Logo Search packages:      
Sourcecode: linux version File versions  Download package

time.c

/*
 * Copyright (C) 2004-2007 Atmel Corporation
 *
 * Based on MIPS implementation arch/mips/kernel/time.c
 *   Copyright 2001 MontaVista Software Inc.
 *
 * 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/clocksource.h>
#include <linux/time.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel_stat.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/profile.h>
#include <linux/sysdev.h>
#include <linux/err.h>

#include <asm/div64.h>
#include <asm/sysreg.h>
#include <asm/io.h>
#include <asm/sections.h>

/* how many counter cycles in a jiffy? */
static u32 cycles_per_jiffy;

/* the count value for the next timer interrupt */
static u32 expirelo;

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

struct clocksource __weak clocksource_avr32 = {
      .name       = "avr32",
      .rating           = 350,
      .read       = read_cycle_count,
      .mask       = CLOCKSOURCE_MASK(32),
      .shift            = 16,
      .flags            = CLOCK_SOURCE_IS_CONTINUOUS,
};

irqreturn_t __weak timer_interrupt(int irq, void *dev_id);

struct irqaction timer_irqaction = {
      .handler    = timer_interrupt,
      .flags            = IRQF_DISABLED,
      .name       = "timer",
};

/*
 * By default we provide the null RTC ops
 */
static unsigned long null_rtc_get_time(void)
{
      return mktime(2007, 1, 1, 0, 0, 0);
}

static int null_rtc_set_time(unsigned long sec)
{
      return 0;
}

static unsigned long (*rtc_get_time)(void) = null_rtc_get_time;
static int (*rtc_set_time)(unsigned long) = null_rtc_set_time;

static void avr32_timer_ack(void)
{
      u32 count;

      /* Ack this timer interrupt and set the next one */
      expirelo += cycles_per_jiffy;
      /* setting COMPARE to 0 stops the COUNT-COMPARE */
      if (expirelo == 0) {
            sysreg_write(COMPARE, expirelo + 1);
      } else {
            sysreg_write(COMPARE, expirelo);
      }

      /* Check to see if we have missed any timer interrupts */
      count = sysreg_read(COUNT);
      if ((count - expirelo) < 0x7fffffff) {
            expirelo = count + cycles_per_jiffy;
            sysreg_write(COMPARE, expirelo);
      }
}

int __weak avr32_hpt_init(void)
{
      int ret;
      unsigned long mult, shift, count_hz;

      count_hz = clk_get_rate(boot_cpu_data.clk);
      shift = clocksource_avr32.shift;
      mult = clocksource_hz2mult(count_hz, shift);
      clocksource_avr32.mult = mult;

      {
            u64 tmp;

            tmp = TICK_NSEC;
            tmp <<= shift;
            tmp += mult / 2;
            do_div(tmp, mult);

            cycles_per_jiffy = tmp;
      }

      ret = setup_irq(0, &timer_irqaction);
      if (ret) {
            pr_debug("timer: could not request IRQ 0: %d\n", ret);
            return -ENODEV;
      }

      printk(KERN_INFO "timer: AT32AP COUNT-COMPARE at irq 0, "
                  "%lu.%03lu MHz\n",
                  ((count_hz + 500) / 1000) / 1000,
                  ((count_hz + 500) / 1000) % 1000);

      return 0;
}

/*
 * Taken from MIPS c0_hpt_timer_init().
 *
 * The reason COUNT is written twice is probably to make sure we don't get any
 * timer interrupts while we are messing with the counter.
 */
int __weak avr32_hpt_start(void)
{
      u32 count = sysreg_read(COUNT);
      expirelo = (count / cycles_per_jiffy + 1) * cycles_per_jiffy;
      sysreg_write(COUNT, expirelo - cycles_per_jiffy);
      sysreg_write(COMPARE, expirelo);
      sysreg_write(COUNT, count);

      return 0;
}

/*
 * local_timer_interrupt() does profiling and process accounting on a
 * per-CPU basis.
 *
 * In UP mode, it is invoked from the (global) timer_interrupt.
 */
void local_timer_interrupt(int irq, void *dev_id)
{
      if (current->pid)
            profile_tick(CPU_PROFILING);
      update_process_times(user_mode(get_irq_regs()));
}

irqreturn_t __weak timer_interrupt(int irq, void *dev_id)
{
      /* ack timer interrupt and try to set next interrupt */
      avr32_timer_ack();

      /*
       * Call the generic timer interrupt handler
       */
      write_seqlock(&xtime_lock);
      do_timer(1);
      write_sequnlock(&xtime_lock);

      /*
       * In UP mode, we call local_timer_interrupt() to do profiling
       * and process accounting.
       *
       * SMP is not supported yet.
       */
      local_timer_interrupt(irq, dev_id);

      return IRQ_HANDLED;
}

void __init time_init(void)
{
      int ret;

      /*
       * Make sure we don't get any COMPARE interrupts before we can
       * handle them.
       */
      sysreg_write(COMPARE, 0);

      xtime.tv_sec = rtc_get_time();
      xtime.tv_nsec = 0;

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

      ret = avr32_hpt_init();
      if (ret) {
            pr_debug("timer: failed setup: %d\n", ret);
            return;
      }

      ret = clocksource_register(&clocksource_avr32);
      if (ret)
            pr_debug("timer: could not register clocksource: %d\n", ret);

      ret = avr32_hpt_start();
      if (ret) {
            pr_debug("timer: failed starting: %d\n", ret);
            return;
      }
}

static struct sysdev_class timer_class = {
      set_kset_name("timer"),
};

static struct sys_device timer_device = {
      .id   = 0,
      .cls  = &timer_class,
};

static int __init init_timer_sysfs(void)
{
      int err = sysdev_class_register(&timer_class);
      if (!err)
            err = sysdev_register(&timer_device);
      return err;
}

device_initcall(init_timer_sysfs);

Generated by  Doxygen 1.6.0   Back to index