From 2262cfeef91458b01a1bfe3812ccbbfdf8b82807 Mon Sep 17 00:00:00 2001
From: wdenk <wdenk>
Date: Mon, 18 Nov 2002 00:14:45 +0000
Subject: =?UTF-8?q?*=20Patch=20by=20Daniel=20Engstr=F6m,=2013=20Nov=202002?=
 =?UTF-8?q?:=20=20=20Add=20support=20for=20i386=20architecture=20and=20AMD?=
 =?UTF-8?q?=20SC520=20board?=
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* Patch by Pierre Aubert, 12 Nov 2002:
  Add support for DOS filesystem and booting from DOS floppy disk
---
 cpu/i386/start16.S | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 cpu/i386/start16.S

(limited to 'cpu/i386/start16.S')

diff --git a/cpu/i386/start16.S b/cpu/i386/start16.S
new file mode 100644
index 0000000..590a5a6
--- /dev/null
+++ b/cpu/i386/start16.S
@@ -0,0 +1,112 @@
+/*
+ *  U-boot - i386 Startup Code 
+ *
+ *  Copyright (c) 2002	Omicron Ceti AB, Daniel Engström <denaiel@omicron.se>
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+
+#define BOOT_SEG	0xffff0000	/* linear segment of boot code */
+#define a32		.byte 0x67;
+#define o32		.byte 0x66;
+
+.section .start16, "ax"
+.code16
+.globl start16
+start16: 
+	/* First we let the BSP do some early initialization
+	 * this code have to map the flash to its final position
+	 */
+	mov	$board_init16_ret, %bp
+	jmp	board_init16
+board_init16_ret:	
+	
+	/* Turn of cache (this might require a 486-class CPU) */
+        movl    %cr0, %eax
+        orl     $060000000,%eax
+        movl    %eax, %cr0
+        wbinvd  		     
+	
+	/* load the descriptor tables */
+o32 cs	lidt	idt_ptr
+o32 cs	lgdt    gdt_ptr		 
+
+
+	/* Now, we enter protected mode */
+        movl    %cr0, %eax               
+        orl     $1,%eax                  
+        movl    %eax, %cr0            
+	
+	/* Flush the prefetch queue */
+        jmp     ff        
+ff:
+
+	/* Finally jump to the 32bit initialization code */
+	movw	$code32start, %ax 
+        movw    %ax,%bp
+o32 cs	ljmp	*(%bp)
+
+	/* 48-bit far pointer */
+code32start:
+	.long	_start                          /* offset */
+	.word	0x10                            /* segment */
+
+idt_ptr:
+	.word	0				/* limit */
+	.long	0		       		/* base */
+	
+gdt_ptr:
+	.word	0x30			        /* limit (48 bytes = 6 GDT entries) */
+	.long	BOOT_SEG + gdt	        	/* base */
+
+	/* The GDT table ... 
+	 *
+	 *       Selector	Type 
+	 * 	 0x00		NULL
+	 * 	 0x08		Unused
+	 *	 0x10		32bit code 
+	 *	 0x18		32bit data/stack
+	 *	 0x20		16bit code
+	 *	 0x28	 	16bit data/stack
+	 */
+
+gdt:
+	.word	0, 0, 0, 0			/* NULL  */
+	.word	0, 0, 0, 0			/* unused */
+
+	.word	0xFFFF				/* 4Gb - (0x100000*0x1000 = 4Gb) */
+	.word	0				/* base address = 0 */
+	.word	0x9B00				/* code read/exec */
+	.word	0x00CF				/* granularity = 4096, 386 (+5th nibble of limit) */
+
+	.word	0xFFFF				/* 4Gb - (0x100000*0x1000 = 4Gb) */
+	.word	0x0				/* base address = 0 */
+	.word	0x9300				/* data read/write */
+	.word	0x00CF				/* granularity = 4096, 386 (+5th nibble of limit) */
+						
+	.word	0xFFFF				/* 64kb */
+	.word	0				/* base address = 0 */
+	.word	0x9b00				/* data read/write */
+	.word	0x0010				/* granularity = 1  (+5th nibble of limit) */
+	
+	.word	0xFFFF				/* 64kb */
+	.word	0				/* base address = 0 */
+	.word	0x9300				/* data read/write */
+	.word	0x0010				/* granularity = 1 (+5th nibble of limit) */
-- 
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