LXR linux/arch/mn10300/kernel/time.c

   1/* MN10300 Low level time management
   2 *
   3 * Copyright (C) 2007-2008 Red Hat, Inc. All Rights Reserved.
   4 * Written by David Howells (dhowells@redhat.com)
   5 * - Derived from arch/i386/kernel/time.c
   6 *
   7 * This program is free software; you can redistribute it and/or
   8 * modify it under the terms of the GNU General Public Licence
   9 * as published by the Free Software Foundation; either version
  10 * 2 of the Licence, or (at your option) any later version.
  11 */
  12#include <linux/sched.h>
  13#include <linux/kernel.h>
  14#include <linux/interrupt.h>
  15#include <linux/time.h>
  16#include <linux/init.h>
  17#include <linux/smp.h>
  18#include <linux/profile.h>
  19#include <linux/cnt32_to_63.h>
  20#include <linux/clocksource.h>
  21#include <linux/clockchips.h>
  22#include <asm/irq.h>
  23#include <asm/div64.h>
  24#include <asm/processor.h>
  25#include <asm/intctl-regs.h>
  26#include <asm/rtc.h>
  27#include "internal.h"
  28
  29static unsigned long mn10300_last_tsc;  /* time-stamp counter at last time
  30                                         * interrupt occurred */
  31
  32static unsigned long sched_clock_multiplier;
  33
  34/*
  35 * scheduler clock - returns current time in nanosec units.
  36 */
  37unsigned long long sched_clock(void)
  38{
  39        union {
  40                unsigned long long ll;
  41                unsigned l[2];
  42        } tsc64, result;
  43        unsigned long tmp;
  44        unsigned product[3]; /* 96-bit intermediate value */
  45
  46        /* cnt32_to_63() is not safe with preemption */
  47        preempt_disable();
  48
  49        /* expand the tsc to 64-bits.
  50         * - sched_clock() must be called once a minute or better or the
  51         *   following will go horribly wrong - see cnt32_to_63()
  52         */
  53        tsc64.ll = cnt32_to_63(get_cycles()) & 0x7fffffffffffffffULL;
  54
  55        preempt_enable();
  56
  57        /* scale the 64-bit TSC value to a nanosecond value via a 96-bit
  58         * intermediate
  59         */
  60        asm("mulu       %2,%0,%3,%0     \n"     /* LSW * mult ->  0:%3:%0 */
  61            "mulu       %2,%1,%2,%1     \n"     /* MSW * mult -> %2:%1:0 */
  62            "add        %3,%1           \n"
  63            "addc       0,%2            \n"     /* result in %2:%1:%0 */
  64            : "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
  65            :  "0"(tsc64.l[0]),  "1"(tsc64.l[1]),  "2"(sched_clock_multiplier)
  66            : "cc");
  67
  68        result.l[0] = product[1] << 16 | product[0] >> 16;
  69        result.l[1] = product[2] << 16 | product[1] >> 16;
  70
  71        return result.ll;
  72}
  73
  74/*
  75 * initialise the scheduler clock
  76 */
  77static void __init mn10300_sched_clock_init(void)
  78{
  79        sched_clock_multiplier =
  80                __muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
  81}
  82
  83/**
  84 * local_timer_interrupt - Local timer interrupt handler
  85 *
  86 * Handle local timer interrupts for this CPU.  They may have been propagated
  87 * to this CPU from the CPU that actually gets them by way of an IPI.
  88 */
  89irqreturn_t local_timer_interrupt(void)
  90{
  91        profile_tick(CPU_PROFILING);
  92        update_process_times(user_mode(get_irq_regs()));
  93        return IRQ_HANDLED;
  94}
  95
  96/*
  97 * initialise the various timers used by the main part of the kernel
  98 */
  99void __init time_init(void)
 100{
 101        /* we need the prescalar running to be able to use IOCLK/8
 102         * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
 103         * - IOCLK runs at Fosc rate (crystal speed)
 104         */
 105        TMPSCNT |= TMPSCNT_ENABLE;
 106
 107        init_clocksource();
 108
 109        printk(KERN_INFO
 110               "timestamp counter I/O clock running at %lu.%02lu"
 111               " (calibrated against RTC)\n",
 112               MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
 113
 114        mn10300_last_tsc = read_timestamp_counter();
 115
 116        init_clockevents();
 117
 118#ifdef CONFIG_MN10300_WD_TIMER
 119        /* start the watchdog timer */
 120        watchdog_go();
 121#endif
 122
 123        mn10300_sched_clock_init();
 124}
 125