time.c

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/*
 *  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 <linux/io.h>

#include <mach/hardware.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_TIMER0, &ioc_timer_irq);
}

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