linux/arch/xtensa/kernel/time.c
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   1/*
   2 * arch/xtensa/kernel/time.c
   3 *
   4 * Timer and clock support.
   5 *
   6 * This file is subject to the terms and conditions of the GNU General Public
   7 * License.  See the file "COPYING" in the main directory of this archive
   8 * for more details.
   9 *
  10 * Copyright (C) 2005 Tensilica Inc.
  11 *
  12 * Chris Zankel <chris@zankel.net>
  13 */
  14
  15#include <linux/errno.h>
  16#include <linux/sched.h>
  17#include <linux/time.h>
  18#include <linux/clocksource.h>
  19#include <linux/interrupt.h>
  20#include <linux/module.h>
  21#include <linux/init.h>
  22#include <linux/irq.h>
  23#include <linux/profile.h>
  24#include <linux/delay.h>
  25
  26#include <asm/timex.h>
  27#include <asm/platform.h>
  28
  29#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  30unsigned long ccount_per_jiffy;         /* per 1/HZ */
  31unsigned long nsec_per_ccount;          /* nsec per ccount increment */
  32#endif
  33
  34static cycle_t ccount_read(void)
  35{
  36        return (cycle_t)get_ccount();
  37}
  38
  39static struct clocksource ccount_clocksource = {
  40        .name = "ccount",
  41        .rating = 200,
  42        .read = ccount_read,
  43        .mask = CLOCKSOURCE_MASK(32),
  44        /*
  45         * With a shift of 22 the lower limit of the cpu clock is
  46         * 1MHz, where NSEC_PER_CCOUNT is 1000 or a bit less than
  47         * 2^10: Since we have 32 bits and the multiplicator can
  48         * already take up as much as 10 bits, this leaves us with
  49         * remaining upper 22 bits.
  50         */
  51        .shift = 22,
  52};
  53
  54static irqreturn_t timer_interrupt(int irq, void *dev_id);
  55static struct irqaction timer_irqaction = {
  56        .handler =      timer_interrupt,
  57        .flags =        IRQF_DISABLED,
  58        .name =         "timer",
  59};
  60
  61void __init time_init(void)
  62{
  63#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  64        printk("Calibrating CPU frequency ");
  65        platform_calibrate_ccount();
  66        printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
  67                        (int)(ccount_per_jiffy/(10000/HZ))%100);
  68#endif
  69        ccount_clocksource.mult =
  70                clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ,
  71                                ccount_clocksource.shift);
  72        clocksource_register(&ccount_clocksource);
  73
  74        /* Initialize the linux timer interrupt. */
  75
  76        setup_irq(LINUX_TIMER_INT, &timer_irqaction);
  77        set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
  78}
  79
  80/*
  81 * The timer interrupt is called HZ times per second.
  82 */
  83
  84irqreturn_t timer_interrupt (int irq, void *dev_id)
  85{
  86
  87        unsigned long next;
  88
  89        next = get_linux_timer();
  90
  91again:
  92        while ((signed long)(get_ccount() - next) > 0) {
  93
  94                profile_tick(CPU_PROFILING);
  95#ifndef CONFIG_SMP
  96                update_process_times(user_mode(get_irq_regs()));
  97#endif
  98
  99                xtime_update(1); /* Linux handler in kernel/time/timekeeping */
 100
 101                /* Note that writing CCOMPARE clears the interrupt. */
 102
 103                next += CCOUNT_PER_JIFFY;
 104                set_linux_timer(next);
 105        }
 106
 107        /* Allow platform to do something useful (Wdog). */
 108
 109        platform_heartbeat();
 110
 111        /* Make sure we didn't miss any tick... */
 112
 113        if ((signed long)(get_ccount() - next) > 0)
 114                goto again;
 115
 116        return IRQ_HANDLED;
 117}
 118
 119#ifndef CONFIG_GENERIC_CALIBRATE_DELAY
 120void __cpuinit calibrate_delay(void)
 121{
 122        loops_per_jiffy = CCOUNT_PER_JIFFY;
 123        printk("Calibrating delay loop (skipped)... "
 124               "%lu.%02lu BogoMIPS preset\n",
 125               loops_per_jiffy/(1000000/HZ),
 126               (loops_per_jiffy/(10000/HZ)) % 100);
 127}
 128#endif
 129