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
23extern unsigned long sn_rtc_cycles_per_second;
24
25static cycle_t read_sn2(struct clocksource *cs)
26{
27	return (cycle_t)readq(RTC_COUNTER_ADDR);
28}
29
30static 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 */
43static void
44ia64_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
54void __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}
61