mmtimer.c

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/*
 * Timer device implementation for SGI SN platforms.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (c) 2001-2006 Silicon Graphics, Inc.  All rights reserved.
 *
 * This driver exports an API that should be supportable by any HPET or IA-PC
 * multimedia timer.  The code below is currently specific to the SGI Altix
 * SHub RTC, however.
 *
 * 11/01/01 - jbarnes - initial revision
 * 9/10/04 - Christoph Lameter - remove interrupt support for kernel inclusion
 * 10/1/04 - Christoph Lameter - provide posix clock CLOCK_SGI_CYCLE
 * 10/13/04 - Christoph Lameter, Dimitri Sivanich - provide timer interrupt
 *      support via the posix timer interface
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ioctl.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/mmtimer.h>
#include <linux/miscdevice.h>
#include <linux/posix-timers.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/math64.h>
#include <linux/mutex.h>
#include <linux/slab.h>

#include <asm/uaccess.h>
#include <asm/sn/addrs.h>
#include <asm/sn/intr.h>
#include <asm/sn/shub_mmr.h>
#include <asm/sn/nodepda.h>
#include <asm/sn/shubio.h>

MODULE_AUTHOR("Jesse Barnes <[email protected]>");
MODULE_DESCRIPTION("SGI Altix RTC Timer");
MODULE_LICENSE("GPL");

/* name of the device, usually in /dev */
#define MMTIMER_NAME "mmtimer"
#define MMTIMER_DESC "SGI Altix RTC Timer"
#define MMTIMER_VERSION "2.1"

#define RTC_BITS 55 /* 55 bits for this implementation */

static struct k_clock sgi_clock;

extern unsigned long sn_rtc_cycles_per_second;

#define RTC_COUNTER_ADDR        ((long *)LOCAL_MMR_ADDR(SH_RTC))

#define rtc_time()              (*RTC_COUNTER_ADDR)

static DEFINE_MUTEX(mmtimer_mutex);
static long mmtimer_ioctl(struct file *file, unsigned int cmd,
                        unsigned long arg);
static int mmtimer_mmap(struct file *file, struct vm_area_struct *vma);

/*
 * Period in femtoseconds (10^-15 s)
 */
static unsigned long mmtimer_femtoperiod = 0;

static const struct file_operations mmtimer_fops = {
    .owner = THIS_MODULE,
    .mmap = mmtimer_mmap,
    .unlocked_ioctl = mmtimer_ioctl,
    .llseek = noop_llseek,
};

/*
 * We only have comparison registers RTC1-4 currently available per
 * node.  RTC0 is used by SAL.
 */
/* Check for an RTC interrupt pending */
static int mmtimer_int_pending(int comparator)
{
    if (HUB_L((unsigned long *)LOCAL_MMR_ADDR(SH_EVENT_OCCURRED)) &
            SH_EVENT_OCCURRED_RTC1_INT_MASK << comparator)
        return 1;
    else
        return 0;
}

/* Clear the RTC interrupt pending bit */
static void mmtimer_clr_int_pending(int comparator)
{
    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_EVENT_OCCURRED_ALIAS),
        SH_EVENT_OCCURRED_RTC1_INT_MASK << comparator);
}

/* Setup timer on comparator RTC1 */
static void mmtimer_setup_int_0(int cpu, u64 expires)
{
    u64 val;

    /* Disable interrupt */
    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC1_INT_ENABLE), 0UL);

    /* Initialize comparator value */
    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_INT_CMPB), -1L);

    /* Clear pending bit */
    mmtimer_clr_int_pending(0);

    val = ((u64)SGI_MMTIMER_VECTOR << SH_RTC1_INT_CONFIG_IDX_SHFT) |
        ((u64)cpu_physical_id(cpu) <<
            SH_RTC1_INT_CONFIG_PID_SHFT);

    /* Set configuration */
    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC1_INT_CONFIG), val);

    /* Enable RTC interrupts */
    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC1_INT_ENABLE), 1UL);

    /* Initialize comparator value */
    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_INT_CMPB), expires);


}

/* Setup timer on comparator RTC2 */
static void mmtimer_setup_int_1(int cpu, u64 expires)
{
    u64 val;

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC2_INT_ENABLE), 0UL);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_INT_CMPC), -1L);

    mmtimer_clr_int_pending(1);

    val = ((u64)SGI_MMTIMER_VECTOR << SH_RTC2_INT_CONFIG_IDX_SHFT) |
        ((u64)cpu_physical_id(cpu) <<
            SH_RTC2_INT_CONFIG_PID_SHFT);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC2_INT_CONFIG), val);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC2_INT_ENABLE), 1UL);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_INT_CMPC), expires);
}

/* Setup timer on comparator RTC3 */
static void mmtimer_setup_int_2(int cpu, u64 expires)
{
    u64 val;

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC3_INT_ENABLE), 0UL);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_INT_CMPD), -1L);

    mmtimer_clr_int_pending(2);

    val = ((u64)SGI_MMTIMER_VECTOR << SH_RTC3_INT_CONFIG_IDX_SHFT) |
        ((u64)cpu_physical_id(cpu) <<
            SH_RTC3_INT_CONFIG_PID_SHFT);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC3_INT_CONFIG), val);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC3_INT_ENABLE), 1UL);

    HUB_S((u64 *)LOCAL_MMR_ADDR(SH_INT_CMPD), expires);
}

/*
 * This function must be called with interrupts disabled and preemption off
 * in order to insure that the setup succeeds in a deterministic time frame.
 * It will check if the interrupt setup succeeded.
 */
static int mmtimer_setup(int cpu, int comparator, unsigned long expires,
    u64 *set_completion_time)
{
    switch (comparator) {
    case 0:
        mmtimer_setup_int_0(cpu, expires);
        break;
    case 1:
        mmtimer_setup_int_1(cpu, expires);
        break;
    case 2:
        mmtimer_setup_int_2(cpu, expires);
        break;
    }
    /* We might've missed our expiration time */
    *set_completion_time = rtc_time();
    if (*set_completion_time <= expires)
        return 1;

    /*
     * If an interrupt is already pending then its okay
     * if not then we failed
     */
    return mmtimer_int_pending(comparator);
}

static int mmtimer_disable_int(long nasid, int comparator)
{
    switch (comparator) {
    case 0:
        nasid == -1 ? HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC1_INT_ENABLE),
            0UL) : REMOTE_HUB_S(nasid, SH_RTC1_INT_ENABLE, 0UL);
        break;
    case 1:
        nasid == -1 ? HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC2_INT_ENABLE),
            0UL) : REMOTE_HUB_S(nasid, SH_RTC2_INT_ENABLE, 0UL);
        break;
    case 2:
        nasid == -1 ? HUB_S((u64 *)LOCAL_MMR_ADDR(SH_RTC3_INT_ENABLE),
            0UL) : REMOTE_HUB_S(nasid, SH_RTC3_INT_ENABLE, 0UL);
        break;
    default:
        return -EFAULT;
    }
    return 0;
}

#define COMPARATOR  1       /* The comparator to use */

#define TIMER_OFF   0xbadcabLL  /* Timer is not setup */
#define TIMER_SET   0       /* Comparator is set for this timer */

#define MMTIMER_INTERVAL_RETRY_INCREMENT_DEFAULT 40

/* There is one of these for each timer */
struct mmtimer {
    struct rb_node list;
    struct k_itimer *timer;
    int cpu;
};

struct mmtimer_node {
    spinlock_t lock ____cacheline_aligned;
    struct rb_root timer_head;
    struct rb_node *next;
    struct tasklet_struct tasklet;
};
static struct mmtimer_node *timers;

static unsigned mmtimer_interval_retry_increment =
    MMTIMER_INTERVAL_RETRY_INCREMENT_DEFAULT;
module_param(mmtimer_interval_retry_increment, uint, 0644);
MODULE_PARM_DESC(mmtimer_interval_retry_increment,
    "RTC ticks to add to expiration on interval retry (default 40)");

/*
 * Add a new mmtimer struct to the node's mmtimer list.
 * This function assumes the struct mmtimer_node is locked.
 */
static void mmtimer_add_list(struct mmtimer *n)
{
    int nodeid = n->timer->it.mmtimer.node;
    unsigned long expires = n->timer->it.mmtimer.expires;
    struct rb_node **link = &timers[nodeid].timer_head.rb_node;
    struct rb_node *parent = NULL;
    struct mmtimer *x;

    /*
     * Find the right place in the rbtree:
     */
    while (*link) {
        parent = *link;
        x = rb_entry(parent, struct mmtimer, list);

        if (expires < x->timer->it.mmtimer.expires)
            link = &(*link)->rb_left;
        else
            link = &(*link)->rb_right;
    }

    /*
     * Insert the timer to the rbtree and check whether it
     * replaces the first pending timer
     */
    rb_link_node(&n->list, parent, link);
    rb_insert_color(&n->list, &timers[nodeid].timer_head);

    if (!timers[nodeid].next || expires < rb_entry(timers[nodeid].next,
            struct mmtimer, list)->timer->it.mmtimer.expires)
        timers[nodeid].next = &n->list;
}

/*
 * Set the comparator for the next timer.
 * This function assumes the struct mmtimer_node is locked.
 */
static void mmtimer_set_next_timer(int nodeid)
{
    struct mmtimer_node *n = &timers[nodeid];
    struct mmtimer *x;
    struct k_itimer *t;
    u64 expires, exp, set_completion_time;
    int i;

restart:
    if (n->next == NULL)
        return;

    x = rb_entry(n->next, struct mmtimer, list);
    t = x->timer;
    if (!t->it.mmtimer.incr) {
        /* Not an interval timer */
        if (!mmtimer_setup(x->cpu, COMPARATOR,
                    t->it.mmtimer.expires,
                    &set_completion_time)) {
            /* Late setup, fire now */
            tasklet_schedule(&n->tasklet);
        }
        return;
    }

    /* Interval timer */
    i = 0;
    expires = exp = t->it.mmtimer.expires;
    while (!mmtimer_setup(x->cpu, COMPARATOR, expires,
                &set_completion_time)) {
        int to;

        i++;
        expires = set_completion_time +
                mmtimer_interval_retry_increment + (1 << i);
        /* Calculate overruns as we go. */
        to = ((u64)(expires - exp) / t->it.mmtimer.incr);
        if (to) {
            t->it_overrun += to;
            t->it.mmtimer.expires += t->it.mmtimer.incr * to;
            exp = t->it.mmtimer.expires;
        }
        if (i > 20) {
            printk(KERN_ALERT "mmtimer: cannot reschedule timer\n");
            t->it.mmtimer.clock = TIMER_OFF;
            n->next = rb_next(&x->list);
            rb_erase(&x->list, &n->timer_head);
            kfree(x);
            goto restart;
        }
    }
}

static long mmtimer_ioctl(struct file *file, unsigned int cmd,
                        unsigned long arg)
{
    int ret = 0;

    mutex_lock(&mmtimer_mutex);

    switch (cmd) {
    case MMTIMER_GETOFFSET: /* offset of the counter */
        /*
         * SN RTC registers are on their own 64k page
         */
        if(PAGE_SIZE <= (1 << 16))
            ret = (((long)RTC_COUNTER_ADDR) & (PAGE_SIZE-1)) / 8;
        else
            ret = -ENOSYS;
        break;

    case MMTIMER_GETRES: /* resolution of the clock in 10^-15 s */
        if(copy_to_user((unsigned long __user *)arg,
                &mmtimer_femtoperiod, sizeof(unsigned long)))
            ret = -EFAULT;
        break;

    case MMTIMER_GETFREQ: /* frequency in Hz */
        if(copy_to_user((unsigned long __user *)arg,
                &sn_rtc_cycles_per_second,
                sizeof(unsigned long)))
            ret = -EFAULT;
        break;

    case MMTIMER_GETBITS: /* number of bits in the clock */
        ret = RTC_BITS;
        break;

    case MMTIMER_MMAPAVAIL: /* can we mmap the clock into userspace? */
        ret = (PAGE_SIZE <= (1 << 16)) ? 1 : 0;
        break;

    case MMTIMER_GETCOUNTER:
        if(copy_to_user((unsigned long __user *)arg,
                RTC_COUNTER_ADDR, sizeof(unsigned long)))
            ret = -EFAULT;
        break;
    default:
        ret = -ENOTTY;
        break;
    }
    mutex_unlock(&mmtimer_mutex);
    return ret;
}

static int mmtimer_mmap(struct file *file, struct vm_area_struct *vma)
{
    unsigned long mmtimer_addr;

    if (vma->vm_end - vma->vm_start != PAGE_SIZE)
        return -EINVAL;

    if (vma->vm_flags & VM_WRITE)
        return -EPERM;

    if (PAGE_SIZE > (1 << 16))
        return -ENOSYS;

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

    mmtimer_addr = __pa(RTC_COUNTER_ADDR);
    mmtimer_addr &= ~(PAGE_SIZE - 1);
    mmtimer_addr &= 0xfffffffffffffffUL;

    if (remap_pfn_range(vma, vma->vm_start, mmtimer_addr >> PAGE_SHIFT,
                    PAGE_SIZE, vma->vm_page_prot)) {
        printk(KERN_ERR "remap_pfn_range failed in mmtimer.c\n");
        return -EAGAIN;
    }

    return 0;
}

static struct miscdevice mmtimer_miscdev = {
    SGI_MMTIMER,
    MMTIMER_NAME,
    &mmtimer_fops
};

static struct timespec sgi_clock_offset;
static int sgi_clock_period;

/*
 * Posix Timer Interface
 */

static struct timespec sgi_clock_offset;
static int sgi_clock_period;

static int sgi_clock_get(clockid_t clockid, struct timespec *tp)
{
    u64 nsec;

    nsec = rtc_time() * sgi_clock_period
            + sgi_clock_offset.tv_nsec;
    *tp = ns_to_timespec(nsec);
    tp->tv_sec += sgi_clock_offset.tv_sec;
    return 0;
};

static int sgi_clock_set(const clockid_t clockid, const struct timespec *tp)
{

    u64 nsec;
    u32 rem;

    nsec = rtc_time() * sgi_clock_period;

    sgi_clock_offset.tv_sec = tp->tv_sec - div_u64_rem(nsec, NSEC_PER_SEC, &rem);

    if (rem <= tp->tv_nsec)
        sgi_clock_offset.tv_nsec = tp->tv_sec - rem;
    else {
        sgi_clock_offset.tv_nsec = tp->tv_sec + NSEC_PER_SEC - rem;
        sgi_clock_offset.tv_sec--;
    }
    return 0;
}

static irqreturn_t
mmtimer_interrupt(int irq, void *dev_id)
{
    unsigned long expires = 0;
    int result = IRQ_NONE;
    unsigned indx = cpu_to_node(smp_processor_id());
    struct mmtimer *base;

    spin_lock(&timers[indx].lock);
    base = rb_entry(timers[indx].next, struct mmtimer, list);
    if (base == NULL) {
        spin_unlock(&timers[indx].lock);
        return result;
    }

    if (base->cpu == smp_processor_id()) {
        if (base->timer)
            expires = base->timer->it.mmtimer.expires;
        /* expires test won't work with shared irqs */
        if ((mmtimer_int_pending(COMPARATOR) > 0) ||
            (expires && (expires <= rtc_time()))) {
            mmtimer_clr_int_pending(COMPARATOR);
            tasklet_schedule(&timers[indx].tasklet);
            result = IRQ_HANDLED;
        }
    }
    spin_unlock(&timers[indx].lock);
    return result;
}

static void mmtimer_tasklet(unsigned long data)
{
    int nodeid = data;
    struct mmtimer_node *mn = &timers[nodeid];
    struct mmtimer *x;
    struct k_itimer *t;
    unsigned long flags;

    /* Send signal and deal with periodic signals */
    spin_lock_irqsave(&mn->lock, flags);
    if (!mn->next)
        goto out;

    x = rb_entry(mn->next, struct mmtimer, list);
    t = x->timer;

    if (t->it.mmtimer.clock == TIMER_OFF)
        goto out;

    t->it_overrun = 0;

    mn->next = rb_next(&x->list);
    rb_erase(&x->list, &mn->timer_head);

    if (posix_timer_event(t, 0) != 0)
        t->it_overrun++;

    if(t->it.mmtimer.incr) {
        t->it.mmtimer.expires += t->it.mmtimer.incr;
        mmtimer_add_list(x);
    } else {
        /* Ensure we don't false trigger in mmtimer_interrupt */
        t->it.mmtimer.clock = TIMER_OFF;
        t->it.mmtimer.expires = 0;
        kfree(x);
    }
    /* Set comparator for next timer, if there is one */
    mmtimer_set_next_timer(nodeid);

    t->it_overrun_last = t->it_overrun;
out:
    spin_unlock_irqrestore(&mn->lock, flags);
}

static int sgi_timer_create(struct k_itimer *timer)
{
    /* Insure that a newly created timer is off */
    timer->it.mmtimer.clock = TIMER_OFF;
    return 0;
}

/* This does not really delete a timer. It just insures
 * that the timer is not active
 *
 * Assumption: it_lock is already held with irq's disabled
 */
static int sgi_timer_del(struct k_itimer *timr)
{
    cnodeid_t nodeid = timr->it.mmtimer.node;
    unsigned long irqflags;

    spin_lock_irqsave(&timers[nodeid].lock, irqflags);
    if (timr->it.mmtimer.clock != TIMER_OFF) {
        unsigned long expires = timr->it.mmtimer.expires;
        struct rb_node *n = timers[nodeid].timer_head.rb_node;
        struct mmtimer *uninitialized_var(t);
        int r = 0;

        timr->it.mmtimer.clock = TIMER_OFF;
        timr->it.mmtimer.expires = 0;

        while (n) {
            t = rb_entry(n, struct mmtimer, list);
            if (t->timer == timr)
                break;

            if (expires < t->timer->it.mmtimer.expires)
                n = n->rb_left;
            else
                n = n->rb_right;
        }

        if (!n) {
            spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);
            return 0;
        }

        if (timers[nodeid].next == n) {
            timers[nodeid].next = rb_next(n);
            r = 1;
        }

        rb_erase(n, &timers[nodeid].timer_head);
        kfree(t);

        if (r) {
            mmtimer_disable_int(cnodeid_to_nasid(nodeid),
                COMPARATOR);
            mmtimer_set_next_timer(nodeid);
        }
    }
    spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);
    return 0;
}

/* Assumption: it_lock is already held with irq's disabled */
static void sgi_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
{

    if (timr->it.mmtimer.clock == TIMER_OFF) {
        cur_setting->it_interval.tv_nsec = 0;
        cur_setting->it_interval.tv_sec = 0;
        cur_setting->it_value.tv_nsec = 0;
        cur_setting->it_value.tv_sec =0;
        return;
    }

    cur_setting->it_interval = ns_to_timespec(timr->it.mmtimer.incr * sgi_clock_period);
    cur_setting->it_value = ns_to_timespec((timr->it.mmtimer.expires - rtc_time()) * sgi_clock_period);
}


static int sgi_timer_set(struct k_itimer *timr, int flags,
    struct itimerspec * new_setting,
    struct itimerspec * old_setting)
{
    unsigned long when, period, irqflags;
    int err = 0;
    cnodeid_t nodeid;
    struct mmtimer *base;
    struct rb_node *n;

    if (old_setting)
        sgi_timer_get(timr, old_setting);

    sgi_timer_del(timr);
    when = timespec_to_ns(&new_setting->it_value);
    period = timespec_to_ns(&new_setting->it_interval);

    if (when == 0)
        /* Clear timer */
        return 0;

    base = kmalloc(sizeof(struct mmtimer), GFP_KERNEL);
    if (base == NULL)
        return -ENOMEM;

    if (flags & TIMER_ABSTIME) {
        struct timespec n;
        unsigned long now;

        getnstimeofday(&n);
        now = timespec_to_ns(&n);
        if (when > now)
            when -= now;
        else
            /* Fire the timer immediately */
            when = 0;
    }

    /*
     * Convert to sgi clock period. Need to keep rtc_time() as near as possible
     * to getnstimeofday() in order to be as faithful as possible to the time
     * specified.
     */
    when = (when + sgi_clock_period - 1) / sgi_clock_period + rtc_time();
    period = (period + sgi_clock_period - 1)  / sgi_clock_period;

    /*
     * We are allocating a local SHub comparator. If we would be moved to another
     * cpu then another SHub may be local to us. Prohibit that by switching off
     * preemption.
     */
    preempt_disable();

    nodeid =  cpu_to_node(smp_processor_id());

    /* Lock the node timer structure */
    spin_lock_irqsave(&timers[nodeid].lock, irqflags);

    base->timer = timr;
    base->cpu = smp_processor_id();

    timr->it.mmtimer.clock = TIMER_SET;
    timr->it.mmtimer.node = nodeid;
    timr->it.mmtimer.incr = period;
    timr->it.mmtimer.expires = when;

    n = timers[nodeid].next;

    /* Add the new struct mmtimer to node's timer list */
    mmtimer_add_list(base);

    if (timers[nodeid].next == n) {
        /* No need to reprogram comparator for now */
        spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);
        preempt_enable();
        return err;
    }

    /* We need to reprogram the comparator */
    if (n)
        mmtimer_disable_int(cnodeid_to_nasid(nodeid), COMPARATOR);

    mmtimer_set_next_timer(nodeid);

    /* Unlock the node timer structure */
    spin_unlock_irqrestore(&timers[nodeid].lock, irqflags);

    preempt_enable();

    return err;
}

static int sgi_clock_getres(const clockid_t which_clock, struct timespec *tp)
{
    tp->tv_sec = 0;
    tp->tv_nsec = sgi_clock_period;
    return 0;
}

static struct k_clock sgi_clock = {
    .clock_set  = sgi_clock_set,
    .clock_get  = sgi_clock_get,
    .clock_getres   = sgi_clock_getres,
    .timer_create   = sgi_timer_create,
    .timer_set  = sgi_timer_set,
    .timer_del  = sgi_timer_del,
    .timer_get  = sgi_timer_get
};

static int __init mmtimer_init(void)
{
    cnodeid_t node, maxn = -1;

    if (!ia64_platform_is("sn2"))
        return 0;

    /*
     * Sanity check the cycles/sec variable
     */
    if (sn_rtc_cycles_per_second < 100000) {
        printk(KERN_ERR "%s: unable to determine clock frequency\n",
               MMTIMER_NAME);
        goto out1;
    }

    mmtimer_femtoperiod = ((unsigned long)1E15 + sn_rtc_cycles_per_second /
                   2) / sn_rtc_cycles_per_second;

    if (request_irq(SGI_MMTIMER_VECTOR, mmtimer_interrupt, IRQF_PERCPU, MMTIMER_NAME, NULL)) {
        printk(KERN_WARNING "%s: unable to allocate interrupt.",
            MMTIMER_NAME);
        goto out1;
    }

    if (misc_register(&mmtimer_miscdev)) {
        printk(KERN_ERR "%s: failed to register device\n",
               MMTIMER_NAME);
        goto out2;
    }

    /* Get max numbered node, calculate slots needed */
    for_each_online_node(node) {
        maxn = node;
    }
    maxn++;

    /* Allocate list of node ptrs to mmtimer_t's */
    timers = kzalloc(sizeof(struct mmtimer_node)*maxn, GFP_KERNEL);
    if (!timers) {
        printk(KERN_ERR "%s: failed to allocate memory for device\n",
                MMTIMER_NAME);
        goto out3;
    }

    /* Initialize struct mmtimer's for each online node */
    for_each_online_node(node) {
        spin_lock_init(&timers[node].lock);
        tasklet_init(&timers[node].tasklet, mmtimer_tasklet,
            (unsigned long) node);
    }

    sgi_clock_period = NSEC_PER_SEC / sn_rtc_cycles_per_second;
    posix_timers_register_clock(CLOCK_SGI_CYCLE, &sgi_clock);

    printk(KERN_INFO "%s: v%s, %ld MHz\n", MMTIMER_DESC, MMTIMER_VERSION,
           sn_rtc_cycles_per_second/(unsigned long)1E6);

    return 0;

out3:
    misc_deregister(&mmtimer_miscdev);
out2:
    free_irq(SGI_MMTIMER_VECTOR, NULL);
out1:
    return -1;
}

module_init(mmtimer_init);