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