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time.c

/*
 * linux/arch/arm/mach-sa1100/time.c
 *
 * Copyright (C) 1998 Deborah Wallach.
 * Twiddles  (C) 1999   Hugo Fiennes <hugo@empeg.com>
 * 
 * 2000/03/29 (C) Nicolas Pitre <nico@cam.org>
 *    Rewritten: big cleanup, much simpler, better HZ accuracy.
 *
 */
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/timex.h>
#include <linux/signal.h>

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

#define RTC_DEF_DIVIDER       (32768 - 1)
#define RTC_DEF_TRIM            0

static unsigned long __init sa1100_get_rtc_time(void)
{
      /*
       * According to the manual we should be able to let RTTR be zero
       * and then a default diviser for a 32.768KHz clock is used.
       * Apparently this doesn't work, at least for my SA1110 rev 5.
       * If the clock divider is uninitialized then reset it to the
       * default value to get the 1Hz clock.
       */
      if (RTTR == 0) {
            RTTR = RTC_DEF_DIVIDER + (RTC_DEF_TRIM << 16);
            printk(KERN_WARNING "Warning: uninitialized Real Time Clock\n");
            /* The current RTC value probably doesn't make sense either */
            RCNR = 0;
            return 0;
      }
      return RCNR;
}

static int sa1100_set_rtc(void)
{
      unsigned long current_time = xtime.tv_sec;

      if (RTSR & RTSR_ALE) {
            /* make sure not to forward the clock over an alarm */
            unsigned long alarm = RTAR;
            if (current_time >= alarm && alarm >= RCNR)
                  return -ERESTARTSYS;
      }
      RCNR = current_time;
      return 0;
}

/* IRQs are disabled before entering here from do_gettimeofday() */
static unsigned long sa1100_gettimeoffset (void)
{
      unsigned long ticks_to_match, elapsed, usec;

      /* Get ticks before next timer match */
      ticks_to_match = OSMR0 - OSCR;

      /* We need elapsed ticks since last match */
      elapsed = LATCH - ticks_to_match;

      /* Now convert them to usec */
      usec = (unsigned long)(elapsed * (tick_nsec / 1000))/LATCH;

      return usec;
}

#ifdef CONFIG_NO_IDLE_HZ
static unsigned long initial_match;
static int match_posponed;
#endif

static irqreturn_t
sa1100_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
      unsigned int next_match;

      write_seqlock(&xtime_lock);

#ifdef CONFIG_NO_IDLE_HZ
      if (match_posponed) {
            match_posponed = 0;
            OSMR0 = initial_match;
      }
#endif

      /*
       * Loop until we get ahead of the free running timer.
       * This ensures an exact clock tick count and time accuracy.
       * Since IRQs are disabled at this point, coherence between
       * lost_ticks(updated in do_timer()) and the match reg value is
       * ensured, hence we can use do_gettimeofday() from interrupt
       * handlers.
       */
      do {
            timer_tick(regs);
            OSSR = OSSR_M0;  /* Clear match on timer 0 */
            next_match = (OSMR0 += LATCH);
      } while ((signed long)(next_match - OSCR) <= 0);

      write_sequnlock(&xtime_lock);

      return IRQ_HANDLED;
}

static struct irqaction sa1100_timer_irq = {
      .name       = "SA11xx Timer Tick",
      .flags            = IRQF_DISABLED | IRQF_TIMER,
      .handler    = sa1100_timer_interrupt,
};

static void __init sa1100_timer_init(void)
{
      struct timespec tv;

      set_rtc = sa1100_set_rtc;

      tv.tv_nsec = 0;
      tv.tv_sec = sa1100_get_rtc_time();
      do_settimeofday(&tv);

      OIER = 0;         /* disable any timer interrupts */
      OSCR = LATCH*2;         /* push OSCR out of the way */
      OSMR0 = LATCH;          /* set initial match */
      OSSR = 0xf;       /* clear status on all timers */
      setup_irq(IRQ_OST0, &sa1100_timer_irq);
      OIER = OIER_E0;         /* enable match on timer 0 to cause interrupts */
      OSCR = 0;         /* initialize free-running timer */
}

#ifdef CONFIG_NO_IDLE_HZ
static int sa1100_dyn_tick_enable_disable(void)
{
      /* nothing to do */
      return 0;
}

static void sa1100_dyn_tick_reprogram(unsigned long ticks)
{
      if (ticks > 1) {
            initial_match = OSMR0;
            OSMR0 = initial_match + ticks * LATCH;
            match_posponed = 1;
      }
}

static irqreturn_t
sa1100_dyn_tick_handler(int irq, void *dev_id, struct pt_regs *regs)
{
      if (match_posponed) {
            match_posponed = 0;
            OSMR0 = initial_match;
            if ((signed long)(initial_match - OSCR) <= 0)
                  return sa1100_timer_interrupt(irq, dev_id, regs);
      }
      return IRQ_NONE;
}

static struct dyn_tick_timer sa1100_dyn_tick = {
      .enable           = sa1100_dyn_tick_enable_disable,
      .disable    = sa1100_dyn_tick_enable_disable,
      .reprogram  = sa1100_dyn_tick_reprogram,
      .handler    = sa1100_dyn_tick_handler,
};
#endif

#ifdef CONFIG_PM
unsigned long osmr[4], oier;

static void sa1100_timer_suspend(void)
{
      osmr[0] = OSMR0;
      osmr[1] = OSMR1;
      osmr[2] = OSMR2;
      osmr[3] = OSMR3;
      oier = OIER;
}

static void sa1100_timer_resume(void)
{
      OSSR = 0x0f;
      OSMR0 = osmr[0];
      OSMR1 = osmr[1];
      OSMR2 = osmr[2];
      OSMR3 = osmr[3];
      OIER = oier;

      /*
       * OSMR0 is the system timer: make sure OSCR is sufficiently behind
       */
      OSCR = OSMR0 - LATCH;
}
#else
#define sa1100_timer_suspend NULL
#define sa1100_timer_resume NULL
#endif

struct sys_timer sa1100_timer = {
      .init       = sa1100_timer_init,
      .suspend    = sa1100_timer_suspend,
      .resume           = sa1100_timer_resume,
      .offset           = sa1100_gettimeoffset,
#ifdef CONFIG_NO_IDLE_HZ
      .dyn_tick   = &sa1100_dyn_tick,
#endif
};

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