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/*

 * drivers/char/watchdog/shwdt.c

 *

 * Watchdog driver for integrated watchdog in the SuperH processors.

 *

 * Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>

 *

 * 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.

 *

 * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>

 *     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT

 *

 * 19-Apr-2002 Rob Radez <rob@osinvestor.com>

 *     Added expect close support, made emulated timeout runtime changeable

 *     general cleanups, add some ioctls

 */

#include <linux/module.h>

#include <linux/moduleparam.h>

#include <linux/init.h>

#include <linux/types.h>

#include <linux/miscdevice.h>

#include <linux/watchdog.h>

#include <linux/reboot.h>

#include <linux/notifier.h>

#include <linux/ioport.h>

#include <linux/fs.h>

#include <linux/mm.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#include <asm/watchdog.h>

#define PFX "shwdt: "

/*

 * Default clock division ratio is 5.25 msecs. For an additional table of

 * values, consult the asm-sh/watchdog.h. Overload this at module load

 * time.

 *

 * In order for this to work reliably we need to have HZ set to 1000 or

 * something quite higher than 100 (or we need a proper high-res timer

 * implementation that will deal with this properly), otherwise the 10ms

 * resolution of a jiffy is enough to trigger the overflow. For things like

 * the SH-4 and SH-5, this isn't necessarily that big of a problem, though

 * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely

 * necssary.

 *

 * As a result of this timing problem, the only modes that are particularly

 * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms

 * overflow periods respectively.

 *

 * Also, since we can't really expect userspace to be responsive enough

 * before the overflow happens, we maintain two seperate timers .. One in

 * the kernel for clearing out WOVF every 2ms or so (again, this depends on

 * HZ == 1000), and another for monitoring userspace writes to the WDT device.

 *

 * As such, we currently use a configurable heartbeat interval which defaults

 * to 30s. In this case, the userspace daemon is only responsible for periodic

 * writes to the device before the next heartbeat is scheduled. If the daemon

 * misses its deadline, the kernel timer will allow the WDT to overflow.

 */

static int clock_division_ratio = WTCSR_CKS_4096;

#define next_ping_period(cks)   msecs_to_jiffies(cks - 4)

static void sh_wdt_ping(unsigned long data);

static unsigned long shwdt_is_open;

static struct watchdog_info sh_wdt_info;

static char shwdt_expect_close;

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

static unsigned long next_heartbeat;

#define WATCHDOG_HEARTBEAT 30                   /* 30 sec default heartbeat */

static int heartbeat = WATCHDOG_HEARTBEAT;      /* in seconds */

static int nowayout = WATCHDOG_NOWAYOUT;

/**

 *      sh_wdt_start - Start the Watchdog

 *

 *      Starts the watchdog.

 */

static void sh_wdt_start(void)

{

        __u8 csr;

        next_heartbeat = jiffies + (heartbeat * HZ);

        mod_timer(&timer, next_ping_period(clock_division_ratio));

        csr = sh_wdt_read_csr();

        csr |= WTCSR_WT | clock_division_ratio;

        sh_wdt_write_csr(csr);

        sh_wdt_write_cnt(0);

        /*

         * These processors have a bit of an inconsistent initialization

         * process.. starting with SH-3, RSTS was moved to WTCSR, and the

         * RSTCSR register was removed.

         *

         * On the SH-2 however, in addition with bits being in different

         * locations, we must deal with RSTCSR outright..

         */

        csr = sh_wdt_read_csr();

        csr |= WTCSR_TME;

        csr &= ~WTCSR_RSTS;

        sh_wdt_write_csr(csr);

#ifdef CONFIG_CPU_SH2

        /*

         * Whoever came up with the RSTCSR semantics must've been smoking

         * some of the good stuff, since in addition to the WTCSR/WTCNT write

         * brain-damage, it's managed to fuck things up one step further..

         *

         * If we need to clear the WOVF bit, the upper byte has to be 0xa5..

         * but if we want to touch RSTE or RSTS, the upper byte has to be

         * 0x5a..

         */

        csr = sh_wdt_read_rstcsr();

        csr &= ~RSTCSR_RSTS;

        sh_wdt_write_rstcsr(csr);

#endif

}

/**

 *      sh_wdt_stop - Stop the Watchdog

 *      Stops the watchdog.

 */

static void sh_wdt_stop(void)

{

        __u8 csr;

        del_timer(&timer);

        csr = sh_wdt_read_csr();

        csr &= ~WTCSR_TME;

        sh_wdt_write_csr(csr);

}

/**

 *      sh_wdt_keepalive - Keep the Userspace Watchdog Alive

 *      The Userspace watchdog got a KeepAlive: schedule the next heartbeat.

 */

static inline void sh_wdt_keepalive(void)

{

        next_heartbeat = jiffies + (heartbeat * HZ);

}

/**

 *      sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat

 *      Set the Userspace Watchdog heartbeat

 */

static int sh_wdt_set_heartbeat(int t)

{

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

                return -EINVAL;

        heartbeat = t;

        return 0;

}

/**

 *      sh_wdt_ping - Ping the Watchdog

 *      @data: Unused

 *

 *      Clears overflow bit, resets timer counter.

 */

static void sh_wdt_ping(unsigned long data)

{

        if (time_before(jiffies, next_heartbeat)) {

                __u8 csr;

                csr = sh_wdt_read_csr();

                csr &= ~WTCSR_IOVF;

                sh_wdt_write_csr(csr);

                sh_wdt_write_cnt(0);

                mod_timer(&timer, next_ping_period(clock_division_ratio));

        } else

                printk(KERN_WARNING PFX "Heartbeat lost! Will not ping "

                       "the watchdog\n");

}

/**

 *      sh_wdt_open - Open the Device

 *      @inode: inode of device

 *      @file: file handle of device

 *

 *      Watchdog device is opened and started.

 */

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

{

        if (test_and_set_bit(0, &shwdt_is_open))

                return -EBUSY;

        if (nowayout)

                __module_get(THIS_MODULE);

        sh_wdt_start();

        return nonseekable_open(inode, file);

}

/**

 *      sh_wdt_close - Close the Device

 *      @inode: inode of device

 *      @file: file handle of device

 *

 *      Watchdog device is closed and stopped.

 */

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

{

        if (shwdt_expect_close == 42) {

                sh_wdt_stop();

        } else {

                printk(KERN_CRIT PFX "Unexpected close, not "

                       "stopping watchdog!\n");

                sh_wdt_keepalive();

        }

        clear_bit(0, &shwdt_is_open);

        shwdt_expect_close = 0;

        return 0;

}

/**

 *      sh_wdt_write - Write to Device

 *      @file: file handle of device

 *      @buf: buffer to write

 *      @count: length of buffer

 *      @ppos: offset

 *

 *      Pings the watchdog on write.

 */

static ssize_t sh_wdt_write(struct file *file, const char *buf,

                            size_t count, loff_t *ppos)

{

        if (count) {

                if (!nowayout) {

                        size_t i;

                        shwdt_expect_close = 0;

                        for (i = 0; i != count; i++) {

                                char c;

                                if (get_user(c, buf + i))

                                        return -EFAULT;

                                if (c == 'V')

                                        shwdt_expect_close = 42;

                        }

                }

                sh_wdt_keepalive();

        }

        return count;

}

/**

 *      sh_wdt_mmap - map WDT/CPG registers into userspace

 *      @file: file structure for the device

 *      @vma: VMA to map the registers into

 *

 *      A simple mmap() implementation for the corner cases where the counter

 *      needs to be mapped in userspace directly. Due to the relatively small

 *      size of the area, neighbouring registers not necessarily tied to the

 *      CPG will also be accessible through the register page, so this remains

 *      configurable for users that really know what they're doing.

 *

 *      Additionaly, the register page maps in the CPG register base relative

 *      to the nearest page-aligned boundary, which requires that userspace do

 *      the appropriate CPU subtype math for calculating the page offset for

 *      the counter value.

 */

static int sh_wdt_mmap(struct file *file, struct vm_area_struct *vma)

{

        int ret = -ENOSYS;

#ifdef CONFIG_SH_WDT_MMAP

        unsigned long addr;

        /* Only support the simple cases where we map in a register page. */

        if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)

                return -EINVAL;

        /*

         * Pick WTCNT as the start, it's usually the first register after the

         * FRQCR, and neither one are generally page-aligned out of the box.

         */

        addr = WTCNT & ~(PAGE_SIZE - 1);

        vma->vm_flags |= VM_IO;

        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);

        if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,

                               PAGE_SIZE, vma->vm_page_prot)) {

                printk(KERN_ERR PFX "%s: io_remap_pfn_range failed\n",

                       __FUNCTION__);

                return -EAGAIN;

        }

        ret = 0;

#endif

        return ret;

}

/**

 *      sh_wdt_ioctl - Query Device

 *      @inode: inode of device

 *      @file: file handle of device

 *      @cmd: watchdog command

 *      @arg: argument

 *

 *      Query basic information from the device or ping it, as outlined by the

 *      watchdog API.

 */

static int sh_wdt_ioctl(struct inode *inode, struct file *file,

                        unsigned int cmd, unsigned long arg)

{

        int new_heartbeat;

        int options, retval = -EINVAL;

        switch (cmd) {

                case WDIOC_GETSUPPORT:

                        return copy_to_user((struct watchdog_info *)arg,

                                          &sh_wdt_info,

                                          sizeof(sh_wdt_info)) ? -EFAULT : 0;

                case WDIOC_GETSTATUS:

                case WDIOC_GETBOOTSTATUS:

                        return put_user(0, (int *)arg);

                case WDIOC_KEEPALIVE:

                        sh_wdt_keepalive();

                        return 0;

                case WDIOC_SETTIMEOUT:

                        if (get_user(new_heartbeat, (int *)arg))

                                return -EFAULT;

                        if (sh_wdt_set_heartbeat(new_heartbeat))

                                return -EINVAL;

                        sh_wdt_keepalive();

                        /* Fall */

                case WDIOC_GETTIMEOUT:

                        return put_user(heartbeat, (int *)arg);

                case WDIOC_SETOPTIONS:

                        if (get_user(options, (int *)arg))

                                return -EFAULT;

                        if (options & WDIOS_DISABLECARD) {

                                sh_wdt_stop();

                                retval = 0;

                        }

                        if (options & WDIOS_ENABLECARD) {

                                sh_wdt_start();

                                retval = 0;

                        }

                        return retval;

                default:

                        return -ENOTTY;

        }

        return 0;

}

/**

 *      sh_wdt_notify_sys - Notifier Handler

 *      @this: notifier block

 *      @code: notifier event

 *      @unused: unused

 *

 *      Handles specific events, such as turning off the watchdog during a

 *      shutdown event.

 */

static int sh_wdt_notify_sys(struct notifier_block *this,

                             unsigned long code, void *unused)

{

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

                sh_wdt_stop();

        return NOTIFY_DONE;

}

static const struct file_operations sh_wdt_fops = {

        .owner          = THIS_MODULE,

        .llseek         = no_llseek,

        .write          = sh_wdt_write,

        .ioctl          = sh_wdt_ioctl,

        .open           = sh_wdt_open,

        .release        = sh_wdt_close,

        .mmap           = sh_wdt_mmap,

};

static struct watchdog_info sh_wdt_info = {

        .options                = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |

                                  WDIOF_MAGICCLOSE,

        .firmware_version       = 1,

        .identity               = "SH WDT",

};

static struct notifier_block sh_wdt_notifier = {

        .notifier_call          = sh_wdt_notify_sys,

};

static struct miscdevice sh_wdt_miscdev = {

        .minor          = WATCHDOG_MINOR,

        .name           = "watchdog",

        .fops           = &sh_wdt_fops,

};

/**

 *      sh_wdt_init - Initialize module

 *      Registers the device and notifier handler. Actual device

 *      initialization is handled by sh_wdt_open().

 */

static int __init sh_wdt_init(void)

{

        int rc;

        if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {

                clock_division_ratio = WTCSR_CKS_4096;

                printk(KERN_INFO PFX "clock_division_ratio value must "

                       "be 0x5<=x<=0x7, using %d\n", clock_division_ratio);

        }

        rc = sh_wdt_set_heartbeat(heartbeat);

        if (unlikely(rc)) {

                heartbeat = WATCHDOG_HEARTBEAT;

                printk(KERN_INFO PFX "heartbeat value must "

                       "be 1<=x<=3600, using %d\n", heartbeat);

        }

        rc = register_reboot_notifier(&sh_wdt_notifier);

        if (unlikely(rc)) {

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

                       rc);

                return rc;

        }

        rc = misc_register(&sh_wdt_miscdev);

        if (unlikely(rc)) {

                printk(KERN_ERR PFX "Can't register miscdev on "

                       "minor=%d (err=%d)\n", sh_wdt_miscdev.minor, rc);

                unregister_reboot_notifier(&sh_wdt_notifier);

                return rc;

        }

        printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",

                heartbeat, nowayout);

        return 0;

}

/**

 *      sh_wdt_exit - Deinitialize module

 *      Unregisters the device and notifier handler. Actual device

 *      deinitialization is handled by sh_wdt_close().

 */

static void __exit sh_wdt_exit(void)

{

        misc_deregister(&sh_wdt_miscdev);

        unregister_reboot_notifier(&sh_wdt_notifier);

}

MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");

MODULE_DESCRIPTION("SuperH watchdog driver");

MODULE_LICENSE("GPL");

MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);

module_param(clock_division_ratio, int, 0);

MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). (default=" __MODULE_STRING(clock_division_ratio) ")");

module_param(heartbeat, int, 0);

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

module_param(nowayout, int, 0);

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

module_init(sh_wdt_init);

module_exit(sh_wdt_exit);