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 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 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 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 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