1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/arch/ia64/sn/kernel/sn2/timer.c 4 * 5 * Copyright (C) 2003 Silicon Graphics, Inc. 6 * Copyright (C) 2003 Hewlett-Packard Co 7 * David Mosberger <davidm@hpl.hp.com>: updated for new timer-interpolation infrastructure 8 */ 9 10 #include <linux/init.h> 11 #include <linux/kernel.h> 12 #include <linux/sched.h> 13 #include <linux/time.h> 14 #include <linux/interrupt.h> 15 #include <linux/clocksource.h> 16 17 #include <asm/hw_irq.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(struct clocksource * cs)26static u64 read_sn2(struct clocksource *cs) 27 { 28 return (u64)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 .flags = CLOCK_SOURCE_IS_CONTINUOUS, 37 }; 38 39 /* 40 * sn udelay uses the RTC instead of the ITC because the ITC is not 41 * synchronized across all CPUs, and the thread may migrate to another CPU 42 * if preemption is enabled. 43 */ 44 static void ia64_sn_udelay(unsigned long usecs)45ia64_sn_udelay (unsigned long usecs) 46 { 47 unsigned long start = rtc_time(); 48 unsigned long end = start + 49 usecs * sn_rtc_cycles_per_second / 1000000; 50 51 while (time_before((unsigned long)rtc_time(), end)) 52 cpu_relax(); 53 } 54 sn_timer_init(void)55void __init sn_timer_init(void) 56 { 57 clocksource_sn2.archdata.fsys_mmio = RTC_COUNTER_ADDR; 58 clocksource_register_hz(&clocksource_sn2, sn_rtc_cycles_per_second); 59 60 ia64_udelay = &ia64_sn_udelay; 61 } 62