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/*
* linux/arch/ia64/sn/kernel/sn2/timer.c
*
* Copyright (C) 2003 Silicon Graphics, Inc.
*/
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <asm/hw_irq.h>
#include <asm/system.h>
#include <asm/sn/leds.h>
#include <asm/sn/clksupport.h>
extern unsigned long sn_rtc_cycles_per_second;
static volatile unsigned long last_wall_rtc;
/**
* gettimeoffset - number of nsecs elapsed since &xtime was last updated
*
* This function is used by do_gettimeofday() to determine the number
* of nsecs that have elapsed since the last update to &xtime. On SN
* this is accomplished using the RTC built in to each Hub chip; each
* is guaranteed to be synchronized by the PROM, so a local read will
* suffice (GET_RTC_COUNTER() does this for us). A snapshot of the RTC
* value is taken every time wall_jiffies is updated by the
* update_wall_time_hook (sn2_update_wall_time) which means we don't
* have to adjust for lost jiffies ticks or anything like that.
*/
static volatile long rtc_offset;
static long rtc_nsecs_per_cycle;
static long rtc_per_timer_tick;
unsigned long
sn_gettimeoffset(void)
{
long current_rtc, elapsed_rtc, old, new_offset;
do {
old = rtc_offset;
current_rtc = GET_RTC_COUNTER();
/*
* Need to address wrapping here!
*/
elapsed_rtc = (long)(current_rtc - last_wall_rtc);
new_offset = max(elapsed_rtc, old);
} while (cmpxchg(&rtc_offset, old, new_offset) != old);
return new_offset * rtc_nsecs_per_cycle;
}
void sn2_update_wall_time(long delta_nsec)
{
rtc_offset -= min(rtc_offset, rtc_per_timer_tick);
last_wall_rtc = GET_RTC_COUNTER();
}
void sn2_reset_wall_time(void)
{
rtc_offset = 0;
last_wall_rtc = GET_RTC_COUNTER();
}
void __init
sn_timer_init(void)
{
rtc_per_timer_tick = sn_rtc_cycles_per_second / HZ;
rtc_nsecs_per_cycle = 1000000000 / sn_rtc_cycles_per_second;
last_wall_rtc = GET_RTC_COUNTER();
update_wall_time_hook = sn2_update_wall_time;
reset_wall_time_hook = sn2_reset_wall_time;
gettimeoffset = sn_gettimeoffset;
}
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