time.c

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/* MN10300 Low level time management
 *
 * Copyright (C) 2007-2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 * - Derived from arch/i386/kernel/time.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/profile.h>
#include <linux/cnt32_to_63.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <asm/irq.h>
#include <asm/div64.h>
#include <asm/processor.h>
#include <asm/intctl-regs.h>
#include <asm/rtc.h>
#include "internal.h"

static unsigned long mn10300_last_tsc;  /* time-stamp counter at last time
                     * interrupt occurred */

static unsigned long sched_clock_multiplier;

/*
 * scheduler clock - returns current time in nanosec units.
 */
unsigned long long sched_clock(void)
{
    union {
        unsigned long long ll;
        unsigned l[2];
    } tsc64, result;
    unsigned long tmp;
    unsigned product[3]; /* 96-bit intermediate value */

    /* cnt32_to_63() is not safe with preemption */
    preempt_disable();

    /* expand the tsc to 64-bits.
     * - sched_clock() must be called once a minute or better or the
     *   following will go horribly wrong - see cnt32_to_63()
     */
    tsc64.ll = cnt32_to_63(get_cycles()) & 0x7fffffffffffffffULL;

    preempt_enable();

    /* scale the 64-bit TSC value to a nanosecond value via a 96-bit
     * intermediate
     */
    asm("mulu   %2,%0,%3,%0 \n" /* LSW * mult ->  0:%3:%0 */
        "mulu   %2,%1,%2,%1 \n" /* MSW * mult -> %2:%1:0 */
        "add    %3,%1       \n"
        "addc   0,%2        \n" /* result in %2:%1:%0 */
        : "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
        :  "0"(tsc64.l[0]),  "1"(tsc64.l[1]),  "2"(sched_clock_multiplier)
        : "cc");

    result.l[0] = product[1] << 16 | product[0] >> 16;
    result.l[1] = product[2] << 16 | product[1] >> 16;

    return result.ll;
}

/*
 * initialise the scheduler clock
 */
static void __init mn10300_sched_clock_init(void)
{
    sched_clock_multiplier =
        __muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
}

irqreturn_t local_timer_interrupt(void)
{
    profile_tick(CPU_PROFILING);
    update_process_times(user_mode(get_irq_regs()));
    return IRQ_HANDLED;
}

/*
 * initialise the various timers used by the main part of the kernel
 */
void __init time_init(void)
{
    /* we need the prescalar running to be able to use IOCLK/8
     * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
     * - IOCLK runs at Fosc rate (crystal speed)
     */
    TMPSCNT |= TMPSCNT_ENABLE;

    init_clocksource();

    printk(KERN_INFO
           "timestamp counter I/O clock running at %lu.%02lu"
           " (calibrated against RTC)\n",
           MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);

    mn10300_last_tsc = read_timestamp_counter();

    init_clockevents();

#ifdef CONFIG_MN10300_WD_TIMER
    /* start the watchdog timer */
    watchdog_go();
#endif

    mn10300_sched_clock_init();
}