diff options
Diffstat (limited to 'arch/x86/kernel/tsc_64.c')
| -rw-r--r-- | arch/x86/kernel/tsc_64.c | 93 |
1 files changed, 92 insertions, 1 deletions
diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c index 2a59bde663f..9f22e542c37 100644 --- a/arch/x86/kernel/tsc_64.c +++ b/arch/x86/kernel/tsc_64.c @@ -6,7 +6,9 @@ #include <linux/time.h> #include <linux/acpi.h> #include <linux/cpufreq.h> +#include <linux/acpi_pmtmr.h> +#include <asm/hpet.h> #include <asm/timex.h> static int notsc __initdata = 0; @@ -18,7 +20,7 @@ EXPORT_SYMBOL(tsc_khz); static unsigned int cyc2ns_scale __read_mostly; -void set_cyc2ns_scale(unsigned long khz) +static inline void set_cyc2ns_scale(unsigned long khz) { cyc2ns_scale = (NSEC_PER_MSEC << NS_SCALE) / khz; } @@ -118,6 +120,95 @@ core_initcall(cpufreq_tsc); #endif +#define MAX_RETRIES 5 +#define SMI_TRESHOLD 50000 + +/* + * Read TSC and the reference counters. Take care of SMI disturbance + */ +static unsigned long __init tsc_read_refs(unsigned long *pm, + unsigned long *hpet) +{ + unsigned long t1, t2; + int i; + + for (i = 0; i < MAX_RETRIES; i++) { + t1 = get_cycles_sync(); + if (hpet) + *hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; + else + *pm = acpi_pm_read_early(); + t2 = get_cycles_sync(); + if ((t2 - t1) < SMI_TRESHOLD) + return t2; + } + return ULONG_MAX; +} + +/** + * tsc_calibrate - calibrate the tsc on boot + */ +void __init tsc_calibrate(void) +{ + unsigned long flags, tsc1, tsc2, tr1, tr2, pm1, pm2, hpet1, hpet2; + int hpet = is_hpet_enabled(); + + 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_sync(); + while ((inb(0x61) & 0x20) == 0); + tr2 = get_cycles_sync(); + + tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL); + + local_irq_restore(flags); + + /* + * Preset the result with the raw and inaccurate PIT + * calibration value + */ + tsc_khz = (tr2 - tr1) / 50; + + /* hpet or pmtimer available ? */ + if (!hpet && !pm1 && !pm2) { + printk(KERN_INFO "TSC calibrated against PIT\n"); + return; + } + + /* Check, whether the sampling was disturbed by an SMI */ + if (tsc1 == ULONG_MAX || tsc2 == ULONG_MAX) { + printk(KERN_WARNING "TSC calibration disturbed by SMI, " + "using PIT calibration result\n"); + return; + } + + tsc2 = (tsc2 - tsc1) * 1000000L; + + if (hpet) { + printk(KERN_INFO "TSC calibrated against HPET\n"); + if (hpet2 < hpet1) + hpet2 += 0x100000000; + hpet2 -= hpet1; + tsc1 = (hpet2 * hpet_readl(HPET_PERIOD)) / 1000000; + } else { + printk(KERN_INFO "TSC calibrated against PM_TIMER\n"); + if (pm2 < pm1) + pm2 += ACPI_PM_OVRRUN; + pm2 -= pm1; + tsc1 = (pm2 * 1000000000) / PMTMR_TICKS_PER_SEC; + } + + tsc_khz = tsc2 / tsc1; + set_cyc2ns_scale(tsc_khz); +} + /* * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. |