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 <stand.h>
28 #include <btxv86.h>
29 #include "bootstrap.h"
30 #include "libi386.h"
31
32 time_t getsecs(void);
33 static int bios_seconds(void);
34
35 /*
36 * Return the BIOS time-of-day value.
37 *
38 * XXX uses undocumented BCD support from libsa.
39 */
40 static int
bios_seconds(void)41 bios_seconds(void)
42 {
43 int hr, minute, sec;
44
45 v86.ctl = 0;
46 v86.addr = 0x1a; /* int 0x1a, function 2 */
47 v86.eax = 0x0200;
48 v86int();
49
50 hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */
51 minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */
52 sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */
53
54 return (hr * 3600 + minute * 60 + sec);
55 }
56
57 /*
58 * Return the time in seconds since the beginning of the day.
59 *
60 * Some BIOSes (notably qemu) don't correctly read the RTC
61 * registers in an atomic way, sometimes returning bogus values.
62 * Therefore we "debounce" the reading by accepting it only when
63 * we got 8 identical values in succession.
64 *
65 * If we pass midnight, don't wrap back to 0.
66 */
67 time_t
time(time_t * t)68 time(time_t *t)
69 {
70 static time_t lasttime;
71 time_t now, check;
72 int same, try;
73
74 same = try = 0;
75 check = bios_seconds();
76 do {
77 now = check;
78 check = bios_seconds();
79 if (check != now)
80 same = 0;
81 } while (++same < 8 && ++try < 1000);
82
83 if (now < lasttime)
84 now += 24 * 3600;
85 lasttime = now;
86
87 if (t != NULL)
88 *t = now;
89 return(now);
90 }
91
92 time_t
getsecs(void)93 getsecs(void)
94 {
95 time_t n = 0;
96 time(&n);
97 return n;
98 }
99
100 /*
101 * Use the BIOS Wait function to pause for (period) microseconds.
102 *
103 * Resolution of this function is variable, but typically around
104 * 1ms.
105 */
106 void
delay(int period)107 delay(int period)
108 {
109 v86.ctl = 0;
110 v86.addr = 0x15; /* int 0x15, function 0x86 */
111 v86.eax = 0x8600;
112 v86.ecx = period >> 16;
113 v86.edx = period & 0xffff;
114 v86int();
115 }
116