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   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
  24 extern unsigned long sn_rtc_cycles_per_second;
  25
  26 static void __iomem *sn2_mc;
  27
  28 static cycle_t read_sn2(void)
  29 {
  30         return (cycle_t)readq(sn2_mc);
  31 }
  32
  33 static struct clocksource clocksource_sn2 = {
  34         .name           = "sn2_rtc",
  35         .rating         = 300,
  36         .read           = read_sn2,
  37         .mask           = (1LL << 55) - 1,
  38         .mult           = 0,
  39         .shift          = 10,
  40         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  41 };
  42
  43 /*
  44  * sn udelay uses the RTC instead of the ITC because the ITC is not
  45  * synchronized across all CPUs, and the thread may migrate to another CPU
  46  * if preemption is enabled.
  47  */
  48 static void
  49 ia64_sn_udelay (unsigned long usecs)
  50 {
  51         unsigned long start = rtc_time();
  52         unsigned long end = start +
  53                         usecs * sn_rtc_cycles_per_second / 1000000;
  54
  55         while (time_before((unsigned long)rtc_time(), end))
  56                 cpu_relax();
  57 }
  58
  59 void __init sn_timer_init(void)
  60 {
  61         sn2_mc = RTC_COUNTER_ADDR;
  62         clocksource_sn2.fsys_mmio = RTC_COUNTER_ADDR;
  63         clocksource_sn2.mult = clocksource_hz2mult(sn_rtc_cycles_per_second,
  64                                                         clocksource_sn2.shift);
  65         clocksource_register(&clocksource_sn2);
  66
  67         ia64_udelay = &ia64_sn_udelay;
  68 }