1/*-
2 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: stable/11/stand/i386/libi386/time.c 329099 2018-02-10 04:37:44Z kevans $");
29
30#include <stand.h>
31#include <btxv86.h>
32#include "bootstrap.h"
33#include "libi386.h"
34
35time_t		getsecs(void);
36static int	bios_seconds(void);
37
38/*
39 * Return the BIOS time-of-day value.
40 *
41 * XXX uses undocumented BCD support from libstand.
42 */
43static int
44bios_seconds(void)
45{
46    int			hr, minute, sec;
47
48    v86.ctl = 0;
49    v86.addr = 0x1a;		/* int 0x1a, function 2 */
50    v86.eax = 0x0200;
51    v86int();
52
53    hr = bcd2bin((v86.ecx & 0xff00) >> 8);	/* hour in %ch */
54    minute = bcd2bin(v86.ecx & 0xff);		/* minute in %cl */
55    sec = bcd2bin((v86.edx & 0xff00) >> 8);	/* second in %dh */
56
57    return (hr * 3600 + minute * 60 + sec);
58}
59
60/*
61 * Return the time in seconds since the beginning of the day.
62 *
63 * Some BIOSes (notably qemu) don't correctly read the RTC
64 * registers in an atomic way, sometimes returning bogus values.
65 * Therefore we "debounce" the reading by accepting it only when
66 * we got 8 identical values in succession.
67 *
68 * If we pass midnight, don't wrap back to 0.
69 */
70time_t
71time(time_t *t)
72{
73    static time_t lasttime;
74    time_t now, check;
75    int same, try;
76
77    same = try = 0;
78    check = bios_seconds();
79    do {
80	now = check;
81	check = bios_seconds();
82	if (check != now)
83	    same = 0;
84    } while (++same < 8 && ++try < 1000);
85
86    if (now < lasttime)
87	now += 24 * 3600;
88    lasttime = now;
89
90    if (t != NULL)
91	*t = now;
92    return(now);
93}
94
95time_t
96getsecs(void)
97{
98	time_t n = 0;
99	time(&n);
100	return n;
101}
102
103/*
104 * Use the BIOS Wait function to pause for (period) microseconds.
105 *
106 * Resolution of this function is variable, but typically around
107 * 1ms.
108 */
109void
110delay(int period)
111{
112    v86.ctl = 0;
113    v86.addr = 0x15;		/* int 0x15, function 0x86 */
114    v86.eax = 0x8600;
115    v86.ecx = period >> 16;
116    v86.edx = period & 0xffff;
117    v86int();
118}
119