[MIPS] Deforest the function pointer jungle in the time code.

[mirror_ubuntu-zesty-kernel.git] / arch / mips / kernel / time.c

/*
 * Copyright 2001 MontaVista Software Inc.
 * Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
 * Copyright (c) 2003, 2004  Maciej W. Rozycki
 *
 * Common time service routines for MIPS machines. See
 * Documentation/mips/time.README.
 *
 * This program is free software; you can redistribute  it and/or modify it
 * under  the terms of  the GNU General  Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 */
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/param.h>
#include <linux/profile.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
#include <linux/spinlock.h>
#include <linux/interrupt.h>
#include <linux/module.h>

#include <asm/bootinfo.h>
#include <asm/cache.h>
#include <asm/compiler.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
#include <asm/div64.h>
#include <asm/sections.h>
#include <asm/time.h>

/*
 * The integer part of the number of usecs per jiffy is taken from tick,
 * but the fractional part is not recorded, so we calculate it using the
 * initial value of HZ.  This aids systems where tick isn't really an
 * integer (e.g. for HZ = 128).
 */
#define USECS_PER_JIFFY         TICK_SIZE
#define USECS_PER_JIFFY_FRAC    ((unsigned long)(u32)((1000000ULL << 32) / HZ))

#define TICK_SIZE       (tick_nsec / 1000)

/*
 * forward reference
 */
DEFINE_SPINLOCK(rtc_lock);
EXPORT_SYMBOL(rtc_lock);

int __weak rtc_mips_set_time(unsigned long sec)
{
        return 0;
}
EXPORT_SYMBOL(rtc_mips_set_time);

int __weak rtc_mips_set_mmss(unsigned long nowtime)
{
        return rtc_mips_set_time(nowtime);
}

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

/* how many counter cycles in a jiffy */
static unsigned long cycles_per_jiffy __read_mostly;

/* expirelo is the count value for next CPU timer interrupt */
static unsigned int expirelo;


/*
 * Null timer ack for systems not needing one (e.g. i8254).
 */
static void null_timer_ack(void) { /* nothing */ }

/*
 * Null high precision timer functions for systems lacking one.
 */
static cycle_t null_hpt_read(void)
{
        return 0;
}

/*
 * Timer ack for an R4k-compatible timer of a known frequency.
 */
static void c0_timer_ack(void)
{
        unsigned int count;

        /* Ack this timer interrupt and set the next one.  */
        expirelo += cycles_per_jiffy;
        write_c0_compare(expirelo);

        /* Check to see if we have missed any timer interrupts.  */
        while (((count = read_c0_count()) - expirelo) < 0x7fffffff) {
                /* missed_timer_count++; */
                expirelo = count + cycles_per_jiffy;
                write_c0_compare(expirelo);
        }
}

/*
 * High precision timer functions for a R4k-compatible timer.
 */
static cycle_t c0_hpt_read(void)
{
        return read_c0_count();
}

/* For use both as a high precision timer and an interrupt source.  */
static void __init c0_hpt_timer_init(void)
{
        expirelo = read_c0_count() + cycles_per_jiffy;
        write_c0_compare(expirelo);
}

int (*mips_timer_state)(void);
void (*mips_timer_ack)(void);

/*
 * local_timer_interrupt() does profiling and process accounting
 * on a per-CPU basis.
 *
 * In UP mode, it is invoked from the (global) timer_interrupt.
 *
 * In SMP mode, it might invoked by per-CPU timer interrupt, or
 * a broadcasted inter-processor interrupt which itself is triggered
 * by the global timer interrupt.
 */
void local_timer_interrupt(int irq, void *dev_id)
{
        profile_tick(CPU_PROFILING);
        update_process_times(user_mode(get_irq_regs()));
}

/*
 * High-level timer interrupt service routines.  This function
 * is set as irqaction->handler and is invoked through do_IRQ.
 */
irqreturn_t timer_interrupt(int irq, void *dev_id)
{
        write_seqlock(&xtime_lock);

        mips_timer_ack();

        /*
         * call the generic timer interrupt handling
         */
        do_timer(1);

        write_sequnlock(&xtime_lock);

        /*
         * In UP mode, we call local_timer_interrupt() to do profiling
         * and process accouting.
         *
         * In SMP mode, local_timer_interrupt() is invoked by appropriate
         * low-level local timer interrupt handler.
         */
        local_timer_interrupt(irq, dev_id);

        return IRQ_HANDLED;
}

int null_perf_irq(void)
{
        return 0;
}

int (*perf_irq)(void) = null_perf_irq;

EXPORT_SYMBOL(null_perf_irq);
EXPORT_SYMBOL(perf_irq);

/*
 * Timer interrupt
 */
int cp0_compare_irq;

/*
 * Performance counter IRQ or -1 if shared with timer
 */
int cp0_perfcount_irq;
EXPORT_SYMBOL_GPL(cp0_perfcount_irq);

/*
 * Possibly handle a performance counter interrupt.
 * Return true if the timer interrupt should not be checked
 */
static inline int handle_perf_irq (int r2)
{
        /*
         * The performance counter overflow interrupt may be shared with the
         * timer interrupt (cp0_perfcount_irq < 0). If it is and a
         * performance counter has overflowed (perf_irq() == IRQ_HANDLED)
         * and we can't reliably determine if a counter interrupt has also
         * happened (!r2) then don't check for a timer interrupt.
         */
        return (cp0_perfcount_irq < 0) &&
                perf_irq() == IRQ_HANDLED &&
                !r2;
}

asmlinkage void ll_timer_interrupt(int irq)
{
        int r2 = cpu_has_mips_r2;

        irq_enter();
        kstat_this_cpu.irqs[irq]++;

        if (handle_perf_irq(r2))
                goto out;

        if (r2 && ((read_c0_cause() & (1 << 30)) == 0))
                goto out;

        timer_interrupt(irq, NULL);

out:
        irq_exit();
}

asmlinkage void ll_local_timer_interrupt(int irq)
{
        irq_enter();
        if (smp_processor_id() != 0)
                kstat_this_cpu.irqs[irq]++;

        /* we keep interrupt disabled all the time */
        local_timer_interrupt(irq, NULL);

        irq_exit();
}

/*
 * time_init() - it does the following things.
 *
 * 1) plat_time_init() -
 *      a) (optional) set up RTC routines,
 *      b) (optional) calibrate and set the mips_hpt_frequency
 *          (only needed if you intended to use cpu counter as timer interrupt
 *           source)
 * 2) calculate a couple of cached variables for later usage
 * 3) plat_timer_setup() -
 *      a) (optional) over-write any choices made above by time_init().
 *      b) machine specific code should setup the timer irqaction.
 *      c) enable the timer interrupt
 */

unsigned int mips_hpt_frequency;

static struct irqaction timer_irqaction = {
        .handler = timer_interrupt,
        .flags = IRQF_DISABLED | IRQF_PERCPU,
        .name = "timer",
};

static unsigned int __init calibrate_hpt(void)
{
        cycle_t frequency, hpt_start, hpt_end, hpt_count, hz;

        const int loops = HZ / 10;
        int log_2_loops = 0;
        int i;

        /*
         * We want to calibrate for 0.1s, but to avoid a 64-bit
         * division we round the number of loops up to the nearest
         * power of 2.
         */
        while (loops > 1 << log_2_loops)
                log_2_loops++;
        i = 1 << log_2_loops;

        /*
         * Wait for a rising edge of the timer interrupt.
         */
        while (mips_timer_state());
        while (!mips_timer_state());

        /*
         * Now see how many high precision timer ticks happen
         * during the calculated number of periods between timer
         * interrupts.
         */
        hpt_start = clocksource_mips.read();
        do {
                while (mips_timer_state());
                while (!mips_timer_state());
        } while (--i);
        hpt_end = clocksource_mips.read();

        hpt_count = (hpt_end - hpt_start) & clocksource_mips.mask;
        hz = HZ;
        frequency = hpt_count * hz;

        return frequency >> log_2_loops;
}

struct clocksource clocksource_mips = {
        .name           = "MIPS",
        .mask           = CLOCKSOURCE_MASK(32),
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

static void __init init_mips_clocksource(void)
{
        u64 temp;
        u32 shift;

        if (!mips_hpt_frequency || clocksource_mips.read == null_hpt_read)
                return;

        /* Calclate a somewhat reasonable rating value */
        clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
        /* Find a shift value */
        for (shift = 32; shift > 0; shift--) {
                temp = (u64) NSEC_PER_SEC << shift;
                do_div(temp, mips_hpt_frequency);
                if ((temp >> 32) == 0)
                        break;
        }
        clocksource_mips.shift = shift;
        clocksource_mips.mult = (u32)temp;

        clocksource_register(&clocksource_mips);
}

void __init __weak plat_time_init(void)
{
}

void __init time_init(void)
{
        plat_time_init();

        /* Choose appropriate high precision timer routines.  */
        if (!cpu_has_counter && !clocksource_mips.read)
                /* No high precision timer -- sorry.  */
                clocksource_mips.read = null_hpt_read;
        else if (!mips_hpt_frequency && !mips_timer_state) {
                /* A high precision timer of unknown frequency.  */
                if (!clocksource_mips.read)
                        /* No external high precision timer -- use R4k.  */
                        clocksource_mips.read = c0_hpt_read;
        } else {
                /* We know counter frequency.  Or we can get it.  */
                if (!clocksource_mips.read) {
                        /* No external high precision timer -- use R4k.  */
                        clocksource_mips.read = c0_hpt_read;

                        if (!mips_timer_state) {
                                /* No external timer interrupt -- use R4k.  */
                                mips_timer_ack = c0_timer_ack;
                                /* Calculate cache parameters.  */
                                cycles_per_jiffy =
                                        (mips_hpt_frequency + HZ / 2) / HZ;
                                /*
                                 * This sets up the high precision
                                 * timer for the first interrupt.
                                 */
                                c0_hpt_timer_init();
                        }
                }
                if (!mips_hpt_frequency)
                        mips_hpt_frequency = calibrate_hpt();

                /* Report the high precision timer rate for a reference.  */
                printk("Using %u.%03u MHz high precision timer.\n",
                       ((mips_hpt_frequency + 500) / 1000) / 1000,
                       ((mips_hpt_frequency + 500) / 1000) % 1000);
        }

        if (!mips_timer_ack)
                /* No timer interrupt ack (e.g. i8254).  */
                mips_timer_ack = null_timer_ack;

        /*
         * Call board specific timer interrupt setup.
         *
         * this pointer must be setup in machine setup routine.
         *
         * Even if a machine chooses to use a low-level timer interrupt,
         * it still needs to setup the timer_irqaction.
         * In that case, it might be better to set timer_irqaction.handler
         * to be NULL function so that we are sure the high-level code
         * is not invoked accidentally.
         */
        plat_timer_setup(&timer_irqaction);

        init_mips_clocksource();
}

#define FEBRUARY                2
#define STARTOFTIME             1970
#define SECDAY                  86400L
#define SECYR                   (SECDAY * 365)
#define leapyear(y)             ((!((y) % 4) && ((y) % 100)) || !((y) % 400))
#define days_in_year(y)         (leapyear(y) ? 366 : 365)
#define days_in_month(m)        (month_days[(m) - 1])

static int month_days[12] = {
        31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
};

void to_tm(unsigned long tim, struct rtc_time *tm)
{
        long hms, day, gday;
        int i;

        gday = day = tim / SECDAY;
        hms = tim % SECDAY;

        /* Hours, minutes, seconds are easy */
        tm->tm_hour = hms / 3600;
        tm->tm_min = (hms % 3600) / 60;
        tm->tm_sec = (hms % 3600) % 60;

        /* Number of years in days */
        for (i = STARTOFTIME; day >= days_in_year(i); i++)
                day -= days_in_year(i);
        tm->tm_year = i;

        /* Number of months in days left */
        if (leapyear(tm->tm_year))
                days_in_month(FEBRUARY) = 29;
        for (i = 1; day >= days_in_month(i); i++)
                day -= days_in_month(i);
        days_in_month(FEBRUARY) = 28;
        tm->tm_mon = i - 1;             /* tm_mon starts from 0 to 11 */

        /* Days are what is left over (+1) from all that. */
        tm->tm_mday = day + 1;

        /*
         * Determine the day of week
         */
        tm->tm_wday = (gday + 4) % 7;   /* 1970/1/1 was Thursday */
}

EXPORT_SYMBOL(to_tm);