LXR linux/arch/ia64/sn/kernel/sn2/timer.c

   1/*
   2 * linux/arch/ia64/sn/kernel/sn2/timer.c
   3 *
   4 * Copyright (C) 2003 Silicon Graphics, Inc.
   5 * Copyright (C) 2003 Hewlett-Packard Co
   6 *      David Mosberger <davidm@hpl.hp.com>: updated for new timer-interpolation infrastructure
   7 */
   8
   9#include <linux/init.h>
  10#include <linux/kernel.h>
  11#include <linux/sched.h>
  12#include <linux/time.h>
  13#include <linux/interrupt.h>
  14
  15#include <asm/hw_irq.h>
  16#include <asm/system.h>
  17#include <asm/timex.h>
  18
  19#include <asm/sn/leds.h>
  20#include <asm/sn/shub_mmr.h>
  21#include <asm/sn/clksupport.h>
  22
  23extern unsigned long sn_rtc_cycles_per_second;
  24
  25static struct time_interpolator sn2_interpolator = {
  26        .drift = -1,
  27        .shift = 10,
  28        .mask = (1LL << 55) - 1,
  29        .source = TIME_SOURCE_MMIO64
  30};
  31
  32/*
  33 * sn udelay uses the RTC instead of the ITC because the ITC is not
  34 * synchronized across all CPUs, and the thread may migrate to another CPU
  35 * if preemption is enabled.
  36 */
  37static void
  38ia64_sn_udelay (unsigned long usecs)
  39{
  40        unsigned long start = rtc_time();
  41        unsigned long end = start +
  42                        usecs * sn_rtc_cycles_per_second / 1000000;
  43
  44        while (time_before((unsigned long)rtc_time(), end))
  45                cpu_relax();
  46}
  47
  48void __init sn_timer_init(void)
  49{
  50        sn2_interpolator.frequency = sn_rtc_cycles_per_second;
  51        sn2_interpolator.addr = RTC_COUNTER_ADDR;
  52        register_time_interpolator(&sn2_interpolator);
  53
  54        ia64_udelay = &ia64_sn_udelay;
  55}
  56