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
read_sn2(void)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
ia64_sn_udelay(unsigned long usecs)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
sn_timer_init(void)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 }
66