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time.c

/* MN10300 Low level time management
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 * - Derived from arch/i386/kernel/time.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/profile.h>
#include <asm/irq.h>
#include <asm/div64.h>
#include <asm/processor.h>
#include <asm/intctl-regs.h>
#include <asm/rtc.h>

#ifdef CONFIG_MN10300_RTC
unsigned long mn10300_ioclk;        /* system I/O clock frequency */
unsigned long mn10300_iobclk;       /* system I/O clock frequency */
unsigned long mn10300_tsc_per_HZ;   /* number of ioclks per jiffy */
#endif /* CONFIG_MN10300_RTC */

static unsigned long mn10300_last_tsc;    /* time-stamp counter at last time
                               * interrupt occurred */

static irqreturn_t timer_interrupt(int irq, void *dev_id);

static struct irqaction timer_irq = {
      .handler    = timer_interrupt,
      .flags            = IRQF_DISABLED | IRQF_SHARED | IRQF_TIMER,
      .mask       = CPU_MASK_NONE,
      .name       = "timer",
};

/*
 * scheduler clock - returns current time in nanosec units.
 */
unsigned long long sched_clock(void)
{
      union {
            unsigned long long l;
            u32 w[2];
      } quot;

      quot.w[0] = mn10300_last_tsc - get_cycles();
      quot.w[1] = 1000000000;

      asm("mulu %2,%3,%0,%1"
          : "=r"(quot.w[1]), "=r"(quot.w[0])
          : "0"(quot.w[1]), "1"(quot.w[0])
          : "cc");

      do_div(quot.l, MN10300_TSCCLK);

      return quot.l;
}

/*
 * advance the kernel's time keeping clocks (xtime and jiffies)
 * - we use Timer 0 & 1 cascaded as a clock to nudge us the next time
 *   there's a need to update
 */
static irqreturn_t timer_interrupt(int irq, void *dev_id)
{
      unsigned tsc, elapse;

      write_seqlock(&xtime_lock);

      while (tsc = get_cycles(),
             elapse = mn10300_last_tsc - tsc, /* time elapsed since last
                                     * tick */
             elapse > MN10300_TSC_PER_HZ
             ) {
            mn10300_last_tsc -= MN10300_TSC_PER_HZ;

            /* advance the kernel's time tracking system */
            profile_tick(CPU_PROFILING);
            do_timer(1);
            check_rtc_time();
      }

      write_sequnlock(&xtime_lock);

      update_process_times(user_mode(get_irq_regs()));

      return IRQ_HANDLED;
}

/*
 * initialise the various timers used by the main part of the kernel
 */
void __init time_init(void)
{
      /* we need the prescalar running to be able to use IOCLK/8
       * - IOCLK runs at 1/4 (ST5 open) or 1/8 (ST5 closed) internal CPU clock
       * - IOCLK runs at Fosc rate (crystal speed)
       */
      TMPSCNT |= TMPSCNT_ENABLE;

      startup_timestamp_counter();

      printk(KERN_INFO
             "timestamp counter I/O clock running at %lu.%02lu"
             " (calibrated against RTC)\n",
             MN10300_TSCCLK / 1000000, (MN10300_TSCCLK / 10000) % 100);

      xtime.tv_sec = get_initial_rtc_time();
      xtime.tv_nsec = 0;

      mn10300_last_tsc = TMTSCBC;

      /* use timer 0 & 1 cascaded to tick at as close to HZ as possible */
      setup_irq(TMJCIRQ, &timer_irq);

      set_intr_level(TMJCIRQ, TMJCICR_LEVEL);

      startup_jiffies_counter();

#ifdef CONFIG_MN10300_WD_TIMER
      /* start the watchdog timer */
      watchdog_go();
#endif
}

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