Initial import

1 files changed, 858 insertions, 0 deletions

diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c
new file mode 100644
index 000000000..3d6c0671e
--- /dev/null
+++ b/drivers/char/mmtimer.c
@@ -0,0 +1,858 @@
+/*
+ * 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);