1 /* $OpenBSD: gateA20.c,v 1.10 2004/03/19 13:48:18 tom Exp $ */
2
3 /*
4 * Ported to boot 386BSD by Julian Elischer (julian@tfs.com) Sept 1992
5 *
6 * Mach Operating System
7 * Copyright (c) 1992, 1991 Carnegie Mellon University
8 * All Rights Reserved.
9 *
10 * Permission to use, copy, modify and distribute this software and its
11 * documentation is hereby granted, provided that both the copyright
12 * notice and this permission notice appear in all copies of the
13 * software, derivative works or modified versions, and any portions
14 * thereof, and that both notices appear in supporting documentation.
15 *
16 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
17 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
18 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
19 *
20 * Carnegie Mellon requests users of this software to return to
21 *
22 * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
23 * School of Computer Science
24 * Carnegie Mellon University
25 * Pittsburgh PA 15213-3890
26 *
27 * any improvements or extensions that they make and grant Carnegie Mellon
28 * the rights to redistribute these changes.
29 */
30
31 #include <sys/param.h>
32 #include <sys/types.h>
33 #include <machine/pio.h>
34 #include <dev/ic/i8042reg.h>
35 #include <dev/isa/isareg.h>
36
37 #include "libsa.h"
38
39 #define KB_A20 0xdf /* enable A20,
40 enable output buffer full interrupt
41 enable data line
42 enable clock line */
43
44
45 /*
46 * "Probe"-style routine (no parameters) to turn A20 on
47 */
48 void
49 gateA20on(void)
50 {
51 gateA20(1);
52 }
53
54
55 /*
56 * Gate A20 for high memory
57 */
58 void
59 gateA20(int on)
60 {
61 if (ps2model == 0xf82 ||
62 (inb(IO_KBD + KBSTATP) == 0xff && inb(IO_KBD + KBDATAP) == 0xff)) {
63 int data;
64
65 /* Try to use 0x92 to turn on A20 */
66 if (on) {
67 data = inb(0x92);
68 outb(0x92, data | 0x2);
69 } else {
70 data = inb(0x92);
71 outb(0x92, data & ~0x2);
72 }
73 } else {
74
75 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
76
77 while (inb(IO_KBD + KBSTATP) & KBS_DIB)
78 (void)inb(IO_KBD + KBDATAP);
79
80 outb(IO_KBD + KBCMDP, KBC_CMDWOUT);
81 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
82
83 if (on)
84 outb(IO_KBD + KBDATAP, KB_A20);
85 else
86 outb(IO_KBD + KBDATAP, 0xcd);
87 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
88
89 while (inb(IO_KBD + KBSTATP) & KBS_DIB)
90 (void)inb(IO_KBD + KBDATAP);
91 }
92 }