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 #include <stand.h>
29 #include <btxv86.h>
30 #include "bootstrap.h"
31 #include "libi386.h"
32
33 time_t getsecs(void);
34 static int bios_seconds(void);
35
36 /*
37 * Return the BIOS time-of-day value.
38 *
39 * XXX uses undocumented BCD support from libsa.
40 */
41 static int
bios_seconds(void)42 bios_seconds(void)
43 {
44 int hr, minute, sec;
45
46 v86.ctl = 0;
47 v86.addr = 0x1a; /* int 0x1a, function 2 */
48 v86.eax = 0x0200;
49 v86int();
50
51 hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */
52 minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */
53 sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */
54
55 return (hr * 3600 + minute * 60 + sec);
56 }
57
58 /*
59 * Return the time in seconds since the beginning of the day.
60 *
61 * Some BIOSes (notably qemu) don't correctly read the RTC
62 * registers in an atomic way, sometimes returning bogus values.
63 * Therefore we "debounce" the reading by accepting it only when
64 * we got 8 identical values in succession.
65 *
66 * If we pass midnight, don't wrap back to 0.
67 */
68 time_t
time(time_t * t)69 time(time_t *t)
70 {
71 static time_t lasttime;
72 time_t now, check;
73 int same, try;
74
75 same = try = 0;
76 check = bios_seconds();
77 do {
78 now = check;
79 check = bios_seconds();
80 if (check != now)
81 same = 0;
82 } while (++same < 8 && ++try < 1000);
83
84 if (now < lasttime)
85 now += 24 * 3600;
86 lasttime = now;
87
88 if (t != NULL)
89 *t = now;
90 return(now);
91 }
92
93 time_t
getsecs(void)94 getsecs(void)
95 {
96 time_t n = 0;
97 time(&n);
98 return n;
99 }
100
101 /*
102 * Use the BIOS Wait function to pause for (period) microseconds.
103 *
104 * Resolution of this function is variable, but typically around
105 * 1ms.
106 */
107 void
delay(int period)108 delay(int period)
109 {
110 v86.ctl = 0;
111 v86.addr = 0x15; /* int 0x15, function 0x86 */
112 v86.eax = 0x8600;
113 v86.ecx = period >> 16;
114 v86.edx = period & 0xffff;
115 v86int();
116 }
117