1 files changed, 535 insertions, 0 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
new file mode 100644
index 0000000..7603c05
--- /dev/null
+++ b/arch/x86/kernel/tsc.c
@@ -0,0 +1,535 @@
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/timer.h>
+#include <linux/acpi_pmtmr.h>
+#include <linux/cpufreq.h>
+#include <linux/dmi.h>
+#include <linux/delay.h>
+#include <linux/clocksource.h>
+#include <linux/percpu.h>
+
+#include <asm/hpet.h>
+#include <asm/timer.h>
+#include <asm/vgtod.h>
+#include <asm/time.h>
+#include <asm/delay.h>
+
+unsigned int cpu_khz;           /* TSC clocks / usec, not used here */
+EXPORT_SYMBOL(cpu_khz);
+unsigned int tsc_khz;
+EXPORT_SYMBOL(tsc_khz);
+
+/*
+ * TSC can be unstable due to cpufreq or due to unsynced TSCs
+ */
+static int tsc_unstable;
+
+/* 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;
+
+/*
+ * Scheduler clock - returns current time in nanosec units.
+ */
+u64 native_sched_clock(void)
+{
+	u64 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
+
+int check_tsc_unstable(void)
+{
+	return tsc_unstable;
+}
+EXPORT_SYMBOL_GPL(check_tsc_unstable);
+
+#ifdef CONFIG_X86_TSC
+int __init notsc_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
+ */
+int __init notsc_setup(char *str)
+{
+	setup_clear_cpu_cap(X86_FEATURE_TSC);
+	return 1;
+}
+#endif
+
+__setup("notsc", notsc_setup);
+
+#define MAX_RETRIES     5
+#define SMI_TRESHOLD    50000
+
+/*
+ * Read TSC and the reference counters. Take care of SMI disturbance
+ */
+static u64 __init tsc_read_refs(u64 *pm, u64 *hpet)
+{
+	u64 t1, t2;
+	int i;
+
+	for (i = 0; i < MAX_RETRIES; i++) {
+		t1 = get_cycles();
+		if (hpet)
+			*hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
+		else
+			*pm = acpi_pm_read_early();
+		t2 = get_cycles();
+		if ((t2 - t1) < SMI_TRESHOLD)
+			return t2;
+	}
+	return ULLONG_MAX;
+}
+
+/**
+ * native_calibrate_tsc - calibrate the tsc on boot
+ */
+unsigned long native_calibrate_tsc(void)
+{
+	unsigned long flags;
+	u64 tsc1, tsc2, tr1, tr2, delta, pm1, pm2, hpet1, hpet2;
+	int hpet = is_hpet_enabled();
+	unsigned int tsc_khz_val = 0;
+
+	local_irq_save(flags);
+
+	tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL);
+
+	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
+
+	outb(0xb0, 0x43);
+	outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
+	outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
+	tr1 = get_cycles();
+	while ((inb(0x61) & 0x20) == 0);
+	tr2 = get_cycles();
+
+	tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
+
+	local_irq_restore(flags);
+
+	/*
+	 * Preset the result with the raw and inaccurate PIT
+	 * calibration value
+	 */
+	delta = (tr2 - tr1);
+	do_div(delta, 50);
+	tsc_khz_val = delta;
+
+	/* hpet or pmtimer available ? */
+	if (!hpet && !pm1 && !pm2) {
+		printk(KERN_INFO "TSC calibrated against PIT\n");
+		goto out;
+	}
+
+	/* Check, whether the sampling was disturbed by an SMI */
+	if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) {
+		printk(KERN_WARNING "TSC calibration disturbed by SMI, "
+				"using PIT calibration result\n");
+		goto out;
+	}
+
+	tsc2 = (tsc2 - tsc1) * 1000000LL;
+
+	if (hpet) {
+		printk(KERN_INFO "TSC calibrated against HPET\n");
+		if (hpet2 < hpet1)
+			hpet2 += 0x100000000ULL;
+		hpet2 -= hpet1;
+		tsc1 = ((u64)hpet2 * hpet_readl(HPET_PERIOD));
+		do_div(tsc1, 1000000);
+	} else {
+		printk(KERN_INFO "TSC calibrated against PM_TIMER\n");
+		if (pm2 < pm1)
+			pm2 += (u64)ACPI_PM_OVRRUN;
+		pm2 -= pm1;
+		tsc1 = pm2 * 1000000000LL;
+		do_div(tsc1, PMTMR_TICKS_PER_SEC);
+	}
+
+	do_div(tsc2, tsc1);
+	tsc_khz_val = tsc2;
+
+out:
+	return tsc_khz_val;
+}
+
+
+#ifdef CONFIG_X86_32
+/* Only called from the Powernow K7 cpu freq driver */
+int recalibrate_cpu_khz(void)
+{
+#ifndef CONFIG_SMP
+	unsigned long cpu_khz_old = cpu_khz;
+
+	if (cpu_has_tsc) {
+		tsc_khz = calibrate_tsc();
+		cpu_khz = tsc_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);
+
+#endif /* CONFIG_X86_32 */
+
+/* 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;
+
+	sched_clock_idle_wakeup_event(0);
+	local_irq_restore(flags);
+}
+
+#ifdef CONFIG_CPU_FREQ
+
+/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
+ * changes.
+ *
+ * RED-PEN: On SMP we assume all CPUs run with the same frequency.  It's
+ * not that important because current Opteron setups do not support
+ * scaling on SMP anyroads.
+ *
+ * Should fix up last_tsc too. Currently gettimeofday in the
+ * first tick after the change will be slightly wrong.
+ */
+
+static unsigned int  ref_freq;
+static unsigned long loops_per_jiffy_ref;
+static unsigned long tsc_khz_ref;
+
+static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
+				void *data)
+{
+	struct cpufreq_freqs *freq = data;
+	unsigned long *lpj, dummy;
+
+	if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC))
+		return 0;
+
+	lpj = &dummy;
+	if (!(freq->flags & CPUFREQ_CONST_LOOPS))
+#ifdef CONFIG_SMP
+		lpj = &cpu_data(freq->cpu).loops_per_jiffy;
+#else
+	lpj = &boot_cpu_data.loops_per_jiffy;
+#endif
+
+	if (!ref_freq) {
+		ref_freq = freq->old;
+		loops_per_jiffy_ref = *lpj;
+		tsc_khz_ref = tsc_khz;
+	}
+	if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
+			(val == CPUFREQ_POSTCHANGE && freq->old > freq->new) ||
+			(val == CPUFREQ_RESUMECHANGE)) {
+		*lpj = 	cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
+
+		tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
+		if (!(freq->flags & CPUFREQ_CONST_LOOPS))
+			mark_tsc_unstable("cpufreq changes");
+	}
+
+	set_cyc2ns_scale(tsc_khz_ref, freq->cpu);
+
+	return 0;
+}
+
+static struct notifier_block time_cpufreq_notifier_block = {
+	.notifier_call  = time_cpufreq_notifier
+};
+
+static int __init cpufreq_tsc(void)
+{
+	cpufreq_register_notifier(&time_cpufreq_notifier_block,
+				CPUFREQ_TRANSITION_NOTIFIER);
+	return 0;
+}
+
+core_initcall(cpufreq_tsc);
+
+#endif /* CONFIG_CPU_FREQ */
+
+/* clocksource code */
+
+static struct clocksource clocksource_tsc;
+
+/*
+ * We compare the TSC to the cycle_last value in the clocksource
+ * structure to avoid a nasty time-warp. This can be observed in a
+ * very small window right after one CPU updated cycle_last under
+ * xtime/vsyscall_gtod 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 = (cycle_t)get_cycles();
+
+	return ret >= clocksource_tsc.cycle_last ?
+		ret : clocksource_tsc.cycle_last;
+}
+
+#ifdef CONFIG_X86_64
+static cycle_t __vsyscall_fn vread_tsc(void)
+{
+	cycle_t ret = (cycle_t)vget_cycles();
+
+	return ret >= __vsyscall_gtod_data.clock.cycle_last ?
+		ret : __vsyscall_gtod_data.clock.cycle_last;
+}
+#endif
+
+static struct clocksource clocksource_tsc = {
+	.name                   = "tsc",
+	.rating                 = 300,
+	.read                   = read_tsc,
+	.mask                   = CLOCKSOURCE_MASK(64),
+	.shift                  = 22,
+	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
+				  CLOCK_SOURCE_MUST_VERIFY,
+#ifdef CONFIG_X86_64
+	.vread                  = vread_tsc,
+#endif
+};
+
+void mark_tsc_unstable(char *reason)
+{
+	if (!tsc_unstable) {
+		tsc_unstable = 1;
+		printk("Marking TSC unstable due to %s\n", reason);
+		/* Change only the rating, when not registered */
+		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"),
+		},
+	},
+	{}
+};
+
+/*
+ * 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
+
+/*
+ * 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;
+
+#ifdef CONFIG_SMP
+	if (apic_is_clustered_box())
+		return 1;
+#endif
+
+	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;
+}
+
+static void __init init_tsc_clocksource(void)
+{
+	clocksource_tsc.mult = clocksource_khz2mult(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);
+}
+
+void __init tsc_init(void)
+{
+	u64 lpj;
+	int cpu;
+
+	if (!cpu_has_tsc)
+		return;
+
+	tsc_khz = calibrate_tsc();
+	cpu_khz = tsc_khz;
+
+	if (!tsc_khz) {
+		mark_tsc_unstable("could not calculate TSC khz");
+		return;
+	}
+
+#ifdef CONFIG_X86_64
+	if (cpu_has(&boot_cpu_data, X86_FEATURE_CONSTANT_TSC) &&
+			(boot_cpu_data.x86_vendor == X86_VENDOR_AMD))
+		cpu_khz = calibrate_cpu();
+#endif
+
+	lpj = ((u64)tsc_khz * 1000);
+	do_div(lpj, HZ);
+	lpj_fine = lpj;
+
+	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);
+
+	if (tsc_disabled > 0)
+		return;
+
+	/* now allow native_sched_clock() to use rdtsc */
+	tsc_disabled = 0;
+
+	use_tsc_delay();
+	/* Check and install the TSC clocksource */
+	dmi_check_system(bad_tsc_dmi_table);
+
+	if (unsynchronized_tsc())
+		mark_tsc_unstable("TSCs unsynchronized");
+
+	check_geode_tsc_reliable();
+	init_tsc_clocksource();
+}
+