LXR linux/arch/avr32/kernel/time.c

   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(struct clocksource *cs)
  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        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  39};
  40
  41static irqreturn_t timer_interrupt(int irq, void *dev_id)
  42{
  43        struct clock_event_device *evdev = dev_id;
  44
  45        if (unlikely(!(intc_get_pending(0) & 1)))
  46                return IRQ_NONE;
  47
  48        /*
  49         * Disable the interrupt until the clockevent subsystem
  50         * reprograms it.
  51         */
  52        sysreg_write(COMPARE, 0);
  53
  54        evdev->event_handler(evdev);
  55        return IRQ_HANDLED;
  56}
  57
  58static struct irqaction timer_irqaction = {
  59        .handler        = timer_interrupt,
  60        /* Oprofile uses the same irq as the timer, so allow it to be shared */
  61        .flags          = IRQF_TIMER | IRQF_DISABLED | IRQF_SHARED,
  62        .name           = "avr32_comparator",
  63};
  64
  65static int comparator_next_event(unsigned long delta,
  66                struct clock_event_device *evdev)
  67{
  68        unsigned long   flags;
  69
  70        raw_local_irq_save(flags);
  71
  72        /* The time to read COUNT then update COMPARE must be less
  73         * than the min_delta_ns value for this clockevent source.
  74         */
  75        sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);
  76
  77        raw_local_irq_restore(flags);
  78
  79        return 0;
  80}
  81
  82static void comparator_mode(enum clock_event_mode mode,
  83                struct clock_event_device *evdev)
  84{
  85        switch (mode) {
  86        case CLOCK_EVT_MODE_ONESHOT:
  87                pr_debug("%s: start\n", evdev->name);
  88                /* FALLTHROUGH */
  89        case CLOCK_EVT_MODE_RESUME:
  90                cpu_disable_idle_sleep();
  91                break;
  92        case CLOCK_EVT_MODE_UNUSED:
  93        case CLOCK_EVT_MODE_SHUTDOWN:
  94                sysreg_write(COMPARE, 0);
  95                pr_debug("%s: stop\n", evdev->name);
  96                cpu_enable_idle_sleep();
  97                break;
  98        default:
  99                BUG();
 100        }
 101}
 102
 103static struct clock_event_device comparator = {
 104        .name           = "avr32_comparator",
 105        .features       = CLOCK_EVT_FEAT_ONESHOT,
 106        .shift          = 16,
 107        .rating         = 50,
 108        .set_next_event = comparator_next_event,
 109        .set_mode       = comparator_mode,
 110};
 111
 112void read_persistent_clock(struct timespec *ts)
 113{
 114        ts->tv_sec = mktime(2007, 1, 1, 0, 0, 0);
 115        ts->tv_nsec = 0;
 116}
 117
 118void __init time_init(void)
 119{
 120        unsigned long counter_hz;
 121        int ret;
 122
 123        /* figure rate for counter */
 124        counter_hz = clk_get_rate(boot_cpu_data.clk);
 125        ret = clocksource_register_hz(&counter, counter_hz);
 126        if (ret)
 127                pr_debug("timer: could not register clocksource: %d\n", ret);
 128
 129        /* setup COMPARE clockevent */
 130        comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
 131        comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
 132        comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;
 133        comparator.cpumask = cpumask_of(0);
 134
 135        sysreg_write(COMPARE, 0);
 136        timer_irqaction.dev_id = &comparator;
 137
 138        ret = setup_irq(0, &timer_irqaction);
 139        if (ret)
 140                pr_debug("timer: could not request IRQ 0: %d\n", ret);
 141        else {
 142                clockevents_register_device(&comparator);
 143
 144                pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
 145                                ((counter_hz + 500) / 1000) / 1000,
 146                                ((counter_hz + 500) / 1000) % 1000);
 147        }
 148}
 149