1 /* $OpenBSD: gateA20.c,v 1.11 2017/09/08 05:36:52 deraadt 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 <machine/pio.h>
33 #include <dev/ic/i8042reg.h>
34 #include <dev/isa/isareg.h>
35
36 #include "libsa.h"
37
38 #define KB_A20 0xdf /* enable A20,
39 enable output buffer full interrupt
40 enable data line
41 enable clock line */
42
43
44 /*
45 * "Probe"-style routine (no parameters) to turn A20 on
46 */
47 void
gateA20on(void)48 gateA20on(void)
49 {
50 gateA20(1);
51 }
52
53
54 /*
55 * Gate A20 for high memory
56 */
57 void
gateA20(int on)58 gateA20(int on)
59 {
60 if (ps2model == 0xf82 ||
61 (inb(IO_KBD + KBSTATP) == 0xff && inb(IO_KBD + KBDATAP) == 0xff)) {
62 int data;
63
64 /* Try to use 0x92 to turn on A20 */
65 if (on) {
66 data = inb(0x92);
67 outb(0x92, data | 0x2);
68 } else {
69 data = inb(0x92);
70 outb(0x92, data & ~0x2);
71 }
72 } else {
73
74 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
75
76 while (inb(IO_KBD + KBSTATP) & KBS_DIB)
77 (void)inb(IO_KBD + KBDATAP);
78
79 outb(IO_KBD + KBCMDP, KBC_CMDWOUT);
80 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
81
82 if (on)
83 outb(IO_KBD + KBDATAP, KB_A20);
84 else
85 outb(IO_KBD + KBDATAP, 0xcd);
86 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
87
88 while (inb(IO_KBD + KBSTATP) & KBS_DIB)
89 (void)inb(IO_KBD + KBDATAP);
90 }
91 }
92