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time.c

/*
 * arch/arm/mach-ks8695/time.c
 *
 * Copyright (C) 2006 Ben Dooks <ben@simtec.co.uk>
 * Copyright (C) 2006 Simtec Electronics
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/sched.h>

#include <asm/io.h>
#include <asm/mach/time.h>

#include <mach/regs-timer.h>
#include <mach/regs-irq.h>

#include "generic.h"

/*
 * Returns number of ms since last clock interrupt.  Note that interrupts
 * will have been disabled by do_gettimeoffset()
 */
static unsigned long ks8695_gettimeoffset (void)
{
      unsigned long elapsed, tick2, intpending;

      /*
       * Get the current number of ticks.  Note that there is a race
       * condition between us reading the timer and checking for an
       * interrupt.  We solve this by ensuring that the counter has not
       * reloaded between our two reads.
       */
      elapsed = __raw_readl(KS8695_TMR_VA + KS8695_T1TC) + __raw_readl(KS8695_TMR_VA + KS8695_T1PD);
      do {
            tick2 = elapsed;
            intpending = __raw_readl(KS8695_IRQ_VA + KS8695_INTST) & (1 << KS8695_IRQ_TIMER1);
            elapsed = __raw_readl(KS8695_TMR_VA + KS8695_T1TC) + __raw_readl(KS8695_TMR_VA + KS8695_T1PD);
      } while (elapsed > tick2);

      /* Convert to number of ticks expired (not remaining) */
      elapsed = (CLOCK_TICK_RATE / HZ) - elapsed;

      /* Is interrupt pending?  If so, then timer has been reloaded already. */
      if (intpending)
            elapsed += (CLOCK_TICK_RATE / HZ);

      /* Convert ticks to usecs */
      return (unsigned long)(elapsed * (tick_nsec / 1000)) / LATCH;
}

/*
 * IRQ handler for the timer.
 */
static irqreturn_t ks8695_timer_interrupt(int irq, void *dev_id)
{
      timer_tick();
      return IRQ_HANDLED;
}

static struct irqaction ks8695_timer_irq = {
      .name       = "ks8695_tick",
      .flags            = IRQF_DISABLED | IRQF_TIMER,
      .handler    = ks8695_timer_interrupt,
};

static void ks8695_timer_setup(void)
{
      unsigned long tmout = CLOCK_TICK_RATE / HZ;
      unsigned long tmcon;

      /* disable timer1 */
      tmcon = __raw_readl(KS8695_TMR_VA + KS8695_TMCON);
      __raw_writel(tmcon & ~TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);

      __raw_writel(tmout / 2, KS8695_TMR_VA + KS8695_T1TC);
      __raw_writel(tmout / 2, KS8695_TMR_VA + KS8695_T1PD);

      /* re-enable timer1 */
      __raw_writel(tmcon | TMCON_T1EN, KS8695_TMR_VA + KS8695_TMCON);
}

static void __init ks8695_timer_init (void)
{
      ks8695_timer_setup();

      /* Enable timer interrupts */
      setup_irq(KS8695_IRQ_TIMER1, &ks8695_timer_irq);
}

struct sys_timer ks8695_timer = {
      .init       = ks8695_timer_init,
      .offset           = ks8695_gettimeoffset,
      .resume           = ks8695_timer_setup,
};

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