cf67fc562054980116484e3dadf9ec6622d6c823
[linux-2.6.git] / 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
24 extern unsigned long sn_rtc_cycles_per_second;
25
26 static cycle_t read_sn2(void)
27 {
28         return (cycle_t)readq(RTC_COUNTER_ADDR);
29 }
30
31 static 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  */
46 static void
47 ia64_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
57 void __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 }