diff options
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 57 |
1 files changed, 55 insertions, 2 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 652bc214eebf..97a0bcbad100 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -17,6 +17,7 @@ #include <asm/time.h> #include <asm/delay.h> #include <asm/hypervisor.h> +#include <asm/nmi.h> unsigned int __read_mostly cpu_khz; /* TSC clocks / usec, not used here */ EXPORT_SYMBOL(cpu_khz); @@ -852,6 +853,60 @@ static void __init init_tsc_clocksource(void) clocksource_register(&clocksource_tsc); } +#ifdef CONFIG_X86_64 +/* + * calibrate_cpu is used on systems with fixed rate TSCs to determine + * processor frequency + */ +#define TICK_COUNT 100000000 +static unsigned long __init calibrate_cpu(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) { + WARN(1, KERN_WARNING "Warning: AMD perfctrs busy ... " + "cpu_khz value may be incorrect.\n"); + 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 measuring 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(); + } 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); +} +#else +static inline unsigned long calibrate_cpu(void) { return cpu_khz; } +#endif + void __init tsc_init(void) { u64 lpj; @@ -870,11 +925,9 @@ void __init tsc_init(void) 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 printk("Detected %lu.%03lu MHz processor.\n", (unsigned long)cpu_khz / 1000, |