arch/x86/platform/uv/uv_time.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * SGI RTC clock/timer routines.
  *
  *  (C) Copyright 2020 Hewlett Packard Enterprise Development LP
  *  Copyright (c) 2009-2013 Silicon Graphics, Inc.  All Rights Reserved.
  *  Copyright (c) Dimitri Sivanich
  */
 #include <linux/clockchips.h>
 #include <linux/slab.h>

 #include <asm/uv/uv_mmrs.h>
 #include <asm/uv/uv_hub.h>
 #include <asm/uv/bios.h>
 #include <asm/uv/uv.h>
 #include <asm/apic.h>
 #include <asm/cpu.h>

 #define RTC_NAME		"sgi_rtc"

 static u64 uv_read_rtc(struct clocksource *cs);
 static int uv_rtc_next_event(unsigned long, struct clock_event_device *);
 static int uv_rtc_shutdown(struct clock_event_device *evt);

 static struct clocksource clocksource_uv = {
 	.name		= RTC_NAME,
 	.rating		= 299,
 	.read		= uv_read_rtc,
 	.mask		= (u64)UVH_RTC_REAL_TIME_CLOCK_MASK,
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };

 static struct clock_event_device clock_event_device_uv = {
 	.name			= RTC_NAME,
 	.features		= CLOCK_EVT_FEAT_ONESHOT,
 	.shift			= 20,
 	.rating			= 400,
 	.irq			= -1,
 	.set_next_event		= uv_rtc_next_event,
 	.set_state_shutdown	= uv_rtc_shutdown,
 	.event_handler		= NULL,
 };

 static DEFINE_PER_CPU(struct clock_event_device, cpu_ced);

 /* There is one of these allocated per node */
 struct uv_rtc_timer_head {
 	spinlock_t	lock;
 	/* next cpu waiting for timer, local node relative: */
 	int		next_cpu;
 	/* number of cpus on this node: */
 	int		ncpus;
 	struct {
 		int	lcpu;		/* systemwide logical cpu number */
 		u64	expires;	/* next timer expiration for this cpu */
 	} cpu[];
 };

 /*
  * Access to uv_rtc_timer_head via blade id.
  */
 static struct uv_rtc_timer_head		**blade_info __read_mostly;

 static int				uv_rtc_evt_enable;

 /*
  * Hardware interface routines
  */

 /* Send IPIs to another node */
 static void uv_rtc_send_IPI(int cpu)
 {
 	unsigned long apicid, val;
 	int pnode;

 	apicid = cpu_physical_id(cpu);
 	pnode = uv_apicid_to_pnode(apicid);
 	val = (1UL << UVH_IPI_INT_SEND_SHFT) |
 	      (apicid << UVH_IPI_INT_APIC_ID_SHFT) |
 	      (X86_PLATFORM_IPI_VECTOR << UVH_IPI_INT_VECTOR_SHFT);

 	uv_write_global_mmr64(pnode, UVH_IPI_INT, val);
 }

 /* Check for an RTC interrupt pending */
 static int uv_intr_pending(int pnode)
 {
 	return uv_read_global_mmr64(pnode, UVH_EVENT_OCCURRED2) &
 		UVH_EVENT_OCCURRED2_RTC_1_MASK;
 }

 /* Setup interrupt and return non-zero if early expiration occurred. */
 static int uv_setup_intr(int cpu, u64 expires)
 {
 	u64 val;
 	unsigned long apicid = cpu_physical_id(cpu);
 	int pnode = uv_cpu_to_pnode(cpu);

 	uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG,
 		UVH_RTC1_INT_CONFIG_M_MASK);
 	uv_write_global_mmr64(pnode, UVH_INT_CMPB, -1L);

 	uv_write_global_mmr64(pnode, UVH_EVENT_OCCURRED2_ALIAS,
 			      UVH_EVENT_OCCURRED2_RTC_1_MASK);

 	val = (X86_PLATFORM_IPI_VECTOR << UVH_RTC1_INT_CONFIG_VECTOR_SHFT) |
 		((u64)apicid << UVH_RTC1_INT_CONFIG_APIC_ID_SHFT);

 	/* Set configuration */
 	uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG, val);
 	/* Initialize comparator value */
 	uv_write_global_mmr64(pnode, UVH_INT_CMPB, expires);

 	if (uv_read_rtc(NULL) <= expires)
 		return 0;

 	return !uv_intr_pending(pnode);
 }

 /*
  * Per-cpu timer tracking routines
  */

 static __init void uv_rtc_deallocate_timers(void)
 {
 	int bid;

 	for_each_possible_blade(bid) {
 		kfree(blade_info[bid]);
 	}
 	kfree(blade_info);
 }

 /* Allocate per-node list of cpu timer expiration times. */
 static __init int uv_rtc_allocate_timers(void)
 {
 	int cpu;

 	blade_info = kcalloc(uv_possible_blades, sizeof(void *), GFP_KERNEL);
 	if (!blade_info)
 		return -ENOMEM;

 	for_each_present_cpu(cpu) {
 		int nid = cpu_to_node(cpu);
 		int bid = uv_cpu_to_blade_id(cpu);
 		int bcpu = uv_cpu_blade_processor_id(cpu);
 		struct uv_rtc_timer_head *head = blade_info[bid];

 		if (!head) {
 			head = kmalloc_node(struct_size(head, cpu,
 				uv_blade_nr_possible_cpus(bid)),
 				GFP_KERNEL, nid);
 			if (!head) {
 				uv_rtc_deallocate_timers();
 				return -ENOMEM;
 			}
 			spin_lock_init(&head->lock);
 			head->ncpus = uv_blade_nr_possible_cpus(bid);
 			head->next_cpu = -1;
 			blade_info[bid] = head;
 		}

 		head->cpu[bcpu].lcpu = cpu;
 		head->cpu[bcpu].expires = ULLONG_MAX;
 	}

 	return 0;
 }

 /* Find and set the next expiring timer.  */
 static void uv_rtc_find_next_timer(struct uv_rtc_timer_head *head, int pnode)
 {
 	u64 lowest = ULLONG_MAX;
 	int c, bcpu = -1;

 	head->next_cpu = -1;
 	for (c = 0; c < head->ncpus; c++) {
 		u64 exp = head->cpu[c].expires;
 		if (exp < lowest) {
 			bcpu = c;
 			lowest = exp;
 		}
 	}
 	if (bcpu >= 0) {
 		head->next_cpu = bcpu;
 		c = head->cpu[bcpu].lcpu;
 		if (uv_setup_intr(c, lowest))
 			/* If we didn't set it up in time, trigger */
 			uv_rtc_send_IPI(c);
 	} else {
 		uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG,
 			UVH_RTC1_INT_CONFIG_M_MASK);
 	}
 }

 /*
  * Set expiration time for current cpu.
  *
  * Returns 1 if we missed the expiration time.
  */
 static int uv_rtc_set_timer(int cpu, u64 expires)
 {
 	int pnode = uv_cpu_to_pnode(cpu);
 	int bid = uv_cpu_to_blade_id(cpu);
 	struct uv_rtc_timer_head *head = blade_info[bid];
 	int bcpu = uv_cpu_blade_processor_id(cpu);
 	u64 *t = &head->cpu[bcpu].expires;
 	unsigned long flags;
 	int next_cpu;

 	spin_lock_irqsave(&head->lock, flags);

 	next_cpu = head->next_cpu;
 	*t = expires;

 	/* Will this one be next to go off? */
 	if (next_cpu < 0 || bcpu == next_cpu ||
 			expires < head->cpu[next_cpu].expires) {
 		head->next_cpu = bcpu;
 		if (uv_setup_intr(cpu, expires)) {
 			*t = ULLONG_MAX;
 			uv_rtc_find_next_timer(head, pnode);
 			spin_unlock_irqrestore(&head->lock, flags);
 			return -ETIME;
 		}
 	}

 	spin_unlock_irqrestore(&head->lock, flags);
 	return 0;
 }

 /*
  * Unset expiration time for current cpu.
  *
  * Returns 1 if this timer was pending.
  */
 static int uv_rtc_unset_timer(int cpu, int force)
 {
 	int pnode = uv_cpu_to_pnode(cpu);
 	int bid = uv_cpu_to_blade_id(cpu);
 	struct uv_rtc_timer_head *head = blade_info[bid];
 	int bcpu = uv_cpu_blade_processor_id(cpu);
 	u64 *t = &head->cpu[bcpu].expires;
 	unsigned long flags;
 	int rc = 0;

 	spin_lock_irqsave(&head->lock, flags);

 	if ((head->next_cpu == bcpu && uv_read_rtc(NULL) >= *t) || force)
 		rc = 1;

 	if (rc) {
 		*t = ULLONG_MAX;
 		/* Was the hardware setup for this timer? */
 		if (head->next_cpu == bcpu)
 			uv_rtc_find_next_timer(head, pnode);
 	}

 	spin_unlock_irqrestore(&head->lock, flags);

 	return rc;
 }


 /*
  * Kernel interface routines.
  */

 /*
  * Read the RTC.
  *
  * Starting with HUB rev 2.0, the UV RTC register is replicated across all
  * cachelines of it's own page.  This allows faster simultaneous reads
  * from a given socket.
  */
 static u64 uv_read_rtc(struct clocksource *cs)
 {
 	unsigned long offset;

 	if (uv_get_min_hub_revision_id() == 1)
 		offset = 0;
 	else
 		offset = (uv_blade_processor_id() * L1_CACHE_BYTES) % PAGE_SIZE;

 	return (u64)uv_read_local_mmr(UVH_RTC | offset);
 }

 /*
  * Program the next event, relative to now
  */
 static int uv_rtc_next_event(unsigned long delta,
 			     struct clock_event_device *ced)
 {
 	int ced_cpu = cpumask_first(ced->cpumask);

 	return uv_rtc_set_timer(ced_cpu, delta + uv_read_rtc(NULL));
 }

 /*
  * Shutdown the RTC timer
  */
 static int uv_rtc_shutdown(struct clock_event_device *evt)
 {
 	int ced_cpu = cpumask_first(evt->cpumask);

 	uv_rtc_unset_timer(ced_cpu, 1);
 	return 0;
 }

 static void uv_rtc_interrupt(void)
 {
 	int cpu = smp_processor_id();
 	struct clock_event_device *ced = &per_cpu(cpu_ced, cpu);

 	if (!ced || !ced->event_handler)
 		return;

 	if (uv_rtc_unset_timer(cpu, 0) != 1)
 		return;

 	ced->event_handler(ced);
 }

 static int __init uv_enable_evt_rtc(char *str)
 {
 	uv_rtc_evt_enable = 1;

 	return 1;
 }
 __setup("uvrtcevt", uv_enable_evt_rtc);

 static __init void uv_rtc_register_clockevents(struct work_struct *dummy)
 {
 	struct clock_event_device *ced = this_cpu_ptr(&cpu_ced);

 	*ced = clock_event_device_uv;
 	ced->cpumask = cpumask_of(smp_processor_id());
 	clockevents_register_device(ced);
 }

 static __init int uv_rtc_setup_clock(void)
 {
 	int rc;

 	if (!is_uv_system())
 		return -ENODEV;

 	rc = clocksource_register_hz(&clocksource_uv, sn_rtc_cycles_per_second);
 	if (rc)
 		printk(KERN_INFO "UV RTC clocksource failed rc %d\n", rc);
 	else
 		printk(KERN_INFO "UV RTC clocksource registered freq %lu MHz\n",
 			sn_rtc_cycles_per_second/(unsigned long)1E6);

 	if (rc || !uv_rtc_evt_enable || x86_platform_ipi_callback)
 		return rc;

 	/* Setup and register clockevents */
 	rc = uv_rtc_allocate_timers();
 	if (rc)
 		goto error;

 	x86_platform_ipi_callback = uv_rtc_interrupt;

 	clock_event_device_uv.mult = div_sc(sn_rtc_cycles_per_second,
 				NSEC_PER_SEC, clock_event_device_uv.shift);

 	clock_event_device_uv.min_delta_ns = NSEC_PER_SEC /
 						sn_rtc_cycles_per_second;
 	clock_event_device_uv.min_delta_ticks = 1;

 	clock_event_device_uv.max_delta_ns = clocksource_uv.mask *
 				(NSEC_PER_SEC / sn_rtc_cycles_per_second);
 	clock_event_device_uv.max_delta_ticks = clocksource_uv.mask;

 	rc = schedule_on_each_cpu(uv_rtc_register_clockevents);
 	if (rc) {
 		x86_platform_ipi_callback = NULL;
 		uv_rtc_deallocate_timers();
 		goto error;
 	}

 	printk(KERN_INFO "UV RTC clockevents registered\n");

 	return 0;

 error:
 	clocksource_unregister(&clocksource_uv);
 	printk(KERN_INFO "UV RTC clockevents failed rc %d\n", rc);

 	return rc;
 }
 arch_initcall(uv_rtc_setup_clock);
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* SGI RTC clock/timer routines.
	*
	* (C) Copyright 2020 Hewlett Packard Enterprise Development LP
	* Copyright (c) 2009-2013 Silicon Graphics, Inc. All Rights Reserved.
	* Copyright (c) Dimitri Sivanich
	*/
	#include <linux/clockchips.h>
	#include <linux/slab.h>

	#include <asm/uv/uv_mmrs.h>
	#include <asm/uv/uv_hub.h>
	#include <asm/uv/bios.h>
	#include <asm/uv/uv.h>
	#include <asm/apic.h>
	#include <asm/cpu.h>

	#define RTC_NAME "sgi_rtc"

	static u64 uv_read_rtc(struct clocksource *cs);
	static int uv_rtc_next_event(unsigned long, struct clock_event_device *);
	static int uv_rtc_shutdown(struct clock_event_device *evt);

	static struct clocksource clocksource_uv = {
	.name = RTC_NAME,
	.rating = 299,
	.read = uv_read_rtc,
	.mask = (u64)UVH_RTC_REAL_TIME_CLOCK_MASK,
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	};

	static struct clock_event_device clock_event_device_uv = {
	.name = RTC_NAME,
	.features = CLOCK_EVT_FEAT_ONESHOT,
	.shift = 20,
	.rating = 400,
	.irq = -1,
	.set_next_event = uv_rtc_next_event,
	.set_state_shutdown = uv_rtc_shutdown,
	.event_handler = NULL,
	};

	static DEFINE_PER_CPU(struct clock_event_device, cpu_ced);

	/* There is one of these allocated per node */
	struct uv_rtc_timer_head {
	spinlock_t lock;
	/* next cpu waiting for timer, local node relative: */
	int next_cpu;
	/* number of cpus on this node: */
	int ncpus;
	struct {
	int lcpu; /* systemwide logical cpu number */
	u64 expires; /* next timer expiration for this cpu */
	} cpu[];
	};

	/*
	* Access to uv_rtc_timer_head via blade id.
	*/
	static struct uv_rtc_timer_head **blade_info __read_mostly;

	static int uv_rtc_evt_enable;

	/*
	* Hardware interface routines
	*/

	/* Send IPIs to another node */
	static void uv_rtc_send_IPI(int cpu)
	{
	unsigned long apicid, val;
	int pnode;

	apicid = cpu_physical_id(cpu);
	pnode = uv_apicid_to_pnode(apicid);
	val = (1UL << UVH_IPI_INT_SEND_SHFT) \|
	(apicid << UVH_IPI_INT_APIC_ID_SHFT) \|
	(X86_PLATFORM_IPI_VECTOR << UVH_IPI_INT_VECTOR_SHFT);

	uv_write_global_mmr64(pnode, UVH_IPI_INT, val);
	}

	/* Check for an RTC interrupt pending */
	static int uv_intr_pending(int pnode)
	{
	return uv_read_global_mmr64(pnode, UVH_EVENT_OCCURRED2) &
	UVH_EVENT_OCCURRED2_RTC_1_MASK;
	}

	/* Setup interrupt and return non-zero if early expiration occurred. */
	static int uv_setup_intr(int cpu, u64 expires)
	{
	u64 val;
	unsigned long apicid = cpu_physical_id(cpu);
	int pnode = uv_cpu_to_pnode(cpu);

	uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG,
	UVH_RTC1_INT_CONFIG_M_MASK);
	uv_write_global_mmr64(pnode, UVH_INT_CMPB, -1L);

	uv_write_global_mmr64(pnode, UVH_EVENT_OCCURRED2_ALIAS,
	UVH_EVENT_OCCURRED2_RTC_1_MASK);

	val = (X86_PLATFORM_IPI_VECTOR << UVH_RTC1_INT_CONFIG_VECTOR_SHFT) \|
	((u64)apicid << UVH_RTC1_INT_CONFIG_APIC_ID_SHFT);

	/* Set configuration */
	uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG, val);
	/* Initialize comparator value */
	uv_write_global_mmr64(pnode, UVH_INT_CMPB, expires);

	if (uv_read_rtc(NULL) <= expires)
	return 0;

	return !uv_intr_pending(pnode);
	}

	/*
	* Per-cpu timer tracking routines
	*/

	static __init void uv_rtc_deallocate_timers(void)
	{
	int bid;

	for_each_possible_blade(bid) {
	kfree(blade_info[bid]);
	}
	kfree(blade_info);
	}

	/* Allocate per-node list of cpu timer expiration times. */
	static __init int uv_rtc_allocate_timers(void)
	{
	int cpu;

	blade_info = kcalloc(uv_possible_blades, sizeof(void *), GFP_KERNEL);
	if (!blade_info)
	return -ENOMEM;

	for_each_present_cpu(cpu) {
	int nid = cpu_to_node(cpu);
	int bid = uv_cpu_to_blade_id(cpu);
	int bcpu = uv_cpu_blade_processor_id(cpu);
	struct uv_rtc_timer_head *head = blade_info[bid];

	if (!head) {
	head = kmalloc_node(struct_size(head, cpu,
	uv_blade_nr_possible_cpus(bid)),
	GFP_KERNEL, nid);
	if (!head) {
	uv_rtc_deallocate_timers();
	return -ENOMEM;
	}
	spin_lock_init(&head->lock);
	head->ncpus = uv_blade_nr_possible_cpus(bid);
	head->next_cpu = -1;
	blade_info[bid] = head;
	}

	head->cpu[bcpu].lcpu = cpu;
	head->cpu[bcpu].expires = ULLONG_MAX;
	}

	return 0;
	}

	/* Find and set the next expiring timer. */
	static void uv_rtc_find_next_timer(struct uv_rtc_timer_head *head, int pnode)
	{
	u64 lowest = ULLONG_MAX;
	int c, bcpu = -1;

	head->next_cpu = -1;
	for (c = 0; c < head->ncpus; c++) {
	u64 exp = head->cpu[c].expires;
	if (exp < lowest) {
	bcpu = c;
	lowest = exp;
	}
	}
	if (bcpu >= 0) {
	head->next_cpu = bcpu;
	c = head->cpu[bcpu].lcpu;
	if (uv_setup_intr(c, lowest))
	/* If we didn't set it up in time, trigger */
	uv_rtc_send_IPI(c);
	} else {
	uv_write_global_mmr64(pnode, UVH_RTC1_INT_CONFIG,
	UVH_RTC1_INT_CONFIG_M_MASK);
	}
	}

	/*
	* Set expiration time for current cpu.
	*
	* Returns 1 if we missed the expiration time.
	*/
	static int uv_rtc_set_timer(int cpu, u64 expires)
	{
	int pnode = uv_cpu_to_pnode(cpu);
	int bid = uv_cpu_to_blade_id(cpu);
	struct uv_rtc_timer_head *head = blade_info[bid];
	int bcpu = uv_cpu_blade_processor_id(cpu);
	u64 *t = &head->cpu[bcpu].expires;
	unsigned long flags;
	int next_cpu;

	spin_lock_irqsave(&head->lock, flags);

	next_cpu = head->next_cpu;
	*t = expires;

	/* Will this one be next to go off? */
	if (next_cpu < 0 \|\| bcpu == next_cpu \|\|
	expires < head->cpu[next_cpu].expires) {
	head->next_cpu = bcpu;
	if (uv_setup_intr(cpu, expires)) {
	*t = ULLONG_MAX;
	uv_rtc_find_next_timer(head, pnode);
	spin_unlock_irqrestore(&head->lock, flags);
	return -ETIME;
	}
	}

	spin_unlock_irqrestore(&head->lock, flags);
	return 0;
	}

	/*
	* Unset expiration time for current cpu.
	*
	* Returns 1 if this timer was pending.
	*/
	static int uv_rtc_unset_timer(int cpu, int force)
	{
	int pnode = uv_cpu_to_pnode(cpu);
	int bid = uv_cpu_to_blade_id(cpu);
	struct uv_rtc_timer_head *head = blade_info[bid];
	int bcpu = uv_cpu_blade_processor_id(cpu);
	u64 *t = &head->cpu[bcpu].expires;
	unsigned long flags;
	int rc = 0;

	spin_lock_irqsave(&head->lock, flags);

	if ((head->next_cpu == bcpu && uv_read_rtc(NULL) >= *t) \|\| force)
	rc = 1;

	if (rc) {
	*t = ULLONG_MAX;
	/* Was the hardware setup for this timer? */
	if (head->next_cpu == bcpu)
	uv_rtc_find_next_timer(head, pnode);
	}

	spin_unlock_irqrestore(&head->lock, flags);

	return rc;
	}


	/*
	* Kernel interface routines.
	*/

	/*
	* Read the RTC.
	*
	* Starting with HUB rev 2.0, the UV RTC register is replicated across all
	* cachelines of it's own page. This allows faster simultaneous reads
	* from a given socket.
	*/
	static u64 uv_read_rtc(struct clocksource *cs)
	{
	unsigned long offset;

	if (uv_get_min_hub_revision_id() == 1)
	offset = 0;
	else
	offset = (uv_blade_processor_id() * L1_CACHE_BYTES) % PAGE_SIZE;

	return (u64)uv_read_local_mmr(UVH_RTC \| offset);
	}

	/*
	* Program the next event, relative to now
	*/
	static int uv_rtc_next_event(unsigned long delta,
	struct clock_event_device *ced)
	{
	int ced_cpu = cpumask_first(ced->cpumask);

	return uv_rtc_set_timer(ced_cpu, delta + uv_read_rtc(NULL));
	}

	/*
	* Shutdown the RTC timer
	*/
	static int uv_rtc_shutdown(struct clock_event_device *evt)
	{
	int ced_cpu = cpumask_first(evt->cpumask);

	uv_rtc_unset_timer(ced_cpu, 1);
	return 0;
	}

	static void uv_rtc_interrupt(void)
	{
	int cpu = smp_processor_id();
	struct clock_event_device *ced = &per_cpu(cpu_ced, cpu);

	if (!ced \|\| !ced->event_handler)
	return;

	if (uv_rtc_unset_timer(cpu, 0) != 1)
	return;

	ced->event_handler(ced);
	}

	static int __init uv_enable_evt_rtc(char *str)
	{
	uv_rtc_evt_enable = 1;

	return 1;
	}
	__setup("uvrtcevt", uv_enable_evt_rtc);

	static __init void uv_rtc_register_clockevents(struct work_struct *dummy)
	{
	struct clock_event_device *ced = this_cpu_ptr(&cpu_ced);

	*ced = clock_event_device_uv;
	ced->cpumask = cpumask_of(smp_processor_id());
	clockevents_register_device(ced);
	}

	static __init int uv_rtc_setup_clock(void)
	{
	int rc;

	if (!is_uv_system())
	return -ENODEV;

	rc = clocksource_register_hz(&clocksource_uv, sn_rtc_cycles_per_second);
	if (rc)
	printk(KERN_INFO "UV RTC clocksource failed rc %d\n", rc);
	else
	printk(KERN_INFO "UV RTC clocksource registered freq %lu MHz\n",
	sn_rtc_cycles_per_second/(unsigned long)1E6);

	if (rc \|\| !uv_rtc_evt_enable \|\| x86_platform_ipi_callback)
	return rc;

	/* Setup and register clockevents */
	rc = uv_rtc_allocate_timers();
	if (rc)
	goto error;

	x86_platform_ipi_callback = uv_rtc_interrupt;

	clock_event_device_uv.mult = div_sc(sn_rtc_cycles_per_second,
	NSEC_PER_SEC, clock_event_device_uv.shift);

	clock_event_device_uv.min_delta_ns = NSEC_PER_SEC /
	sn_rtc_cycles_per_second;
	clock_event_device_uv.min_delta_ticks = 1;

	clock_event_device_uv.max_delta_ns = clocksource_uv.mask *
	(NSEC_PER_SEC / sn_rtc_cycles_per_second);
	clock_event_device_uv.max_delta_ticks = clocksource_uv.mask;

	rc = schedule_on_each_cpu(uv_rtc_register_clockevents);
	if (rc) {
	x86_platform_ipi_callback = NULL;
	uv_rtc_deallocate_timers();
	goto error;
	}

	printk(KERN_INFO "UV RTC clockevents registered\n");

	return 0;

	error:
	clocksource_unregister(&clocksource_uv);
	printk(KERN_INFO "UV RTC clockevents failed rc %d\n", rc);

	return rc;
	}
	arch_initcall(uv_rtc_setup_clock);