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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/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 
read_sn2(struct clocksource * cs)25 static cycle_t read_sn2(struct clocksource *cs)
26 {
27 	return (cycle_t)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
ia64_sn_udelay(unsigned long usecs)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 
sn_timer_init(void)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 }
61