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time-acorn.c

/*
 *  linux/arch/arm/common/time-acorn.c
 *
 *  Copyright (c) 1996-2000 Russell King.
 *
 * 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.
 *
 *  Changelog:
 *   24-Sep-1996  RMK   Created
 *   10-Oct-1996  RMK   Brought up to date with arch-sa110eval
 *   04-Dec-1997  RMK   Updated for new arch/arm/time.c
 *   13=Jun-2004  DS    Moved to arch/arm/common b/c shared w/CLPS7500
 */
#include <linux/timex.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>

#include <mach/hardware.h>
#include <asm/io.h>
#include <asm/hardware/ioc.h>

#include <asm/mach/time.h>

unsigned long ioc_timer_gettimeoffset(void)
{
      unsigned int count1, count2, status;
      long offset;

      ioc_writeb (0, IOC_T0LATCH);
      barrier ();
      count1 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);
      barrier ();
      status = ioc_readb(IOC_IRQREQA);
      barrier ();
      ioc_writeb (0, IOC_T0LATCH);
      barrier ();
      count2 = ioc_readb(IOC_T0CNTL) | (ioc_readb(IOC_T0CNTH) << 8);

      offset = count2;
      if (count2 < count1) {
            /*
             * We have not had an interrupt between reading count1
             * and count2.
             */
            if (status & (1 << 5))
                  offset -= LATCH;
      } else if (count2 > count1) {
            /*
             * We have just had another interrupt between reading
             * count1 and count2.
             */
            offset -= LATCH;
      }

      offset = (LATCH - offset) * (tick_nsec / 1000);
      return (offset + LATCH/2) / LATCH;
}

void __init ioctime_init(void)
{
      ioc_writeb(LATCH & 255, IOC_T0LTCHL);
      ioc_writeb(LATCH >> 8, IOC_T0LTCHH);
      ioc_writeb(0, IOC_T0GO);
}

static irqreturn_t
ioc_timer_interrupt(int irq, void *dev_id)
{
      timer_tick();
      return IRQ_HANDLED;
}

static struct irqaction ioc_timer_irq = {
      .name       = "timer",
      .flags            = IRQF_DISABLED,
      .handler    = ioc_timer_interrupt
};

/*
 * Set up timer interrupt.
 */
static void __init ioc_timer_init(void)
{
      ioctime_init();
      setup_irq(IRQ_TIMER, &ioc_timer_irq);
}

struct sys_timer ioc_timer = {
      .init       = ioc_timer_init,
      .offset           = ioc_timer_gettimeoffset,
};


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