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gatea20.c revision 1.5 
      1 /*	$NetBSD: gatea20.c,v 1.5 2002/08/12 14:27:34 thorpej Exp $	*/
      2 
      3 /* extracted from freebsd:sys/i386/boot/biosboot/io.c */
      4 
      5 #include <sys/types.h>
      6 #include <machine/pio.h>
      7 
      8 #include <lib/libsa/stand.h>
      9 
     10 #include "libi386.h"
     11 #include "biosmca.h"
     12 
     13 #define K_RDWR 		0x60		/* keyboard data & cmds (read/write) */
     14 #define K_STATUS 	0x64		/* keyboard status */
     15 #define K_CMD	 	0x64		/* keybd ctlr command (write-only) */
     16 
     17 #define K_OBUF_FUL 	0x01		/* output buffer full */
     18 #define K_IBUF_FUL 	0x02		/* input buffer full */
     19 
     20 #define KC_CMD_WIN	0xd0		/* read  output port */
     21 #define KC_CMD_WOUT	0xd1		/* write output port */
     22 #define KB_A20		0x9f		/* enable A20,
     23 					   reset (!),
     24 					   enable output buffer full interrupt
     25 					   enable data line
     26 					   disable clock line */
     27 
     28 /*
     29  * Gate A20 for high memory
     30  */
     31 static unsigned char	x_20 = KB_A20;
     32 void gateA20()
     33 {
     34 	__asm("pushfl ; cli");
     35 	/*
     36 	 * Not all systems enable A20 via the keyboard controller.
     37 	 *	* IBM PS/2 L40
     38 	 *	* AMD Elan SC520-based systems
     39 	 */
     40 	if (
     41 #ifdef SUPPORT_PS2
     42 	    biosmca_ps2model == 0xf82 ||
     43 #endif
     44 	    /* XXX How to check for AMD Elan SC520? */
     45 	    0) {
     46 		outb(0x92, 0x2);
     47 	} else {
     48 		while (inb(K_STATUS) & K_IBUF_FUL);
     49 		while (inb(K_STATUS) & K_OBUF_FUL)
     50 			(void)inb(K_RDWR);
     51 
     52 		outb(K_CMD, KC_CMD_WOUT);
     53 		delay(100);
     54 		while (inb(K_STATUS) & K_IBUF_FUL);
     55 		outb(K_RDWR, x_20);
     56 		delay(100);
     57 		while (inb(K_STATUS) & K_IBUF_FUL);
     58 	}
     59 	__asm("popfl");
     60 }
     61