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#include <linux/irqdomain.h>
  26
  27#include <asm/timex.h>
  28#include <asm/platform.h>
  29
  30#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  31unsigned long ccount_per_jiffy;         /* per 1/HZ */
  32unsigned long nsec_per_ccount;          /* nsec per ccount increment */
  33#endif
  34
  35static u64 ccount_read(struct clocksource *cs)
  36{
  37        return (u64)get_ccount();
  38}
  39
  40static struct clocksource ccount_clocksource = {
  41        .name = "ccount",
  42        .rating = 200,
  43        .read = ccount_read,
  44        .mask = CLOCKSOURCE_MASK(32),
  45};
  46
  47static irqreturn_t timer_interrupt(int irq, void *dev_id);
  48static struct irqaction timer_irqaction = {
  49        .handler =      timer_interrupt,
  50        .flags =        IRQF_DISABLED,
  51        .name =         "timer",
  52};
  53
  54void __init time_init(void)
  55{
  56        unsigned int irq;
  57#ifdef CONFIG_XTENSA_CALIBRATE_CCOUNT
  58        printk("Calibrating CPU frequency ");
  59        platform_calibrate_ccount();
  60        printk("%d.%02d MHz\n", (int)ccount_per_jiffy/(1000000/HZ),
  61                        (int)(ccount_per_jiffy/(10000/HZ))%100);
  62#endif
  63        clocksource_register_hz(&ccount_clocksource, CCOUNT_PER_JIFFY * HZ);
  64
  65        /* Initialize the linux timer interrupt. */
  66
  67        irq = irq_create_mapping(NULL, LINUX_TIMER_INT);
  68        setup_irq(irq, &timer_irqaction);
  69        set_linux_timer(get_ccount() + CCOUNT_PER_JIFFY);
  70}
  71
  72/*
  73 * The timer interrupt is called HZ times per second.
  74 */
  75
  76irqreturn_t timer_interrupt (int irq, void *dev_id)
  77{
  78
  79        unsigned long next;
  80
  81        next = get_linux_timer();
  82
  83again:
  84        while ((signed long)(get_ccount() - next) > 0) {
  85
  86                profile_tick(CPU_PROFILING);
  87#ifndef CONFIG_SMP
  88                update_process_times(user_mode(get_irq_regs()));
  89#endif
  90
  91                xtime_update(1); /* Linux handler in kernel/time/timekeeping */
  92
  93                /* Note that writing CCOMPARE clears the interrupt. */
  94
  95                next += CCOUNT_PER_JIFFY;
  96                set_linux_timer(next);
  97        }
  98
  99        /* Allow platform to do something useful (Wdog). */
 100
 101        platform_heartbeat();
 102
 103        /* Make sure we didn't miss any tick... */
 104
 105        if ((signed long)(get_ccount() - next) > 0)
 106                goto again;
 107
 108        return IRQ_HANDLED;
 109}
 110
 111#ifndef CONFIG_GENERIC_CALIBRATE_DELAY
 112void __cpuinit calibrate_delay(void)
 113{
 114        loops_per_jiffy = CCOUNT_PER_JIFFY;
 115        printk("Calibrating delay loop (skipped)... "
 116               "%lu.%02lu BogoMIPS preset\n",
 117               loops_per_jiffy/(1000000/HZ),
 118               (loops_per_jiffy/(10000/HZ)) % 100);
 119}
 120#endif
 121