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