linux/arch/mn10300/kernel/time.c
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   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 <asm/irq.h>
  21#include <asm/div64.h>
  22#include <asm/processor.h>
  23#include <asm/intctl-regs.h>
  24#include <asm/rtc.h>
  25
  26#ifdef CONFIG_MN10300_RTC
  27unsigned long mn10300_ioclk;            /* system I/O clock frequency */
  28unsigned long mn10300_iobclk;           /* system I/O clock frequency */
  29unsigned long mn10300_tsc_per_HZ;       /* number of ioclks per jiffy */
  30#endif /* CONFIG_MN10300_RTC */
  31
  32static unsigned long mn10300_last_tsc;  /* time-stamp counter at last time
  33                                         * interrupt occurred */
  34
  35static irqreturn_t timer_interrupt(int irq, void *dev_id);
  36
  37static struct irqaction timer_irq = {
  38        .handler        = timer_interrupt,
  39        .flags          = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
  40        .mask           = CPU_MASK_NONE,
  41        .name           = "timer",
  42};
  43
  44static unsigned long sched_clock_multiplier;
  45
  46/*
  47 * scheduler clock - returns current time in nanosec units.
  48 */
  49unsigned long long sched_clock(void)
  50{
  51        union {
  52                unsigned long long ll;
  53                unsigned l[2];
  54        } tsc64, result;
  55        unsigned long tsc, tmp;
  56        unsigned product[3]; /* 96-bit intermediate value */
  57
  58        /* read the TSC value
  59         */
  60        tsc = 0 - get_cycles(); /* get_cycles() counts down */
  61
  62        /* expand to 64-bits.
  63         * - sched_clock() must be called once a minute or better or the
  64         *   following will go horribly wrong - see cnt32_to_63()
  65         */
  66        tsc64.ll = cnt32_to_63(tsc) & 0x7fffffffffffffffULL;
  67
  68        /* scale the 64-bit TSC value to a nanosecond value via a 96-bit
  69         * intermediate
  70         */
  71        asm("mulu       %2,%0,%3,%0     \n"     /* LSW * mult ->  0:%3:%0 */
  72            "mulu       %2,%1,%2,%1     \n"     /* MSW * mult -> %2:%1:0 */
  73            "add        %3,%1           \n"
  74            "addc       0,%2            \n"     /* result in %2:%1:%0 */
  75            : "=r"(product[0]), "=r"(product[1]), "=r"(product[2]), "=r"(tmp)
  76            :  "0"(tsc64.l[0]),  "1"(tsc64.l[1]),  "2"(sched_clock_multiplier)
  77            : "cc");
  78
  79        result.l[0] = product[1] << 16 | product[0] >> 16;
  80        result.l[1] = product[2] << 16 | product[1] >> 16;
  81
  82        return result.ll;
  83}
  84
  85/*
  86 * initialise the scheduler clock
  87 */
  88static void __init mn10300_sched_clock_init(void)
  89{
  90        sched_clock_multiplier =
  91                __muldiv64u(NSEC_PER_SEC, 1 << 16, MN10300_TSCCLK);
  92}
  93
  94/*
  95 * advance the kernel's time keeping clocks (xtime and jiffies)
  96 * - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
  97 *   there's a need to update
  98 */
  99static irqreturn_t timer_interrupt(int irq, void *dev_id)
 100{
 101        unsigned tsc, elapse;
 102
 103        write_seqlock(&xtime_lock);
 104
 105        while (tsc = get_cycles(),
 106               elapse = mn10300_last_tsc - tsc, /* time elapsed since last
 107                                                 * tick */
 108               elapse > MN10300_TSC_PER_HZ
 109               ) {
 110                mn10300_last_tsc -= MN10300_TSC_PER_HZ;
 111
 112                /* advance the kernel's time tracking system */
 113                profile_tick(CPU_PROFILING);
 114                do_timer(1);
 115                check_rtc_time();
 116        }
 117
 118        write_sequnlock(&xtime_lock);
 119
 120        update_process_times(user_mode(get_irq_regs()));
 121
 122        return IRQ_HANDLED;
 123}
 124
 125/*
 126 * initialise the various timers used by the main part of the kernel
 127 */
 128void __init time_init(void)
 129{
 130        /* we need the prescalar running to be able to use IOCLK/8
 131         * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
 132         * - IOCLK runs at Fosc rate (crystal speed)
 133         */
 134        TMPSCNT |= TMPSCNT_ENABLE;
 135
 136        startup_timestamp_counter();
 137
 138        printk(KERN_INFO
 139               "timestamp counter I/O clock running at %lu.%02lu"
 140               " (calibrated against RTC)\n",
 141               MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);
 142
 143        xtime.tv_sec = get_initial_rtc_time();
 144        xtime.tv_nsec = 0;
 145
 146        mn10300_last_tsc = TMTSCBC;
 147
 148        /* use timer 0 & 1 cascaded to tick at as close to HZ as possible */
 149        setup_irq(TMJCIRQ, &timer_irq);
 150
 151        set_intr_level(TMJCIRQ, TMJCICR_LEVEL);
 152
 153        startup_jiffies_counter();
 154
 155#ifdef CONFIG_MN10300_WD_TIMER
 156        /* start the watchdog timer */
 157        watchdog_go();
 158#endif
 159
 160        mn10300_sched_clock_init();
 161}
 162