arch/alpha/kernel/time.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/arch/alpha/kernel/time.c
  *
  *  Copyright (C) 1991, 1992, 1995, 1999, 2000  Linus Torvalds
  *
  * This file contains the clocksource time handling.
  * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
  *		"A Kernel Model for Precision Timekeeping" by Dave Mills
  * 1997-01-09    Adrian Sun
  *      use interval timer if CONFIG_RTC=y
  * 1997-10-29    John Bowman (bowman@math.ualberta.ca)
  *      fixed tick loss calculation in timer_interrupt
  *      (round system clock to nearest tick instead of truncating)
  *      fixed algorithm in time_init for getting time from CMOS clock
  * 1999-04-16	Thorsten Kranzkowski (dl8bcu@gmx.net)
  *	fixed algorithm in do_gettimeofday() for calculating the precise time
  *	from processor cycle counter (now taking lost_ticks into account)
  * 2003-06-03	R. Scott Bailey <scott.bailey@eds.com>
  *	Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
  */
 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/param.h>
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/delay.h>
 #include <linux/ioport.h>
 #include <linux/irq.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
 #include <linux/bcd.h>
 #include <linux/profile.h>
 #include <linux/irq_work.h>

 #include <linux/uaccess.h>
 #include <asm/io.h>
 #include <asm/hwrpb.h>

 #include <linux/mc146818rtc.h>
 #include <linux/time.h>
 #include <linux/timex.h>
 #include <linux/clocksource.h>
 #include <linux/clockchips.h>

 #include "proto.h"
 #include "irq_impl.h"

 DEFINE_SPINLOCK(rtc_lock);
 EXPORT_SYMBOL(rtc_lock);

 unsigned long est_cycle_freq;

 #ifdef CONFIG_IRQ_WORK

 DEFINE_PER_CPU(u8, irq_work_pending);

 #define set_irq_work_pending_flag()  __this_cpu_write(irq_work_pending, 1)
 #define test_irq_work_pending()      __this_cpu_read(irq_work_pending)
 #define clear_irq_work_pending()     __this_cpu_write(irq_work_pending, 0)

 void arch_irq_work_raise(void)
 {
 	set_irq_work_pending_flag();
 }

 #else  /* CONFIG_IRQ_WORK */

 #define test_irq_work_pending()      0
 #define clear_irq_work_pending()

 #endif /* CONFIG_IRQ_WORK */


 static inline __u32 rpcc(void)
 {
 	return __builtin_alpha_rpcc();
 }


 /*
  * The RTC as a clock_event_device primitive.
  */

 static DEFINE_PER_CPU(struct clock_event_device, cpu_ce);

 irqreturn_t
 rtc_timer_interrupt(int irq, void *dev)
 {
 	int cpu = smp_processor_id();
 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

 	/* Don't run the hook for UNUSED or SHUTDOWN.  */
 	if (likely(clockevent_state_periodic(ce)))
 		ce->event_handler(ce);

 	if (test_irq_work_pending()) {
 		clear_irq_work_pending();
 		irq_work_run();
 	}

 	return IRQ_HANDLED;
 }

 static int
 rtc_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
 {
 	/* This hook is for oneshot mode, which we don't support.  */
 	return -EINVAL;
 }

 static void __init
 init_rtc_clockevent(void)
 {
 	int cpu = smp_processor_id();
 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

 	*ce = (struct clock_event_device){
 		.name = "rtc",
 		.features = CLOCK_EVT_FEAT_PERIODIC,
 		.rating = 100,
 		.cpumask = cpumask_of(cpu),
 		.set_next_event = rtc_ce_set_next_event,
 	};

 	clockevents_config_and_register(ce, CONFIG_HZ, 0, 0);
 }


 /*
  * The QEMU clock as a clocksource primitive.
  */

 static u64
 qemu_cs_read(struct clocksource *cs)
 {
 	return qemu_get_vmtime();
 }

 static struct clocksource qemu_cs = {
 	.name                   = "qemu",
 	.rating                 = 400,
 	.read                   = qemu_cs_read,
 	.mask                   = CLOCKSOURCE_MASK(64),
 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS,
 	.max_idle_ns		= LONG_MAX
 };


 /*
  * The QEMU alarm as a clock_event_device primitive.
  */

 static int qemu_ce_shutdown(struct clock_event_device *ce)
 {
 	/* The mode member of CE is updated for us in generic code.
 	   Just make sure that the event is disabled.  */
 	qemu_set_alarm_abs(0);
 	return 0;
 }

 static int
 qemu_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
 {
 	qemu_set_alarm_rel(evt);
 	return 0;
 }

 static irqreturn_t
 qemu_timer_interrupt(int irq, void *dev)
 {
 	int cpu = smp_processor_id();
 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

 	ce->event_handler(ce);
 	return IRQ_HANDLED;
 }

 static void __init
 init_qemu_clockevent(void)
 {
 	int cpu = smp_processor_id();
 	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

 	*ce = (struct clock_event_device){
 		.name = "qemu",
 		.features = CLOCK_EVT_FEAT_ONESHOT,
 		.rating = 400,
 		.cpumask = cpumask_of(cpu),
 		.set_state_shutdown = qemu_ce_shutdown,
 		.set_state_oneshot = qemu_ce_shutdown,
 		.tick_resume = qemu_ce_shutdown,
 		.set_next_event = qemu_ce_set_next_event,
 	};

 	clockevents_config_and_register(ce, NSEC_PER_SEC, 1000, LONG_MAX);
 }


 void __init
 common_init_rtc(void)
 {
 	unsigned char x, sel = 0;

 	/* Reset periodic interrupt frequency.  */
 #if CONFIG_HZ == 1024 || CONFIG_HZ == 1200
  	x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
 	/* Test includes known working values on various platforms
 	   where 0x26 is wrong; we refuse to change those. */
  	if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
 		sel = RTC_REF_CLCK_32KHZ + 6;
 	}
 #elif CONFIG_HZ == 256 || CONFIG_HZ == 128 || CONFIG_HZ == 64 || CONFIG_HZ == 32
 	sel = RTC_REF_CLCK_32KHZ + __builtin_ffs(32768 / CONFIG_HZ);
 #else
 # error "Unknown HZ from arch/alpha/Kconfig"
 #endif
 	if (sel) {
 		printk(KERN_INFO "Setting RTC_FREQ to %d Hz (%x)\n",
 		       CONFIG_HZ, sel);
 		CMOS_WRITE(sel, RTC_FREQ_SELECT);
  	}

 	/* Turn on periodic interrupts.  */
 	x = CMOS_READ(RTC_CONTROL);
 	if (!(x & RTC_PIE)) {
 		printk("Turning on RTC interrupts.\n");
 		x |= RTC_PIE;
 		x &= ~(RTC_AIE | RTC_UIE);
 		CMOS_WRITE(x, RTC_CONTROL);
 	}
 	(void) CMOS_READ(RTC_INTR_FLAGS);

 	outb(0x36, 0x43);	/* pit counter 0: system timer */
 	outb(0x00, 0x40);
 	outb(0x00, 0x40);

 	outb(0xb6, 0x43);	/* pit counter 2: speaker */
 	outb(0x31, 0x42);
 	outb(0x13, 0x42);

 	init_rtc_irq(NULL);
 }


 #ifndef CONFIG_ALPHA_WTINT
 /*
  * The RPCC as a clocksource primitive.
  *
  * While we have free-running timecounters running on all CPUs, and we make
  * a half-hearted attempt in init_rtc_rpcc_info to sync the timecounter
  * with the wall clock, that initialization isn't kept up-to-date across
  * different time counters in SMP mode.  Therefore we can only use this
  * method when there's only one CPU enabled.
  *
  * When using the WTINT PALcall, the RPCC may shift to a lower frequency,
  * or stop altogether, while waiting for the interrupt.  Therefore we cannot
  * use this method when WTINT is in use.
  */

 static u64 read_rpcc(struct clocksource *cs)
 {
 	return rpcc();
 }

 static struct clocksource clocksource_rpcc = {
 	.name                   = "rpcc",
 	.rating                 = 300,
 	.read                   = read_rpcc,
 	.mask                   = CLOCKSOURCE_MASK(32),
 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS
 };
 #endif /* ALPHA_WTINT */


 /* Validate a computed cycle counter result against the known bounds for
    the given processor core.  There's too much brokenness in the way of
    timing hardware for any one method to work everywhere.  :-(

    Return 0 if the result cannot be trusted, otherwise return the argument.  */

 static unsigned long __init
 validate_cc_value(unsigned long cc)
 {
 	static struct bounds {
 		unsigned int min, max;
 	} cpu_hz[] __initdata = {
 		[EV3_CPU]    = {   50000000,  200000000 },	/* guess */
 		[EV4_CPU]    = {  100000000,  300000000 },
 		[LCA4_CPU]   = {  100000000,  300000000 },	/* guess */
 		[EV45_CPU]   = {  200000000,  300000000 },
 		[EV5_CPU]    = {  250000000,  433000000 },
 		[EV56_CPU]   = {  333000000,  667000000 },
 		[PCA56_CPU]  = {  400000000,  600000000 },	/* guess */
 		[PCA57_CPU]  = {  500000000,  600000000 },	/* guess */
 		[EV6_CPU]    = {  466000000,  600000000 },
 		[EV67_CPU]   = {  600000000,  750000000 },
 		[EV68AL_CPU] = {  750000000,  940000000 },
 		[EV68CB_CPU] = { 1000000000, 1333333333 },
 		/* None of the following are shipping as of 2001-11-01.  */
 		[EV68CX_CPU] = { 1000000000, 1700000000 },	/* guess */
 		[EV69_CPU]   = { 1000000000, 1700000000 },	/* guess */
 		[EV7_CPU]    = {  800000000, 1400000000 },	/* guess */
 		[EV79_CPU]   = { 1000000000, 2000000000 },	/* guess */
 	};

 	/* Allow for some drift in the crystal.  10MHz is more than enough.  */
 	const unsigned int deviation = 10000000;

 	struct percpu_struct *cpu;
 	unsigned int index;

 	cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);
 	index = cpu->type & 0xffffffff;

 	/* If index out of bounds, no way to validate.  */
 	if (index >= ARRAY_SIZE(cpu_hz))
 		return cc;

 	/* If index contains no data, no way to validate.  */
 	if (cpu_hz[index].max == 0)
 		return cc;

 	if (cc < cpu_hz[index].min - deviation
 	    || cc > cpu_hz[index].max + deviation)
 		return 0;

 	return cc;
 }


 /*
  * Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
  * arch/i386/time.c.
  */

 #define CALIBRATE_LATCH	0xffff
 #define TIMEOUT_COUNT	0x100000

 static unsigned long __init
 calibrate_cc_with_pit(void)
 {
 	int cc, count = 0;

 	/* Set the Gate high, disable speaker */
 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);

 	/*
 	 * Now let's take care of CTC channel 2
 	 *
 	 * Set the Gate high, program CTC channel 2 for mode 0,
 	 * (interrupt on terminal count mode), binary count,
 	 * load 5 * LATCH count, (LSB and MSB) to begin countdown.
 	 */
 	outb(0xb0, 0x43);		/* binary, mode 0, LSB/MSB, Ch 2 */
 	outb(CALIBRATE_LATCH & 0xff, 0x42);	/* LSB of count */
 	outb(CALIBRATE_LATCH >> 8, 0x42);	/* MSB of count */

 	cc = rpcc();
 	do {
 		count++;
 	} while ((inb(0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
 	cc = rpcc() - cc;

 	/* Error: ECTCNEVERSET or ECPUTOOFAST.  */
 	if (count <= 1 || count == TIMEOUT_COUNT)
 		return 0;

 	return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
 }

 /* The Linux interpretation of the CMOS clock register contents:
    When the Update-In-Progress (UIP) flag goes from 1 to 0, the
    RTC registers show the second which has precisely just started.
    Let's hope other operating systems interpret the RTC the same way.  */

 static unsigned long __init
 rpcc_after_update_in_progress(void)
 {
 	do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
 	do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);

 	return rpcc();
 }

 void __init
 time_init(void)
 {
 	unsigned int cc1, cc2;
 	unsigned long cycle_freq, tolerance;
 	long diff;

 	if (alpha_using_qemu) {
 		clocksource_register_hz(&qemu_cs, NSEC_PER_SEC);
 		init_qemu_clockevent();
 		init_rtc_irq(qemu_timer_interrupt);
 		return;
 	}

 	/* Calibrate CPU clock -- attempt #1.  */
 	if (!est_cycle_freq)
 		est_cycle_freq = validate_cc_value(calibrate_cc_with_pit());

 	cc1 = rpcc();

 	/* Calibrate CPU clock -- attempt #2.  */
 	if (!est_cycle_freq) {
 		cc1 = rpcc_after_update_in_progress();
 		cc2 = rpcc_after_update_in_progress();
 		est_cycle_freq = validate_cc_value(cc2 - cc1);
 		cc1 = cc2;
 	}

 	cycle_freq = hwrpb->cycle_freq;
 	if (est_cycle_freq) {
 		/* If the given value is within 250 PPM of what we calculated,
 		   accept it.  Otherwise, use what we found.  */
 		tolerance = cycle_freq / 4000;
 		diff = cycle_freq - est_cycle_freq;
 		if (diff < 0)
 			diff = -diff;
 		if ((unsigned long)diff > tolerance) {
 			cycle_freq = est_cycle_freq;
 			printk("HWRPB cycle frequency bogus.  "
 			       "Estimated %lu Hz\n", cycle_freq);
 		} else {
 			est_cycle_freq = 0;
 		}
 	} else if (! validate_cc_value (cycle_freq)) {
 		printk("HWRPB cycle frequency bogus, "
 		       "and unable to estimate a proper value!\n");
 	}

 	/* See above for restrictions on using clocksource_rpcc.  */
 #ifndef CONFIG_ALPHA_WTINT
 	if (hwrpb->nr_processors == 1)
 		clocksource_register_hz(&clocksource_rpcc, cycle_freq);
 #endif

 	/* Startup the timer source. */
 	alpha_mv.init_rtc();
 	init_rtc_clockevent();
 }

 /* Initialize the clock_event_device for secondary cpus.  */
 #ifdef CONFIG_SMP
 void __init
 init_clockevent(void)
 {
 	if (alpha_using_qemu)
 		init_qemu_clockevent();
 	else
 		init_rtc_clockevent();
 }
 #endif
	// SPDX-License-Identifier: GPL-2.0
	/*
	* linux/arch/alpha/kernel/time.c
	*
	* Copyright (C) 1991, 1992, 1995, 1999, 2000 Linus Torvalds
	*
	* This file contains the clocksource time handling.
	* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
	* "A Kernel Model for Precision Timekeeping" by Dave Mills
	* 1997-01-09 Adrian Sun
	* use interval timer if CONFIG_RTC=y
	* 1997-10-29 John Bowman (bowman@math.ualberta.ca)
	* fixed tick loss calculation in timer_interrupt
	* (round system clock to nearest tick instead of truncating)
	* fixed algorithm in time_init for getting time from CMOS clock
	* 1999-04-16 Thorsten Kranzkowski (dl8bcu@gmx.net)
	* fixed algorithm in do_gettimeofday() for calculating the precise time
	* from processor cycle counter (now taking lost_ticks into account)
	* 2003-06-03 R. Scott Bailey <scott.bailey@eds.com>
	* Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
	*/
	#include <linux/errno.h>
	#include <linux/module.h>
	#include <linux/sched.h>
	#include <linux/kernel.h>
	#include <linux/param.h>
	#include <linux/string.h>
	#include <linux/mm.h>
	#include <linux/delay.h>
	#include <linux/ioport.h>
	#include <linux/irq.h>
	#include <linux/interrupt.h>
	#include <linux/init.h>
	#include <linux/bcd.h>
	#include <linux/profile.h>
	#include <linux/irq_work.h>

	#include <linux/uaccess.h>
	#include <asm/io.h>
	#include <asm/hwrpb.h>

	#include <linux/mc146818rtc.h>
	#include <linux/time.h>
	#include <linux/timex.h>
	#include <linux/clocksource.h>
	#include <linux/clockchips.h>

	#include "proto.h"
	#include "irq_impl.h"

	DEFINE_SPINLOCK(rtc_lock);
	EXPORT_SYMBOL(rtc_lock);

	unsigned long est_cycle_freq;

	#ifdef CONFIG_IRQ_WORK

	DEFINE_PER_CPU(u8, irq_work_pending);

	#define set_irq_work_pending_flag() __this_cpu_write(irq_work_pending, 1)
	#define test_irq_work_pending() __this_cpu_read(irq_work_pending)
	#define clear_irq_work_pending() __this_cpu_write(irq_work_pending, 0)

	void arch_irq_work_raise(void)
	{
	set_irq_work_pending_flag();
	}

	#else /* CONFIG_IRQ_WORK */

	#define test_irq_work_pending() 0
	#define clear_irq_work_pending()

	#endif /* CONFIG_IRQ_WORK */


	static inline __u32 rpcc(void)
	{
	return __builtin_alpha_rpcc();
	}



	/*
	* The RTC as a clock_event_device primitive.
	*/

	static DEFINE_PER_CPU(struct clock_event_device, cpu_ce);

	irqreturn_t
	rtc_timer_interrupt(int irq, void *dev)
	{
	int cpu = smp_processor_id();
	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

	/* Don't run the hook for UNUSED or SHUTDOWN. */
	if (likely(clockevent_state_periodic(ce)))
	ce->event_handler(ce);

	if (test_irq_work_pending()) {
	clear_irq_work_pending();
	irq_work_run();
	}

	return IRQ_HANDLED;
	}

	static int
	rtc_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
	{
	/* This hook is for oneshot mode, which we don't support. */
	return -EINVAL;
	}

	static void __init
	init_rtc_clockevent(void)
	{
	int cpu = smp_processor_id();
	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

	*ce = (struct clock_event_device){
	.name = "rtc",
	.features = CLOCK_EVT_FEAT_PERIODIC,
	.rating = 100,
	.cpumask = cpumask_of(cpu),
	.set_next_event = rtc_ce_set_next_event,
	};

	clockevents_config_and_register(ce, CONFIG_HZ, 0, 0);
	}


	/*
	* The QEMU clock as a clocksource primitive.
	*/

	static u64
	qemu_cs_read(struct clocksource *cs)
	{
	return qemu_get_vmtime();
	}

	static struct clocksource qemu_cs = {
	.name = "qemu",
	.rating = 400,
	.read = qemu_cs_read,
	.mask = CLOCKSOURCE_MASK(64),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	.max_idle_ns = LONG_MAX
	};


	/*
	* The QEMU alarm as a clock_event_device primitive.
	*/

	static int qemu_ce_shutdown(struct clock_event_device *ce)
	{
	/* The mode member of CE is updated for us in generic code.
	Just make sure that the event is disabled. */
	qemu_set_alarm_abs(0);
	return 0;
	}

	static int
	qemu_ce_set_next_event(unsigned long evt, struct clock_event_device *ce)
	{
	qemu_set_alarm_rel(evt);
	return 0;
	}

	static irqreturn_t
	qemu_timer_interrupt(int irq, void *dev)
	{
	int cpu = smp_processor_id();
	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

	ce->event_handler(ce);
	return IRQ_HANDLED;
	}

	static void __init
	init_qemu_clockevent(void)
	{
	int cpu = smp_processor_id();
	struct clock_event_device *ce = &per_cpu(cpu_ce, cpu);

	*ce = (struct clock_event_device){
	.name = "qemu",
	.features = CLOCK_EVT_FEAT_ONESHOT,
	.rating = 400,
	.cpumask = cpumask_of(cpu),
	.set_state_shutdown = qemu_ce_shutdown,
	.set_state_oneshot = qemu_ce_shutdown,
	.tick_resume = qemu_ce_shutdown,
	.set_next_event = qemu_ce_set_next_event,
	};

	clockevents_config_and_register(ce, NSEC_PER_SEC, 1000, LONG_MAX);
	}


	void __init
	common_init_rtc(void)
	{
	unsigned char x, sel = 0;

	/* Reset periodic interrupt frequency. */
	#if CONFIG_HZ == 1024 \|\| CONFIG_HZ == 1200
	x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
	/* Test includes known working values on various platforms
	where 0x26 is wrong; we refuse to change those. */
	if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
	sel = RTC_REF_CLCK_32KHZ + 6;
	}
	#elif CONFIG_HZ == 256 \|\| CONFIG_HZ == 128 \|\| CONFIG_HZ == 64 \|\| CONFIG_HZ == 32
	sel = RTC_REF_CLCK_32KHZ + __builtin_ffs(32768 / CONFIG_HZ);
	#else
	# error "Unknown HZ from arch/alpha/Kconfig"
	#endif
	if (sel) {
	printk(KERN_INFO "Setting RTC_FREQ to %d Hz (%x)\n",
	CONFIG_HZ, sel);
	CMOS_WRITE(sel, RTC_FREQ_SELECT);
	}

	/* Turn on periodic interrupts. */
	x = CMOS_READ(RTC_CONTROL);
	if (!(x & RTC_PIE)) {
	printk("Turning on RTC interrupts.\n");
	x \|= RTC_PIE;
	x &= ~(RTC_AIE \| RTC_UIE);
	CMOS_WRITE(x, RTC_CONTROL);
	}
	(void) CMOS_READ(RTC_INTR_FLAGS);

	outb(0x36, 0x43); /* pit counter 0: system timer */
	outb(0x00, 0x40);
	outb(0x00, 0x40);

	outb(0xb6, 0x43); /* pit counter 2: speaker */
	outb(0x31, 0x42);
	outb(0x13, 0x42);

	init_rtc_irq(NULL);
	}


	#ifndef CONFIG_ALPHA_WTINT
	/*
	* The RPCC as a clocksource primitive.
	*
	* While we have free-running timecounters running on all CPUs, and we make
	* a half-hearted attempt in init_rtc_rpcc_info to sync the timecounter
	* with the wall clock, that initialization isn't kept up-to-date across
	* different time counters in SMP mode. Therefore we can only use this
	* method when there's only one CPU enabled.
	*
	* When using the WTINT PALcall, the RPCC may shift to a lower frequency,
	* or stop altogether, while waiting for the interrupt. Therefore we cannot
	* use this method when WTINT is in use.
	*/

	static u64 read_rpcc(struct clocksource *cs)
	{
	return rpcc();
	}

	static struct clocksource clocksource_rpcc = {
	.name = "rpcc",
	.rating = 300,
	.read = read_rpcc,
	.mask = CLOCKSOURCE_MASK(32),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS
	};
	#endif /* ALPHA_WTINT */


	/* Validate a computed cycle counter result against the known bounds for
	the given processor core. There's too much brokenness in the way of
	timing hardware for any one method to work everywhere. :-(

	Return 0 if the result cannot be trusted, otherwise return the argument. */

	static unsigned long __init
	validate_cc_value(unsigned long cc)
	{
	static struct bounds {
	unsigned int min, max;
	} cpu_hz[] __initdata = {
	[EV3_CPU] = { 50000000, 200000000 }, /* guess */
	[EV4_CPU] = { 100000000, 300000000 },
	[LCA4_CPU] = { 100000000, 300000000 }, /* guess */
	[EV45_CPU] = { 200000000, 300000000 },
	[EV5_CPU] = { 250000000, 433000000 },
	[EV56_CPU] = { 333000000, 667000000 },
	[PCA56_CPU] = { 400000000, 600000000 }, /* guess */
	[PCA57_CPU] = { 500000000, 600000000 }, /* guess */
	[EV6_CPU] = { 466000000, 600000000 },
	[EV67_CPU] = { 600000000, 750000000 },
	[EV68AL_CPU] = { 750000000, 940000000 },
	[EV68CB_CPU] = { 1000000000, 1333333333 },
	/* None of the following are shipping as of 2001-11-01. */
	[EV68CX_CPU] = { 1000000000, 1700000000 }, /* guess */
	[EV69_CPU] = { 1000000000, 1700000000 }, /* guess */
	[EV7_CPU] = { 800000000, 1400000000 }, /* guess */
	[EV79_CPU] = { 1000000000, 2000000000 }, /* guess */
	};

	/* Allow for some drift in the crystal. 10MHz is more than enough. */
	const unsigned int deviation = 10000000;

	struct percpu_struct *cpu;
	unsigned int index;

	cpu = (struct percpu_struct )((char)hwrpb + hwrpb->processor_offset);
	index = cpu->type & 0xffffffff;

	/* If index out of bounds, no way to validate. */
	if (index >= ARRAY_SIZE(cpu_hz))
	return cc;

	/* If index contains no data, no way to validate. */
	if (cpu_hz[index].max == 0)
	return cc;

	if (cc < cpu_hz[index].min - deviation
	\|\| cc > cpu_hz[index].max + deviation)
	return 0;

	return cc;
	}


	/*
	* Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
	* arch/i386/time.c.
	*/

	#define CALIBRATE_LATCH 0xffff
	#define TIMEOUT_COUNT 0x100000

	static unsigned long __init
	calibrate_cc_with_pit(void)
	{
	int cc, count = 0;

	/* Set the Gate high, disable speaker */
	outb((inb(0x61) & ~0x02) \| 0x01, 0x61);

	/*
	* Now let's take care of CTC channel 2
	*
	* Set the Gate high, program CTC channel 2 for mode 0,
	* (interrupt on terminal count mode), binary count,
	* load 5 * LATCH count, (LSB and MSB) to begin countdown.
	*/
	outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
	outb(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
	outb(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */

	cc = rpcc();
	do {
	count++;
	} while ((inb(0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
	cc = rpcc() - cc;

	/* Error: ECTCNEVERSET or ECPUTOOFAST. */
	if (count <= 1 \|\| count == TIMEOUT_COUNT)
	return 0;

	return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
	}

	/* The Linux interpretation of the CMOS clock register contents:
	When the Update-In-Progress (UIP) flag goes from 1 to 0, the
	RTC registers show the second which has precisely just started.
	Let's hope other operating systems interpret the RTC the same way. */

	static unsigned long __init
	rpcc_after_update_in_progress(void)
	{
	do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
	do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);

	return rpcc();
	}

	void __init
	time_init(void)
	{
	unsigned int cc1, cc2;
	unsigned long cycle_freq, tolerance;
	long diff;

	if (alpha_using_qemu) {
	clocksource_register_hz(&qemu_cs, NSEC_PER_SEC);
	init_qemu_clockevent();
	init_rtc_irq(qemu_timer_interrupt);
	return;
	}

	/* Calibrate CPU clock -- attempt #1. */
	if (!est_cycle_freq)
	est_cycle_freq = validate_cc_value(calibrate_cc_with_pit());

	cc1 = rpcc();

	/* Calibrate CPU clock -- attempt #2. */
	if (!est_cycle_freq) {
	cc1 = rpcc_after_update_in_progress();
	cc2 = rpcc_after_update_in_progress();
	est_cycle_freq = validate_cc_value(cc2 - cc1);
	cc1 = cc2;
	}

	cycle_freq = hwrpb->cycle_freq;
	if (est_cycle_freq) {
	/* If the given value is within 250 PPM of what we calculated,
	accept it. Otherwise, use what we found. */
	tolerance = cycle_freq / 4000;
	diff = cycle_freq - est_cycle_freq;
	if (diff < 0)
	diff = -diff;
	if ((unsigned long)diff > tolerance) {
	cycle_freq = est_cycle_freq;
	printk("HWRPB cycle frequency bogus. "
	"Estimated %lu Hz\n", cycle_freq);
	} else {
	est_cycle_freq = 0;
	}
	} else if (! validate_cc_value (cycle_freq)) {
	printk("HWRPB cycle frequency bogus, "
	"and unable to estimate a proper value!\n");
	}

	/* See above for restrictions on using clocksource_rpcc. */
	#ifndef CONFIG_ALPHA_WTINT
	if (hwrpb->nr_processors == 1)
	clocksource_register_hz(&clocksource_rpcc, cycle_freq);
	#endif

	/* Startup the timer source. */
	alpha_mv.init_rtc();
	init_rtc_clockevent();
	}

	/* Initialize the clock_event_device for secondary cpus. */
	#ifdef CONFIG_SMP
	void __init
	init_clockevent(void)
	{
	if (alpha_using_qemu)
	init_qemu_clockevent();
	else
	init_rtc_clockevent();
	}
	#endif