blob: 77b400f06ea2335fa770fb3273ce5cd7e5820c18 [file] [log] [blame]
* Copyright (C) 1991, 1992, 1995 Linus Torvalds
* This file contains the PC-specific time handling details:
* reading the RTC at bootup, etc..
* 1994-07-02 Alan Modra
* fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
* 1995-03-26 Markus Kuhn
* fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
* precision CMOS clock update
* 1996-05-03 Ingo Molnar
* fixed time warps in do_[slow|fast]_gettimeoffset()
* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* 1998-09-05 (Various)
* More robust do_fast_gettimeoffset() algorithm implemented
* (works with APM, Cyrix 6x86MX and Centaur C6),
* monotonic gettimeofday() with fast_get_timeoffset(),
* drift-proof precision TSC calibration on boot
* (C. Scott Ananian <>, Andrew D.
* Balsa <>, Philip Gladstone <>;
* ported from 2.0.35 Jumbo-9 by Michael Krause <>).
* 1998-12-16 Andrea Arcangeli
* Fixed Jumbo-9 code in 2.1.131: do_gettimeofday was missing 1 jiffy
* because was not accounting lost_ticks.
* 1998-12-24 Copyright (C) 1998 Andrea Arcangeli
* Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
* serialize accesses to xtime/lost_ticks).
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/mca.h>
#include <asm/arch_hooks.h>
#include <asm/hpet.h>
#include <asm/time.h>
#include <asm/timer.h>
#include "do_timer.h"
int timer_ack;
unsigned long profile_pc(struct pt_regs *regs)
unsigned long pc = instruction_pointer(regs);
if (!user_mode_vm(regs) && in_lock_functions(pc)) {
return *(unsigned long *)(regs->bp + sizeof(long));
unsigned long *sp = (unsigned long *)&regs->sp;
/* Return address is either directly at stack pointer
or above a saved flags. Eflags has bits 22-31 zero,
kernel addresses don't. */
if (sp[0] >> 22)
return sp[0];
if (sp[1] >> 22)
return sp[1];
return pc;
* This is the same as the above, except we _also_ save the current
* Time Stamp Counter value at the time of the timer interrupt, so that
* we later on can estimate the time of day more exactly.
irqreturn_t timer_interrupt(int irq, void *dev_id)
/* Keep nmi watchdog up to date */
per_cpu(irq_stat, smp_processor_id()).irq0_irqs++;
if (timer_ack) {
* Subtle, when I/O APICs are used we have to ack timer IRQ
* manually to deassert NMI lines for the watchdog if run
* on an 82489DX-based system.
outb(0x0c, PIC_MASTER_OCW3);
/* Ack the IRQ; AEOI will end it automatically. */
if (MCA_bus) {
/* The PS/2 uses level-triggered interrupts. You can't
turn them off, nor would you want to (any attempt to
enable edge-triggered interrupts usually gets intercepted by a
special hardware circuit). Hence we have to acknowledge
the timer interrupt. Through some incredibly stupid
design idea, the reset for IRQ 0 is done by setting the
high bit of the PPI port B (0x61). Note that some PS/2s,
notably the 55SX, work fine if this is removed. */
u8 irq_v = inb_p( 0x61 ); /* read the current state */
outb_p( irq_v|0x80, 0x61 ); /* reset the IRQ */
/* Duplicate of time_init() below, with hpet_enable part added */
void __init hpet_time_init(void)
if (!hpet_enable())
* This is called directly from init code; we must delay timer setup in the
* HPET case as we can't make the decision to turn on HPET this early in the
* boot process.
* The chosen time_init function will usually be hpet_time_init, above, but
* in the case of virtual hardware, an alternative function may be substituted.
void __init time_init(void)
late_time_init = choose_time_init();