time.c

Go to the documentation of this file.

/*
 *  linux/arch/alpha/kernel/time.c
 *
 *  Copyright (C) 1991, 1992, 1995, 1999, 2000  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
 * 1997-09-10   Updated NTP code according to technical memorandum Jan '96
 *      "A Kernel Model for Precision Timekeeping" by Dave Mills
 * 1997-01-09    Adrian Sun
 *      use interval timer if CONFIG_RTC=y
 * 1997-10-29    John Bowman ([email protected])
 *      fixed tick loss calculation in timer_interrupt
 *      (round system clock to nearest tick instead of truncating)
 *      fixed algorithm in time_init for getting time from CMOS clock
 * 1999-04-16   Thorsten Kranzkowski ([email protected])
 *  fixed algorithm in do_gettimeofday() for calculating the precise time
 *  from processor cycle counter (now taking lost_ticks into account)
 * 2000-08-13   Jan-Benedict Glaw <[email protected]>
 *  Fixed time_init to be aware of epoches != 1900. This prevents
 *  booting up in 2048 for me;) Code is stolen from rtc.c.
 * 2003-06-03   R. Scott Bailey <[email protected]>
 *  Tighten sanity in time_init from 1% (10,000 PPM) to 250 PPM
 */
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/bcd.h>
#include <linux/profile.h>
#include <linux/irq_work.h>

#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/hwrpb.h>
#include <asm/rtc.h>

#include <linux/mc146818rtc.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/clocksource.h>

#include "proto.h"
#include "irq_impl.h"

static int set_rtc_mmss(unsigned long);

DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);

#define TICK_SIZE (tick_nsec / 1000)

/*
 * Shift amount by which scaled_ticks_per_cycle is scaled.  Shifting
 * by 48 gives us 16 bits for HZ while keeping the accuracy good even
 * for large CPU clock rates.
 */
#define FIX_SHIFT   48

/* lump static variables together for more efficient access: */
static struct {
    /* cycle counter last time it got invoked */
    __u32 last_time;
    /* ticks/cycle * 2^48 */
    unsigned long scaled_ticks_per_cycle;
    /* partial unused tick */
    unsigned long partial_tick;
} state;

unsigned long est_cycle_freq;

#ifdef CONFIG_IRQ_WORK

DEFINE_PER_CPU(u8, irq_work_pending);

#define set_irq_work_pending_flag()  __get_cpu_var(irq_work_pending) = 1
#define test_irq_work_pending()      __get_cpu_var(irq_work_pending)
#define clear_irq_work_pending()     __get_cpu_var(irq_work_pending) = 0

void arch_irq_work_raise(void)
{
    set_irq_work_pending_flag();
}

#else  /* CONFIG_IRQ_WORK */

#define test_irq_work_pending()      0
#define clear_irq_work_pending()

#endif /* CONFIG_IRQ_WORK */


static inline __u32 rpcc(void)
{
    __u32 result;
    asm volatile ("rpcc %0" : "=r"(result));
    return result;
}

int update_persistent_clock(struct timespec now)
{
    return set_rtc_mmss(now.tv_sec);
}

void read_persistent_clock(struct timespec *ts)
{
    unsigned int year, mon, day, hour, min, sec, epoch;

    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);

    if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
        sec = bcd2bin(sec);
        min = bcd2bin(min);
        hour = bcd2bin(hour);
        day = bcd2bin(day);
        mon = bcd2bin(mon);
        year = bcd2bin(year);
    }

    /* PC-like is standard; used for year >= 70 */
    epoch = 1900;
    if (year < 20)
        epoch = 2000;
    else if (year >= 20 && year < 48)
        /* NT epoch */
        epoch = 1980;
    else if (year >= 48 && year < 70)
        /* Digital UNIX epoch */
        epoch = 1952;

    printk(KERN_INFO "Using epoch = %d\n", epoch);

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

    ts->tv_sec = mktime(year, mon, day, hour, min, sec);
    ts->tv_nsec = 0;
}



/*
 * timer_interrupt() needs to keep up the real-time clock,
 * as well as call the "xtime_update()" routine every clocktick
 */
irqreturn_t timer_interrupt(int irq, void *dev)
{
    unsigned long delta;
    __u32 now;
    long nticks;

#ifndef CONFIG_SMP
    /* Not SMP, do kernel PC profiling here.  */
    profile_tick(CPU_PROFILING);
#endif

    /*
     * Calculate how many ticks have passed since the last update,
     * including any previous partial leftover.  Save any resulting
     * fraction for the next pass.
     */
    now = rpcc();
    delta = now - state.last_time;
    state.last_time = now;
    delta = delta * state.scaled_ticks_per_cycle + state.partial_tick;
    state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1); 
    nticks = delta >> FIX_SHIFT;

    if (nticks)
        xtime_update(nticks);

    if (test_irq_work_pending()) {
        clear_irq_work_pending();
        irq_work_run();
    }

#ifndef CONFIG_SMP
    while (nticks--)
        update_process_times(user_mode(get_irq_regs()));
#endif

    return IRQ_HANDLED;
}

void __init
common_init_rtc(void)
{
    unsigned char x;

    /* Reset periodic interrupt frequency.  */
    x = CMOS_READ(RTC_FREQ_SELECT) & 0x3f;
        /* Test includes known working values on various platforms
           where 0x26 is wrong; we refuse to change those. */
    if (x != 0x26 && x != 0x25 && x != 0x19 && x != 0x06) {
        printk("Setting RTC_FREQ to 1024 Hz (%x)\n", x);
        CMOS_WRITE(0x26, RTC_FREQ_SELECT);
    }

    /* Turn on periodic interrupts.  */
    x = CMOS_READ(RTC_CONTROL);
    if (!(x & RTC_PIE)) {
        printk("Turning on RTC interrupts.\n");
        x |= RTC_PIE;
        x &= ~(RTC_AIE | RTC_UIE);
        CMOS_WRITE(x, RTC_CONTROL);
    }
    (void) CMOS_READ(RTC_INTR_FLAGS);

    outb(0x36, 0x43);   /* pit counter 0: system timer */
    outb(0x00, 0x40);
    outb(0x00, 0x40);

    outb(0xb6, 0x43);   /* pit counter 2: speaker */
    outb(0x31, 0x42);
    outb(0x13, 0x42);

    init_rtc_irq();
}

unsigned int common_get_rtc_time(struct rtc_time *time)
{
    return __get_rtc_time(time);
}

int common_set_rtc_time(struct rtc_time *time)
{
    return __set_rtc_time(time);
}

/* Validate a computed cycle counter result against the known bounds for
   the given processor core.  There's too much brokenness in the way of
   timing hardware for any one method to work everywhere.  :-(

   Return 0 if the result cannot be trusted, otherwise return the argument.  */

static unsigned long __init
validate_cc_value(unsigned long cc)
{
    static struct bounds {
        unsigned int min, max;
    } cpu_hz[] __initdata = {
        [EV3_CPU]    = {   50000000,  200000000 },  /* guess */
        [EV4_CPU]    = {  100000000,  300000000 },
        [LCA4_CPU]   = {  100000000,  300000000 },  /* guess */
        [EV45_CPU]   = {  200000000,  300000000 },
        [EV5_CPU]    = {  250000000,  433000000 },
        [EV56_CPU]   = {  333000000,  667000000 },
        [PCA56_CPU]  = {  400000000,  600000000 },  /* guess */
        [PCA57_CPU]  = {  500000000,  600000000 },  /* guess */
        [EV6_CPU]    = {  466000000,  600000000 },
        [EV67_CPU]   = {  600000000,  750000000 },
        [EV68AL_CPU] = {  750000000,  940000000 },
        [EV68CB_CPU] = { 1000000000, 1333333333 },
        /* None of the following are shipping as of 2001-11-01.  */
        [EV68CX_CPU] = { 1000000000, 1700000000 },  /* guess */
        [EV69_CPU]   = { 1000000000, 1700000000 },  /* guess */
        [EV7_CPU]    = {  800000000, 1400000000 },  /* guess */
        [EV79_CPU]   = { 1000000000, 2000000000 },  /* guess */
    };

    /* Allow for some drift in the crystal.  10MHz is more than enough.  */
    const unsigned int deviation = 10000000;

    struct percpu_struct *cpu;
    unsigned int index;

    cpu = (struct percpu_struct *)((char*)hwrpb + hwrpb->processor_offset);
    index = cpu->type & 0xffffffff;

    /* If index out of bounds, no way to validate.  */
    if (index >= ARRAY_SIZE(cpu_hz))
        return cc;

    /* If index contains no data, no way to validate.  */
    if (cpu_hz[index].max == 0)
        return cc;

    if (cc < cpu_hz[index].min - deviation
        || cc > cpu_hz[index].max + deviation)
        return 0;

    return cc;
}


/*
 * Calibrate CPU clock using legacy 8254 timer/counter. Stolen from
 * arch/i386/time.c.
 */

#define CALIBRATE_LATCH 0xffff
#define TIMEOUT_COUNT   0x100000

static unsigned long __init
calibrate_cc_with_pit(void)
{
    int cc, count = 0;

    /* Set the Gate high, disable speaker */
    outb((inb(0x61) & ~0x02) | 0x01, 0x61);

    /*
     * Now let's take care of CTC channel 2
     *
     * Set the Gate high, program CTC channel 2 for mode 0,
     * (interrupt on terminal count mode), binary count,
     * load 5 * LATCH count, (LSB and MSB) to begin countdown.
     */
    outb(0xb0, 0x43);       /* binary, mode 0, LSB/MSB, Ch 2 */
    outb(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
    outb(CALIBRATE_LATCH >> 8, 0x42);   /* MSB of count */

    cc = rpcc();
    do {
        count++;
    } while ((inb(0x61) & 0x20) == 0 && count < TIMEOUT_COUNT);
    cc = rpcc() - cc;

    /* Error: ECTCNEVERSET or ECPUTOOFAST.  */
    if (count <= 1 || count == TIMEOUT_COUNT)
        return 0;

    return ((long)cc * PIT_TICK_RATE) / (CALIBRATE_LATCH + 1);
}

/* 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.
   Let's hope other operating systems interpret the RTC the same way.  */

static unsigned long __init
rpcc_after_update_in_progress(void)
{
    do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
    do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);

    return rpcc();
}

#ifndef CONFIG_SMP
/* Until and unless we figure out how to get cpu cycle counters
   in sync and keep them there, we can't use the rpcc.  */
static cycle_t read_rpcc(struct clocksource *cs)
{
    cycle_t ret = (cycle_t)rpcc();
    return ret;
}

static struct clocksource clocksource_rpcc = {
    .name                   = "rpcc",
    .rating                 = 300,
    .read                   = read_rpcc,
    .mask                   = CLOCKSOURCE_MASK(32),
    .flags                  = CLOCK_SOURCE_IS_CONTINUOUS
};

static inline void register_rpcc_clocksource(long cycle_freq)
{
    clocksource_register_hz(&clocksource_rpcc, cycle_freq);
}
#else /* !CONFIG_SMP */
static inline void register_rpcc_clocksource(long cycle_freq)
{
}
#endif /* !CONFIG_SMP */

void __init
time_init(void)
{
    unsigned int cc1, cc2;
    unsigned long cycle_freq, tolerance;
    long diff;

    /* Calibrate CPU clock -- attempt #1.  */
    if (!est_cycle_freq)
        est_cycle_freq = validate_cc_value(calibrate_cc_with_pit());

    cc1 = rpcc();

    /* Calibrate CPU clock -- attempt #2.  */
    if (!est_cycle_freq) {
        cc1 = rpcc_after_update_in_progress();
        cc2 = rpcc_after_update_in_progress();
        est_cycle_freq = validate_cc_value(cc2 - cc1);
        cc1 = cc2;
    }

    cycle_freq = hwrpb->cycle_freq;
    if (est_cycle_freq) {
        /* If the given value is within 250 PPM of what we calculated,
           accept it.  Otherwise, use what we found.  */
        tolerance = cycle_freq / 4000;
        diff = cycle_freq - est_cycle_freq;
        if (diff < 0)
            diff = -diff;
        if ((unsigned long)diff > tolerance) {
            cycle_freq = est_cycle_freq;
            printk("HWRPB cycle frequency bogus.  "
                   "Estimated %lu Hz\n", cycle_freq);
        } else {
            est_cycle_freq = 0;
        }
    } else if (! validate_cc_value (cycle_freq)) {
        printk("HWRPB cycle frequency bogus, "
               "and unable to estimate a proper value!\n");
    }

    /* From John Bowman <[email protected]>: allow the values
       to settle, as the Update-In-Progress bit going low isn't good
       enough on some hardware.  2ms is our guess; we haven't found 
       bogomips yet, but this is close on a 500Mhz box.  */
    __delay(1000000);


    if (HZ > (1<<16)) {
        extern void __you_loose (void);
        __you_loose();
    }

    register_rpcc_clocksource(cycle_freq);

    state.last_time = cc1;
    state.scaled_ticks_per_cycle
        = ((unsigned long) HZ << FIX_SHIFT) / cycle_freq;
    state.partial_tick = 0L;

    /* Startup the timer source. */
    alpha_mv.init_rtc();
}

/*
 * 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.
 *
 * BUG: This routine does not handle hour overflow properly; it just
 *      sets the minutes. Usually you won't notice until after reboot!
 */


static int
set_rtc_mmss(unsigned long nowtime)
{
    int retval = 0;
    int real_seconds, real_minutes, cmos_minutes;
    unsigned char save_control, save_freq_select;

    /* irq are locally disabled here */
    spin_lock(&rtc_lock);
    /* Tell the clock it's being set */
    save_control = CMOS_READ(RTC_CONTROL);
    CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);

    /* Stop and reset prescaler */
    save_freq_select = CMOS_READ(RTC_FREQ_SELECT);
    CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);

    cmos_minutes = CMOS_READ(RTC_MINUTES);
    if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
        cmos_minutes = bcd2bin(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
     */
    real_seconds = nowtime % 60;
    real_minutes = nowtime / 60;
    if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1) {
        /* correct for half hour time zone */
        real_minutes += 30;
    }
    real_minutes %= 60;

    if (abs(real_minutes - cmos_minutes) < 30) {
        if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
            real_seconds = bin2bcd(real_seconds);
            real_minutes = bin2bcd(real_minutes);
        }
        CMOS_WRITE(real_seconds,RTC_SECONDS);
        CMOS_WRITE(real_minutes,RTC_MINUTES);
    } else {
        printk_once(KERN_NOTICE
               "set_rtc_mmss: can't update from %d to %d\n",
               cmos_minutes, real_minutes);
        retval = -1;
    }

    /* 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(save_control, RTC_CONTROL);
    CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
    spin_unlock(&rtc_lock);

    return retval;
}