[net-next-2.6.git] / arch / i386 / kernel / tsc.c

/*
 * This code largely moved from arch/i386/kernel/timer/timer_tsc.c
 * which was originally moved from arch/i386/kernel/time.c.
 * See comments there for proper credits.
 */

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

#include "mach_timer.h"

/*
 * 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;

int tsc_disable __cpuinitdata = 0;

#ifdef CONFIG_X86_TSC
static int __init tsc_setup(char *str)
{
	printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
				"cannot disable TSC.\n");
	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)
{
	tsc_disable = 1;

	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;

static inline int check_tsc_unstable(void)
{
	return tsc_unstable;
}

void mark_tsc_unstable(void)
{
	tsc_unstable = 1;
}
EXPORT_SYMBOL_GPL(mark_tsc_unstable);

/* Accellerators 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 percision, 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!"
 */
static unsigned long cyc2ns_scale __read_mostly;

#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */

static inline void set_cyc2ns_scale(unsigned long cpu_khz)
{
	cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
}

static inline unsigned long long cycles_2_ns(unsigned long long cyc)
{
	return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
}

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

	/*
	 * in the NUMA case we dont use the TSC as they are not
	 * synchronized across all CPUs.
	 */
#ifndef CONFIG_NUMA
	if (!cpu_khz || check_tsc_unstable())
#endif
		/* 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);
}

static unsigned long calculate_cpu_khz(void)
{
	unsigned long long start, end;
	unsigned long count;
	u64 delta64;
	int i;
	unsigned long flags;

	local_irq_save(flags);

	/* run 3 times to ensure the cache is warm */
	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)
		goto err;

	delta64 = end - start;

	/* cpu freq too fast: */
	if (delta64 > (1ULL<<32))
		goto err;

	/* cpu freq too slow: */
	if (delta64 <= CALIBRATE_TIME_MSEC)
		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);

void tsc_init(void)
{
	if (!cpu_has_tsc || tsc_disable)
		return;

	cpu_khz = calculate_cpu_khz();
	tsc_khz = cpu_khz;

	if (!cpu_khz)
		return;

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

	set_cyc2ns_scale(cpu_khz);
	use_tsc_delay();
}

#ifdef CONFIG_CPU_FREQ

static unsigned int cpufreq_delayed_issched = 0;
static unsigned int cpufreq_init = 0;
static struct work_struct cpufreq_delayed_get_work;

static void handle_cpufreq_delayed_get(void *v)
{
	unsigned int cpu;

	for_each_online_cpu(cpu)
		cpufreq_get(cpu);

	cpufreq_delayed_issched = 0;
}

/*
 * if we notice cpufreq oddness, schedule a call to cpufreq_get() as it tries
 * to verify the CPU frequency the timing core thinks the CPU is running
 * at is still correct.
 */
static inline void cpufreq_delayed_get(void)
{
	if (cpufreq_init && !cpufreq_delayed_issched) {
		cpufreq_delayed_issched = 1;
		printk(KERN_DEBUG "Checking if CPU frequency changed.\n");
		schedule_work(&cpufreq_delayed_get_work);
	}
}

/*
 * 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 = 0;
static unsigned long loops_per_jiffy_ref = 0;
static unsigned long cpu_khz_ref = 0;

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

	if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
		write_seqlock_irq(&xtime_lock);

	if (!ref_freq) {
		if (!freq->old){
			ref_freq = freq->new;
			goto end;
		}
		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);
				/*
				 * TSC based sched_clock turns
				 * to junk w/ cpufreq
				 */
				mark_tsc_unstable();
			}
		}
	}
end:
	if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
		write_sequnlock_irq(&xtime_lock);

	return 0;
}

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

static int __init cpufreq_tsc(void)
{
	int ret;

	INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get, NULL);
	ret = cpufreq_register_notifier(&time_cpufreq_notifier_block,
					CPUFREQ_TRANSITION_NOTIFIER);
	if (!ret)
		cpufreq_init = 1;

	return ret;
}

core_initcall(cpufreq_tsc);

#endif

/* clock source code */

static unsigned long current_tsc_khz = 0;
static int tsc_update_callback(void);

static cycle_t read_tsc(void)
{
	cycle_t ret;

	rdtscll(ret);

	return ret;
}

static struct clocksource clocksource_tsc = {
	.name			= "tsc",
	.rating			= 300,
	.read			= read_tsc,
	.mask			= CLOCKSOURCE_MASK(64),
	.mult			= 0, /* to be set */
	.shift			= 22,
	.update_callback	= tsc_update_callback,
	.is_continuous		= 1,
};

static int tsc_update_callback(void)
{
	int change = 0;

	/* check to see if we should switch to the safe clocksource: */
	if (clocksource_tsc.rating != 50 && check_tsc_unstable()) {
		clocksource_tsc.rating = 50;
		clocksource_reselect();
		change = 1;
	}

	/* only update if tsc_khz has changed: */
	if (current_tsc_khz != tsc_khz) {
		current_tsc_khz = tsc_khz;
		clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
							clocksource_tsc.shift);
		change = 1;
	}

	return change;
}

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

#define TSC_FREQ_CHECK_INTERVAL (10*MSEC_PER_SEC) /* 10sec in MS */
static struct timer_list verify_tsc_freq_timer;

/* XXX - Probably should add locking */
static void verify_tsc_freq(unsigned long unused)
{
	static u64 last_tsc;
	static unsigned long last_jiffies;

	u64 now_tsc, interval_tsc;
	unsigned long now_jiffies, interval_jiffies;


	if (check_tsc_unstable())
		return;

	rdtscll(now_tsc);
	now_jiffies = jiffies;

	if (!last_jiffies) {
		goto out;
	}

	interval_jiffies = now_jiffies - last_jiffies;
	interval_tsc = now_tsc - last_tsc;
	interval_tsc *= HZ;
	do_div(interval_tsc, cpu_khz*1000);

	if (interval_tsc < (interval_jiffies * 3 / 4)) {
		printk("TSC appears to be running slowly. "
			"Marking it as unstable\n");
		mark_tsc_unstable();
		return;
	}

out:
	last_tsc = now_tsc;
	last_jiffies = now_jiffies;
	/* set us up to go off on the next interval: */
	mod_timer(&verify_tsc_freq_timer,
		jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL));
}

/*
 * Make an educated guess if the TSC is trustworthy and synchronized
 * over all CPUs.
 */
static __init int unsynchronized_tsc(void)
{
	/*
	 * Intel systems are normally all synchronized.
	 * Exceptions must mark TSC as unstable:
	 */
	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
 		return 0;

	/* assume multi socket systems are not synchronized: */
 	return num_possible_cpus() > 1;
}

static int __init init_tsc_clocksource(void)
{

	if (cpu_has_tsc && tsc_khz && !tsc_disable) {
		/* check blacklist */
		dmi_check_system(bad_tsc_dmi_table);

		if (unsynchronized_tsc()) /* mark unstable if unsynced */
			mark_tsc_unstable();
		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 = 50;

		init_timer(&verify_tsc_freq_timer);
		verify_tsc_freq_timer.function = verify_tsc_freq;
		verify_tsc_freq_timer.expires =
			jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL);
		add_timer(&verify_tsc_freq_timer);

		return clocksource_register(&clocksource_tsc);
	}

	return 0;
}

module_init(init_tsc_clocksource);
Commit	Line	Data
539eb11e JS	1	/*
	2	* This code largely moved from arch/i386/kernel/timer/timer_tsc.c
	3	* which was originally moved from arch/i386/kernel/time.c.
	4	* See comments there for proper credits.
	5	*/
	6
5d0cf410	7	#include <linux/clocksource.h>
539eb11e JS	8	#include <linux/workqueue.h>
	9	#include <linux/cpufreq.h>
	10	#include <linux/jiffies.h>
	11	#include <linux/init.h>
5d0cf410	12	#include <linux/dmi.h>
539eb11e	13
5d0cf410	14	#include <asm/delay.h>
539eb11e	15	#include <asm/tsc.h>
6f84fa2f	16	#include <asm/delay.h>
539eb11e JS	17	#include <asm/io.h>
	18
	19	#include "mach_timer.h"
	20
	21	/*
	22	* On some systems the TSC frequency does not
	23	* change with the cpu frequency. So we need
	24	* an extra value to store the TSC freq
	25	*/
	26	unsigned int tsc_khz;
	27
	28	int tsc_disable __cpuinitdata = 0;
	29
	30	#ifdef CONFIG_X86_TSC
	31	static int __init tsc_setup(char *str)
	32	{
	33	printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
	34	"cannot disable TSC.\n");
	35	return 1;
	36	}
	37	#else
	38	/*
	39	* disable flag for tsc. Takes effect by clearing the TSC cpu flag
	40	* in cpu/common.c
	41	*/
	42	static int __init tsc_setup(char *str)
	43	{
	44	tsc_disable = 1;
	45
	46	return 1;
	47	}
	48	#endif
	49
	50	__setup("notsc", tsc_setup);
	51
539eb11e JS	52	/*
	53	* code to mark and check if the TSC is unstable
	54	* due to cpufreq or due to unsynced TSCs
	55	*/
	56	static int tsc_unstable;
	57
	58	static inline int check_tsc_unstable(void)
	59	{
	60	return tsc_unstable;
	61	}
	62
	63	void mark_tsc_unstable(void)
	64	{
	65	tsc_unstable = 1;
	66	}
	67	EXPORT_SYMBOL_GPL(mark_tsc_unstable);
	68
	69	/* Accellerators for sched_clock()
	70	* convert from cycles(64bits) => nanoseconds (64bits)
	71	* basic equation:
	72	* ns = cycles / (freq / ns_per_sec)
	73	* ns = cycles * (ns_per_sec / freq)
	74	* ns = cycles * (10^9 / (cpu_khz * 10^3))
	75	* ns = cycles * (10^6 / cpu_khz)
	76	*
	77	* Then we use scaling math (suggested by george@mvista.com) to get:
	78	* ns = cycles * (10^6 * SC / cpu_khz) / SC
	79	* ns = cycles * cyc2ns_scale / SC
	80	*
	81	* And since SC is a constant power of two, we can convert the div
	82	* into a shift.
	83	*
	84	* We can use khz divisor instead of mhz to keep a better percision, since
	85	* cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits.
	86	* (mathieu.desnoyers@polymtl.ca)
	87	*
	88	* -johnstul@us.ibm.com "math is hard, lets go shopping!"
	89	*/
	90	static unsigned long cyc2ns_scale __read_mostly;
	91
	92	#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */
	93
	94	static inline void set_cyc2ns_scale(unsigned long cpu_khz)
	95	{
	96	cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz;
	97	}
	98
	99	static inline unsigned long long cycles_2_ns(unsigned long long cyc)
	100	{
	101	return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
	102	}
	103
	104	/*
	105	* Scheduler clock - returns current time in nanosec units.
	106	*/
	107	unsigned long long sched_clock(void)
	108	{
	109	unsigned long long this_offset;
	110
	111	/*
	112	* in the NUMA case we dont use the TSC as they are not
	113	* synchronized across all CPUs.
	114	*/
	115	#ifndef CONFIG_NUMA
116	if (!cpu_khz \|\| check_tsc_unstable())
117	#endif
118	/* no locking but a rare wrong value is not a big deal */
119	return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
120
121	/* read the Time Stamp Counter: */
122	rdtscll(this_offset);
123
124	/* return the value in ns */
125	return cycles_2_ns(this_offset);
126	}
127
128	static unsigned long calculate_cpu_khz(void)
129	{
130	unsigned long long start, end;
131	unsigned long count;
132	u64 delta64;
133	int i;
134	unsigned long flags;
135
136	local_irq_save(flags);
137
138	/* run 3 times to ensure the cache is warm */
139	for (i = 0; i < 3; i++) {
140	mach_prepare_counter();
141	rdtscll(start);
142	mach_countup(&count);
143	rdtscll(end);
144	}
145	/*
146	* Error: ECTCNEVERSET
147	* The CTC wasn't reliable: we got a hit on the very first read,
148	* or the CPU was so fast/slow that the quotient wouldn't fit in
149	* 32 bits..
150	*/
151	if (count <= 1)
152	goto err;
153
154	delta64 = end - start;
155
156	/* cpu freq too fast: */
157	if (delta64 > (1ULL<<32))
158	goto err;
159
160	/* cpu freq too slow: */
161	if (delta64 <= CALIBRATE_TIME_MSEC)
162	goto err;
163
164	delta64 += CALIBRATE_TIME_MSEC/2; /* round for do_div */
165	do_div(delta64,CALIBRATE_TIME_MSEC);
166
167	local_irq_restore(flags);
168	return (unsigned long)delta64;
169	err:
170	local_irq_restore(flags);
171	return 0;
172	}
173
174	int recalibrate_cpu_khz(void)
175	{
176	#ifndef CONFIG_SMP
177	unsigned long cpu_khz_old = cpu_khz;
178
179	if (cpu_has_tsc) {
180	cpu_khz = calculate_cpu_khz();
181	tsc_khz = cpu_khz;
182	cpu_data[0].loops_per_jiffy =
183	cpufreq_scale(cpu_data[0].loops_per_jiffy,
184	cpu_khz_old, cpu_khz);
185	return 0;
186	} else
187	return -ENODEV;
188	#else
189	return -ENODEV;
190	#endif
191	}
192
193	EXPORT_SYMBOL(recalibrate_cpu_khz);
194
195	void tsc_init(void)
196	{
197	if (!cpu_has_tsc \|\| tsc_disable)
198	return;
199
200	cpu_khz = calculate_cpu_khz();
201	tsc_khz = cpu_khz;
202
203	if (!cpu_khz)
204	return;
205
206	printk("Detected %lu.%03lu MHz processor.\n",
207	(unsigned long)cpu_khz / 1000,
208	(unsigned long)cpu_khz % 1000);
209
210	set_cyc2ns_scale(cpu_khz);
6f84fa2f	211	use_tsc_delay();
539eb11e JS	212	}
	213
	214	#ifdef CONFIG_CPU_FREQ
	215
	216	static unsigned int cpufreq_delayed_issched = 0;
	217	static unsigned int cpufreq_init = 0;
	218	static struct work_struct cpufreq_delayed_get_work;
	219
	220	static void handle_cpufreq_delayed_get(void *v)
	221	{
	222	unsigned int cpu;
	223
	224	for_each_online_cpu(cpu)
	225	cpufreq_get(cpu);
	226
	227	cpufreq_delayed_issched = 0;
	228	}
	229
	230	/*
	231	* if we notice cpufreq oddness, schedule a call to cpufreq_get() as it tries
	232	* to verify the CPU frequency the timing core thinks the CPU is running
	233	* at is still correct.
	234	*/
	235	static inline void cpufreq_delayed_get(void)
	236	{
	237	if (cpufreq_init && !cpufreq_delayed_issched) {
	238	cpufreq_delayed_issched = 1;
	239	printk(KERN_DEBUG "Checking if CPU frequency changed.\n");
	240	schedule_work(&cpufreq_delayed_get_work);
	241	}
	242	}
	243
	244	/*
	245	* if the CPU frequency is scaled, TSC-based delays will need a different
	246	* loops_per_jiffy value to function properly.
	247	*/
	248	static unsigned int ref_freq = 0;
	249	static unsigned long loops_per_jiffy_ref = 0;
	250	static unsigned long cpu_khz_ref = 0;
	251
	252	static int
	253	time_cpufreq_notifier(struct notifier_block nb, unsigned long val, void data)
	254	{
	255	struct cpufreq_freqs *freq = data;
	256
	257	if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
	258	write_seqlock_irq(&xtime_lock);
	259
	260	if (!ref_freq) {
	261	if (!freq->old){
	262	ref_freq = freq->new;
	263	goto end;
	264	}
	265	ref_freq = freq->old;
	266	loops_per_jiffy_ref = cpu_data[freq->cpu].loops_per_jiffy;
	267	cpu_khz_ref = cpu_khz;
	268	}
	269
	270	if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) \|\|
	271	(val == CPUFREQ_POSTCHANGE && freq->old > freq->new) \|\|
	272	(val == CPUFREQ_RESUMECHANGE)) {
	273	if (!(freq->flags & CPUFREQ_CONST_LOOPS))
	274	cpu_data[freq->cpu].loops_per_jiffy =
	275	cpufreq_scale(loops_per_jiffy_ref,
276	ref_freq, freq->new);
277
278	if (cpu_khz) {
279
280	if (num_online_cpus() == 1)
281	cpu_khz = cpufreq_scale(cpu_khz_ref,
282	ref_freq, freq->new);
283	if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
284	tsc_khz = cpu_khz;
285	set_cyc2ns_scale(cpu_khz);
286	/*
287	* TSC based sched_clock turns
288	* to junk w/ cpufreq
289	*/
290	mark_tsc_unstable();
291	}
292	}
293	}
294	end:
295	if (val != CPUFREQ_RESUMECHANGE && val != CPUFREQ_SUSPENDCHANGE)
296	write_sequnlock_irq(&xtime_lock);
297
298	return 0;
299	}
300
301	static struct notifier_block time_cpufreq_notifier_block = {
302	.notifier_call = time_cpufreq_notifier
303	};
304
305	static int __init cpufreq_tsc(void)
306	{
307	int ret;
308
309	INIT_WORK(&cpufreq_delayed_get_work, handle_cpufreq_delayed_get, NULL);
310	ret = cpufreq_register_notifier(&time_cpufreq_notifier_block,
311	CPUFREQ_TRANSITION_NOTIFIER);
312	if (!ret)
313	cpufreq_init = 1;
314
315	return ret;
316	}
317
318	core_initcall(cpufreq_tsc);
319
320	#endif
5d0cf410 JS	321
	322	/* clock source code */
	323
	324	static unsigned long current_tsc_khz = 0;
	325	static int tsc_update_callback(void);
	326
	327	static cycle_t read_tsc(void)
	328	{
	329	cycle_t ret;
	330
	331	rdtscll(ret);
	332
	333	return ret;
	334	}
	335
	336	static struct clocksource clocksource_tsc = {
	337	.name = "tsc",
	338	.rating = 300,
	339	.read = read_tsc,
7f9f303a	340	.mask = CLOCKSOURCE_MASK(64),
5d0cf410 JS	341	.mult = 0, /* to be set */
	342	.shift = 22,
	343	.update_callback = tsc_update_callback,
	344	.is_continuous = 1,
	345	};
	346
	347	static int tsc_update_callback(void)
	348	{
	349	int change = 0;
	350
	351	/* check to see if we should switch to the safe clocksource: */
	352	if (clocksource_tsc.rating != 50 && check_tsc_unstable()) {
	353	clocksource_tsc.rating = 50;
a2752549	354	clocksource_reselect();
5d0cf410 JS	355	change = 1;
	356	}
	357
	358	/* only update if tsc_khz has changed: */
	359	if (current_tsc_khz != tsc_khz) {
	360	current_tsc_khz = tsc_khz;
	361	clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
	362	clocksource_tsc.shift);
	363	change = 1;
	364	}
	365
	366	return change;
	367	}
	368
	369	static int __init dmi_mark_tsc_unstable(struct dmi_system_id *d)
	370	{
	371	printk(KERN_NOTICE "%s detected: marking TSC unstable.\n",
	372	d->ident);
	373	mark_tsc_unstable();
	374	return 0;
	375	}
	376
	377	/* List of systems that have known TSC problems */
	378	static struct dmi_system_id __initdata bad_tsc_dmi_table[] = {
	379	{
	380	.callback = dmi_mark_tsc_unstable,
	381	.ident = "IBM Thinkpad 380XD",
	382	.matches = {
	383	DMI_MATCH(DMI_BOARD_VENDOR, "IBM"),
	384	DMI_MATCH(DMI_BOARD_NAME, "2635FA0"),
	385	},
	386	},
	387	{}
	388	};
	389
	390	#define TSC_FREQ_CHECK_INTERVAL (10MSEC_PER_SEC) / 10sec in MS */
	391	static struct timer_list verify_tsc_freq_timer;
	392
	393	/* XXX - Probably should add locking */
	394	static void verify_tsc_freq(unsigned long unused)
	395	{
	396	static u64 last_tsc;
	397	static unsigned long last_jiffies;
	398
	399	u64 now_tsc, interval_tsc;
	400	unsigned long now_jiffies, interval_jiffies;
	401
	402
	403	if (check_tsc_unstable())
	404	return;
	405
	406	rdtscll(now_tsc);
	407	now_jiffies = jiffies;
	408
	409	if (!last_jiffies) {
	410	goto out;
	411	}
	412
	413	interval_jiffies = now_jiffies - last_jiffies;
	414	interval_tsc = now_tsc - last_tsc;
	415	interval_tsc *= HZ;
	416	do_div(interval_tsc, cpu_khz*1000);
	417
	418	if (interval_tsc < (interval_jiffies * 3 / 4)) {
419	printk("TSC appears to be running slowly. "
420	"Marking it as unstable\n");
421	mark_tsc_unstable();
422	return;
423	}
424
425	out:
426	last_tsc = now_tsc;
427	last_jiffies = now_jiffies;
428	/* set us up to go off on the next interval: */
429	mod_timer(&verify_tsc_freq_timer,
430	jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL));
431	}
432
433	/*
434	* Make an educated guess if the TSC is trustworthy and synchronized
435	* over all CPUs.
436	*/
437	static __init int unsynchronized_tsc(void)
438	{
439	/*
440	* Intel systems are normally all synchronized.
441	* Exceptions must mark TSC as unstable:
442	*/
443	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
444	return 0;
445
446	/* assume multi socket systems are not synchronized: */
447	return num_possible_cpus() > 1;
448	}
449
450	static int __init init_tsc_clocksource(void)
451	{
452
453	if (cpu_has_tsc && tsc_khz && !tsc_disable) {
454	/* check blacklist */
455	dmi_check_system(bad_tsc_dmi_table);
456
457	if (unsynchronized_tsc()) /* mark unstable if unsynced */
458	mark_tsc_unstable();
459	current_tsc_khz = tsc_khz;
460	clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
461	clocksource_tsc.shift);
462	/* lower the rating if we already know its unstable: */
463	if (check_tsc_unstable())
464	clocksource_tsc.rating = 50;
465
466	init_timer(&verify_tsc_freq_timer);
467	verify_tsc_freq_timer.function = verify_tsc_freq;
468	verify_tsc_freq_timer.expires =
469	jiffies + msecs_to_jiffies(TSC_FREQ_CHECK_INTERVAL);
470	add_timer(&verify_tsc_freq_timer);
471
a2752549	472	return clocksource_register(&clocksource_tsc);
5d0cf410 JS	473	}
	474
	475	return 0;
	476	}
	477
	478	module_init(init_tsc_clocksource);