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#include <linux/clocksource.h>
  15
  16#include <asm/hw_irq.h>
  17#include <asm/system.h>
  18#include <asm/timex.h>
  19
  20#include <asm/sn/leds.h>
  21#include <asm/sn/shub_mmr.h>
  22#include <asm/sn/clksupport.h>
  23
  24extern unsigned long sn_rtc_cycles_per_second;
  25
  26static cycle_t read_sn2(void)
  27{
  28        return (cycle_t)readq(RTC_COUNTER_ADDR);
  29}
  30
  31static struct clocksource clocksource_sn2 = {
  32        .name           = "sn2_rtc",
  33        .rating         = 450,
  34        .read           = read_sn2,
  35        .mask           = (1LL << 55) - 1,
  36        .mult           = 0,
  37        .shift          = 10,
  38        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  39};
  40
  41/*
  42 * sn udelay uses the RTC instead of the ITC because the ITC is not
  43 * synchronized across all CPUs, and the thread may migrate to another CPU
  44 * if preemption is enabled.
  45 */
  46static void
  47ia64_sn_udelay (unsigned long usecs)
  48{
  49        unsigned long start = rtc_time();
  50        unsigned long end = start +
  51                        usecs * sn_rtc_cycles_per_second / 1000000;
  52
  53        while (time_before((unsigned long)rtc_time(), end))
  54                cpu_relax();
  55}
  56
  57void __init sn_timer_init(void)
  58{
  59        clocksource_sn2.fsys_mmio = RTC_COUNTER_ADDR;
  60        clocksource_sn2.mult = clocksource_hz2mult(sn_rtc_cycles_per_second,
  61                                                        clocksource_sn2.shift);
  62        clocksource_register(&clocksource_sn2);
  63
  64        ia64_udelay = &ia64_sn_udelay;
  65}
  66