wdtmrctl);

err_out_region2:

        return rc;

}

module_init(sc520_wdt_init);

module_exit(sc520_wdt_unload);

MODULE_AUTHOR("Scott and Bill Jennings");

MODULE_DESCRIPTION("Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");

MODULE_LICENSE("GPL");

MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);