linux/arch/avr32/kernel/time.c
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   1/*
   2 * Copyright (C) 2004-2007 Atmel Corporation
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 */
   8#include <linux/clk.h>
   9#include <linux/clockchips.h>
  10#include <linux/init.h>
  11#include <linux/interrupt.h>
  12#include <linux/irq.h>
  13#include <linux/kernel.h>
  14#include <linux/time.h>
  15
  16#include <asm/sysreg.h>
  17
  18#include <mach/pm.h>
  19
  20
  21static cycle_t read_cycle_count(void)
  22{
  23        return (cycle_t)sysreg_read(COUNT);
  24}
  25
  26/*
  27 * The architectural cycle count registers are a fine clocksource unless
  28 * the system idle loop use sleep states like "idle":  the CPU cycles
  29 * measured by COUNT (and COMPARE) don't happen during sleep states.
  30 * Their duration also changes if cpufreq changes the CPU clock rate.
  31 * So we rate the clocksource using COUNT as very low quality.
  32 */
  33static struct clocksource counter = {
  34        .name           = "avr32_counter",
  35        .rating         = 50,
  36        .read           = read_cycle_count,
  37        .mask           = CLOCKSOURCE_MASK(32),
  38        .shift          = 16,
  39        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  40};
  41
  42static irqreturn_t timer_interrupt(int irq, void *dev_id)
  43{
  44        struct clock_event_device *evdev = dev_id;
  45
  46        if (unlikely(!(intc_get_pending(0) & 1)))
  47                return IRQ_NONE;
  48
  49        /*
  50         * Disable the interrupt until the clockevent subsystem
  51         * reprograms it.
  52         */
  53        sysreg_write(COMPARE, 0);
  54
  55        evdev->event_handler(evdev);
  56        return IRQ_HANDLED;
  57}
  58
  59static struct irqaction timer_irqaction = {
  60        .handler        = timer_interrupt,
  61        /* Oprofile uses the same irq as the timer, so allow it to be shared */
  62        .flags          = IRQF_TIMER | IRQF_DISABLED | IRQF_SHARED,
  63        .name           = "avr32_comparator",
  64};
  65
  66static int comparator_next_event(unsigned long delta,
  67                struct clock_event_device *evdev)
  68{
  69        unsigned long   flags;
  70
  71        raw_local_irq_save(flags);
  72
  73        /* The time to read COUNT then update COMPARE must be less
  74         * than the min_delta_ns value for this clockevent source.
  75         */
  76        sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);
  77
  78        raw_local_irq_restore(flags);
  79
  80        return 0;
  81}
  82
  83static void comparator_mode(enum clock_event_mode mode,
  84                struct clock_event_device *evdev)
  85{
  86        switch (mode) {
  87        case CLOCK_EVT_MODE_ONESHOT:
  88                pr_debug("%s: start\n", evdev->name);
  89                /* FALLTHROUGH */
  90        case CLOCK_EVT_MODE_RESUME:
  91                cpu_disable_idle_sleep();
  92                break;
  93        case CLOCK_EVT_MODE_UNUSED:
  94        case CLOCK_EVT_MODE_SHUTDOWN:
  95                sysreg_write(COMPARE, 0);
  96                pr_debug("%s: stop\n", evdev->name);
  97                cpu_enable_idle_sleep();
  98                break;
  99        default:
 100                BUG();
 101        }
 102}
 103
 104static struct clock_event_device comparator = {
 105        .name           = "avr32_comparator",
 106        .features       = CLOCK_EVT_FEAT_ONESHOT,
 107        .shift          = 16,
 108        .rating         = 50,
 109        .cpumask        = CPU_MASK_CPU0,
 110        .set_next_event = comparator_next_event,
 111        .set_mode       = comparator_mode,
 112};
 113
 114void __init time_init(void)
 115{
 116        unsigned long counter_hz;
 117        int ret;
 118
 119        xtime.tv_sec = mktime(2007, 1, 1, 0, 0, 0);
 120        xtime.tv_nsec = 0;
 121
 122        set_normalized_timespec(&wall_to_monotonic,
 123                                -xtime.tv_sec, -xtime.tv_nsec);
 124
 125        /* figure rate for counter */
 126        counter_hz = clk_get_rate(boot_cpu_data.clk);
 127        counter.mult = clocksource_hz2mult(counter_hz, counter.shift);
 128
 129        ret = clocksource_register(&counter);
 130        if (ret)
 131                pr_debug("timer: could not register clocksource: %d\n", ret);
 132
 133        /* setup COMPARE clockevent */
 134        comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
 135        comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
 136        comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;
 137
 138        sysreg_write(COMPARE, 0);
 139        timer_irqaction.dev_id = &comparator;
 140
 141        ret = setup_irq(0, &timer_irqaction);
 142        if (ret)
 143                pr_debug("timer: could not request IRQ 0: %d\n", ret);
 144        else {
 145                clockevents_register_device(&comparator);
 146
 147                pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
 148                                ((counter_hz + 500) / 1000) / 1000,
 149                                ((counter_hz + 500) / 1000) % 1000);
 150        }
 151}
 152