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

   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        /* FIXME: xtime&wall_to_monotonic are set in timekeeping_init. */
  64        read_persistent_clock(&xtime);
  65        set_normalized_timespec(&wall_to_monotonic,
  66                -xtime.tv_sec, -xtime.tv_nsec);
  67
  68#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  69        printk("Calibrating CPU frequency ");
  70        platform_calibrate_ccount();
  71        printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
  72                        (int)(ccount_per_jiffy/(10000/HZ))%100);
  73#endif
  74        ccount_clocksource.mult =
  75                clocksource_hz2mult(CCOUNT_PER_JIFFY * HZ,
  76                                ccount_clocksource.shift);
  77        clocksource_register(&ccount_clocksource);
  78
  79        /* Initialize the linux timer interrupt. */
  80
  81        setup_irq(LINUX_TIMER_INT, &timer_irqaction);
  82        set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
  83}
  84
  85/*
  86 * The timer interrupt is called HZ times per second.
  87 */
  88
  89irqreturn_t timer_interrupt (int irq, void *dev_id)
  90{
  91
  92        unsigned long next;
  93
  94        next = get_linux_timer();
  95
  96again:
  97        while ((signed long)(get_ccount() - next) > 0) {
  98
  99                profile_tick(CPU_PROFILING);
 100#ifndef CONFIG_SMP
 101                update_process_times(user_mode(get_irq_regs()));
 102#endif
 103
 104                write_seqlock(&xtime_lock);
 105
 106                do_timer(1); /* Linux handler in kernel/timer.c */
 107
 108                /* Note that writing CCOMPARE clears the interrupt. */
 109
 110                next += CCOUNT_PER_JIFFY;
 111                set_linux_timer(next);
 112
 113                write_sequnlock(&xtime_lock);
 114        }
 115
 116        /* Allow platform to do something useful (Wdog). */
 117
 118        platform_heartbeat();
 119
 120        /* Make sure we didn't miss any tick... */
 121
 122        if ((signed long)(get_ccount() - next) > 0)
 123                goto again;
 124
 125        return IRQ_HANDLED;
 126}
 127
 128#ifndef CONFIG_GENERIC_CALIBRATE_DELAY
 129void __cpuinit calibrate_delay(void)
 130{
 131        loops_per_jiffy = CCOUNT_PER_JIFFY;
 132        printk("Calibrating delay loop (skipped)... "
 133               "%lu.%02lu BogoMIPS preset\n",
 134               loops_per_jiffy/(1000000/HZ),
 135               (loops_per_jiffy/(10000/HZ)) % 100);
 136}
 137#endif
 138