time.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 1,154 行 · 第 1/2 页

/*
 *  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 <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>
#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 int using_apic_timer;

spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
spinlock_t i8253_lock = SPIN_LOCK_UNLOCKED;

static int nohpet __initdata = 0;

#undef HPET_HACK_ENABLE_DANGEROUS


unsigned int cpu_khz;					/* TSC clocks / usec, not used here */
unsigned long hpet_period;				/* fsecs / HPET clock */
unsigned long hpet_tick;				/* HPET clocks / interrupt */
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; /* hack */
	x = ((t - vxtime.last_tsc) * vxtime.tsc_quot) >> 32;
	return x;
}

static inline unsigned int do_gettimeoffset_hpet(void)
{
	return ((hpet_readl(HPET_COUNTER) - vxtime.last) * vxtime.quot) >> 32;
}

unsigned int (*do_gettimeoffset)(void) = do_gettimeoffset_tsc;

/*
 * This version of gettimeofday() has microsecond resolution and better than
 * microsecond precision, as we're using at least a 10 MHz (usually 14.31818
 * MHz) HPET timer.
 */

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

	do {
		seq = read_seqbegin(&xtime_lock);

		sec = xtime.tv_sec;
		usec = xtime.tv_nsec / 1000;

		/* i386 does some correction here to keep the clock 
		   monotonous even when ntpd is fixing drift.
		   But they didn't work for me, there is a non monotonic
		   clock anyways with ntp.
		   I dropped all corrections now until a real solution can
		   be found. Note when you fix it here you need to do the same
		   in arch/x86_64/kernel/vsyscall.c and export all needed
		   variables in vmlinux.lds. -AK */ 

		t = (jiffies - wall_jiffies) * (1000000L / HZ) +
			do_gettimeoffset();
		usec += t;

	} while (read_seqretry(&xtime_lock, seq));

	tv->tv_sec = sec + usec / 1000000;
	tv->tv_usec = usec % 1000000;
}

EXPORT_SYMBOL(do_gettimeofday);

/*
 * settimeofday() first undoes the correction that gettimeofday would do
 * on the time, and then saves it. This is ugly, but has been like this for
 * ages already.
 */

int do_settimeofday(struct timespec *tv)
{
	time_t wtm_sec, sec = tv->tv_sec;
	long wtm_nsec, nsec = tv->tv_nsec;

	if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
		return -EINVAL;

	write_seqlock_irq(&xtime_lock);

	nsec -= do_gettimeoffset() * 1000 +
		(jiffies - wall_jiffies) * (NSEC_PER_SEC/HZ);

	wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
	wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);

	set_normalized_timespec(&xtime, sec, nsec);
	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_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);

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

	/* Assume the lock function has either no stack frame or only a single word.
	   This checks if the address on the stack looks like a kernel text address.
	   There is a small window for false hits, but in that case the tick
	   is just accounted to the spinlock function.
	   Better would be to write these functions in assembler again
	   and check exactly. */
	if (in_lock_functions(pc)) {
		char *v = *(char **)regs->rsp;
		if ((v >= _stext && v <= _etext) ||
			(v >= _sinittext && v <= _einittext) ||
			(v >= (char *)MODULES_VADDR  && v <= (char *)MODULES_END))
			return (unsigned long)v;
		return ((unsigned long *)regs->rsp)[1];
	}
	return pc;
}
EXPORT_SYMBOL(profile_pc);

/*
 * In order to set the CMOS clock precisely, set_rtc_mmss has to be called 500
 * ms after the second nowtime has started, because when nowtime is written
 * into the registers of the CMOS clock, it will jump to the next second
 * precisely 500 ms later. Check the Motorola MC146818A or Dallas DS12887 data
 * sheet for details.
 */

static void set_rtc_mmss(unsigned long nowtime)
{
	int real_seconds, real_minutes, cmos_minutes;
	unsigned char control, freq_select;

/*
 * IRQs are disabled when we're called from the timer interrupt,
 * no need for spin_lock_irqsave()
 */

	spin_lock(&rtc_lock);

/*
 * Tell the clock it's being set and stop it.
 */

	control = CMOS_READ(RTC_CONTROL);
	CMOS_WRITE(control | RTC_SET, RTC_CONTROL);

	freq_select = CMOS_READ(RTC_FREQ_SELECT);
	CMOS_WRITE(freq_select | RTC_DIV_RESET2, RTC_FREQ_SELECT);

	cmos_minutes = CMOS_READ(RTC_MINUTES);
		BCD_TO_BIN(cmos_minutes);

/*
 * since we're only adjusting minutes and seconds, don't interfere with hour
 * overflow. This avoids messing with unknown time zones but requires your RTC
 * not to be off by more than 15 minutes. Since we're calling it only when
 * our clock is externally synchronized using NTP, this shouldn't be a problem.
 */

	real_seconds = nowtime % 60;
	real_minutes = nowtime / 60;
	if (((abs(real_minutes - cmos_minutes) + 15) / 30) & 1)
		real_minutes += 30;		/* correct for half hour time zone */
	real_minutes %= 60;

#if 0
	/* AMD 8111 is a really bad time keeper and hits this regularly. 
	   It probably was an attempt to avoid screwing up DST, but ignore
	   that for now. */	   
	if (abs(real_minutes - cmos_minutes) >= 30) {
		printk(KERN_WARNING "time.c: can't update CMOS clock "
		       "from %d to %d\n", cmos_minutes, real_minutes);
	} else
#endif

	{
			BIN_TO_BCD(real_seconds);
			BIN_TO_BCD(real_minutes);
		CMOS_WRITE(real_seconds, RTC_SECONDS);
		CMOS_WRITE(real_minutes, RTC_MINUTES);
	}

/*
 * The following flags have to be released exactly in this order, otherwise the
 * DS12887 (popular MC146818A clone with integrated battery and quartz) will
 * not reset the oscillator and will not update precisely 500 ms later. You
 * won't find this mentioned in the Dallas Semiconductor data sheets, but who
 * believes data sheets anyway ... -- Markus Kuhn
 */

	CMOS_WRITE(control, RTC_CONTROL);
	CMOS_WRITE(freq_select, RTC_FREQ_SELECT);

	spin_unlock(&rtc_lock);
}


/* monotonic_clock(): returns # of nanoseconds passed since time_init()
 *		Note: This function is required to return accurate
 *		time even in the absence of multiple timer ticks.
 */
unsigned long long monotonic_clock(void)
{
	unsigned long seq;
 	u32 last_offset, this_offset, offset;
	unsigned long long base;

	if (vxtime.mode == VXTIME_HPET) {
		do {
			seq = read_seqbegin(&xtime_lock);

			last_offset = vxtime.last;
			base = monotonic_base;
			this_offset = hpet_readl(HPET_T0_CMP) - hpet_tick;

		} while (read_seqretry(&xtime_lock, seq));
		offset = (this_offset - last_offset);
		offset *=(NSEC_PER_SEC/HZ)/hpet_tick;
		return base + offset;
	}else{
		do {
			seq = read_seqbegin(&xtime_lock);

			last_offset = vxtime.last_tsc;
			base = monotonic_base;
		} while (read_seqretry(&xtime_lock, seq));
		sync_core();
		rdtscll(this_offset);
		offset = (this_offset - last_offset)*1000/cpu_khz; 
		return base + offset;
	}


}
EXPORT_SYMBOL(monotonic_clock);

static noinline void handle_lost_ticks(int lost, struct pt_regs *regs)
{
    static long lost_count;
    static int warned;

    if (report_lost_ticks) {
	    printk(KERN_WARNING "time.c: Lost %d timer "
		   "tick(s)! ", lost);
	    print_symbol("rip %s)\n", regs->rip);
    }

    if (lost_count == 100 && !warned) {
	    printk(KERN_WARNING
		   "warning: many lost ticks.\n"
		   KERN_WARNING "Your time source seems to be instable or "
		   		"some driver is hogging interupts\n");
	    print_symbol("rip %s\n", regs->rip);
	    if (vxtime.mode == VXTIME_TSC && vxtime.hpet_address) {
		    printk(KERN_WARNING "Falling back to HPET\n");
		    vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick;
		    vxtime.mode = VXTIME_HPET;
		    do_gettimeoffset = do_gettimeoffset_hpet;
	    }
	    /* else should fall back to PIT, but code missing. */
	    warned = 1;
    } else
	    lost_count++;

#ifdef CONFIG_CPU_FREQ
    /* In some cases the CPU can change frequency without us noticing
       (like going into thermal throttle)
       Give cpufreq a change to catch up. */
    if ((lost_count+1) % 25 == 0) {
	    cpufreq_delayed_get();
    }
#endif
}

static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	static unsigned long rtc_update = 0;
	unsigned long tsc;
	int delay, offset = 0, lost = 0;

/*
 * Here we are in the timer irq handler. We have irqs locally disabled (so we
 * don't need spin_lock_irqsave()) but we don't know if the timer_bh is running
 * on the other CPU, so we need a lock. We also need to lock the vsyscall
 * variables, because both do_timer() and us change them -arca+vojtech
 */

	write_seqlock(&xtime_lock);

	if (vxtime.hpet_address) {
		offset = hpet_readl(HPET_T0_CMP) - hpet_tick;
		delay = hpet_readl(HPET_COUNTER) - offset;
	} else {
		spin_lock(&i8253_lock);
		outb_p(0x00, 0x43);
		delay = inb_p(0x40);
		delay |= inb(0x40) << 8;
		spin_unlock(&i8253_lock);
		delay = LATCH - 1 - delay;
	}

	rdtscll_sync(&tsc);

	if (vxtime.mode == VXTIME_HPET) {
		if (offset - vxtime.last > hpet_tick) {
			lost = (offset - vxtime.last) / hpet_tick - 1;
		}

		monotonic_base += 
			(offset - vxtime.last)*(NSEC_PER_SEC/HZ) / hpet_tick;

		vxtime.last = offset;
	} else {
		offset = (((tsc - vxtime.last_tsc) *
			   vxtime.tsc_quot) >> 32) - (USEC_PER_SEC / HZ);

		if (offset < 0)
			offset = 0;

		if (offset > (USEC_PER_SEC / HZ)) {
			lost = offset / (USEC_PER_SEC / HZ);
			offset %= (USEC_PER_SEC / HZ);
		}

		monotonic_base += (tsc - vxtime.last_tsc)*1000000/cpu_khz ;

		vxtime.last_tsc = tsc - vxtime.quot * delay / vxtime.tsc_quot;

		if ((((tsc - vxtime.last_tsc) *
		      vxtime.tsc_quot) >> 32) < offset)
			vxtime.last_tsc = tsc -
				(((long) offset << 32) / vxtime.tsc_quot) - 1;
	}

	if (lost > 0) {
		handle_lost_ticks(lost, regs);
		jiffies += lost;
	}

/*
 * Do the timer stuff.
 */

	do_timer(regs);

/*
 * In the SMP case we use the local APIC timer interrupt to do the profiling,
 * except when we simulate SMP mode on a uniprocessor system, in that case we
 * have to call the local interrupt handler.
 */

#ifndef CONFIG_X86_LOCAL_APIC
	profile_tick(CPU_PROFILING, regs);
#else
	if (!using_apic_timer)
		smp_local_timer_interrupt(regs);
#endif

/*
 * If we have an externally synchronized Linux clock, then update CMOS clock
 * accordingly every ~11 minutes. set_rtc_mmss() will be called in the jiffy
 * closest to exactly 500 ms before the next second. If the update fails, we
 * don't care, as it'll be updated on the next turn, and the problem (time way
 * off) isn't likely to go away much sooner anyway.
 */

	if ((~time_status & STA_UNSYNC) && xtime.tv_sec > rtc_update &&
		abs(xtime.tv_nsec - 500000000) <= tick_nsec / 2) {
		set_rtc_mmss(xtime.tv_sec);
		rtc_update = xtime.tv_sec + 660;
	}
 
	write_sequnlock(&xtime_lock);

	return IRQ_HANDLED;
}

static unsigned int cyc2ns_scale;
#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */

static inline void set_cyc2ns_scale(unsigned long cpu_mhz)
{
	cyc2ns_scale = (1000 << CYC2NS_SCALE_FACTOR)/cpu_mhz;
}

static inline unsigned long long cycles_2_ns(unsigned long long cyc)
{
	return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR;
}

unsigned long long sched_clock(void)
{
	unsigned long a = 0;

#if 0
	/* Don't do a HPET read here. Using TSC always is much faster
	   and HPET may not be mapped yet when the scheduler first runs.
           Disadvantage is a small drift between CPUs in some configurations,
	   but that should be tolerable. */
	if (__vxtime.mode == VXTIME_HPET)
		return (hpet_readl(HPET_COUNTER) * vxtime.quot) >> 32;
#endif

	/* Could do CPU core sync here. Opteron can execute rdtsc speculatively,
	   which means it is not completely exact and may not be monotonous between
	   CPUs. But the errors should be too small to matter for scheduling
	   purposes. */

	rdtscll(a);
	return cycles_2_ns(a);
}

unsigned long get_cmos_time(void)
{
	unsigned int timeout, year, mon, day, hour, min, sec;
	unsigned char last, this;
	unsigned long flags;

/*
 * The Linux interpretation of the CMOS clock register contents: When the
 * Update-In-Progress (UIP) flag goes from 1 to 0, the RTC registers show the
 * second which has precisely just started. Waiting for this can take up to 1
 * second, we timeout approximately after 2.4 seconds on a machine with
 * standard 8.3 MHz ISA bus.
 */

	spin_lock_irqsave(&rtc_lock, flags);

	timeout = 1000000;
	last = this = 0;

	while (timeout && last && !this) {
		last = this;
		this = CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP;
		timeout--;
	}

/*
 * Here we are safe to assume the registers won't change for a whole second, so
 * we just go ahead and read them.
	 */

		sec = CMOS_READ(RTC_SECONDS);
		min = CMOS_READ(RTC_MINUTES);
		hour = CMOS_READ(RTC_HOURS);
		day = CMOS_READ(RTC_DAY_OF_MONTH);
		mon = CMOS_READ(RTC_MONTH);
		year = CMOS_READ(RTC_YEAR);

	spin_unlock_irqrestore(&rtc_lock, flags);

/*
 * We know that x86-64 always uses BCD format, no need to check the config
 * register.
 */

	    BCD_TO_BIN(sec);
	    BCD_TO_BIN(min);
	    BCD_TO_BIN(hour);
	    BCD_TO_BIN(day);
	    BCD_TO_BIN(mon);
	    BCD_TO_BIN(year);

/*
 * This will work up to Dec 31, 2069.
 */

	if ((year += 1900) < 1970)
		year += 100;

	return mktime(year, mon, day, hour, min, sec);
}

#ifdef CONFIG_CPU_FREQ

/* Frequency scaling support. Adjust the TSC based timer when the cpu frequency
   changes.
   
   RED-PEN: On SMP we assume all CPUs run with the same frequency.  It's
   not that important because current Opteron setups do not support
   scaling on SMP anyroads.

   Should fix up last_tsc too. Currently gettimeofday in the
   first tick after the change will be slightly wrong. */

#include <linux/workqueue.h>

static unsigned int cpufreq_delayed_issched = 0;
static unsigned int cpufreq_init = 0;
static struct work_struct cpufreq_delayed_get_work;

static void handle_cpufreq_delayed_get(void *v)