/*      $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);
}