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1623 |
jcastillo |
/*
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* linux/arch/i386/kernel/time.c
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*
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* Copyright (C) 1991, 1992, 1995 Linus Torvalds
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*
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* This file contains the PC-specific time handling details:
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* reading the RTC at bootup, etc..
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* 1994-07-02 Alan Modra
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* fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
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* 1995-03-26 Markus Kuhn
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* fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
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* precision CMOS clock update
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* 1996-05-03 Ingo Molnar
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* fixed time warps in do_[slow|fast]_gettimeoffset()
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* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
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* "A Kernel Model for Precision Timekeeping" by Dave Mills
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*/
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/param.h>
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#include <linux/string.h>
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#include <linux/mm.h>
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#include <linux/interrupt.h>
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#include <linux/time.h>
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#include <linux/delay.h>
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#include <asm/segment.h>
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#include <asm/io.h>
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#include <asm/irq.h>
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#include <asm/delay.h>
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#include <linux/mc146818rtc.h>
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#include <linux/timex.h>
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#include <linux/config.h>
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extern int setup_x86_irq(int, struct irqaction *);
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#ifndef CONFIG_APM /* cycle counter may be unreliable */
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/* Cycle counter value at the previous timer interrupt.. */
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static struct {
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unsigned long low;
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unsigned long high;
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} init_timer_cc, last_timer_cc;
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/*
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* This is more assembly than C, but it's also rather
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* timing-critical and we have to use assembler to get
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* reasonable 64-bit arithmetic
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*/
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static unsigned long do_fast_gettimeoffset(void)
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{
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register unsigned long eax asm("ax");
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register unsigned long edx asm("dx");
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unsigned long tmp, quotient, low_timer, missing_time;
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/* Last jiffy when do_fast_gettimeoffset() was called.. */
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static unsigned long last_jiffies=0;
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/* Cached "clocks per usec" value.. */
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static unsigned long cached_quotient=0;
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/* The "clocks per usec" value is calculated once each jiffy */
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tmp = jiffies;
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quotient = cached_quotient;
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low_timer = last_timer_cc.low;
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missing_time = 0;
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if (last_jiffies != tmp) {
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last_jiffies = tmp;
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/*
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* test for hanging bottom handler (this means xtime is not
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* updated yet)
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*/
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if (test_bit(TIMER_BH, &bh_active) )
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{
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missing_time = 1000020/HZ;
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}
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/* Get last timer tick in absolute kernel time */
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eax = low_timer;
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edx = last_timer_cc.high;
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__asm__("subl "SYMBOL_NAME_STR(init_timer_cc)",%0\n\t"
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"sbbl "SYMBOL_NAME_STR(init_timer_cc)"+4,%1"
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:"=a" (eax), "=d" (edx)
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:"0" (eax), "1" (edx));
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/*
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* Divide the 64-bit time with the 32-bit jiffy counter,
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* getting the quotient in clocks.
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*
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* Giving quotient = "average internal clocks per usec"
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*/
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__asm__("divl %2"
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:"=a" (eax), "=d" (edx)
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:"r" (tmp),
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"0" (eax), "1" (edx));
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edx = 1000020/HZ;
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tmp = eax;
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eax = 0;
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__asm__("divl %2"
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:"=a" (eax), "=d" (edx)
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:"r" (tmp),
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"0" (eax), "1" (edx));
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cached_quotient = eax;
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quotient = eax;
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}
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/* Read the time counter */
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__asm__(".byte 0x0f,0x31"
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:"=a" (eax), "=d" (edx));
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/* .. relative to previous jiffy (32 bits is enough) */
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edx = 0;
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eax -= low_timer;
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/*
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* Time offset = (1000020/HZ * time_low) / quotient.
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*/
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__asm__("mull %2"
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:"=a" (eax), "=d" (edx)
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:"r" (quotient),
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"0" (eax), "1" (edx));
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/*
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* Due to rounding errors (and jiffies inconsistencies),
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* we need to check the result so that we'll get a timer
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* that is monotonic.
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*/
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if (edx >= 1000020/HZ)
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edx = 1000020/HZ-1;
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eax = edx + missing_time;
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return eax;
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}
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#endif
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/* This function must be called with interrupts disabled
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* It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs
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*
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* However, the pc-audio speaker driver changes the divisor so that
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* it gets interrupted rather more often - it loads 64 into the
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* counter rather than 11932! This has an adverse impact on
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* do_gettimeoffset() -- it stops working! What is also not
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* good is that the interval that our timer function gets called
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* is no longer 10.0002 ms, but 9.9767 ms. To get around this
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* would require using a different timing source. Maybe someone
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* could use the RTC - I know that this can interrupt at frequencies
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* ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix
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* it so that at startup, the timer code in sched.c would select
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* using either the RTC or the 8253 timer. The decision would be
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* based on whether there was any other device around that needed
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* to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz,
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* and then do some jiggery to have a version of do_timer that
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* advanced the clock by 1/1024 s. Every time that reached over 1/100
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* of a second, then do all the old code. If the time was kept correct
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* then do_gettimeoffset could just return 0 - there is no low order
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* divider that can be accessed.
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*
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* Ideally, you would be able to use the RTC for the speaker driver,
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* but it appears that the speaker driver really needs interrupt more
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* often than every 120 us or so.
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*
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* Anyway, this needs more thought.... pjsg (1993-08-28)
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*
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* If you are really that interested, you should be reading
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* comp.protocols.time.ntp!
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*/
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#define TICK_SIZE tick
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static unsigned long do_slow_gettimeoffset(void)
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{
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int count;
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static int count_p = 0;
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unsigned long offset = 0;
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static unsigned long jiffies_p = 0;
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/*
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* cache volatile jiffies temporarily; we have IRQs turned off.
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*/
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unsigned long jiffies_t;
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/* timer count may underflow right here */
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outb_p(0x00, 0x43); /* latch the count ASAP */
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count = inb_p(0x40); /* read the latched count */
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count |= inb(0x40) << 8;
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jiffies_t = jiffies;
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/*
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* avoiding timer inconsistencies (they are rare, but they happen)...
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* there are three kinds of problems that must be avoided here:
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* 1. the timer counter underflows
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* 2. hardware problem with the timer, not giving us continuous time,
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* the counter does small "jumps" upwards on some Pentium systems,
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* thus causes time warps
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* 3. we are after the timer interrupt, but the bottom half handler
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* hasn't executed yet.
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*/
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if( count > count_p ) {
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if( jiffies_t == jiffies_p ) {
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if( count > LATCH-LATCH/100 )
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offset = TICK_SIZE;
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else
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/*
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* argh, the timer is bugging we cant do nothing
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* but to give the previous clock value.
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*/
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count = count_p;
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} else {
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if( test_bit(TIMER_BH, &bh_active) ) {
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/*
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* we have detected a counter underflow.
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*/
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offset = TICK_SIZE;
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count_p = count;
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} else {
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count_p = count;
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jiffies_p = jiffies_t;
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}
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}
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} else {
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count_p = count;
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jiffies_p = jiffies_t;
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}
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count = ((LATCH-1) - count) * TICK_SIZE;
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count = (count + LATCH/2) / LATCH;
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return offset + count;
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}
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static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset;
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/*
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* This version of gettimeofday has near microsecond resolution.
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*/
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void do_gettimeofday(struct timeval *tv)
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{
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unsigned long flags;
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save_flags(flags);
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cli();
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*tv = xtime;
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tv->tv_usec += do_gettimeoffset();
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if (tv->tv_usec >= 1000000) {
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tv->tv_usec -= 1000000;
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tv->tv_sec++;
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}
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restore_flags(flags);
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}
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void do_settimeofday(struct timeval *tv)
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{
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cli();
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260 |
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/* This is revolting. We need to set the xtime.tv_usec
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* correctly. However, the value in this location is
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* is value at the last tick.
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* Discover what correction gettimeofday
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* would have done, and then undo it!
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*/
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tv->tv_usec -= do_gettimeoffset();
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if (tv->tv_usec < 0) {
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tv->tv_usec += 1000000;
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tv->tv_sec--;
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}
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xtime = *tv;
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time_adjust = 0; /* stop active adjtime() */
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time_status |= STA_UNSYNC;
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time_state = TIME_ERROR; /* p. 24, (a) */
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time_maxerror = NTP_PHASE_LIMIT;
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time_esterror = NTP_PHASE_LIMIT;
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sti();
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}
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282 |
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283 |
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/*
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284 |
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* In order to set the CMOS clock precisely, set_rtc_mmss has to be
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* called 500 ms after the second nowtime has started, because when
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* nowtime is written into the registers of the CMOS clock, it will
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* jump to the next second precisely 500 ms later. Check the Motorola
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* MC146818A or Dallas DS12887 data sheet for details.
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*
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* BUG: This routine does not handle hour overflow properly; it just
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* sets the minutes. Usually you'll only notice that after reboot!
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*/
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static int set_rtc_mmss(unsigned long nowtime)
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{
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int retval = 0;
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int real_seconds, real_minutes, cmos_minutes;
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unsigned char save_control, save_freq_select;
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save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
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CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
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save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
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CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
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304 |
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305 |
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cmos_minutes = CMOS_READ(RTC_MINUTES);
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306 |
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if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
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307 |
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BCD_TO_BIN(cmos_minutes);
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308 |
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309 |
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/*
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310 |
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* since we're only adjusting minutes and seconds,
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311 |
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* don't interfere with hour overflow. This avoids
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312 |
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* messing with unknown time zones but requires your
|
313 |
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* RTC not to be off by more than 15 minutes
|
314 |
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*/
|
315 |
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real_seconds = nowtime % 60;
|
316 |
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real_minutes = nowtime / 60;
|
317 |
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if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
|
318 |
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real_minutes += 30; /* correct for half hour time zone */
|
319 |
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real_minutes %= 60;
|
320 |
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|
321 |
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if (abs(real_minutes - cmos_minutes) < 30) {
|
322 |
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if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
|
323 |
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BIN_TO_BCD(real_seconds);
|
324 |
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BIN_TO_BCD(real_minutes);
|
325 |
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}
|
326 |
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CMOS_WRITE(real_seconds,RTC_SECONDS);
|
327 |
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CMOS_WRITE(real_minutes,RTC_MINUTES);
|
328 |
|
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} else {
|
329 |
|
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printk(KERN_WARNING
|
330 |
|
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"set_rtc_mmss: can't update from %d to %d\n",
|
331 |
|
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cmos_minutes, real_minutes);
|
332 |
|
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retval = -1;
|
333 |
|
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}
|
334 |
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|
335 |
|
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/* The following flags have to be released exactly in this order,
|
336 |
|
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* otherwise the DS12887 (popular MC146818A clone with integrated
|
337 |
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* battery and quartz) will not reset the oscillator and will not
|
338 |
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* update precisely 500 ms later. You won't find this mentioned in
|
339 |
|
|
* the Dallas Semiconductor data sheets, but who believes data
|
340 |
|
|
* sheets anyway ... -- Markus Kuhn
|
341 |
|
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*/
|
342 |
|
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CMOS_WRITE(save_control, RTC_CONTROL);
|
343 |
|
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CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
|
344 |
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|
345 |
|
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return retval;
|
346 |
|
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}
|
347 |
|
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|
348 |
|
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/* last time the cmos clock got updated */
|
349 |
|
|
static long last_rtc_update = 0;
|
350 |
|
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|
351 |
|
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/*
|
352 |
|
|
* timer_interrupt() needs to keep up the real-time clock,
|
353 |
|
|
* as well as call the "do_timer()" routine every clocktick
|
354 |
|
|
*/
|
355 |
|
|
static inline void timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
|
356 |
|
|
{
|
357 |
|
|
do_timer(regs);
|
358 |
|
|
|
359 |
|
|
/*
|
360 |
|
|
* If we have an externally synchronized Linux clock, then update
|
361 |
|
|
* CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
|
362 |
|
|
* called as close as possible to 500 ms before the new second starts.
|
363 |
|
|
*/
|
364 |
|
|
if ((time_status & STA_UNSYNC) == 0 &&
|
365 |
|
|
xtime.tv_sec > last_rtc_update + 660 &&
|
366 |
|
|
xtime.tv_usec > 500000 - (tick >> 1) &&
|
367 |
|
|
xtime.tv_usec < 500000 + (tick >> 1))
|
368 |
|
|
if (set_rtc_mmss(xtime.tv_sec) == 0)
|
369 |
|
|
last_rtc_update = xtime.tv_sec;
|
370 |
|
|
else
|
371 |
|
|
last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
|
372 |
|
|
/* As we return to user mode fire off the other CPU schedulers.. this is
|
373 |
|
|
basically because we don't yet share IRQ's around. This message is
|
374 |
|
|
rigged to be safe on the 386 - basically it's a hack, so don't look
|
375 |
|
|
closely for now.. */
|
376 |
|
|
/*smp_message_pass(MSG_ALL_BUT_SELF, MSG_RESCHEDULE, 0L, 0); */
|
377 |
|
|
|
378 |
|
|
}
|
379 |
|
|
|
380 |
|
|
#ifndef CONFIG_APM /* cycle counter may be unreliable */
|
381 |
|
|
/*
|
382 |
|
|
* This is the same as the above, except we _also_ save the current
|
383 |
|
|
* cycle counter value at the time of the timer interrupt, so that
|
384 |
|
|
* we later on can estimate the time of day more exactly.
|
385 |
|
|
*/
|
386 |
|
|
static void pentium_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
|
387 |
|
|
{
|
388 |
|
|
/* read Pentium cycle counter */
|
389 |
|
|
__asm__(".byte 0x0f,0x31"
|
390 |
|
|
:"=a" (last_timer_cc.low),
|
391 |
|
|
"=d" (last_timer_cc.high));
|
392 |
|
|
timer_interrupt(irq, NULL, regs);
|
393 |
|
|
}
|
394 |
|
|
#endif
|
395 |
|
|
|
396 |
|
|
/* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
|
397 |
|
|
* Assumes input in normal date format, i.e. 1980-12-31 23:59:59
|
398 |
|
|
* => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
|
399 |
|
|
*
|
400 |
|
|
* [For the Julian calendar (which was used in Russia before 1917,
|
401 |
|
|
* Britain & colonies before 1752, anywhere else before 1582,
|
402 |
|
|
* and is still in use by some communities) leave out the
|
403 |
|
|
* -year/100+year/400 terms, and add 10.]
|
404 |
|
|
*
|
405 |
|
|
* This algorithm was first published by Gauss (I think).
|
406 |
|
|
*
|
407 |
|
|
* WARNING: this function will overflow on 2106-02-07 06:28:16 on
|
408 |
|
|
* machines were long is 32-bit! (However, as time_t is signed, we
|
409 |
|
|
* will already get problems at other places on 2038-01-19 03:14:08)
|
410 |
|
|
*/
|
411 |
|
|
static inline unsigned long mktime(unsigned int year, unsigned int mon,
|
412 |
|
|
unsigned int day, unsigned int hour,
|
413 |
|
|
unsigned int min, unsigned int sec)
|
414 |
|
|
{
|
415 |
|
|
if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */
|
416 |
|
|
mon += 12; /* Puts Feb last since it has leap day */
|
417 |
|
|
year -= 1;
|
418 |
|
|
}
|
419 |
|
|
return (((
|
420 |
|
|
(unsigned long)(year/4 - year/100 + year/400 + 367*mon/12 + day) +
|
421 |
|
|
year*365 - 719499
|
422 |
|
|
)*24 + hour /* now have hours */
|
423 |
|
|
)*60 + min /* now have minutes */
|
424 |
|
|
)*60 + sec; /* finally seconds */
|
425 |
|
|
}
|
426 |
|
|
|
427 |
|
|
/* not static: needed by APM */
|
428 |
|
|
unsigned long get_cmos_time(void)
|
429 |
|
|
{
|
430 |
|
|
unsigned int year, mon, day, hour, min, sec;
|
431 |
|
|
int i;
|
432 |
|
|
|
433 |
|
|
/* The Linux interpretation of the CMOS clock register contents:
|
434 |
|
|
* When the Update-In-Progress (UIP) flag goes from 1 to 0, the
|
435 |
|
|
* RTC registers show the second which has precisely just started.
|
436 |
|
|
* Let's hope other operating systems interpret the RTC the same way.
|
437 |
|
|
*/
|
438 |
|
|
/* read RTC exactly on falling edge of update flag */
|
439 |
|
|
for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
|
440 |
|
|
if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
|
441 |
|
|
break;
|
442 |
|
|
for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
|
443 |
|
|
if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
|
444 |
|
|
break;
|
445 |
|
|
do { /* Isn't this overkill ? UIP above should guarantee consistency */
|
446 |
|
|
sec = CMOS_READ(RTC_SECONDS);
|
447 |
|
|
min = CMOS_READ(RTC_MINUTES);
|
448 |
|
|
hour = CMOS_READ(RTC_HOURS);
|
449 |
|
|
day = CMOS_READ(RTC_DAY_OF_MONTH);
|
450 |
|
|
mon = CMOS_READ(RTC_MONTH);
|
451 |
|
|
year = CMOS_READ(RTC_YEAR);
|
452 |
|
|
} while (sec != CMOS_READ(RTC_SECONDS));
|
453 |
|
|
if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
|
454 |
|
|
{
|
455 |
|
|
BCD_TO_BIN(sec);
|
456 |
|
|
BCD_TO_BIN(min);
|
457 |
|
|
BCD_TO_BIN(hour);
|
458 |
|
|
BCD_TO_BIN(day);
|
459 |
|
|
BCD_TO_BIN(mon);
|
460 |
|
|
BCD_TO_BIN(year);
|
461 |
|
|
}
|
462 |
|
|
if ((year += 1900) < 1970)
|
463 |
|
|
year += 100;
|
464 |
|
|
return mktime(year, mon, day, hour, min, sec);
|
465 |
|
|
}
|
466 |
|
|
|
467 |
|
|
static struct irqaction irq0 = { timer_interrupt, 0, 0, "timer", NULL, NULL};
|
468 |
|
|
|
469 |
|
|
void time_init(void)
|
470 |
|
|
{
|
471 |
|
|
xtime.tv_sec = get_cmos_time();
|
472 |
|
|
xtime.tv_usec = 0;
|
473 |
|
|
|
474 |
|
|
/* If we have the CPU hardware time counters, use them */
|
475 |
|
|
#ifndef CONFIG_APM
|
476 |
|
|
/* Don't use them if a suspend/resume could
|
477 |
|
|
corrupt the timer value. This problem
|
478 |
|
|
needs more debugging. */
|
479 |
|
|
if (x86_capability & 16)
|
480 |
|
|
if (strncmp(x86_vendor_id, "Cyrix", 5) != 0) {
|
481 |
|
|
do_gettimeoffset = do_fast_gettimeoffset;
|
482 |
|
|
|
483 |
|
|
if( strcmp( x86_vendor_id, "AuthenticAMD" ) == 0 ) {
|
484 |
|
|
if( x86 == 5 ) {
|
485 |
|
|
if( x86_model == 0 ) {
|
486 |
|
|
/* turn on cycle counters during power down */
|
487 |
|
|
__asm__ __volatile__ (" movl $0x83, %%ecx \n \
|
488 |
|
|
.byte 0x0f,0x32 \n \
|
489 |
|
|
orl $1,%%eax \n \
|
490 |
|
|
.byte 0x0f,0x30 \n "
|
491 |
|
|
: : : "ax", "cx", "dx" );
|
492 |
|
|
udelay(500);
|
493 |
|
|
}
|
494 |
|
|
}
|
495 |
|
|
}
|
496 |
|
|
|
497 |
|
|
/* read Pentium cycle counter */
|
498 |
|
|
__asm__(".byte 0x0f,0x31"
|
499 |
|
|
:"=a" (init_timer_cc.low),
|
500 |
|
|
"=d" (init_timer_cc.high));
|
501 |
|
|
irq0.handler = pentium_timer_interrupt;
|
502 |
|
|
}
|
503 |
|
|
#endif
|
504 |
|
|
setup_x86_irq(0, &irq0);
|
505 |
|
|
}
|