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) 2002,2006  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/time.h>
#include <linux/ioport.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/sysdev.h>
#include <linux/bcd.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/kallsyms.h>
#include <linux/acpi.h>
#ifdef CONFIG_ACPI
#include <acpi/achware.h>	/* for PM timer frequency */
#include <acpi/acpi_bus.h>
#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>
#include <asm/apic.h>
#include <asm/hpet.h>

extern void i8254_timer_resume(void);
extern int using_apic_timer;

static char *timename = NULL;

DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);
DEFINE_SPINLOCK(i8253_lock);

volatile unsigned long __jiffies __section_jiffies = INITIAL_JIFFIES;

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

	/* Assume the lock function has either no stack frame or a copy
	   of eflags from PUSHF
	   Eflags always has bits 22 and up cleared unlike kernel addresses. */
	if (!user_mode(regs) && in_lock_functions(pc)) {
		unsigned long *sp = (unsigned long *)regs->rsp;
		if (sp[0] >> 22)
			return sp[0];
		if (sp[1] >> 22)
			return sp[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 (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 {
		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);
}


void main_timer_handler(void)
{
	static unsigned long rtc_update = 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);

/*
 * Do the timer stuff.
 */

	do_timer(1);
#ifndef CONFIG_SMP
	update_process_times(user_mode(get_irq_regs()));
#endif

/*
 * 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.
 */

	if (!using_apic_timer)
		smp_local_timer_interrupt();

/*
 * 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 (ntp_synced() && 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);
}

static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
	if (apic_runs_main_timer > 1)
		return IRQ_HANDLED;
	main_timer_handler();
	if (using_apic_timer)
		smp_send_timer_broadcast_ipi();
	return IRQ_HANDLED;
}

static unsigned long get_cmos_time(void)
{
	unsigned int year, mon, day, hour, min, sec;
	unsigned long flags;
	unsigned century = 0;

	spin_lock_irqsave(&rtc_lock, flags);

	do {
		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);
#ifdef CONFIG_ACPI
		if (acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID &&
					acpi_gbl_FADT.century)
			century = CMOS_READ(acpi_gbl_FADT.century);
#endif
	} while (sec != CMOS_READ(RTC_SECONDS));

	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);

	if (century) {
		BCD_TO_BIN(century);
		year += century * 100;
		printk(KERN_INFO "Extended CMOS year: %d\n", century * 100);
	} else { 
		/*
		 * x86-64 systems only exists since 2002.
		 * This will work up to Dec 31, 2100
	 	 */
		year += 2000;
	}

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


/*
 * pit_calibrate_tsc() uses the speaker output (channel 2) of
 * the PIT. This is better than using the timer interrupt output,
 * because we can read the value of the speaker with just one inb(),
 * where we need three i/o operations for the interrupt channel.
 * We count how many ticks the TSC does in 50 ms.
 */

static unsigned int __init pit_calibrate_tsc(void)
{
	unsigned long start, end;
	unsigned long flags;

	spin_lock_irqsave(&i8253_lock, flags);

	outb((inb(0x61) & ~0x02) | 0x01, 0x61);

	outb(0xb0, 0x43);
	outb((PIT_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
	outb((PIT_TICK_RATE / (1000 / 50)) >> 8, 0x42);
	start = get_cycles_sync();
	while ((inb(0x61) & 0x20) == 0);
	end = get_cycles_sync();

	spin_unlock_irqrestore(&i8253_lock, flags);
	
	return (end - start) / 50;
}

#define PIT_MODE 0x43
#define PIT_CH0  0x40

static void __init __pit_init(int val, u8 mode)
{
	unsigned long flags;

	spin_lock_irqsave(&i8253_lock, flags);
	outb_p(mode, PIT_MODE);
	outb_p(val & 0xff, PIT_CH0);	/* LSB */
	outb_p(val >> 8, PIT_CH0);	/* MSB */
	spin_unlock_irqrestore(&i8253_lock, flags);
}

void __init pit_init(void)
{
	__pit_init(LATCH, 0x34); /* binary, mode 2, LSB/MSB, ch 0 */
}

void __init pit_stop_interrupt(void)
{
	__pit_init(0, 0x30); /* mode 0 */
}

void __init stop_timer_interrupt(void)
{
	char *name;
	if (hpet_address) {
		name = "HPET";
		hpet_timer_stop_set_go(0);
	} else {
		name = "PIT";
		pit_stop_interrupt();
	}
	printk(KERN_INFO "timer: %s interrupt stopped.\n", name);
}

static struct irqaction irq0 = {
	timer_interrupt, IRQF_DISABLED, CPU_MASK_NONE, "timer", NULL, NULL
};

void __init time_init(void)
{
	if (nohpet)
		hpet_address = 0;
	xtime.tv_sec = get_cmos_time();
	xtime.tv_nsec = 0;

	set_normalized_timespec(&wall_to_monotonic,
	                        -xtime.tv_sec, -xtime.tv_nsec);

	if (hpet_arch_init())
		hpet_address = 0;

	if (hpet_use_timer) {
		/* set tick_nsec to use the proper rate for HPET */
	  	tick_nsec = TICK_NSEC_HPET;
		cpu_khz = hpet_calibrate_tsc();
		timename = "HPET";
	} else {
		pit_init();
		cpu_khz = pit_calibrate_tsc();
		timename = "PIT";
	}

	if (unsynchronized_tsc())
		mark_tsc_unstable();

	if (cpu_has(&boot_cpu_data, X86_FEATURE_RDTSCP))
		vgetcpu_mode = VGETCPU_RDTSCP;
	else
		vgetcpu_mode = VGETCPU_LSL;

	set_cyc2ns_scale(cpu_khz);
	printk(KERN_INFO "time.c: Detected %d.%03d MHz processor.\n",
		cpu_khz / 1000, cpu_khz % 1000);
	init_tsc_clocksource();

	setup_irq(0, &irq0);
}


static long clock_cmos_diff;
static unsigned long sleep_start;

/*
 * sysfs support for the timer.
 */

static int timer_suspend(struct sys_device *dev, pm_message_t state)
{
	/*
	 * Estimate time zone so that set_time can update the clock
	 */
	long cmos_time =  get_cmos_time();

	clock_cmos_diff = -cmos_time;
	clock_cmos_diff += get_seconds();
	sleep_start = cmos_time;
	return 0;
}

static int timer_resume(struct sys_device *dev)
{
	unsigned long flags;
	unsigned long sec;
	unsigned long ctime = get_cmos_time();
	long sleep_length = (ctime - sleep_start) * HZ;

	if (sleep_length < 0) {
		printk(KERN_WARNING "Time skew detected in timer resume!\n");
		/* The time after the resume must not be earlier than the time
		 * before the suspend or some nasty things will happen
		 */
		sleep_length = 0;
		ctime = sleep_start;
	}
	if (hpet_address)
		hpet_reenable();
	else
		i8254_timer_resume();

	sec = ctime + clock_cmos_diff;
	write_seqlock_irqsave(&xtime_lock,flags);
	xtime.tv_sec = sec;
	xtime.tv_nsec = 0;
	jiffies += sleep_length;
	write_sequnlock_irqrestore(&xtime_lock,flags);
	touch_softlockup_watchdog();
	return 0;
}

static struct sysdev_class timer_sysclass = {
	.resume = timer_resume,
	.suspend = timer_suspend,
	set_kset_name("timer"),
};

/* XXX this sysfs stuff should probably go elsewhere later -john */
static struct sys_device device_timer = {
	.id	= 0,
	.cls	= &timer_sysclass,
};

static int time_init_device(void)
{
	int error = sysdev_class_register(&timer_sysclass);
	if (!error)
		error = sysdev_register(&device_timer);
	return error;
}

device_initcall(time_init_device);