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/* $OpenBSD: gateA20.c,v 1.11 2017/09/08 05:36:52 deraadt Exp $ */
/*
* Ported to boot 386BSD by Julian Elischer (julian@tfs.com) Sept 1992
*
* Mach Operating System
* Copyright (c) 1992, 1991 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/
#include <sys/param.h>
#include <machine/pio.h>
#include <dev/ic/i8042reg.h>
#include <dev/isa/isareg.h>
#include "libsa.h"
#define KB_A20 0xdf /* enable A20,
enable output buffer full interrupt
enable data line
enable clock line */
/*
* "Probe"-style routine (no parameters) to turn A20 on
*/
void
gateA20on(void)
{
gateA20(1);
}
/*
* Gate A20 for high memory
*/
void
gateA20(int on)
{
if (ps2model == 0xf82 ||
(inb(IO_KBD + KBSTATP) == 0xff && inb(IO_KBD + KBDATAP) == 0xff)) {
int data;
/* Try to use 0x92 to turn on A20 */
if (on) {
data = inb(0x92);
outb(0x92, data | 0x2);
} else {
data = inb(0x92);
outb(0x92, data & ~0x2);
}
} else {
while (inb(IO_KBD + KBSTATP) & KBS_IBF);
while (inb(IO_KBD + KBSTATP) & KBS_DIB)
(void)inb(IO_KBD + KBDATAP);
outb(IO_KBD + KBCMDP, KBC_CMDWOUT);
while (inb(IO_KBD + KBSTATP) & KBS_IBF);
if (on)
outb(IO_KBD + KBDATAP, KB_A20);
else
outb(IO_KBD + KBDATAP, 0xcd);
while (inb(IO_KBD + KBSTATP) & KBS_IBF);
while (inb(IO_KBD + KBSTATP) & KBS_DIB)
(void)inb(IO_KBD + KBDATAP);
}
}
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