diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/hpet_64.c | 49 | ||||
| -rw-r--r-- | arch/x86/kernel/time_64.c | 33 | ||||
| -rw-r--r-- | arch/x86/kernel/tsc_64.c | 90 |
3 files changed, 92 insertions, 80 deletions
diff --git a/arch/x86/kernel/hpet_64.c b/arch/x86/kernel/hpet_64.c index e2d1b912e15..1ebce2ec7ea 100644 --- a/arch/x86/kernel/hpet_64.c +++ b/arch/x86/kernel/hpet_64.c @@ -184,55 +184,6 @@ int hpet_reenable(void) return hpet_timer_stop_set_go(hpet_tick); } -/* - * calibrate_tsc() calibrates the processor TSC in a very simple way, comparing - * it to the HPET timer of known frequency. - */ - -#define TICK_COUNT 100000000 -#define SMI_THRESHOLD 50000 -#define MAX_TRIES 5 - -/* - * Some platforms take periodic SMI interrupts with 5ms duration. Make sure none - * occurs between the reads of the hpet & TSC. - */ -static void __init read_hpet_tsc(int *hpet, int *tsc) -{ - int tsc1, tsc2, hpet1, i; - - for (i = 0; i < MAX_TRIES; i++) { - tsc1 = get_cycles_sync(); - hpet1 = hpet_readl(HPET_COUNTER); - tsc2 = get_cycles_sync(); - if ((tsc2 - tsc1) < SMI_THRESHOLD) - break; - } - *hpet = hpet1; - *tsc = tsc2; -} - -unsigned int __init hpet_calibrate_tsc(void) -{ - int tsc_start, hpet_start; - int tsc_now, hpet_now; - unsigned long flags; - - local_irq_save(flags); - - read_hpet_tsc(&hpet_start, &tsc_start); - - do { - local_irq_disable(); - read_hpet_tsc(&hpet_now, &tsc_now); - local_irq_restore(flags); - } while ((tsc_now - tsc_start) < TICK_COUNT && - (hpet_now - hpet_start) < TICK_COUNT); - - return (tsc_now - tsc_start) * 1000000000L - / ((hpet_now - hpet_start) * hpet_period / 1000); -} - #ifdef CONFIG_HPET_EMULATE_RTC /* HPET in LegacyReplacement Mode eats up RTC interrupt line. When, HPET * is enabled, we support RTC interrupt functionality in software. diff --git a/arch/x86/kernel/time_64.c b/arch/x86/kernel/time_64.c index 2db4d698a2d..e97a3ee1355 100644 --- a/arch/x86/kernel/time_64.c +++ b/arch/x86/kernel/time_64.c @@ -292,35 +292,6 @@ static unsigned int __init tsc_calibrate_cpu_khz(void) return pmc_now * tsc_khz / (tsc_now - tsc_start); } -/* - * pit_calibrate_tsc() uses the speaker output (channel 2) of - * the PIT. This is better than using the timer interrupt output, - * because we can read the value of the speaker with just one inb(), - * where we need three i/o operations for the interrupt channel. - * We count how many ticks the TSC does in 50 ms. - */ - -static unsigned int __init pit_calibrate_tsc(void) -{ - unsigned long start, end; - unsigned long flags; - - spin_lock_irqsave(&i8253_lock, flags); - - outb((inb(0x61) & ~0x02) | 0x01, 0x61); - - outb(0xb0, 0x43); - outb((PIT_TICK_RATE / (1000 / 50)) & 0xff, 0x42); - outb((PIT_TICK_RATE / (1000 / 50)) >> 8, 0x42); - start = get_cycles_sync(); - while ((inb(0x61) & 0x20) == 0); - end = get_cycles_sync(); - - spin_unlock_irqrestore(&i8253_lock, flags); - - return (end - start) / 50; -} - #define PIT_MODE 0x43 #define PIT_CH0 0x40 @@ -376,14 +347,14 @@ void __init time_init(void) if (hpet_use_timer) { /* set tick_nsec to use the proper rate for HPET */ tick_nsec = TICK_NSEC_HPET; - tsc_khz = hpet_calibrate_tsc(); timename = "HPET"; } else { pit_init(); - tsc_khz = pit_calibrate_tsc(); timename = "PIT"; } + tsc_calibrate(); + cpu_khz = tsc_khz; if (cpu_has(&boot_cpu_data, X86_FEATURE_CONSTANT_TSC) && boot_cpu_data.x86_vendor == X86_VENDOR_AMD && diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c index 2a59bde663f..59baecd135a 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; @@ -118,6 +120,94 @@ 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; +} + /* * Make an educated guess if the TSC is trustworthy and synchronized * over all CPUs. |