#include <asm/hpet.h>
#include <asm/timex.h>
+#include <asm/timer.h>
+#include <asm/vgtod.h>
static int notsc __initdata = 0;
unsigned int tsc_khz;
EXPORT_SYMBOL(tsc_khz);
-static unsigned int cyc2ns_scale __read_mostly;
+/* 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 inline void set_cyc2ns_scale(unsigned long khz)
+static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu)
{
- cyc2ns_scale = (NSEC_PER_MSEC << NS_SCALE) / khz;
-}
+ unsigned long flags, prev_scale, *scale;
+ unsigned long long tsc_now, ns_now;
-static unsigned long long cycles_2_ns(unsigned long long cyc)
-{
- return (cyc * cyc2ns_scale) >> NS_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);
+
+ prev_scale = *scale;
+ if (cpu_khz)
+ *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz;
+
+ sched_clock_idle_wakeup_event(0);
+ local_irq_restore(flags);
}
-unsigned long long sched_clock(void)
+unsigned long long native_sched_clock(void)
{
unsigned long a = 0;
return cycles_2_ns(a);
}
+/* 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
+
+
static int tsc_unstable;
-inline int check_tsc_unstable(void)
+int check_tsc_unstable(void)
{
return tsc_unstable;
}
+EXPORT_SYMBOL_GPL(check_tsc_unstable);
+
#ifdef CONFIG_CPU_FREQ
/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
struct cpufreq_freqs *freq = data;
unsigned long *lpj, dummy;
- if (cpu_has(&cpu_data[freq->cpu], X86_FEATURE_CONSTANT_TSC))
+ 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;
+ lpj = &cpu_data(freq->cpu).loops_per_jiffy;
#else
lpj = &boot_cpu_data.loops_per_jiffy;
#endif
mark_tsc_unstable("cpufreq changes");
}
- set_cyc2ns_scale(tsc_khz_ref);
+ preempt_disable();
+ set_cyc2ns_scale(tsc_khz_ref, smp_processor_id());
+ preempt_enable();
return 0;
}
int i;
for (i = 0; i < MAX_RETRIES; i++) {
- t1 = get_cycles_sync();
+ t1 = get_cycles();
if (hpet)
*hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
else
*pm = acpi_pm_read_early();
- t2 = get_cycles_sync();
+ t2 = get_cycles();
if ((t2 - t1) < SMI_TRESHOLD)
return t2;
}
void __init tsc_calibrate(void)
{
unsigned long flags, tsc1, tsc2, tr1, tr2, pm1, pm2, hpet1, hpet2;
- int hpet = is_hpet_enabled();
+ int hpet = is_hpet_enabled(), cpu;
local_irq_save(flags);
outb(0xb0, 0x43);
outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
- tr1 = get_cycles_sync();
+ tr1 = get_cycles();
while ((inb(0x61) & 0x20) == 0);
- tr2 = get_cycles_sync();
+ tr2 = get_cycles();
tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
}
tsc_khz = tsc2 / tsc1;
- set_cyc2ns_scale(tsc_khz);
+
+ for_each_possible_cpu(cpu)
+ set_cyc2ns_scale(tsc_khz, cpu);
}
/*
if (apic_is_clustered_box())
return 1;
#endif
- /* Most intel systems have synchronized TSCs except for
- multi node systems */
- if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) {
-#ifdef CONFIG_ACPI
- /* But TSC doesn't tick in C3 so don't use it there */
- if (acpi_gbl_FADT.header.length > 0 &&
- acpi_gbl_FADT.C3latency < 1000)
- return 1;
-#endif
+
+ if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
return 0;
- }
/* Assume multi socket systems are not synchronized */
return num_present_cpus() > 1;
__setup("notsc", notsc_setup);
+static struct clocksource clocksource_tsc;
-/* clock source code: */
+/*
+ * 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_sync();
- return ret;
+ cycle_t ret = (cycle_t)get_cycles();
+
+ return ret >= clocksource_tsc.cycle_last ?
+ ret : clocksource_tsc.cycle_last;
}
static cycle_t __vsyscall_fn vread_tsc(void)
{
- cycle_t ret = (cycle_t)get_cycles_sync();
- return ret;
+ cycle_t ret = (cycle_t)vget_cycles();
+
+ return ret >= __vsyscall_gtod_data.clock.cycle_last ?
+ ret : __vsyscall_gtod_data.clock.cycle_last;
}
static struct clocksource clocksource_tsc = {
git.samba.org / sfrench / cifs-2.6.git / blobdiff