1 /* $OpenBSD: gateA20.c,v 1.3 2017/09/08 05:36:51 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 int ps2model = 0; /* Not set in amd64 */
39
40 #define KB_A20 0xdf /* enable A20,
41 enable output buffer full interrupt
42 enable data line
43 enable clock line */
44
45
46 /*
47 * "Probe"-style routine (no parameters) to turn A20 on
48 */
49 void
gateA20on(void)50 gateA20on(void)
51 {
52 gateA20(1);
53 }
54
55
56 /*
57 * Gate A20 for high memory
58 */
59 void
gateA20(int on)60 gateA20(int on)
61 {
62 if (ps2model == 0xf82 ||
63 (inb(IO_KBD + KBSTATP) == 0xff && inb(IO_KBD + KBDATAP) == 0xff)) {
64 int data;
65
66 /* Try to use 0x92 to turn on A20 */
67 if (on) {
68 data = inb(0x92);
69 outb(0x92, data | 0x2);
70 } else {
71 data = inb(0x92);
72 outb(0x92, data & ~0x2);
73 }
74 } else {
75
76 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
77
78 while (inb(IO_KBD + KBSTATP) & KBS_DIB)
79 (void)inb(IO_KBD + KBDATAP);
80
81 outb(IO_KBD + KBCMDP, KBC_CMDWOUT);
82 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
83
84 if (on)
85 outb(IO_KBD + KBDATAP, KB_A20);
86 else
87 outb(IO_KBD + KBDATAP, 0xcd);
88 while (inb(IO_KBD + KBSTATP) & KBS_IBF);
89
90 while (inb(IO_KBD + KBSTATP) & KBS_DIB)
91 (void)inb(IO_KBD + KBDATAP);
92 }
93 }
94