Initial source

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 0000000..5e91f86
--- /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;
+