diff options
Diffstat (limited to 'arch/x86_64/kernel/tsc_64.c')
| -rw-r--r-- | arch/x86_64/kernel/tsc_64.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/arch/x86_64/kernel/tsc_64.c b/arch/x86_64/kernel/tsc_64.c new file mode 100644 index 00000000000..2a59bde663f --- /dev/null +++ b/arch/x86_64/kernel/tsc_64.c @@ -0,0 +1,207 @@ +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/interrupt.h> +#include <linux/init.h> +#include <linux/clocksource.h> +#include <linux/time.h> +#include <linux/acpi.h> +#include <linux/cpufreq.h> + +#include <asm/timex.h> + +static int notsc __initdata = 0; + +unsigned int cpu_khz; /* TSC clocks / usec, not used here */ +EXPORT_SYMBOL(cpu_khz); +unsigned int tsc_khz; +EXPORT_SYMBOL(tsc_khz); + +static unsigned int cyc2ns_scale __read_mostly; + +void set_cyc2ns_scale(unsigned long khz) +{ + cyc2ns_scale = (NSEC_PER_MSEC << NS_SCALE) / khz; +} + +static unsigned long long cycles_2_ns(unsigned long long cyc) +{ + return (cyc * cyc2ns_scale) >> NS_SCALE; +} + +unsigned long long sched_clock(void) +{ + unsigned long a = 0; + + /* Could do CPU core sync here. Opteron can execute rdtsc speculatively, + * which means it is not completely exact and may not be monotonous + * between CPUs. But the errors should be too small to matter for + * scheduling purposes. + */ + + rdtscll(a); + return cycles_2_ns(a); +} + +static int tsc_unstable; + +inline int check_tsc_unstable(void) +{ + return tsc_unstable; +} +#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); + + 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 + +/* + * Make an educated guess if the TSC is trustworthy and synchronized + * over all CPUs. + */ +__cpuinit int unsynchronized_tsc(void) +{ + if (tsc_unstable) + return 1; + +#ifdef CONFIG_SMP + 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 + return 0; + } + + /* Assume multi socket systems are not synchronized */ + return num_present_cpus() > 1; +} + +int __init notsc_setup(char *s) +{ + notsc = 1; + return 1; +} + +__setup("notsc", notsc_setup); + + +/* clock source code: */ +static cycle_t read_tsc(void) +{ + cycle_t ret = (cycle_t)get_cycles_sync(); + return ret; +} + +static cycle_t __vsyscall_fn vread_tsc(void) +{ + cycle_t ret = (cycle_t)get_cycles_sync(); + return ret; +} + +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, + .vread = vread_tsc, +}; + +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); + +void __init init_tsc_clocksource(void) +{ + if (!notsc) { + clocksource_tsc.mult = clocksource_khz2mult(tsc_khz, + clocksource_tsc.shift); + if (check_tsc_unstable()) + clocksource_tsc.rating = 0; + + clocksource_register(&clocksource_tsc); + } +} |