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/* $NetBSD: gatea20.c,v 1.12 2009/08/23 12:31:05 jmcneill Exp $ */
/* extracted from freebsd:sys/i386/boot/biosboot/io.c */
#include <sys/types.h>
#include <lib/libsa/stand.h>
#include "libi386.h"
#include "biosmca.h"
#include "cpufunc.h"
#define K_RDWR 0x60 /* keyboard data & cmds (read/write) */
#define K_STATUS 0x64 /* keyboard status */
#define K_CMD 0x64 /* keybd ctlr command (write-only) */
#define K_OBUF_FUL 0x01 /* output buffer full */
#define K_IBUF_FUL 0x02 /* input buffer full */
#define KC_CMD_WIN 0xd0 /* read output port */
#define KC_CMD_WOUT 0xd1 /* write output port */
#define KB_A20 0x9f /* enable A20,
reset (!),
enable output buffer full interrupt
enable data line
disable clock line */
/*
* Gate A20 for high memory
*/
static unsigned char x_20 = KB_A20;
void
gateA20(void)
{
int biosA20(void);
u_long psl;
/*
* First, try asking the BIOS to enable A20.
*
* If that fails, try system configuration port 0x92 but only
* if known to be necessary. Not all systems enable A20 via the
* keyboard controller, some don't have keyboard controllers,
* and playing with port 0x92 may cause some systems to break.
*
* Otherwise, use the traditional method (keyboard controller).
*/
if (!biosA20())
return;
psl = x86_read_psl();
x86_disable_intr();
if (
#ifdef SUPPORT_PS2
biosmca_ps2model == 0xf82 ||
#endif
(inb(K_STATUS) == 0xff && inb(K_RDWR) == 0xff)) {
int data;
data = inb(0x92);
outb(0x92, data | 0x2);
} else {
while (inb(K_STATUS) & K_IBUF_FUL);
while (inb(K_STATUS) & K_OBUF_FUL)
(void)inb(K_RDWR);
outb(K_CMD, KC_CMD_WOUT);
while (inb(K_STATUS) & K_IBUF_FUL);
outb(K_RDWR, x_20);
while (inb(K_STATUS) & K_IBUF_FUL);
while (inb(K_STATUS) & K_OBUF_FUL)
(void)inb(K_RDWR);
}
x86_write_psl(psl);
}
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