diff options
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 212 |
1 files changed, 209 insertions, 3 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 595f78a2221..94c16bdd569 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -5,8 +5,16 @@ #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); @@ -16,12 +24,12 @@ EXPORT_SYMBOL(tsc_khz); /* * TSC can be unstable due to cpufreq or due to unsynced TSCs */ -int tsc_unstable; +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 */ -int tsc_disabled = -1; +static int tsc_disabled = -1; /* * Scheduler clock - returns current time in nanosec units. @@ -241,7 +249,7 @@ EXPORT_SYMBOL(recalibrate_cpu_khz); DEFINE_PER_CPU(unsigned long, cyc2ns); -void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) +static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) { unsigned long long tsc_now, ns_now; unsigned long flags, *scale; @@ -329,3 +337,201 @@ static int __init cpufreq_tsc(void) 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; +} + +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; +} + +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; + + cpu_khz = calculate_cpu_khz(); + tsc_khz = cpu_khz; + + if (!cpu_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(); +} + |