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/timex.h>
  18
  19 #include <asm/sn/leds.h>
  20 #include <asm/sn/shub_mmr.h>
  21 #include <asm/sn/clksupport.h>
  22
  23 extern unsigned long sn_rtc_cycles_per_second;
  24
  25 static u64 read_sn2(struct clocksource *cs)
  26 {
  27         return (u64)readq(RTC_COUNTER_ADDR);
  28 }
  29
  30 static struct clocksource clocksource_sn2 = {
  31         .name           = "sn2_rtc",
  32         .rating         = 450,
  33         .read           = read_sn2,
  34         .mask           = (1LL << 55) - 1,
  35         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  36 };
  37
  38 /*
  39  * sn udelay uses the RTC instead of the ITC because the ITC is not
  40  * synchronized across all CPUs, and the thread may migrate to another CPU
  41  * if preemption is enabled.
  42  */
  43 static void
  44 ia64_sn_udelay (unsigned long usecs)
  45 {
  46         unsigned long start = rtc_time();
  47         unsigned long end = start +
  48                         usecs * sn_rtc_cycles_per_second / 1000000;
  49
  50         while (time_before((unsigned long)rtc_time(), end))
  51                 cpu_relax();
  52 }
  53
  54 void __init sn_timer_init(void)
  55 {
  56         clocksource_sn2.archdata.fsys_mmio = RTC_COUNTER_ADDR;
  57         clocksource_register_hz(&clocksource_sn2, sn_rtc_cycles_per_second);
  58
  59         ia64_udelay = &ia64_sn_udelay;
  60 }