diff options
Diffstat (limited to 'i386/pc/i16/i16_a20.c')
| -rw-r--r-- | i386/pc/i16/i16_a20.c | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/i386/pc/i16/i16_a20.c b/i386/pc/i16/i16_a20.c new file mode 100644 index 00000000..5e91f86c --- /dev/null +++ b/i386/pc/i16/i16_a20.c @@ -0,0 +1,144 @@ +/* + * Copyright (c) 1995-1994 The University of Utah and + * the Computer Systems Laboratory at the University of Utah (CSL). + * All rights reserved. + * + * Permission to use, copy, modify and distribute this software is hereby + * granted provided that (1) source code retains these copyright, permission, + * and disclaimer notices, and (2) redistributions including binaries + * reproduce the notices in supporting documentation, and (3) all advertising + * materials mentioning features or use of this software display the following + * acknowledgement: ``This product includes software developed by the + * Computer Systems Laboratory at the University of Utah.'' + * + * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS + * IS" CONDITION. THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF + * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. + * + * CSL requests users of this software to return to csl-dist@cs.utah.edu any + * improvements that they make and grant CSL redistribution rights. + * + * Author: Bryan Ford, University of Utah CSL + */ + + +#include <mach/machine/pio.h> +#include <mach/machine/code16.h> + +#include "i16_a20.h" + + +/* Keyboard stuff for turning on the A20 address line (gak!). */ +#define K_RDWR 0x60 /* keyboard data & cmds (read/write) */ +#define K_STATUS 0x64 /* keyboard status (read-only) */ +#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_ENABLE_A20 0xdf /* Linux and my BIOS uses this, + and I trust them more than Mach 3.0, + but I'd like to know what the difference is + and if it matters. */ + /*0x9f*/ /* enable A20, + enable output buffer full interrupt + enable data line + disable clock line */ +#define KB_DISABLE_A20 0xdd + + +CODE16 + + +/* + This routine ensures that the keyboard command queue is empty + (after emptying the output buffers) + + No timeout is used - if this hangs there is something wrong with + the machine, and we probably couldn't proceed anyway. + XXX should at least die properly +*/ +static void i16_empty_8042(void) +{ + int status; + +retry: + i16_nanodelay(1000); + status = i16_inb(K_STATUS); + + if (status & K_OBUF_FUL) + { + i16_nanodelay(1000); + i16_inb(K_RDWR); + goto retry; + } + + if (status & K_IBUF_FUL) + goto retry; +} + +int i16_raw_test_a20(void); + +/* Enable the A20 address line. */ +void i16_raw_enable_a20(void) +{ + int v; + + /* XXX try int 15h function 24h */ + + if (i16_raw_test_a20()) + return; + + /* PS/2 */ + v = i16_inb(0x92); + i16_nanodelay(1000); + i16_outb(0x92,v | 2); + + if (i16_raw_test_a20()) + return; + + /* AT */ + i16_empty_8042(); + i16_outb(K_CMD, KC_CMD_WOUT); + i16_empty_8042(); + i16_outb(K_RDWR, KB_ENABLE_A20); + i16_empty_8042(); + + /* Wait until the a20 line gets enabled. */ + while (!i16_raw_test_a20()); +} + +/* Disable the A20 address line. */ +void i16_raw_disable_a20(void) +{ + int v; + + if (!i16_raw_test_a20()) + return; + + /* PS/2 */ + v = i16_inb(0x92); + i16_nanodelay(1000); + i16_outb(0x92, v & ~2); + + if (!i16_raw_test_a20()) + return; + + /* AT */ + i16_empty_8042(); + i16_outb(K_CMD, KC_CMD_WOUT); + i16_empty_8042(); + i16_outb(K_RDWR, KB_DISABLE_A20); + i16_empty_8042(); + + /* Wait until the a20 line gets disabled. */ + while (i16_raw_test_a20()); +} + + +void (*i16_enable_a20)(void) = i16_raw_enable_a20; +void (*i16_disable_a20)(void) = i16_raw_disable_a20; + |