ocfs2: Fix possible deadlock in quota recovery

[linux-2.6/linux-2.6-openrd.git] / drivers / char / rtc.c

/*
 *      Real Time Clock interface for Linux
 *
 *      Copyright (C) 1996 Paul Gortmaker
 *
 *      This driver allows use of the real time clock (built into
 *      nearly all computers) from user space. It exports the /dev/rtc
 *      interface supporting various ioctl() and also the
 *      /proc/driver/rtc pseudo-file for status information.
 *
 *      The ioctls can be used to set the interrupt behaviour and
 *      generation rate from the RTC via IRQ 8. Then the /dev/rtc
 *      interface can be used to make use of these timer interrupts,
 *      be they interval or alarm based.
 *
 *      The /dev/rtc interface will block on reads until an interrupt
 *      has been received. If a RTC interrupt has already happened,
 *      it will output an unsigned long and then block. The output value
 *      contains the interrupt status in the low byte and the number of
 *      interrupts since the last read in the remaining high bytes. The
 *      /dev/rtc interface can also be used with the select(2) call.
 *
 *      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.
 *
 *      Based on other minimal char device drivers, like Alan's
 *      watchdog, Ted's random, etc. etc.
 *
 *      1.07    Paul Gortmaker.
 *      1.08    Miquel van Smoorenburg: disallow certain things on the
 *              DEC Alpha as the CMOS clock is also used for other things.
 *      1.09    Nikita Schmidt: epoch support and some Alpha cleanup.
 *      1.09a   Pete Zaitcev: Sun SPARC
 *      1.09b   Jeff Garzik: Modularize, init cleanup
 *      1.09c   Jeff Garzik: SMP cleanup
 *      1.10    Paul Barton-Davis: add support for async I/O
 *      1.10a   Andrea Arcangeli: Alpha updates
 *      1.10b   Andrew Morton: SMP lock fix
 *      1.10c   Cesar Barros: SMP locking fixes and cleanup
 *      1.10d   Paul Gortmaker: delete paranoia check in rtc_exit
 *      1.10e   Maciej W. Rozycki: Handle DECstation's year weirdness.
 *      1.11    Takashi Iwai: Kernel access functions
 *                            rtc_register/rtc_unregister/rtc_control
 *      1.11a   Daniele Bellucci: Audit create_proc_read_entry in rtc_init
 *      1.12    Venkatesh Pallipadi: Hooks for emulating rtc on HPET base-timer
 *              CONFIG_HPET_EMULATE_RTC
 *      1.12a   Maciej W. Rozycki: Handle memory-mapped chips properly.
 *      1.12ac  Alan Cox: Allow read access to the day of week register
 *      1.12b   David John: Remove calls to the BKL.
 */

#define RTC_VERSION             "1.12b"

/*
 *      Note that *all* calls to CMOS_READ and CMOS_WRITE are done with
 *      interrupts disabled. Due to the index-port/data-port (0x70/0x71)
 *      design of the RTC, we don't want two different things trying to
 *      get to it at once. (e.g. the periodic 11 min sync from time.c vs.
 *      this driver.)
 */

#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/ioport.h>
#include <linux/fcntl.h>
#include <linux/mc146818rtc.h>
#include <linux/init.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/spinlock.h>
#include <linux/sysctl.h>
#include <linux/wait.h>
#include <linux/bcd.h>
#include <linux/delay.h>
#include <linux/uaccess.h>

#include <asm/current.h>
#include <asm/system.h>

#ifdef CONFIG_X86
#include <asm/hpet.h>
#endif

#ifdef CONFIG_SPARC32
#include <linux/of.h>
#include <linux/of_device.h>
#include <asm/io.h>

static unsigned long rtc_port;
static int rtc_irq;
#endif

#ifdef  CONFIG_HPET_EMULATE_RTC
#undef  RTC_IRQ
#endif

#ifdef RTC_IRQ
static int rtc_has_irq = 1;
#endif

#ifndef CONFIG_HPET_EMULATE_RTC
#define is_hpet_enabled()                       0
#define hpet_set_alarm_time(hrs, min, sec)      0
#define hpet_set_periodic_freq(arg)             0
#define hpet_mask_rtc_irq_bit(arg)              0
#define hpet_set_rtc_irq_bit(arg)               0
#define hpet_rtc_timer_init()                   do { } while (0)
#define hpet_rtc_dropped_irq()                  0
#define hpet_register_irq_handler(h)            ({ 0; })
#define hpet_unregister_irq_handler(h)          ({ 0; })
#ifdef RTC_IRQ
static irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id)
{
        return 0;
}
#endif
#endif

/*
 *      We sponge a minor off of the misc major. No need slurping
 *      up another valuable major dev number for this. If you add
 *      an ioctl, make sure you don't conflict with SPARC's RTC
 *      ioctls.
 */

static struct fasync_struct *rtc_async_queue;

static DECLARE_WAIT_QUEUE_HEAD(rtc_wait);

#ifdef RTC_IRQ
static void rtc_dropped_irq(unsigned long data);

static DEFINE_TIMER(rtc_irq_timer, rtc_dropped_irq, 0, 0);
#endif

static ssize_t rtc_read(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos);

static long rtc_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
static void rtc_get_rtc_time(struct rtc_time *rtc_tm);

#ifdef RTC_IRQ
static unsigned int rtc_poll(struct file *file, poll_table *wait);
#endif

static void get_rtc_alm_time(struct rtc_time *alm_tm);
#ifdef RTC_IRQ
static void set_rtc_irq_bit_locked(unsigned char bit);
static void mask_rtc_irq_bit_locked(unsigned char bit);

static inline void set_rtc_irq_bit(unsigned char bit)
{
        spin_lock_irq(&rtc_lock);
        set_rtc_irq_bit_locked(bit);
        spin_unlock_irq(&rtc_lock);
}

static void mask_rtc_irq_bit(unsigned char bit)
{
        spin_lock_irq(&rtc_lock);
        mask_rtc_irq_bit_locked(bit);
        spin_unlock_irq(&rtc_lock);
}
#endif

#ifdef CONFIG_PROC_FS
static int rtc_proc_open(struct inode *inode, struct file *file);
#endif

/*
 *      Bits in rtc_status. (6 bits of room for future expansion)
 */

#define RTC_IS_OPEN             0x01    /* means /dev/rtc is in use     */
#define RTC_TIMER_ON            0x02    /* missed irq timer active      */

/*
 * rtc_status is never changed by rtc_interrupt, and ioctl/open/close is
 * protected by the spin lock rtc_lock. However, ioctl can still disable the
 * timer in rtc_status and then with del_timer after the interrupt has read
 * rtc_status but before mod_timer is called, which would then reenable the
 * timer (but you would need to have an awful timing before you'd trip on it)
 */
static unsigned long rtc_status;        /* bitmapped status byte.       */
static unsigned long rtc_freq;          /* Current periodic IRQ rate    */
static unsigned long rtc_irq_data;      /* our output to the world      */
static unsigned long rtc_max_user_freq = 64; /* > this, need CAP_SYS_RESOURCE */

#ifdef RTC_IRQ
/*
 * rtc_task_lock nests inside rtc_lock.
 */
static DEFINE_SPINLOCK(rtc_task_lock);
static rtc_task_t *rtc_callback;
#endif

/*
 *      If this driver ever becomes modularised, it will be really nice
 *      to make the epoch retain its value across module reload...
 */

static unsigned long epoch = 1900;      /* year corresponding to 0x00   */

static const unsigned char days_in_mo[] =
{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

/*
 * Returns true if a clock update is in progress
 */
static inline unsigned char rtc_is_updating(void)
{
        unsigned long flags;
        unsigned char uip;

        spin_lock_irqsave(&rtc_lock, flags);
        uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
        spin_unlock_irqrestore(&rtc_lock, flags);
        return uip;
}

#ifdef RTC_IRQ
/*
 *      A very tiny interrupt handler. It runs with IRQF_DISABLED set,
 *      but there is possibility of conflicting with the set_rtc_mmss()
 *      call (the rtc irq and the timer irq can easily run at the same
 *      time in two different CPUs). So we need to serialize
 *      accesses to the chip with the rtc_lock spinlock that each
 *      architecture should implement in the timer code.
 *      (See ./arch/XXXX/kernel/time.c for the set_rtc_mmss() function.)
 */

static irqreturn_t rtc_interrupt(int irq, void *dev_id)
{
        /*
         *      Can be an alarm interrupt, update complete interrupt,
         *      or a periodic interrupt. We store the status in the
         *      low byte and the number of interrupts received since
         *      the last read in the remainder of rtc_irq_data.
         */

        spin_lock(&rtc_lock);
        rtc_irq_data += 0x100;
        rtc_irq_data &= ~0xff;
        if (is_hpet_enabled()) {
                /*
                 * In this case it is HPET RTC interrupt handler
                 * calling us, with the interrupt information
                 * passed as arg1, instead of irq.
                 */
                rtc_irq_data |= (unsigned long)irq & 0xF0;
        } else {
                rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);
        }

        if (rtc_status & RTC_TIMER_ON)
                mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);

        spin_unlock(&rtc_lock);

        /* Now do the rest of the actions */
        spin_lock(&rtc_task_lock);
        if (rtc_callback)
                rtc_callback->func(rtc_callback->private_data);
        spin_unlock(&rtc_task_lock);
        wake_up_interruptible(&rtc_wait);

        kill_fasync(&rtc_async_queue, SIGIO, POLL_IN);

        return IRQ_HANDLED;
}
#endif

/*
 * sysctl-tuning infrastructure.
 */
static ctl_table rtc_table[] = {
        {
                .ctl_name       = CTL_UNNUMBERED,
                .procname       = "max-user-freq",
                .data           = &rtc_max_user_freq,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,
        },
        { .ctl_name = 0 }
};

static ctl_table rtc_root[] = {
        {
                .ctl_name       = CTL_UNNUMBERED,
                .procname       = "rtc",
                .mode           = 0555,
                .child          = rtc_table,
        },
        { .ctl_name = 0 }
};

static ctl_table dev_root[] = {
        {
                .ctl_name       = CTL_DEV,
                .procname       = "dev",
                .mode           = 0555,
                .child          = rtc_root,
        },
        { .ctl_name = 0 }
};

static struct ctl_table_header *sysctl_header;

static int __init init_sysctl(void)
{
    sysctl_header = register_sysctl_table(dev_root);
    return 0;
}

static void __exit cleanup_sysctl(void)
{
    unregister_sysctl_table(sysctl_header);
}

/*
 *      Now all the various file operations that we export.
 */

static ssize_t rtc_read(struct file *file, char __user *buf,
                        size_t count, loff_t *ppos)
{
#ifndef RTC_IRQ
        return -EIO;
#else
        DECLARE_WAITQUEUE(wait, current);
        unsigned long data;
        ssize_t retval;

        if (rtc_has_irq == 0)
                return -EIO;

        /*
         * Historically this function used to assume that sizeof(unsigned long)
         * is the same in userspace and kernelspace.  This lead to problems
         * for configurations with multiple ABIs such a the MIPS o32 and 64
         * ABIs supported on the same kernel.  So now we support read of both
         * 4 and 8 bytes and assume that's the sizeof(unsigned long) in the
         * userspace ABI.
         */
        if (count != sizeof(unsigned int) && count !=  sizeof(unsigned long))
                return -EINVAL;

        add_wait_queue(&rtc_wait, &wait);

        do {
                /* First make it right. Then make it fast. Putting this whole
                 * block within the parentheses of a while would be too
                 * confusing. And no, xchg() is not the answer. */

                __set_current_state(TASK_INTERRUPTIBLE);

                spin_lock_irq(&rtc_lock);
                data = rtc_irq_data;
                rtc_irq_data = 0;
                spin_unlock_irq(&rtc_lock);

                if (data != 0)
                        break;

                if (file->f_flags & O_NONBLOCK) {
                        retval = -EAGAIN;
                        goto out;
                }
                if (signal_pending(current)) {
                        retval = -ERESTARTSYS;
                        goto out;
                }
                schedule();
        } while (1);

        if (count == sizeof(unsigned int)) {
                retval = put_user(data,
                                  (unsigned int __user *)buf) ?: sizeof(int);
        } else {
                retval = put_user(data,
                                  (unsigned long __user *)buf) ?: sizeof(long);
        }
        if (!retval)
                retval = count;
 out:
        __set_current_state(TASK_RUNNING);
        remove_wait_queue(&rtc_wait, &wait);

        return retval;
#endif
}

static int rtc_do_ioctl(unsigned int cmd, unsigned long arg, int kernel)
{
        struct rtc_time wtime;

#ifdef RTC_IRQ
        if (rtc_has_irq == 0) {
                switch (cmd) {
                case RTC_AIE_OFF:
                case RTC_AIE_ON:
                case RTC_PIE_OFF:
                case RTC_PIE_ON:
                case RTC_UIE_OFF:
                case RTC_UIE_ON:
                case RTC_IRQP_READ:
                case RTC_IRQP_SET:
                        return -EINVAL;
                };
        }
#endif

        switch (cmd) {
#ifdef RTC_IRQ
        case RTC_AIE_OFF:       /* Mask alarm int. enab. bit    */
        {
                mask_rtc_irq_bit(RTC_AIE);
                return 0;
        }
        case RTC_AIE_ON:        /* Allow alarm interrupts.      */
        {
                set_rtc_irq_bit(RTC_AIE);
                return 0;
        }
        case RTC_PIE_OFF:       /* Mask periodic int. enab. bit */
        {
                /* can be called from isr via rtc_control() */
                unsigned long flags;

                spin_lock_irqsave(&rtc_lock, flags);
                mask_rtc_irq_bit_locked(RTC_PIE);
                if (rtc_status & RTC_TIMER_ON) {
                        rtc_status &= ~RTC_TIMER_ON;
                        del_timer(&rtc_irq_timer);
                }
                spin_unlock_irqrestore(&rtc_lock, flags);

                return 0;
        }
        case RTC_PIE_ON:        /* Allow periodic ints          */
        {
                /* can be called from isr via rtc_control() */
                unsigned long flags;

                /*
                 * We don't really want Joe User enabling more
                 * than 64Hz of interrupts on a multi-user machine.
                 */
                if (!kernel && (rtc_freq > rtc_max_user_freq) &&
                                                (!capable(CAP_SYS_RESOURCE)))
                        return -EACCES;

                spin_lock_irqsave(&rtc_lock, flags);
                if (!(rtc_status & RTC_TIMER_ON)) {
                        mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq +
                                        2*HZ/100);
                        rtc_status |= RTC_TIMER_ON;
                }
                set_rtc_irq_bit_locked(RTC_PIE);
                spin_unlock_irqrestore(&rtc_lock, flags);

                return 0;
        }
        case RTC_UIE_OFF:       /* Mask ints from RTC updates.  */
        {
                mask_rtc_irq_bit(RTC_UIE);
                return 0;
        }
        case RTC_UIE_ON:        /* Allow ints for RTC updates.  */
        {
                set_rtc_irq_bit(RTC_UIE);
                return 0;
        }
#endif
        case RTC_ALM_READ:      /* Read the present alarm time */
        {
                /*
                 * This returns a struct rtc_time. Reading >= 0xc0
                 * means "don't care" or "match all". Only the tm_hour,
                 * tm_min, and tm_sec values are filled in.
                 */
                memset(&wtime, 0, sizeof(struct rtc_time));
                get_rtc_alm_time(&wtime);
                break;
        }
        case RTC_ALM_SET:       /* Store a time into the alarm */
        {
                /*
                 * This expects a struct rtc_time. Writing 0xff means
                 * "don't care" or "match all". Only the tm_hour,
                 * tm_min and tm_sec are used.
                 */
                unsigned char hrs, min, sec;
                struct rtc_time alm_tm;

                if (copy_from_user(&alm_tm, (struct rtc_time __user *)arg,
                                   sizeof(struct rtc_time)))
                        return -EFAULT;

                hrs = alm_tm.tm_hour;
                min = alm_tm.tm_min;
                sec = alm_tm.tm_sec;

                spin_lock_irq(&rtc_lock);
                if (hpet_set_alarm_time(hrs, min, sec)) {
                        /*
                         * Fallthru and set alarm time in CMOS too,
                         * so that we will get proper value in RTC_ALM_READ
                         */
                }
                if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) ||
                                                        RTC_ALWAYS_BCD) {
                        if (sec < 60)
                                sec = bin2bcd(sec);
                        else
                                sec = 0xff;

                        if (min < 60)
                                min = bin2bcd(min);
                        else
                                min = 0xff;

                        if (hrs < 24)
                                hrs = bin2bcd(hrs);
                        else
                                hrs = 0xff;
                }
                CMOS_WRITE(hrs, RTC_HOURS_ALARM);
                CMOS_WRITE(min, RTC_MINUTES_ALARM);
                CMOS_WRITE(sec, RTC_SECONDS_ALARM);
                spin_unlock_irq(&rtc_lock);

                return 0;
        }
        case RTC_RD_TIME:       /* Read the time/date from RTC  */
        {
                memset(&wtime, 0, sizeof(struct rtc_time));
                rtc_get_rtc_time(&wtime);
                break;
        }
        case RTC_SET_TIME:      /* Set the RTC */
        {
                struct rtc_time rtc_tm;
                unsigned char mon, day, hrs, min, sec, leap_yr;
                unsigned char save_control, save_freq_select;
                unsigned int yrs;
#ifdef CONFIG_MACH_DECSTATION
                unsigned int real_yrs;
#endif

                if (!capable(CAP_SYS_TIME))
                        return -EACCES;

                if (copy_from_user(&rtc_tm, (struct rtc_time __user *)arg,
                                   sizeof(struct rtc_time)))
                        return -EFAULT;

                yrs = rtc_tm.tm_year + 1900;
                mon = rtc_tm.tm_mon + 1;   /* tm_mon starts at zero */
                day = rtc_tm.tm_mday;
                hrs = rtc_tm.tm_hour;
                min = rtc_tm.tm_min;
                sec = rtc_tm.tm_sec;

                if (yrs < 1970)
                        return -EINVAL;

                leap_yr = ((!(yrs % 4) && (yrs % 100)) || !(yrs % 400));

                if ((mon > 12) || (day == 0))
                        return -EINVAL;

                if (day > (days_in_mo[mon] + ((mon == 2) && leap_yr)))
                        return -EINVAL;

                if ((hrs >= 24) || (min >= 60) || (sec >= 60))
                        return -EINVAL;

                yrs -= epoch;
                if (yrs > 255)          /* They are unsigned */
                        return -EINVAL;

                spin_lock_irq(&rtc_lock);
#ifdef CONFIG_MACH_DECSTATION
                real_yrs = yrs;
                yrs = 72;

                /*
                 * We want to keep the year set to 73 until March
                 * for non-leap years, so that Feb, 29th is handled
                 * correctly.
                 */
                if (!leap_yr && mon < 3) {
                        real_yrs--;
                        yrs = 73;
                }
#endif
                /* These limits and adjustments are independent of
                 * whether the chip is in binary mode or not.
                 */
                if (yrs > 169) {
                        spin_unlock_irq(&rtc_lock);
                        return -EINVAL;
                }
                if (yrs >= 100)
                        yrs -= 100;

                if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
                    || RTC_ALWAYS_BCD) {
                        sec = bin2bcd(sec);
                        min = bin2bcd(min);
                        hrs = bin2bcd(hrs);
                        day = bin2bcd(day);
                        mon = bin2bcd(mon);
                        yrs = bin2bcd(yrs);
                }

                save_control = CMOS_READ(RTC_CONTROL);
                CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
                save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
                CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);

#ifdef CONFIG_MACH_DECSTATION
                CMOS_WRITE(real_yrs, RTC_DEC_YEAR);
#endif
                CMOS_WRITE(yrs, RTC_YEAR);
                CMOS_WRITE(mon, RTC_MONTH);
                CMOS_WRITE(day, RTC_DAY_OF_MONTH);
                CMOS_WRITE(hrs, RTC_HOURS);
                CMOS_WRITE(min, RTC_MINUTES);
                CMOS_WRITE(sec, RTC_SECONDS);

                CMOS_WRITE(save_control, RTC_CONTROL);
                CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);

                spin_unlock_irq(&rtc_lock);
                return 0;
        }
#ifdef RTC_IRQ
        case RTC_IRQP_READ:     /* Read the periodic IRQ rate.  */
        {
                return put_user(rtc_freq, (unsigned long __user *)arg);
        }
        case RTC_IRQP_SET:      /* Set periodic IRQ rate.       */
        {
                int tmp = 0;
                unsigned char val;
                /* can be called from isr via rtc_control() */
                unsigned long flags;

                /*
                 * The max we can do is 8192Hz.
                 */
                if ((arg < 2) || (arg > 8192))
                        return -EINVAL;
                /*
                 * We don't really want Joe User generating more
                 * than 64Hz of interrupts on a multi-user machine.
                 */
                if (!kernel && (arg > rtc_max_user_freq) &&
                                        !capable(CAP_SYS_RESOURCE))
                        return -EACCES;

                while (arg > (1<<tmp))
                        tmp++;

                /*
                 * Check that the input was really a power of 2.
                 */
                if (arg != (1<<tmp))
                        return -EINVAL;

                rtc_freq = arg;

                spin_lock_irqsave(&rtc_lock, flags);
                if (hpet_set_periodic_freq(arg)) {
                        spin_unlock_irqrestore(&rtc_lock, flags);
                        return 0;
                }

                val = CMOS_READ(RTC_FREQ_SELECT) & 0xf0;
                val |= (16 - tmp);
                CMOS_WRITE(val, RTC_FREQ_SELECT);
                spin_unlock_irqrestore(&rtc_lock, flags);
                return 0;
        }
#endif
        case RTC_EPOCH_READ:    /* Read the epoch.      */
        {
                return put_user(epoch, (unsigned long __user *)arg);
        }
        case RTC_EPOCH_SET:     /* Set the epoch.       */
        {
                /*
                 * There were no RTC clocks before 1900.
                 */
                if (arg < 1900)
                        return -EINVAL;

                if (!capable(CAP_SYS_TIME))
                        return -EACCES;

                epoch = arg;
                return 0;
        }
        default:
                return -ENOTTY;
        }
        return copy_to_user((void __user *)arg,
                            &wtime, sizeof wtime) ? -EFAULT : 0;
}

static long rtc_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        long ret;
        ret = rtc_do_ioctl(cmd, arg, 0);
        return ret;
}

/*
 *      We enforce only one user at a time here with the open/close.
 *      Also clear the previous interrupt data on an open, and clean
 *      up things on a close.
 */
static int rtc_open(struct inode *inode, struct file *file)
{
        spin_lock_irq(&rtc_lock);

        if (rtc_status & RTC_IS_OPEN)
                goto out_busy;

        rtc_status |= RTC_IS_OPEN;

        rtc_irq_data = 0;
        spin_unlock_irq(&rtc_lock);
        return 0;

out_busy:
        spin_unlock_irq(&rtc_lock);
        return -EBUSY;
}

static int rtc_fasync(int fd, struct file *filp, int on)
{
        return fasync_helper(fd, filp, on, &rtc_async_queue);
}

static int rtc_release(struct inode *inode, struct file *file)
{
#ifdef RTC_IRQ
        unsigned char tmp;

        if (rtc_has_irq == 0)
                goto no_irq;

        /*
         * Turn off all interrupts once the device is no longer
         * in use, and clear the data.
         */

        spin_lock_irq(&rtc_lock);
        if (!hpet_mask_rtc_irq_bit(RTC_PIE | RTC_AIE | RTC_UIE)) {
                tmp = CMOS_READ(RTC_CONTROL);
                tmp &=  ~RTC_PIE;
                tmp &=  ~RTC_AIE;
                tmp &=  ~RTC_UIE;
                CMOS_WRITE(tmp, RTC_CONTROL);
                CMOS_READ(RTC_INTR_FLAGS);
        }
        if (rtc_status & RTC_TIMER_ON) {
                rtc_status &= ~RTC_TIMER_ON;
                del_timer(&rtc_irq_timer);
        }
        spin_unlock_irq(&rtc_lock);

no_irq:
#endif

        spin_lock_irq(&rtc_lock);
        rtc_irq_data = 0;
        rtc_status &= ~RTC_IS_OPEN;
        spin_unlock_irq(&rtc_lock);

        return 0;
}

#ifdef RTC_IRQ
static unsigned int rtc_poll(struct file *file, poll_table *wait)
{
        unsigned long l;

        if (rtc_has_irq == 0)
                return 0;

        poll_wait(file, &rtc_wait, wait);

        spin_lock_irq(&rtc_lock);
        l = rtc_irq_data;
        spin_unlock_irq(&rtc_lock);

        if (l != 0)
                return POLLIN | POLLRDNORM;
        return 0;
}
#endif

int rtc_register(rtc_task_t *task)
{
#ifndef RTC_IRQ
        return -EIO;
#else
        if (task == NULL || task->func == NULL)
                return -EINVAL;
        spin_lock_irq(&rtc_lock);
        if (rtc_status & RTC_IS_OPEN) {
                spin_unlock_irq(&rtc_lock);
                return -EBUSY;
        }
        spin_lock(&rtc_task_lock);
        if (rtc_callback) {
                spin_unlock(&rtc_task_lock);
                spin_unlock_irq(&rtc_lock);
                return -EBUSY;
        }
        rtc_status |= RTC_IS_OPEN;
        rtc_callback = task;
        spin_unlock(&rtc_task_lock);
        spin_unlock_irq(&rtc_lock);
        return 0;
#endif
}
EXPORT_SYMBOL(rtc_register);

int rtc_unregister(rtc_task_t *task)
{
#ifndef RTC_IRQ
        return -EIO;
#else
        unsigned char tmp;

        spin_lock_irq(&rtc_lock);
        spin_lock(&rtc_task_lock);
        if (rtc_callback != task) {
                spin_unlock(&rtc_task_lock);
                spin_unlock_irq(&rtc_lock);
                return -ENXIO;
        }
        rtc_callback = NULL;

        /* disable controls */
        if (!hpet_mask_rtc_irq_bit(RTC_PIE | RTC_AIE | RTC_UIE)) {
                tmp = CMOS_READ(RTC_CONTROL);
                tmp &= ~RTC_PIE;
                tmp &= ~RTC_AIE;
                tmp &= ~RTC_UIE;
                CMOS_WRITE(tmp, RTC_CONTROL);
                CMOS_READ(RTC_INTR_FLAGS);
        }
        if (rtc_status & RTC_TIMER_ON) {
                rtc_status &= ~RTC_TIMER_ON;
                del_timer(&rtc_irq_timer);
        }
        rtc_status &= ~RTC_IS_OPEN;
        spin_unlock(&rtc_task_lock);
        spin_unlock_irq(&rtc_lock);
        return 0;
#endif
}
EXPORT_SYMBOL(rtc_unregister);

int rtc_control(rtc_task_t *task, unsigned int cmd, unsigned long arg)
{
#ifndef RTC_IRQ
        return -EIO;
#else
        unsigned long flags;
        if (cmd != RTC_PIE_ON && cmd != RTC_PIE_OFF && cmd != RTC_IRQP_SET)
                return -EINVAL;
        spin_lock_irqsave(&rtc_task_lock, flags);
        if (rtc_callback != task) {
                spin_unlock_irqrestore(&rtc_task_lock, flags);
                return -ENXIO;
        }
        spin_unlock_irqrestore(&rtc_task_lock, flags);
        return rtc_do_ioctl(cmd, arg, 1);
#endif
}
EXPORT_SYMBOL(rtc_control);

/*
 *      The various file operations we support.
 */

static const struct file_operations rtc_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .read           = rtc_read,
#ifdef RTC_IRQ
        .poll           = rtc_poll,
#endif
        .unlocked_ioctl = rtc_ioctl,
        .open           = rtc_open,
        .release        = rtc_release,
        .fasync         = rtc_fasync,
};

static struct miscdevice rtc_dev = {
        .minor          = RTC_MINOR,
        .name           = "rtc",
        .fops           = &rtc_fops,
};

#ifdef CONFIG_PROC_FS
static const struct file_operations rtc_proc_fops = {
        .owner          = THIS_MODULE,
        .open           = rtc_proc_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = single_release,
};
#endif

static resource_size_t rtc_size;

static struct resource * __init rtc_request_region(resource_size_t size)
{
        struct resource *r;

        if (RTC_IOMAPPED)
                r = request_region(RTC_PORT(0), size, "rtc");
        else
                r = request_mem_region(RTC_PORT(0), size, "rtc");

        if (r)
                rtc_size = size;

        return r;
}

static void rtc_release_region(void)
{
        if (RTC_IOMAPPED)
                release_region(RTC_PORT(0), rtc_size);
        else
                release_mem_region(RTC_PORT(0), rtc_size);
}

static int __init rtc_init(void)
{
#ifdef CONFIG_PROC_FS
        struct proc_dir_entry *ent;
#endif
#if defined(__alpha__) || defined(__mips__)
        unsigned int year, ctrl;
        char *guess = NULL;
#endif
#ifdef CONFIG_SPARC32
        struct device_node *ebus_dp;
        struct of_device *op;
#else
        void *r;
#ifdef RTC_IRQ
        irq_handler_t rtc_int_handler_ptr;
#endif
#endif

#ifdef CONFIG_SPARC32
        for_each_node_by_name(ebus_dp, "ebus") {
                struct device_node *dp;
                for (dp = ebus_dp; dp; dp = dp->sibling) {
                        if (!strcmp(dp->name, "rtc")) {
                                op = of_find_device_by_node(dp);
                                if (op) {
                                        rtc_port = op->resource[0].start;
                                        rtc_irq = op->irqs[0];
                                        goto found;
                                }
                        }
                }
        }
        rtc_has_irq = 0;
        printk(KERN_ERR "rtc_init: no PC rtc found\n");
        return -EIO;

found:
        if (!rtc_irq) {
                rtc_has_irq = 0;
                goto no_irq;
        }

        /*
         * XXX Interrupt pin #7 in Espresso is shared between RTC and
         * PCI Slot 2 INTA# (and some INTx# in Slot 1).
         */
        if (request_irq(rtc_irq, rtc_interrupt, IRQF_SHARED, "rtc",
                        (void *)&rtc_port)) {
                rtc_has_irq = 0;
                printk(KERN_ERR "rtc: cannot register IRQ %d\n", rtc_irq);
                return -EIO;
        }
no_irq:
#else
        r = rtc_request_region(RTC_IO_EXTENT);

        /*
         * If we've already requested a smaller range (for example, because
         * PNPBIOS or ACPI told us how the device is configured), the request
         * above might fail because it's too big.
         *
         * If so, request just the range we actually use.
         */
        if (!r)
                r = rtc_request_region(RTC_IO_EXTENT_USED);
        if (!r) {
#ifdef RTC_IRQ
                rtc_has_irq = 0;
#endif
                printk(KERN_ERR "rtc: I/O resource %lx is not free.\n",
                       (long)(RTC_PORT(0)));
                return -EIO;
        }

#ifdef RTC_IRQ
        if (is_hpet_enabled()) {
                int err;

                rtc_int_handler_ptr = hpet_rtc_interrupt;
                err = hpet_register_irq_handler(rtc_interrupt);
                if (err != 0) {
                        printk(KERN_WARNING "hpet_register_irq_handler failed "
                                        "in rtc_init().");
                        return err;
                }
        } else {
                rtc_int_handler_ptr = rtc_interrupt;
        }

        if (request_irq(RTC_IRQ, rtc_int_handler_ptr, IRQF_DISABLED,
                        "rtc", NULL)) {
                /* Yeah right, seeing as irq 8 doesn't even hit the bus. */
                rtc_has_irq = 0;
                printk(KERN_ERR "rtc: IRQ %d is not free.\n", RTC_IRQ);
                rtc_release_region();

                return -EIO;
        }
        hpet_rtc_timer_init();

#endif

#endif /* CONFIG_SPARC32 vs. others */

        if (misc_register(&rtc_dev)) {
#ifdef RTC_IRQ
                free_irq(RTC_IRQ, NULL);
                hpet_unregister_irq_handler(rtc_interrupt);
                rtc_has_irq = 0;
#endif
                rtc_release_region();
                return -ENODEV;
        }

#ifdef CONFIG_PROC_FS
        ent = proc_create("driver/rtc", 0, NULL, &rtc_proc_fops);
        if (!ent)
                printk(KERN_WARNING "rtc: Failed to register with procfs.\n");
#endif

#if defined(__alpha__) || defined(__mips__)
        rtc_freq = HZ;

        /* Each operating system on an Alpha uses its own epoch.
           Let's try to guess which one we are using now. */

        if (rtc_is_updating() != 0)
                msleep(20);

        spin_lock_irq(&rtc_lock);
        year = CMOS_READ(RTC_YEAR);
        ctrl = CMOS_READ(RTC_CONTROL);
        spin_unlock_irq(&rtc_lock);

        if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
                year = bcd2bin(year);       /* This should never happen... */

        if (year < 20) {
                epoch = 2000;
                guess = "SRM (post-2000)";
        } else if (year >= 20 && year < 48) {
                epoch = 1980;
                guess = "ARC console";
        } else if (year >= 48 && year < 72) {
                epoch = 1952;
                guess = "Digital UNIX";
#if defined(__mips__)
        } else if (year >= 72 && year < 74) {
                epoch = 2000;
                guess = "Digital DECstation";
#else
        } else if (year >= 70) {
                epoch = 1900;
                guess = "Standard PC (1900)";
#endif
        }
        if (guess)
                printk(KERN_INFO "rtc: %s epoch (%lu) detected\n",
                        guess, epoch);
#endif
#ifdef RTC_IRQ
        if (rtc_has_irq == 0)
                goto no_irq2;

        spin_lock_irq(&rtc_lock);
        rtc_freq = 1024;
        if (!hpet_set_periodic_freq(rtc_freq)) {
                /*
                 * Initialize periodic frequency to CMOS reset default,
                 * which is 1024Hz
                 */
                CMOS_WRITE(((CMOS_READ(RTC_FREQ_SELECT) & 0xF0) | 0x06),
                           RTC_FREQ_SELECT);
        }
        spin_unlock_irq(&rtc_lock);
no_irq2:
#endif

        (void) init_sysctl();

        printk(KERN_INFO "Real Time Clock Driver v" RTC_VERSION "\n");

        return 0;
}

static void __exit rtc_exit(void)
{
        cleanup_sysctl();
        remove_proc_entry("driver/rtc", NULL);
        misc_deregister(&rtc_dev);

#ifdef CONFIG_SPARC32
        if (rtc_has_irq)
                free_irq(rtc_irq, &rtc_port);
#else
        rtc_release_region();
#ifdef RTC_IRQ
        if (rtc_has_irq) {
                free_irq(RTC_IRQ, NULL);
                hpet_unregister_irq_handler(hpet_rtc_interrupt);
        }
#endif
#endif /* CONFIG_SPARC32 */
}

module_init(rtc_init);
module_exit(rtc_exit);

#ifdef RTC_IRQ
/*
 *      At IRQ rates >= 4096Hz, an interrupt may get lost altogether.
 *      (usually during an IDE disk interrupt, with IRQ unmasking off)
 *      Since the interrupt handler doesn't get called, the IRQ status
 *      byte doesn't get read, and the RTC stops generating interrupts.
 *      A timer is set, and will call this function if/when that happens.
 *      To get it out of this stalled state, we just read the status.
 *      At least a jiffy of interrupts (rtc_freq/HZ) will have been lost.
 *      (You *really* shouldn't be trying to use a non-realtime system
 *      for something that requires a steady > 1KHz signal anyways.)
 */

static void rtc_dropped_irq(unsigned long data)
{
        unsigned long freq;

        spin_lock_irq(&rtc_lock);

        if (hpet_rtc_dropped_irq()) {
                spin_unlock_irq(&rtc_lock);
                return;
        }

        /* Just in case someone disabled the timer from behind our back... */
        if (rtc_status & RTC_TIMER_ON)
                mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);

        rtc_irq_data += ((rtc_freq/HZ)<<8);
        rtc_irq_data &= ~0xff;
        rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);     /* restart */

        freq = rtc_freq;

        spin_unlock_irq(&rtc_lock);

        if (printk_ratelimit()) {
                printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n",
                        freq);
        }

        /* Now we have new data */
        wake_up_interruptible(&rtc_wait);

        kill_fasync(&rtc_async_queue, SIGIO, POLL_IN);
}
#endif

#ifdef CONFIG_PROC_FS
/*
 *      Info exported via "/proc/driver/rtc".
 */

static int rtc_proc_show(struct seq_file *seq, void *v)
{
#define YN(bit) ((ctrl & bit) ? "yes" : "no")
#define NY(bit) ((ctrl & bit) ? "no" : "yes")
        struct rtc_time tm;
        unsigned char batt, ctrl;
        unsigned long freq;

        spin_lock_irq(&rtc_lock);
        batt = CMOS_READ(RTC_VALID) & RTC_VRT;
        ctrl = CMOS_READ(RTC_CONTROL);
        freq = rtc_freq;
        spin_unlock_irq(&rtc_lock);


        rtc_get_rtc_time(&tm);

        /*
         * There is no way to tell if the luser has the RTC set for local
         * time or for Universal Standard Time (GMT). Probably local though.
         */
        seq_printf(seq,
                   "rtc_time\t: %02d:%02d:%02d\n"
                   "rtc_date\t: %04d-%02d-%02d\n"
                   "rtc_epoch\t: %04lu\n",
                   tm.tm_hour, tm.tm_min, tm.tm_sec,
                   tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, epoch);

        get_rtc_alm_time(&tm);

        /*
         * We implicitly assume 24hr mode here. Alarm values >= 0xc0 will
         * match any value for that particular field. Values that are
         * greater than a valid time, but less than 0xc0 shouldn't appear.
         */
        seq_puts(seq, "alarm\t\t: ");
        if (tm.tm_hour <= 24)
                seq_printf(seq, "%02d:", tm.tm_hour);
        else
                seq_puts(seq, "**:");

        if (tm.tm_min <= 59)
                seq_printf(seq, "%02d:", tm.tm_min);
        else
                seq_puts(seq, "**:");

        if (tm.tm_sec <= 59)
                seq_printf(seq, "%02d\n", tm.tm_sec);
        else
                seq_puts(seq, "**\n");

        seq_printf(seq,
                   "DST_enable\t: %s\n"
                   "BCD\t\t: %s\n"
                   "24hr\t\t: %s\n"
                   "square_wave\t: %s\n"
                   "alarm_IRQ\t: %s\n"
                   "update_IRQ\t: %s\n"
                   "periodic_IRQ\t: %s\n"
                   "periodic_freq\t: %ld\n"
                   "batt_status\t: %s\n",
                   YN(RTC_DST_EN),
                   NY(RTC_DM_BINARY),
                   YN(RTC_24H),
                   YN(RTC_SQWE),
                   YN(RTC_AIE),
                   YN(RTC_UIE),
                   YN(RTC_PIE),
                   freq,
                   batt ? "okay" : "dead");

        return  0;
#undef YN
#undef NY
}

static int rtc_proc_open(struct inode *inode, struct file *file)
{
        return single_open(file, rtc_proc_show, NULL);
}
#endif

static void rtc_get_rtc_time(struct rtc_time *rtc_tm)
{
        unsigned long uip_watchdog = jiffies, flags;
        unsigned char ctrl;
#ifdef CONFIG_MACH_DECSTATION
        unsigned int real_year;
#endif

        /*
         * read RTC once any update in progress is done. The update
         * can take just over 2ms. We wait 20ms. There is no need to
         * to poll-wait (up to 1s - eeccch) for the falling edge of RTC_UIP.
         * If you need to know *exactly* when a second has started, enable
         * periodic update complete interrupts, (via ioctl) and then
         * immediately read /dev/rtc which will block until you get the IRQ.
         * Once the read clears, read the RTC time (again via ioctl). Easy.
         */

        while (rtc_is_updating() != 0 &&
               time_before(jiffies, uip_watchdog + 2*HZ/100))
                cpu_relax();

        /*
         * Only the values that we read from the RTC are set. We leave
         * tm_wday, tm_yday and tm_isdst untouched. Note that while the
         * RTC has RTC_DAY_OF_WEEK, we should usually ignore it, as it is
         * only updated by the RTC when initially set to a non-zero value.
         */
        spin_lock_irqsave(&rtc_lock, flags);
        rtc_tm->tm_sec = CMOS_READ(RTC_SECONDS);
        rtc_tm->tm_min = CMOS_READ(RTC_MINUTES);
        rtc_tm->tm_hour = CMOS_READ(RTC_HOURS);
        rtc_tm->tm_mday = CMOS_READ(RTC_DAY_OF_MONTH);
        rtc_tm->tm_mon = CMOS_READ(RTC_MONTH);
        rtc_tm->tm_year = CMOS_READ(RTC_YEAR);
        /* Only set from 2.6.16 onwards */
        rtc_tm->tm_wday = CMOS_READ(RTC_DAY_OF_WEEK);

#ifdef CONFIG_MACH_DECSTATION
        real_year = CMOS_READ(RTC_DEC_YEAR);
#endif
        ctrl = CMOS_READ(RTC_CONTROL);
        spin_unlock_irqrestore(&rtc_lock, flags);

        if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
                rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
                rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
                rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
                rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon);
                rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
                rtc_tm->tm_wday = bcd2bin(rtc_tm->tm_wday);
        }

#ifdef CONFIG_MACH_DECSTATION
        rtc_tm->tm_year += real_year - 72;
#endif

        /*
         * Account for differences between how the RTC uses the values
         * and how they are defined in a struct rtc_time;
         */
        rtc_tm->tm_year += epoch - 1900;
        if (rtc_tm->tm_year <= 69)
                rtc_tm->tm_year += 100;

        rtc_tm->tm_mon--;
}

static void get_rtc_alm_time(struct rtc_time *alm_tm)
{
        unsigned char ctrl;

        /*
         * Only the values that we read from the RTC are set. That
         * means only tm_hour, tm_min, and tm_sec.
         */
        spin_lock_irq(&rtc_lock);
        alm_tm->tm_sec = CMOS_READ(RTC_SECONDS_ALARM);
        alm_tm->tm_min = CMOS_READ(RTC_MINUTES_ALARM);
        alm_tm->tm_hour = CMOS_READ(RTC_HOURS_ALARM);
        ctrl = CMOS_READ(RTC_CONTROL);
        spin_unlock_irq(&rtc_lock);

        if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
                alm_tm->tm_sec = bcd2bin(alm_tm->tm_sec);
                alm_tm->tm_min = bcd2bin(alm_tm->tm_min);
                alm_tm->tm_hour = bcd2bin(alm_tm->tm_hour);
        }
}

#ifdef RTC_IRQ
/*
 * Used to disable/enable interrupts for any one of UIE, AIE, PIE.
 * Rumour has it that if you frob the interrupt enable/disable
 * bits in RTC_CONTROL, you should read RTC_INTR_FLAGS, to
 * ensure you actually start getting interrupts. Probably for
 * compatibility with older/broken chipset RTC implementations.
 * We also clear out any old irq data after an ioctl() that
 * meddles with the interrupt enable/disable bits.
 */

static void mask_rtc_irq_bit_locked(unsigned char bit)
{
        unsigned char val;

        if (hpet_mask_rtc_irq_bit(bit))
                return;
        val = CMOS_READ(RTC_CONTROL);
        val &=  ~bit;
        CMOS_WRITE(val, RTC_CONTROL);
        CMOS_READ(RTC_INTR_FLAGS);

        rtc_irq_data = 0;
}

static void set_rtc_irq_bit_locked(unsigned char bit)
{
        unsigned char val;

        if (hpet_set_rtc_irq_bit(bit))
                return;
        val = CMOS_READ(RTC_CONTROL);
        val |= bit;
        CMOS_WRITE(val, RTC_CONTROL);
        CMOS_READ(RTC_INTR_FLAGS);

        rtc_irq_data = 0;
}
#endif

MODULE_AUTHOR("Paul Gortmaker");
MODULE_LICENSE("GPL");
MODULE_ALIAS_MISCDEV(RTC_MINOR);