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time.c

/*
 *  linux/arch/arm/mach-imx/time.c
 *
 *  Copyright (C) 2000-2001 Deep Blue Solutions
 *  Copyright (C) 2002 Shane Nay (shane@minirl.com)
 *
 * 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/kernel.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/time.h>

#include <asm/hardware.h>
#include <asm/io.h>
#include <asm/leds.h>
#include <asm/irq.h>
#include <asm/mach/time.h>

/* Use timer 1 as system timer */
#define TIMER_BASE IMX_TIM1_BASE

/*
 * Returns number of us since last clock interrupt.  Note that interrupts
 * will have been disabled by do_gettimeoffset()
 */
static unsigned long imx_gettimeoffset(void)
{
      unsigned long ticks;

      /*
       * Get the current number of ticks.  Note that there is a race
       * condition between us reading the timer and checking for
       * an interrupt.  We get around this by ensuring that the
       * counter has not reloaded between our two reads.
       */
      ticks = IMX_TCN(TIMER_BASE);

      /*
       * Interrupt pending?  If so, we've reloaded once already.
       */
      if (IMX_TSTAT(TIMER_BASE) & TSTAT_COMP)
            ticks += LATCH;

      /*
       * Convert the ticks to usecs
       */
      return (1000000 / CLK32) * ticks;
}

/*
 * IRQ handler for the timer
 */
static irqreturn_t
imx_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
      write_seqlock(&xtime_lock);

      /* clear the interrupt */
      if (IMX_TSTAT(TIMER_BASE))
            IMX_TSTAT(TIMER_BASE) = 0;

      timer_tick(regs);
      write_sequnlock(&xtime_lock);

      return IRQ_HANDLED;
}

static struct irqaction imx_timer_irq = {
      .name       = "i.MX Timer Tick",
      .flags            = IRQF_DISABLED | IRQF_TIMER,
      .handler    = imx_timer_interrupt,
};

/*
 * Set up timer interrupt, and return the current time in seconds.
 */
static void __init imx_timer_init(void)
{
      /*
       * Initialise to a known state (all timers off, and timing reset)
       */
      IMX_TCTL(TIMER_BASE) = 0;
      IMX_TPRER(TIMER_BASE) = 0;
      IMX_TCMP(TIMER_BASE) = LATCH - 1;
      IMX_TCTL(TIMER_BASE) = TCTL_CLK_32 | TCTL_IRQEN | TCTL_TEN;

      /*
       * Make irqs happen for the system timer
       */
      setup_irq(TIM1_INT, &imx_timer_irq);
}

struct sys_timer imx_timer = {
      .init       = imx_timer_init,
      .offset           = imx_gettimeoffset,
};

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