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
29 #include <stand.h>
30 #include <btxv86.h>
31 #include "bootstrap.h"
32 #include "libi386.h"
33
34 time_t getsecs(void);
35 static int bios_seconds(void);
36
37 /*
38 * Return the BIOS time-of-day value.
39 *
40 * XXX uses undocumented BCD support from libstand.
41 */
42 static int
bios_seconds(void)43 bios_seconds(void)
44 {
45 int hr, minute, sec;
46
47 v86.ctl = 0;
48 v86.addr = 0x1a; /* int 0x1a, function 2 */
49 v86.eax = 0x0200;
50 v86int();
51
52 hr = bcd2bin((v86.ecx & 0xff00) >> 8); /* hour in %ch */
53 minute = bcd2bin(v86.ecx & 0xff); /* minute in %cl */
54 sec = bcd2bin((v86.edx & 0xff00) >> 8); /* second in %dh */
55
56 return (hr * 3600 + minute * 60 + sec);
57 }
58
59 /*
60 * Return the time in seconds since the beginning of the day.
61 *
62 * Some BIOSes (notably qemu) don't correctly read the RTC
63 * registers in an atomic way, sometimes returning bogus values.
64 * Therefore we "debounce" the reading by accepting it only when
65 * we got 8 identical values in succession.
66 *
67 * If we pass midnight, don't wrap back to 0.
68 */
69 time_t
time(time_t * t)70 time(time_t *t)
71 {
72 static time_t lasttime;
73 time_t now, check;
74 int same, try;
75
76 same = try = 0;
77 check = bios_seconds();
78 do {
79 now = check;
80 check = bios_seconds();
81 if (check != now)
82 same = 0;
83 } while (++same < 8 && ++try < 1000);
84
85 if (now < lasttime)
86 now += 24 * 3600;
87 lasttime = now;
88
89 if (t != NULL)
90 *t = now;
91 return(now);
92 }
93
94 time_t
getsecs(void)95 getsecs(void)
96 {
97 time_t n = 0;
98 time(&n);
99 return n;
100 }
101
102 /*
103 * Use the BIOS Wait function to pause for (period) microseconds.
104 *
105 * Resolution of this function is variable, but typically around
106 * 1ms.
107 */
108 void
delay(int period)109 delay(int period)
110 {
111 v86.ctl = 0;
112 v86.addr = 0x15; /* int 0x15, function 0x86 */
113 v86.eax = 0x8600;
114 v86.ecx = period >> 16;
115 v86.edx = period & 0xffff;
116 v86int();
117 }
118