Linux 4.2.1

[linux/fpc-iii.git] / drivers / char / mmtimer.c

/*
 * 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 <jbarnes@sgi.com>");
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;
                }
        }
}

/**
 * mmtimer_ioctl - ioctl interface for /dev/mmtimer
 * @file: file structure for the device
 * @cmd: command to execute
 * @arg: optional argument to command
 *
 * Executes the command specified by @cmd.  Returns 0 for success, < 0 for
 * failure.
 *
 * Valid commands:
 *
 * %MMTIMER_GETOFFSET - Should return the offset (relative to the start
 * of the page where the registers are mapped) for the counter in question.
 *
 * %MMTIMER_GETRES - Returns the resolution of the clock in femto (10^-15)
 * seconds
 *
 * %MMTIMER_GETFREQ - Copies the frequency of the clock in Hz to the address
 * specified by @arg
 *
 * %MMTIMER_GETBITS - Returns the number of bits in the clock's counter
 *
 * %MMTIMER_MMAPAVAIL - Returns 1 if the registers can be mmap'd into userspace
 *
 * %MMTIMER_GETCOUNTER - Gets the current value in the counter and places it
 * in the address specified by @arg.
 */
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;
}

/**
 * mmtimer_mmap - maps the clock's registers into userspace
 * @file: file structure for the device
 * @vma: VMA to map the registers into
 *
 * Calls remap_pfn_range() to map the clock's registers into
 * the calling process' address space.
 */
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;
}

/**
 * mmtimer_interrupt - timer interrupt handler
 * @irq: irq received
 * @dev_id: device the irq came from
 *
 * Called when one of the comarators matches the counter, This
 * routine will send signals to processes that have requested
 * them.
 *
 * This interrupt is run in an interrupt context
 * by the SHUB. It is therefore safe to locally access SHub
 * registers.
 */
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
};

/**
 * mmtimer_init - device initialization routine
 *
 * Does initial setup for the mmtimer device.
 */
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);