time.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 192 行

/*
 *  linux/arch/arm26/kernel/time.c
 *
 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
 *  Modifications for ARM (C) 1994-2001 Russell King
 *  Mods for ARM26 (C) 2003 Ian Molton
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  This file contains the ARM-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
 *  1998-12-20  Updated NTP code according to technical memorandum Jan '96
 *              "A Kernel Model for Precision Timekeeping" by Dave Mills
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/timex.h>
#include <linux/errno.h>
#include <linux/profile.h>

#include <asm/hardware.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/leds.h>

u64 jiffies_64 = INITIAL_JIFFIES;

EXPORT_SYMBOL(jiffies_64);

extern unsigned long wall_jiffies;

/* this needs a better home */
spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;

/* change this if you have some constant time drift */
#define USECS_PER_JIFFY	(1000000/HZ)

static int dummy_set_rtc(void)
{
	return 0;
}

/*
 * hook for setting the RTC's idea of the current time.
 */
int (*set_rtc)(void) = dummy_set_rtc;

static unsigned long dummy_gettimeoffset(void)
{
	return 0;
}

/*
 * hook for getting the time offset.  Note that it is
 * always called with interrupts disabled.
 */
unsigned long (*gettimeoffset)(void) = dummy_gettimeoffset;

static unsigned long next_rtc_update;

/*
 * If we have an externally synchronized linux clock, then update
 * CMOS clock accordingly every ~11 minutes.  set_rtc() has to be
 * called as close as possible to 500 ms before the new second
 * starts.
 */
static inline void do_set_rtc(void)
{
	if (time_status & STA_UNSYNC || set_rtc == NULL)
		return;

//FIXME - timespec.tv_sec is a time_t not unsigned long
	if (next_rtc_update &&
	    time_before((unsigned long)xtime.tv_sec, next_rtc_update))
		return;

	if (xtime.tv_nsec < 500000000 - ((unsigned) tick_nsec >> 1) &&
	    xtime.tv_nsec >= 500000000 + ((unsigned) tick_nsec >> 1))
		return;

	if (set_rtc())
		/*
		 * rtc update failed.  Try again in 60s
		 */
		next_rtc_update = xtime.tv_sec + 60;
	else
		next_rtc_update = xtime.tv_sec + 660;
}

#define do_leds()

void do_gettimeofday(struct timeval *tv)
{
	unsigned long flags;
	unsigned long seq;
	unsigned long usec, sec, lost;

	do {
		seq = read_seqbegin_irqsave(&xtime_lock, flags);
		usec = gettimeoffset();

		lost = jiffies - wall_jiffies;
		if (lost)
			usec += lost * USECS_PER_JIFFY;

		sec = xtime.tv_sec;
		usec += xtime.tv_nsec / 1000;
	} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));

	/* usec may have gone up a lot: be safe */
	while (usec >= 1000000) {
		usec -= 1000000;
		sec++;
	}

	tv->tv_sec = sec;
	tv->tv_usec = usec;
}

EXPORT_SYMBOL(do_gettimeofday);

int do_settimeofday(struct timespec *tv)
{
	if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
		return -EINVAL;

	write_seqlock_irq(&xtime_lock);
	/*
	 * This is revolting. We need to set "xtime" correctly. However, the
	 * value in this location is the value at the most recent update of
	 * wall time.  Discover what correction gettimeofday() would have
	 * done, and then undo it!
	 */
	tv->tv_nsec -= 1000 * (gettimeoffset() +
			(jiffies - wall_jiffies) * USECS_PER_JIFFY);

	while (tv->tv_nsec < 0) {
		tv->tv_nsec += NSEC_PER_SEC;
		tv->tv_sec--;
	}

	xtime.tv_sec = tv->tv_sec;
	xtime.tv_nsec = tv->tv_nsec;
	time_adjust = 0;		/* stop active adjtime() */
	time_status |= STA_UNSYNC;
	time_maxerror = NTP_PHASE_LIMIT;
	time_esterror = NTP_PHASE_LIMIT;
	write_sequnlock_irq(&xtime_lock);
	clock_was_set();
	return 0;
}

EXPORT_SYMBOL(do_settimeofday);

static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
        do_timer(regs);
        do_set_rtc(); //FIME - EVERY timer IRQ?
        profile_tick(CPU_PROFILING, regs);
	return IRQ_HANDLED; //FIXME - is this right?
}

static struct irqaction timer_irq = {
	.name	= "timer",
	.flags	= SA_INTERRUPT,
	.handler = timer_interrupt,
};

extern void ioctime_init(void);

/*
 * Set up timer interrupt.
 */
void __init time_init(void)
{
        ioctime_init();

        setup_irq(IRQ_TIMER, &timer_irq);
}