arch/x86/kernel/tsc_32.c - arm/linux-arm64-legacy - Git at Google

 #include <linux/sched.h>
 #include <linux/clocksource.h>
 #include <linux/workqueue.h>
 #include <linux/cpufreq.h>
 #include <linux/jiffies.h>
 #include <linux/init.h>
 #include <linux/dmi.h>
 #include <linux/percpu.h>

 #include <asm/delay.h>
 #include <asm/tsc.h>
 #include <asm/io.h>
 #include <asm/timer.h>

 #include "mach_timer.h"

 /* native_sched_clock() is called before tsc_init(), so
    we must start with the TSC soft disabled to prevent
    erroneous rdtsc usage on !cpu_has_tsc processors */
 static int tsc_disabled = -1;

 /*
  * On some systems the TSC frequency does not
  * change with the cpu frequency. So we need
  * an extra value to store the TSC freq
  */
 unsigned int tsc_khz;
 EXPORT_SYMBOL_GPL(tsc_khz);

 #ifdef CONFIG_X86_TSC
 static int __init tsc_setup(char *str)
 {
 	printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
 	       "cannot disable TSC completely.\n");
 	tsc_disabled = 1;
 	return 1;
 }
 #else
 /*
  * disable flag for tsc. Takes effect by clearing the TSC cpu flag
  * in cpu/common.c
  */
 static int __init tsc_setup(char *str)
 {
 	setup_clear_cpu_cap(X86_FEATURE_TSC);
 	return 1;
 }
 #endif

 __setup("notsc", tsc_setup);

 /*
  * code to mark and check if the TSC is unstable
  * due to cpufreq or due to unsynced TSCs
  */
 static int tsc_unstable;

 int check_tsc_unstable(void)
 {
 	return tsc_unstable;
 }
 EXPORT_SYMBOL_GPL(check_tsc_unstable);

 /* Accelerators for sched_clock()
  * convert from cycles(64bits) => nanoseconds (64bits)
  *  basic equation:
  *		ns = cycles / (freq / ns_per_sec)
  *		ns = cycles * (ns_per_sec / freq)
  *		ns = cycles * (10^9 / (cpu_khz * 10^3))
  *		ns = cycles * (10^6 / cpu_khz)
  *
  *	Then we use scaling math (suggested by george@mvista.com) to get:
  *		ns = cycles * (10^6 * SC / cpu_khz) / SC
  *		ns = cycles * cyc2ns_scale / SC
  *
  *	And since SC is a constant power of two, we can convert the div
  *  into a shift.
  *
  *  We can use khz divisor instead of mhz to keep a better precision, since
  *  cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
  *  (mathieu.desnoyers@polymtl.ca)
  *
  *			-johnstul@us.ibm.com "math is hard, lets go shopping!"
  */

 DEFINE_PER_CPU(unsigned long, cyc2ns);

 static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
 {
 	unsigned long long tsc_now, ns_now;
 	unsigned long flags, *scale;

 	local_irq_save(flags);
 	sched_clock_idle_sleep_event();

 	scale = &per_cpu(cyc2ns, cpu);

 	rdtscll(tsc_now);
 	ns_now = __cycles_2_ns(tsc_now);

 	if (cpu_khz)
 		*scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;

 	/*
 	 * Start smoothly with the new frequency:
 	 */
 	sched_clock_idle_wakeup_event(0);
 	local_irq_restore(flags);
 }

 /*
  * Scheduler clock - returns current time in nanosec units.
  */
 unsigned long long native_sched_clock(void)
 {
 	unsigned long long this_offset;

 	/*
 	 * Fall back to jiffies if there's no TSC available:
 	 * ( But note that we still use it if the TSC is marked
 	 *   unstable. We do this because unlike Time Of Day,
 	 *   the scheduler clock tolerates small errors and it's
 	 *   very important for it to be as fast as the platform
 	 *   can achive it. )
 	 */
 	if (unlikely(tsc_disabled))
 		/* No locking but a rare wrong value is not a big deal: */
 		return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);

 	/* read the Time Stamp Counter: */
 	rdtscll(this_offset);

 	/* return the value in ns */
 	return cycles_2_ns(this_offset);
 }

 /* We need to define a real function for sched_clock, to override the
    weak default version */
 #ifdef CONFIG_PARAVIRT
 unsigned long long sched_clock(void)
 {
 	return paravirt_sched_clock();
 }
 #else
 unsigned long long sched_clock(void)
 	__attribute__((alias("native_sched_clock")));
 #endif

 unsigned long native_calculate_cpu_khz(void)
 {
 	unsigned long long start, end;
 	unsigned long count;
 	u64 delta64 = (u64)ULLONG_MAX;
 	int i;
 	unsigned long flags;

 	local_irq_save(flags);

 	/* run 3 times to ensure the cache is warm and to get an accurate reading */
 	for (i = 0; i < 3; i++) {
 		mach_prepare_counter();
 		rdtscll(start);
 		mach_countup(&count);
 		rdtscll(end);

 		/*
 		 * Error: ECTCNEVERSET
 		 * The CTC wasn't reliable: we got a hit on the very first read,
 		 * or the CPU was so fast/slow that the quotient wouldn't fit in
 		 * 32 bits..
 		 */
 		if (count <= 1)
 			continue;

 		/* cpu freq too slow: */
 		if ((end - start) <= CALIBRATE_TIME_MSEC)
 			continue;

 		/*
 		 * We want the minimum time of all runs in case one of them
 		 * is inaccurate due to SMI or other delay
 		 */
 		delta64 = min(delta64, (end - start));
 	}

 	/* cpu freq too fast (or every run was bad): */
 	if (delta64 > (1ULL<<32))
 		goto err;

 	delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
 	do_div(delta64,CALIBRATE_TIME_MSEC);

 	local_irq_restore(flags);
 	return (unsigned long)delta64;
 err:
 	local_irq_restore(flags);
 	return 0;
 }

 int recalibrate_cpu_khz(void)
 {
 #ifndef CONFIG_SMP
 	unsigned long cpu_khz_old = cpu_khz;

 	if (cpu_has_tsc) {
 		cpu_khz = calculate_cpu_khz();
 		tsc_khz = cpu_khz;
 		cpu_data(0).loops_per_jiffy =
 			cpufreq_scale(cpu_data(0).loops_per_jiffy,
 					cpu_khz_old, cpu_khz);
 		return 0;
 	} else
 		return -ENODEV;
 #else
 	return -ENODEV;
 #endif
 }

 EXPORT_SYMBOL(recalibrate_cpu_khz);

 #ifdef CONFIG_CPU_FREQ

 /*
  * if the CPU frequency is scaled, TSC-based delays will need a different
  * loops_per_jiffy value to function properly.
  */
 static unsigned int ref_freq;
 static unsigned long loops_per_jiffy_ref;
 static unsigned long cpu_khz_ref;

 static int
 time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data)
 {
 	struct cpufreq_freqs *freq = data;

 	if (!ref_freq) {
 		if (!freq->old){
 			ref_freq = freq->new;
 			return 0;
 		}
 		ref_freq = freq->old;
 		loops_per_jiffy_ref = cpu_data(freq->cpu).loops_per_jiffy;
 		cpu_khz_ref = cpu_khz;
 	}

 	if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
 	    (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
 	    (val == CPUFREQ_RESUMECHANGE)) {
 		if (!(freq->flags & CPUFREQ_CONST_LOOPS))
 			cpu_data(freq->cpu).loops_per_jiffy =
 				cpufreq_scale(loops_per_jiffy_ref,
 						ref_freq, freq->new);

 		if (cpu_khz) {

 			if (num_online_cpus() == 1)
 				cpu_khz = cpufreq_scale(cpu_khz_ref,
 						ref_freq, freq->new);
 			if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
 				tsc_khz = cpu_khz;
 				set_cyc2ns_scale(cpu_khz, freq->cpu);
 				/*
 				 * TSC based sched_clock turns
 				 * to junk w/ cpufreq
 				 */
 				mark_tsc_unstable("cpufreq changes");
 			}
 		}
 	}

 	return 0;
 }

 static struct notifier_block time_cpufreq_notifier_block = {
 	.notifier_call	= time_cpufreq_notifier
 };

 static int __init cpufreq_tsc(void)
 {
 	return cpufreq_register_notifier(&time_cpufreq_notifier_block,
 					 CPUFREQ_TRANSITION_NOTIFIER);
 }
 core_initcall(cpufreq_tsc);

 #endif

 /* clock source code */

 static unsigned long current_tsc_khz;
 static struct clocksource clocksource_tsc;

 /*
  * We compare the TSC to the cycle_last value in the clocksource
  * structure to avoid a nasty time-warp issue. This can be observed in
  * a very small window right after one CPU updated cycle_last under
  * xtime lock and the other CPU reads a TSC value which is smaller
  * than the cycle_last reference value due to a TSC which is slighty
  * behind. This delta is nowhere else observable, but in that case it
  * results in a forward time jump in the range of hours due to the
  * unsigned delta calculation of the time keeping core code, which is
  * necessary to support wrapping clocksources like pm timer.
  */
 static cycle_t read_tsc(void)
 {
 	cycle_t ret;

 	rdtscll(ret);

 	return ret >= clocksource_tsc.cycle_last ?
 		ret : clocksource_tsc.cycle_last;
 }

 static struct clocksource clocksource_tsc = {
 	.name			= "tsc",
 	.rating			= 300,
 	.read			= read_tsc,
 	.mask			= CLOCKSOURCE_MASK(64),
 	.mult			= 0, /* to be set */
 	.shift			= 22,
 	.flags			= CLOCK_SOURCE_IS_CONTINUOUS |
 				  CLOCK_SOURCE_MUST_VERIFY,
 };

 void mark_tsc_unstable(char *reason)
 {
 	if (!tsc_unstable) {
 		tsc_unstable = 1;
 		printk("Marking TSC unstable due to: %s.\n", reason);
 		/* Can be called before registration */
 		if (clocksource_tsc.mult)
 			clocksource_change_rating(&clocksource_tsc, 0);
 		else
 			clocksource_tsc.rating = 0;
 	}
 }
 EXPORT_SYMBOL_GPL(mark_tsc_unstable);

 static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
 {
 	printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
 	       d->ident);
 	tsc_unstable = 1;
 	return 0;
 }

 /* List of systems that have known TSC problems */
 static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
 	{
 	 .callback = dmi_mark_tsc_unstable,
 	 .ident = "IBM Thinkpad 380XD",
 	 .matches = {
 		     DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
 		     DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
 		     },
 	 },
 	 {}
 };

 /*
  * Make an educated guess if the TSC is trustworthy and synchronized
  * over all CPUs.
  */
 __cpuinit int unsynchronized_tsc(void)
 {
 	if (!cpu_has_tsc || tsc_unstable)
 		return 1;

 	/* Anything with constant TSC should be synchronized */
 	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
 		return 0;

 	/*
 	 * Intel systems are normally all synchronized.
 	 * Exceptions must mark TSC as unstable:
 	 */
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
 		/* assume multi socket systems are not synchronized: */
 		if (num_possible_cpus() > 1)
 			tsc_unstable = 1;
 	}
 	return tsc_unstable;
 }

 /*
  * Geode_LX - the OLPC CPU has a possibly a very reliable TSC
  */
 #ifdef CONFIG_MGEODE_LX
 /* RTSC counts during suspend */
 #define RTSC_SUSP 0x100

 static void __init check_geode_tsc_reliable(void)
 {
 	unsigned long res_low, res_high;

 	rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
 	if (res_low & RTSC_SUSP)
 		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
 }
 #else
 static inline void check_geode_tsc_reliable(void) { }
 #endif


 void __init tsc_init(void)
 {
 	int cpu;

 	if (!cpu_has_tsc || tsc_disabled > 0)
 		return;

 	cpu_khz = calculate_cpu_khz();
 	tsc_khz = cpu_khz;

 	if (!cpu_khz) {
 		mark_tsc_unstable("could not calculate TSC khz");
 		return;
 	}

 	/* now allow native_sched_clock() to use rdtsc */
 	tsc_disabled = 0;

 	printk("Detected %lu.%03lu MHz processor.\n",
 				(unsigned long)cpu_khz / 1000,
 				(unsigned long)cpu_khz % 1000);

 	/*
 	 * Secondary CPUs do not run through tsc_init(), so set up
 	 * all the scale factors for all CPUs, assuming the same
 	 * speed as the bootup CPU. (cpufreq notifiers will fix this
 	 * up if their speed diverges)
 	 */
 	for_each_possible_cpu(cpu)
 		set_cyc2ns_scale(cpu_khz, cpu);

 	use_tsc_delay();

 	/* Check and install the TSC clocksource */
 	dmi_check_system(bad_tsc_dmi_table);

 	unsynchronized_tsc();
 	check_geode_tsc_reliable();
 	current_tsc_khz = tsc_khz;
 	clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
 							clocksource_tsc.shift);
 	/* lower the rating if we already know its unstable: */
 	if (check_tsc_unstable()) {
 		clocksource_tsc.rating = 0;
 		clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
 	}
 	clocksource_register(&clocksource_tsc);
 }
	#include <linux/sched.h>
	#include <linux/clocksource.h>
	#include <linux/workqueue.h>
	#include <linux/cpufreq.h>
	#include <linux/jiffies.h>
	#include <linux/init.h>
	#include <linux/dmi.h>
	#include <linux/percpu.h>

	#include <asm/delay.h>
	#include <asm/tsc.h>
	#include <asm/io.h>
	#include <asm/timer.h>

	#include "mach_timer.h"

	/* native_sched_clock() is called before tsc_init(), so
	we must start with the TSC soft disabled to prevent
	erroneous rdtsc usage on !cpu_has_tsc processors */
	static int tsc_disabled = -1;

	/*
	* On some systems the TSC frequency does not
	* change with the cpu frequency. So we need
	* an extra value to store the TSC freq
	*/
	unsigned int tsc_khz;
	EXPORT_SYMBOL_GPL(tsc_khz);

	#ifdef CONFIG_X86_TSC
	static int __init tsc_setup(char *str)
	{
	printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
	"cannot disable TSC completely.\n");
	tsc_disabled = 1;
	return 1;
	}
	#else
	/*
	* disable flag for tsc. Takes effect by clearing the TSC cpu flag
	* in cpu/common.c
	*/
	static int __init tsc_setup(char *str)
	{
	setup_clear_cpu_cap(X86_FEATURE_TSC);
	return 1;
	}
	#endif

	__setup("notsc", tsc_setup);

	/*
	* code to mark and check if the TSC is unstable
	* due to cpufreq or due to unsynced TSCs
	*/
	static int tsc_unstable;

	int check_tsc_unstable(void)
	{
	return tsc_unstable;
	}
	EXPORT_SYMBOL_GPL(check_tsc_unstable);

	/* Accelerators for sched_clock()
	* convert from cycles(64bits) => nanoseconds (64bits)
	* basic equation:
	* ns = cycles / (freq / ns_per_sec)
	* ns = cycles * (ns_per_sec / freq)
	* ns = cycles * (10^9 / (cpu_khz * 10^3))
	* ns = cycles * (10^6 / cpu_khz)
	*
	* Then we use scaling math (suggested by george@mvista.com) to get:
	* ns = cycles * (10^6 * SC / cpu_khz) / SC
	* ns = cycles * cyc2ns_scale / SC
	*
	* And since SC is a constant power of two, we can convert the div
	* into a shift.
	*
	* We can use khz divisor instead of mhz to keep a better precision, since
	* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
	* (mathieu.desnoyers@polymtl.ca)
	*
	* -johnstul@us.ibm.com "math is hard, lets go shopping!"
	*/

	DEFINE_PER_CPU(unsigned long, cyc2ns);

	static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
	{
	unsigned long long tsc_now, ns_now;
	unsigned long flags, *scale;

	local_irq_save(flags);
	sched_clock_idle_sleep_event();

	scale = &per_cpu(cyc2ns, cpu);

	rdtscll(tsc_now);
	ns_now = __cycles_2_ns(tsc_now);

	if (cpu_khz)
	*scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;

	/*
	* Start smoothly with the new frequency:
	*/
	sched_clock_idle_wakeup_event(0);
	local_irq_restore(flags);
	}

	/*
	* Scheduler clock - returns current time in nanosec units.
	*/
	unsigned long long native_sched_clock(void)
	{
	unsigned long long this_offset;

	/*
	* Fall back to jiffies if there's no TSC available:
	* ( But note that we still use it if the TSC is marked
	* unstable. We do this because unlike Time Of Day,
	* the scheduler clock tolerates small errors and it's
	* very important for it to be as fast as the platform
	* can achive it. )
	*/
	if (unlikely(tsc_disabled))
	/* No locking but a rare wrong value is not a big deal: */
	return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);

	/* read the Time Stamp Counter: */
	rdtscll(this_offset);

	/* return the value in ns */
	return cycles_2_ns(this_offset);
	}

	/* We need to define a real function for sched_clock, to override the
	weak default version */
	#ifdef CONFIG_PARAVIRT
	unsigned long long sched_clock(void)
	{
	return paravirt_sched_clock();
	}
	#else
	unsigned long long sched_clock(void)
	__attribute__((alias("native_sched_clock")));
	#endif

	unsigned long native_calculate_cpu_khz(void)
	{
	unsigned long long start, end;
	unsigned long count;
	u64 delta64 = (u64)ULLONG_MAX;
	int i;
	unsigned long flags;

	local_irq_save(flags);

	/* run 3 times to ensure the cache is warm and to get an accurate reading */
	for (i = 0; i < 3; i++) {
	mach_prepare_counter();
	rdtscll(start);
	mach_countup(&count);
	rdtscll(end);

	/*
	* Error: ECTCNEVERSET
	* The CTC wasn't reliable: we got a hit on the very first read,
	* or the CPU was so fast/slow that the quotient wouldn't fit in
	* 32 bits..
	*/
	if (count <= 1)
	continue;

	/* cpu freq too slow: */
	if ((end - start) <= CALIBRATE_TIME_MSEC)
	continue;

	/*
	* We want the minimum time of all runs in case one of them
	* is inaccurate due to SMI or other delay
	*/
	delta64 = min(delta64, (end - start));
	}

	/* cpu freq too fast (or every run was bad): */
	if (delta64 > (1ULL<<32))
	goto err;

	delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
	do_div(delta64,CALIBRATE_TIME_MSEC);

	local_irq_restore(flags);
	return (unsigned long)delta64;
	err:
	local_irq_restore(flags);
	return 0;
	}

	int recalibrate_cpu_khz(void)
	{
	#ifndef CONFIG_SMP
	unsigned long cpu_khz_old = cpu_khz;

	if (cpu_has_tsc) {
	cpu_khz = calculate_cpu_khz();
	tsc_khz = cpu_khz;
	cpu_data(0).loops_per_jiffy =
	cpufreq_scale(cpu_data(0).loops_per_jiffy,
	cpu_khz_old, cpu_khz);
	return 0;
	} else
	return -ENODEV;
	#else
	return -ENODEV;
	#endif
	}

	EXPORT_SYMBOL(recalibrate_cpu_khz);

	#ifdef CONFIG_CPU_FREQ

	/*
	* if the CPU frequency is scaled, TSC-based delays will need a different
	* loops_per_jiffy value to function properly.
	*/
	static unsigned int ref_freq;
	static unsigned long loops_per_jiffy_ref;
	static unsigned long cpu_khz_ref;

	static int
	time_cpufreq_notifier(struct notifier_block nb, unsigned long val, void data)
	{
	struct cpufreq_freqs *freq = data;

	if (!ref_freq) {
	if (!freq->old){
	ref_freq = freq->new;
	return 0;
	}
	ref_freq = freq->old;
	loops_per_jiffy_ref = cpu_data(freq->cpu).loops_per_jiffy;
	cpu_khz_ref = cpu_khz;
	}

	if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) \|\|
	(val == CPUFREQ_POSTCHANGE && freq->old > freq->new) \|\|
	(val == CPUFREQ_RESUMECHANGE)) {
	if (!(freq->flags & CPUFREQ_CONST_LOOPS))
	cpu_data(freq->cpu).loops_per_jiffy =
	cpufreq_scale(loops_per_jiffy_ref,
	ref_freq, freq->new);

	if (cpu_khz) {

	if (num_online_cpus() == 1)
	cpu_khz = cpufreq_scale(cpu_khz_ref,
	ref_freq, freq->new);
	if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
	tsc_khz = cpu_khz;
	set_cyc2ns_scale(cpu_khz, freq->cpu);
	/*
	* TSC based sched_clock turns
	* to junk w/ cpufreq
	*/
	mark_tsc_unstable("cpufreq changes");
	}
	}
	}

	return 0;
	}

	static struct notifier_block time_cpufreq_notifier_block = {
	.notifier_call = time_cpufreq_notifier
	};

	static int __init cpufreq_tsc(void)
	{
	return cpufreq_register_notifier(&time_cpufreq_notifier_block,
	CPUFREQ_TRANSITION_NOTIFIER);
	}
	core_initcall(cpufreq_tsc);

	#endif

	/* clock source code */

	static unsigned long current_tsc_khz;
	static struct clocksource clocksource_tsc;

	/*
	* We compare the TSC to the cycle_last value in the clocksource
	* structure to avoid a nasty time-warp issue. This can be observed in
	* a very small window right after one CPU updated cycle_last under
	* xtime lock and the other CPU reads a TSC value which is smaller
	* than the cycle_last reference value due to a TSC which is slighty
	* behind. This delta is nowhere else observable, but in that case it
	* results in a forward time jump in the range of hours due to the
	* unsigned delta calculation of the time keeping core code, which is
	* necessary to support wrapping clocksources like pm timer.
	*/
	static cycle_t read_tsc(void)
	{
	cycle_t ret;

	rdtscll(ret);

	return ret >= clocksource_tsc.cycle_last ?
	ret : clocksource_tsc.cycle_last;
	}

	static struct clocksource clocksource_tsc = {
	.name = "tsc",
	.rating = 300,
	.read = read_tsc,
	.mask = CLOCKSOURCE_MASK(64),
	.mult = 0, /* to be set */
	.shift = 22,
	.flags = CLOCK_SOURCE_IS_CONTINUOUS \|
	CLOCK_SOURCE_MUST_VERIFY,
	};

	void mark_tsc_unstable(char *reason)
	{
	if (!tsc_unstable) {
	tsc_unstable = 1;
	printk("Marking TSC unstable due to: %s.\n", reason);
	/* Can be called before registration */
	if (clocksource_tsc.mult)
	clocksource_change_rating(&clocksource_tsc, 0);
	else
	clocksource_tsc.rating = 0;
	}
	}
	EXPORT_SYMBOL_GPL(mark_tsc_unstable);

	static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d)
	{
	printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
	d->ident);
	tsc_unstable = 1;
	return 0;
	}

	/* List of systems that have known TSC problems */
	static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
	{
	.callback = dmi_mark_tsc_unstable,
	.ident = "IBM Thinkpad 380XD",
	.matches = {
	DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
	DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
	},
	},
	{}
	};

	/*
	* Make an educated guess if the TSC is trustworthy and synchronized
	* over all CPUs.
	*/
	__cpuinit int unsynchronized_tsc(void)
	{
	if (!cpu_has_tsc \|\| tsc_unstable)
	return 1;

	/* Anything with constant TSC should be synchronized */
	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
	return 0;

	/*
	* Intel systems are normally all synchronized.
	* Exceptions must mark TSC as unstable:
	*/
	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
	/* assume multi socket systems are not synchronized: */
	if (num_possible_cpus() > 1)
	tsc_unstable = 1;
	}
	return tsc_unstable;
	}

	/*
	* Geode_LX - the OLPC CPU has a possibly a very reliable TSC
	*/
	#ifdef CONFIG_MGEODE_LX
	/* RTSC counts during suspend */
	#define RTSC_SUSP 0x100

	static void __init check_geode_tsc_reliable(void)
	{
	unsigned long res_low, res_high;

	rdmsr_safe(MSR_GEODE_BUSCONT_CONF0, &res_low, &res_high);
	if (res_low & RTSC_SUSP)
	clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
	}
	#else
	static inline void check_geode_tsc_reliable(void) { }
	#endif


	void __init tsc_init(void)
	{
	int cpu;

	if (!cpu_has_tsc \|\| tsc_disabled > 0)
	return;

	cpu_khz = calculate_cpu_khz();
	tsc_khz = cpu_khz;

	if (!cpu_khz) {
	mark_tsc_unstable("could not calculate TSC khz");
	return;
	}

	/* now allow native_sched_clock() to use rdtsc */
	tsc_disabled = 0;

	printk("Detected %lu.%03lu MHz processor.\n",
	(unsigned long)cpu_khz / 1000,
	(unsigned long)cpu_khz % 1000);

	/*
	* Secondary CPUs do not run through tsc_init(), so set up
	* all the scale factors for all CPUs, assuming the same
	* speed as the bootup CPU. (cpufreq notifiers will fix this
	* up if their speed diverges)
	*/
	for_each_possible_cpu(cpu)
	set_cyc2ns_scale(cpu_khz, cpu);

	use_tsc_delay();

	/* Check and install the TSC clocksource */
	dmi_check_system(bad_tsc_dmi_table);

	unsynchronized_tsc();
	check_geode_tsc_reliable();
	current_tsc_khz = tsc_khz;
	clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
	clocksource_tsc.shift);
	/* lower the rating if we already know its unstable: */
	if (check_tsc_unstable()) {
	clocksource_tsc.rating = 0;
	clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
	}
	clocksource_register(&clocksource_tsc);
	}