/*
 *  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 (bowman@math.ualberta.ca)
 *      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 (dl8bcu@gmx.net)
 *      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 <jbglaw@lug-owl.de>
 *      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 <scott.bailey@eds.com>
 *      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 <asm/uaccess.h>
#include <asm/io.h>
#include <asm/hwrpb.h>
#include <asm/8253pit.h>
#include <asm/rtc.h>

#include <linux/mc146818rtc.h>
#include <linux/time.h>
#include <linux/timex.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;
        /* last time the CMOS clock got updated */
        time_t last_rtc_update;
        /* partial unused tick */
        unsigned long partial_tick;
} state;

unsigned long est_cycle_freq;


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

/*
 * timer_interrupt() needs to keep up the real-time clock,
 * as well as call the "do_timer()" 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

        write_seqlock(&xtime_lock);

        /*
         * 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)
                do_timer(nticks);

        /*
         * If we have an externally synchronized Linux clock, then update
         * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
         * called as close as possible to 500 ms before the new second starts.
         */
        if (ntp_synced()
            && xtime.tv_sec > state.last_rtc_update + 660
            && xtime.tv_nsec >= 500000 - ((unsigned) TICK_SIZE) / 2
            && xtime.tv_nsec <= 500000 + ((unsigned) TICK_SIZE) / 2) {
                int tmp = set_rtc_mmss(xtime.tv_sec);
                state.last_rtc_update = xtime.tv_sec - (tmp ? 600 : 0);
        }

        write_sequnlock(&xtime_lock);

#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();
}

void __init
time_init(void)
{
        unsigned int year, mon, day, hour, min, sec, cc1, cc2, epoch;
        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 <bowman@math.ualberta.ca>: 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);

        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;

        xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
        xtime.tv_nsec = 0;

        wall_to_monotonic.tv_sec -= xtime.tv_sec;
        wall_to_monotonic.tv_nsec = 0;

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

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

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

/*
 * Use the cycle counter to estimate an displacement from the last time
 * tick.  Unfortunately the Alpha designers made only the low 32-bits of
 * the cycle counter active, so we overflow on 8.2 seconds on a 500MHz
 * part.  So we can't do the "find absolute time in terms of cycles" thing
 * that the other ports do.
 */
u32 arch_gettimeoffset(void)
{
#ifdef 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 tricks.  */
        return 0;
#else
        unsigned long delta_cycles, delta_usec, partial_tick;

        delta_cycles = rpcc() - state.last_time;
        partial_tick = state.partial_tick;
        /*
         * usec = cycles * ticks_per_cycle * 2**48 * 1e6 / (2**48 * ticks)
         *      = cycles * (s_t_p_c) * 1e6 / (2**48 * ticks)
         *      = cycles * (s_t_p_c) * 15625 / (2**42 * ticks)
         *
         * which, given a 600MHz cycle and a 1024Hz tick, has a
         * dynamic range of about 1.7e17, which is less than the
         * 1.8e19 in an unsigned long, so we are safe from overflow.
         *
         * Round, but with .5 up always, since .5 to even is harder
         * with no clear gain.
         */

        delta_usec = (delta_cycles * state.scaled_ticks_per_cycle 
                      + partial_tick) * 15625;
        delta_usec = ((delta_usec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;
        return delta_usec * 1000;
#endif
}

/*
 * 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(KERN_WARNING
                       "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;
}