diff options
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 5d0be778fad..e6ee14533c7 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -1,7 +1,11 @@ +#include <linux/kernel.h> #include <linux/sched.h> #include <linux/init.h> #include <linux/module.h> #include <linux/timer.h> +#include <linux/acpi_pmtmr.h> + +#include <asm/hpet.h> unsigned int cpu_khz; /* TSC clocks / usec, not used here */ EXPORT_SYMBOL(cpu_khz); @@ -84,3 +88,130 @@ int __init notsc_setup(char *str) #endif __setup("notsc", notsc_setup); + +#define MAX_RETRIES 5 +#define SMI_TRESHOLD 50000 + +/* + * Read TSC and the reference counters. Take care of SMI disturbance + */ +static u64 __init tsc_read_refs(u64 *pm, u64 *hpet) +{ + u64 t1, t2; + int i; + + for (i = 0; i < MAX_RETRIES; i++) { + t1 = get_cycles(); + if (hpet) + *hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; + else + *pm = acpi_pm_read_early(); + t2 = get_cycles(); + if ((t2 - t1) < SMI_TRESHOLD) + return t2; + } + return ULLONG_MAX; +} + +/** + * tsc_calibrate - calibrate the tsc on boot + */ +static unsigned int __init tsc_calibrate(void) +{ + unsigned long flags; + u64 tsc1, tsc2, tr1, tr2, delta, pm1, pm2, hpet1, hpet2; + int hpet = is_hpet_enabled(); + unsigned int tsc_khz_val = 0; + + local_irq_save(flags); + + tsc1 = tsc_read_refs(&pm1, hpet ? &hpet1 : NULL); + + outb((inb(0x61) & ~0x02) | 0x01, 0x61); + + outb(0xb0, 0x43); + outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42); + outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42); + tr1 = get_cycles(); + while ((inb(0x61) & 0x20) == 0); + tr2 = get_cycles(); + + tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL); + + local_irq_restore(flags); + + /* + * Preset the result with the raw and inaccurate PIT + * calibration value + */ + delta = (tr2 - tr1); + do_div(delta, 50); + tsc_khz_val = delta; + + /* hpet or pmtimer available ? */ + if (!hpet && !pm1 && !pm2) { + printk(KERN_INFO "TSC calibrated against PIT\n"); + goto out; + } + + /* Check, whether the sampling was disturbed by an SMI */ + if (tsc1 == ULLONG_MAX || tsc2 == ULLONG_MAX) { + printk(KERN_WARNING "TSC calibration disturbed by SMI, " + "using PIT calibration result\n"); + goto out; + } + + tsc2 = (tsc2 - tsc1) * 1000000LL; + + if (hpet) { + printk(KERN_INFO "TSC calibrated against HPET\n"); + if (hpet2 < hpet1) + hpet2 += 0x100000000ULL; + hpet2 -= hpet1; + tsc1 = ((u64)hpet2 * hpet_readl(HPET_PERIOD)); + do_div(tsc1, 1000000); + } else { + printk(KERN_INFO "TSC calibrated against PM_TIMER\n"); + if (pm2 < pm1) + pm2 += (u64)ACPI_PM_OVRRUN; + pm2 -= pm1; + tsc1 = pm2 * 1000000000LL; + do_div(tsc1, PMTMR_TICKS_PER_SEC); + } + + do_div(tsc2, tsc1); + tsc_khz_val = tsc2; + +out: + return tsc_khz_val; +} + +unsigned long native_calculate_cpu_khz(void) +{ + return tsc_calibrate(); +} + +#ifdef CONFIG_X86_32 +/* Only called from the Powernow K7 cpu freq driver */ +int recalibrate_cpu_khz(void) +{ +#ifndef CONFIG_SMP + unsigned long cpu_khz_old = cpu_khz; + + if (cpu_has_tsc) { + cpu_khz = calculate_cpu_khz(); + tsc_khz = cpu_khz; + cpu_data(0).loops_per_jiffy = + cpufreq_scale(cpu_data(0).loops_per_jiffy, + cpu_khz_old, cpu_khz); + return 0; + } else + return -ENODEV; +#else + return -ENODEV; +#endif +} + +EXPORT_SYMBOL(recalibrate_cpu_khz); + +#endif /* CONFIG_X86_32 */ |