linux/arch/x86/kernel/time_32.c

/*
 *  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 <cananian@alumni.princeton.edu>, Andrew D.
 *	Balsa <andrebalsa@altern.org>, Philip Gladstone <philip@raptor.com>;
 *	ported from 2.0.35 Jumbo-9 by Michael Krause <m.krause@tu-harburg.de>).
 * 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/clockchips.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/mca.h>

#include <asm/setup.h>
#include <asm/hpet.h>
#include <asm/time.h>
#include <asm/timer.h>
#include <asm/i8259.h>
#include <asm/i8253.h>

int timer_ack;

unsigned long profile_pc(struct pt_regs *regs)
{
	unsigned long pc = instruction_pointer(regs);

#ifdef CONFIG_SMP
	if (!user_mode_vm(regs) && in_lock_functions(pc)) {
#ifdef CONFIG_FRAME_POINTER
		return *(unsigned long *)(regs->bp + sizeof(long));
#else
		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];
#endif
	}
#endif
	return pc;
}
EXPORT_SYMBOL(profile_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.
 */
static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
	/* Keep nmi watchdog up to date */
	inc_irq_stat(irq0_irqs);

#ifdef CONFIG_X86_IO_APIC
	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.
		 */
		spin_lock(&i8259A_lock);
		outb(0x0c, PIC_MASTER_OCW3);
		/* Ack the IRQ; AEOI will end it automatically. */
		inb(PIC_MASTER_POLL);
		spin_unlock(&i8259A_lock);
	}
#endif

	global_clock_event->event_handler(global_clock_event);

#ifdef CONFIG_MCA
	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 */
	}
#endif

	return IRQ_HANDLED;
}

static struct irqaction irq0  = {
	.handler = timer_interrupt,
	.flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_IRQPOLL | IRQF_TIMER,
	.name = "timer"
};

void __init setup_default_timer_irq(void)
{
	irq0.mask = cpumask_of_cpu(0);
	setup_irq(0, &irq0);
}

/* Default timer init function */
void __init hpet_time_init(void)
{
	if (!hpet_enable())
		setup_pit_timer();
	setup_default_timer_irq();
}

static void x86_late_time_init(void)
{
	x86_init.timers.timer_init();
}

/*
 * Initialize TSC and delay the periodic timer init to
 * late x86_late_time_init() so ioremap works.
 */
void __init time_init(void)
{
	tsc_init();
	late_time_init = x86_late_time_init;
}