path: root/arch/x86_64/kernel/time.c

/*
 *  linux/arch/x86-64/kernel/time.c
 *
 *  "High Precision Event Timer" based timekeeping.
 *
 *  Copyright (c) 1991,1992,1995  Linus Torvalds
 *  Copyright (c) 1994  Alan Modra
 *  Copyright (c) 1995  Markus Kuhn
 *  Copyright (c) 1996  Ingo Molnar
 *  Copyright (c) 1998  Andrea Arcangeli
 *  Copyright (c) 2002  Vojtech Pavlik
 *  Copyright (c) 2003  Andi Kleen
 *  RTC support code taken from arch/i386/kernel/timers/time_hpet.c
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/mc146818rtc.h>
#include <linux/irq.h>
#include <linux/time.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/sysdev.h>
#include <linux/bcd.h>
#include <linux/kallsyms.h>
#include <linux/acpi.h>
#ifdef CONFIG_ACPI
#include <acpi/achware.h>	/* for PM timer frequency */
#endif
#include <asm/8253pit.h>
#include <asm/pgtable.h>
#include <asm/vsyscall.h>
#include <asm/timex.h>
#include <asm/proto.h>
#include <asm/hpet.h>
#include <asm/sections.h>
#include <linux/cpufreq.h>
#include <linux/hpet.h>
#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/apic.h>
#endif

u64 jiffies_64 = INITIAL_JIFFIES;

EXPORT_SYMBOL(jiffies_64);

#ifdef CONFIG_CPU_FREQ
static void cpufreq_delayed_get(void);
#endif
extern void i8254_timer_resume(void);
extern int using_apic_timer;

DEFINE_SPINLOCK(rtc_lock);
DEFINE_SPINLOCK(i8253_lock);

static int nohpet __initdata = 0;
static int notsc __initdata = 0;

#undef HPET_HACK_ENABLE_DANGEROUS

unsigned int cpu_khz;					/* TSC clocks / usec, not used here */
static unsigned long hpet_period;			/* fsecs / HPET clock */
unsigned long hpet_tick;				/* HPET clocks / interrupt */
static int hpet_use_timer;
unsigned long vxtime_hz = PIT_TICK_RATE;
int report_lost_ticks;				/* command line option */
unsigned long long monotonic_base;

struct vxtime_data __vxtime __section_vxtime;	/* for vsyscalls */

volatile unsigned long __jiffies __section_jiffies = INITIAL_JIFFIES;
unsigned long __wall_jiffies __section_wall_jiffies = INITIAL_JIFFIES;
struct timespec __xtime __section_xtime;
struct timezone __sys_tz __section_sys_tz;

static inline void rdtscll_sync(unsigned long *tsc)
{
#ifdef CONFIG_SMP
	sync_core();
#endif
	rdtscll(*tsc);
}

/*
 * do_gettimeoffset() returns microseconds since last timer interrupt was
 * triggered by hardware. A memory read of HPET is slower than a register read
 * of TSC, but much more reliable. It's also synchronized to the timer
 * interrupt. Note that do_gettimeoffset() may return more than hpet_tick, if a
 * timer interrupt has happened already, but vxtime.trigger wasn't updated yet.
 * This is not a problem, because jiffies hasn't updated either. They are bound
 * together by xtime_lock.
 */

static inline unsigned int do_gettimeoffset_tsc(void)
{
	unsigned long t;
	unsigned long x;
	rdtscll_sync(&t);
	if (t < vxtime.last_tsc) t = vxtime.last_tsc