freebsd-nq/sys/boot/i386/libi386/time.c

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/*-
* Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <stand.h>
#include <btxv86.h>
#include "bootstrap.h"
#include "libi386.h"
static int bios_seconds(void);
/*
* Return the BIOS time-of-day value.
*
* XXX uses undocumented BCD support from libstand.
*/
static int
bios_seconds(void)
{
int hr, minute, sec;
v86.ctl = 0;
v86.addr = 0x1a; /* int 0x1a, function 2 */
v86.eax = 0x0200;
v86int();
hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */
minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */
sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */
return (hr * 3600 + minute * 60 + sec);
}
/*
* Return the time in seconds since the beginning of the day.
*
* Some BIOSes (notably qemu) don't correctly read the RTC
* registers in an atomic way, sometimes returning bogus values.
* Therefore we "debounce" the reading by accepting it only when
* we got two identical values in succession.
*
* If we pass midnight, don't wrap back to 0.
*/
time_t
time(time_t *t)
{
static time_t lasttime;
time_t now, check;
int try;
try = 0;
check = bios_seconds();
do {
now = check;
check = bios_seconds();
} while (now != check && ++try < 1000);
if (now < lasttime)
now += 24 * 3600;
lasttime = now;
if (t != NULL)
*t = now;
return(now);
}
/*
* Use the BIOS Wait function to pause for (period) microseconds.
*
* Resolution of this function is variable, but typically around
* 1ms.
*/
void
delay(int period)
{
v86.ctl = 0;
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v86.addr = 0x15; /* int 0x15, function 0x86 */
v86.eax = 0x8600;
v86.ecx = period >> 16;
v86.edx = period & 0xffff;
v86int();
}