diff options
Diffstat (limited to 'arch/x86_64/kernel/time.c')
| -rw-r--r-- | arch/x86_64/kernel/time.c | 58 |
1 files changed, 55 insertions, 3 deletions
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 811b8f987b5..5f862e216a4 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -43,6 +43,7 @@ #include <asm/apic.h> #include <asm/hpet.h> #include <asm/mpspec.h> +#include <asm/nmi.h> static char *timename = NULL; @@ -249,6 +250,51 @@ static unsigned long get_cmos_time(void) return mktime(year, mon, day, hour, min, sec); } +/* calibrate_cpu is used on systems with fixed rate TSCs to determine + * processor frequency */ +#define TICK_COUNT 100000000 +static unsigned int __init tsc_calibrate_cpu_khz(void) +{ + int tsc_start, tsc_now; + int i, no_ctr_free; + unsigned long evntsel3 = 0, pmc3 = 0, pmc_now = 0; + unsigned long flags; + + for (i = 0; i < 4; i++) + if (avail_to_resrv_perfctr_nmi_bit(i)) + break; + no_ctr_free = (i == 4); + if (no_ctr_free) { + i = 3; + rdmsrl(MSR_K7_EVNTSEL3, evntsel3); + wrmsrl(MSR_K7_EVNTSEL3, 0); + rdmsrl(MSR_K7_PERFCTR3, pmc3); + } else { + reserve_perfctr_nmi(MSR_K7_PERFCTR0 + i); + reserve_evntsel_nmi(MSR_K7_EVNTSEL0 + i); + } + local_irq_save(flags); + /* start meauring cycles, incrementing from 0 */ + wrmsrl(MSR_K7_PERFCTR0 + i, 0); + wrmsrl(MSR_K7_EVNTSEL0 + i, 1 << 22 | 3 << 16 | 0x76); + rdtscl(tsc_start); + do { + rdmsrl(MSR_K7_PERFCTR0 + i, pmc_now); + tsc_now = get_cycles_sync(); + } while ((tsc_now - tsc_start) < TICK_COUNT); + + local_irq_restore(flags); + if (no_ctr_free) { + wrmsrl(MSR_K7_EVNTSEL3, 0); + wrmsrl(MSR_K7_PERFCTR3, pmc3); + wrmsrl(MSR_K7_EVNTSEL3, evntsel3); + } else { + release_perfctr_nmi(MSR_K7_PERFCTR0 + i); + release_evntsel_nmi(MSR_K7_EVNTSEL0 + i); + } + + return pmc_now * tsc_khz / (tsc_now - tsc_start); +} /* * pit_calibrate_tsc() uses the speaker output (channel 2) of @@ -336,14 +382,20 @@ void __init time_init(void) if (hpet_use_timer) { /* set tick_nsec to use the proper rate for HPET */ tick_nsec = TICK_NSEC_HPET; - cpu_khz = hpet_calibrate_tsc(); + tsc_khz = hpet_calibrate_tsc(); timename = "HPET"; } else { pit_init(); - cpu_khz = pit_calibrate_tsc(); + tsc_khz = pit_calibrate_tsc(); timename = "PIT"; } + cpu_khz = tsc_khz; + if (cpu_has(&boot_cpu_data, X86_FEATURE_CONSTANT_TSC) && + boot_cpu_data.x86_vendor == X86_VENDOR_AMD && + boot_cpu_data.x86 == 16) + cpu_khz = tsc_calibrate_cpu_khz(); + if (unsynchronized_tsc()) mark_tsc_unstable(); @@ -352,7 +404,7 @@ void __init time_init(void) else vgetcpu_mode = VGETCPU_LSL; - set_cyc2ns_scale(cpu_khz); + set_cyc2ns_scale(tsc_khz); printk(KERN_INFO "time.c: Detected %d.%03d MHz processor.\n", cpu_khz / 1000, cpu_khz % 1000); init_tsc_clocksource(); |