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time.c

/*
 * Copyright (C) 2004-2007 Atmel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/clk.h>
#include <linux/clockchips.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/time.h>

#include <asm/sysreg.h>

#include <mach/pm.h>


static cycle_t read_cycle_count(void)
{
      return (cycle_t)sysreg_read(COUNT);
}

/*
 * The architectural cycle count registers are a fine clocksource unless
 * the system idle loop use sleep states like "idle":  the CPU cycles
 * measured by COUNT (and COMPARE) don't happen during sleep states.
 * Their duration also changes if cpufreq changes the CPU clock rate.
 * So we rate the clocksource using COUNT as very low quality.
 */
static struct clocksource counter = {
      .name       = "avr32_counter",
      .rating           = 50,
      .read       = read_cycle_count,
      .mask       = CLOCKSOURCE_MASK(32),
      .shift            = 16,
      .flags            = CLOCK_SOURCE_IS_CONTINUOUS,
};

static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
      struct clock_event_device *evdev = dev_id;

      if (unlikely(!(intc_get_pending(0) & 1)))
            return IRQ_NONE;

      /*
       * Disable the interrupt until the clockevent subsystem
       * reprograms it.
       */
      sysreg_write(COMPARE, 0);

      evdev->event_handler(evdev);
      return IRQ_HANDLED;
}

static struct irqaction timer_irqaction = {
      .handler    = timer_interrupt,
      /* Oprofile uses the same irq as the timer, so allow it to be shared */
      .flags            = IRQF_TIMER | IRQF_DISABLED | IRQF_SHARED,
      .name       = "avr32_comparator",
};

static int comparator_next_event(unsigned long delta,
            struct clock_event_device *evdev)
{
      unsigned long     flags;

      raw_local_irq_save(flags);

      /* The time to read COUNT then update COMPARE must be less
       * than the min_delta_ns value for this clockevent source.
       */
      sysreg_write(COMPARE, (sysreg_read(COUNT) + delta) ? : 1);

      raw_local_irq_restore(flags);

      return 0;
}

static void comparator_mode(enum clock_event_mode mode,
            struct clock_event_device *evdev)
{
      switch (mode) {
      case CLOCK_EVT_MODE_ONESHOT:
            pr_debug("%s: start\n", evdev->name);
            /* FALLTHROUGH */
      case CLOCK_EVT_MODE_RESUME:
            cpu_disable_idle_sleep();
            break;
      case CLOCK_EVT_MODE_UNUSED:
      case CLOCK_EVT_MODE_SHUTDOWN:
            sysreg_write(COMPARE, 0);
            pr_debug("%s: stop\n", evdev->name);
            cpu_enable_idle_sleep();
            break;
      default:
            BUG();
      }
}

static struct clock_event_device comparator = {
      .name       = "avr32_comparator",
      .features   = CLOCK_EVT_FEAT_ONESHOT,
      .shift            = 16,
      .rating           = 50,
      .cpumask    = CPU_MASK_CPU0,
      .set_next_event   = comparator_next_event,
      .set_mode   = comparator_mode,
};

void __init time_init(void)
{
      unsigned long counter_hz;
      int ret;

      xtime.tv_sec = mktime(2007, 1, 1, 0, 0, 0);
      xtime.tv_nsec = 0;

      set_normalized_timespec(&wall_to_monotonic,
                        -xtime.tv_sec, -xtime.tv_nsec);

      /* figure rate for counter */
      counter_hz = clk_get_rate(boot_cpu_data.clk);
      counter.mult = clocksource_hz2mult(counter_hz, counter.shift);

      ret = clocksource_register(&counter);
      if (ret)
            pr_debug("timer: could not register clocksource: %d\n", ret);

      /* setup COMPARE clockevent */
      comparator.mult = div_sc(counter_hz, NSEC_PER_SEC, comparator.shift);
      comparator.max_delta_ns = clockevent_delta2ns((u32)~0, &comparator);
      comparator.min_delta_ns = clockevent_delta2ns(50, &comparator) + 1;

      sysreg_write(COMPARE, 0);
      timer_irqaction.dev_id = &comparator;

      ret = setup_irq(0, &timer_irqaction);
      if (ret)
            pr_debug("timer: could not request IRQ 0: %d\n", ret);
      else {
            clockevents_register_device(&comparator);

            pr_info("%s: irq 0, %lu.%03lu MHz\n", comparator.name,
                        ((counter_hz + 500) / 1000) / 1000,
                        ((counter_hz + 500) / 1000) % 1000);
      }
}

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