arch/i386/cpu/start.S - u-boot-sam460ex - Git at Google

 /*
  *  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
  */


 #include <config.h>
 #include <version.h>


 .section .text
 .code32
 .globl _start
 .type _start, @function
 .globl _i386boot_start
 _i386boot_start:
 	/*
 	 * This is the fail safe 32-bit bootstrap entry point. The
 	 * following code is not executed from a cold-reset (actually, a
 	 * lot of it is, but from real-mode after cold reset. It is
 	 * repeated here to put the board into a state as close to cold
 	 * reset as necessary)
 	 */
 	cli
 	cld

 	/* Turn of cache (this might require a 486-class CPU) */
 	movl	%cr0, %eax
 	orl	$0x60000000,%eax
 	movl	%eax, %cr0
 	wbinvd

 	/* Tell 32-bit code it is being entered from an in-RAM copy */
 	movw	$0x0000, %bx
 _start:
 	/* This is the 32-bit cold-reset entry point */

 	movl    $0x18,%eax	/* Load our segement registes, the
 				 * gdt have already been loaded by start16.S */
 	movw    %ax,%fs
 	movw	%ax,%ds
 	movw    %ax,%gs
 	movw    %ax,%es
 	movw    %ax,%ss

 	/* Clear the interupt vectors */
 	lidt	blank_idt_ptr

 	/*
 	 * Skip low-level board and memory initialization if not starting
 	 * from cold-reset. This allows us to do a fail safe boot-strap
 	 * into a new build of U-Boot from a known-good boot flash
 	 */
 	movw	$0x0001, %ax
 	cmpw	%ax, %bx
 	jne	mem_init_ret

 	/* We call a few functions in the board support package
 	 * since we have no stack yet we'll have to use %ebp
 	 * to store the return address */

 	/* Early platform init (setup gpio, etc ) */
 	mov     $early_board_init_ret, %ebp
 	jmp	early_board_init
 early_board_init_ret:

 	/* The __port80 entry-point should be usabe by now */
 	/* so we try to indicate progress */
 	movw	$0x01, %ax
 	movl	$.progress0, %ebp
 	jmp	show_boot_progress_asm
 .progress0:

 	/* size memory */
 	mov	$mem_init_ret, %ebp
 	jmp     mem_init
 mem_init_ret:

 	/* fetch memory size (into %eax) */
 	mov	$get_mem_size_ret, %ebp
 	jmp     get_mem_size
 get_mem_size_ret:

 	/*
 	 * We are now in 'Flat Protected Mode' and we know how much memory
 	 * the board has. The (temporary) Global Descriptor Table is not
 	 * in a 'Safe' place (it is either in Flash which can be erased or
 	 * reprogrammed or in a fail-safe boot-strap image which could be
 	 * over-written).
 	 *
 	 * Move the final gdt to a safe place (top of RAM) and load it.
 	 * This is not a trivial excercise - the lgdt instruction does not
 	 * have a register operand (memory only) and we may well be
 	 * running from Flash, so self modifying code will not work here.
 	 * To overcome this, we copy a stub into upper memory along with
 	 * the GDT.
 	 */

 	/* Reduce upper memory limit by (Stub + GDT Pointer + GDT) */
 	subl	$(end_gdt_setup - start_gdt_setup), %eax

 	/* Copy the GDT and Stub */
 	movl	$start_gdt_setup, %esi
 	movl	%eax, %edi
 	movl	$(end_gdt_setup - start_gdt_setup), %ecx
 	shrl	$2, %ecx
 	cld
 	rep	movsl

 	/* write the lgdt 'parameter' */
 	subl	$(jmp_instr - start_gdt_setup - 4), %ebp
 	addl	%eax, %ebp
 	movl	$(gdt_ptr - start_gdt_setup), %ebx
 	addl	%eax, %ebx
 	movl	%ebx, (%ebp)

 	/* write the gdt address into the pointer */
 	movl	$(gdt_addr - start_gdt_setup), %ebp
 	addl	%eax, %ebp
 	movl	$(gdt - start_gdt_setup), %ebx
 	addl	%eax, %ebx
 	movl	%ebx, (%ebp)

 	/* Save the return address */
 	movl	$load_gdt_ret, %ebp

 	/* Load the new (safe) Global Descriptor Table */
 	jmp	*%eax

 load_gdt_ret:
 	/* Check we have enough memory for stack */
 	movl	$CONFIG_SYS_STACK_SIZE, %ecx
 	cmpl	%ecx, %eax
 	jae	mem_ok

 	/* indicate (lack of) progress */
 	movw	$0x81, %ax
 	movl	$.progress0a, %ebp
 	jmp	show_boot_progress_asm
 .progress0a:
 	jmp	die
 mem_ok:
 	/* Set stack pointer to upper memory limit*/
 	movl    %eax, %esp

 	/* indicate progress */
 	movw	$0x02, %ax
 	movl	$.progress1, %ebp
 	jmp	show_boot_progress_asm
 .progress1:

 	/* Test the stack */
 	pushl	$0
 	popl	%eax
 	cmpl	$0, %eax
 	jne	no_stack
 	push	$0x55aa55aa
 	popl	%ebx
 	cmpl	$0x55aa55aa, %ebx
 	je	stack_ok

 no_stack:
 	/* indicate (lack of) progress */
 	movw	$0x82, %ax
 	movl	$.progress1a, %ebp
 	jmp	show_boot_progress_asm
 .progress1a:
 	jmp die


 stack_ok:
 	/* indicate progress */
 	movw	$0x03, %ax
 	movl	$.progress2, %ebp
 	jmp	show_boot_progress_asm
 .progress2:

 	wbinvd

 	/* Get upper memory limit */
 	movl %esp, %ecx
 	subl $CONFIG_SYS_STACK_SIZE, %ecx

 	/* Create a Stack Frame */
 	pushl %ebp
 	movl %esp, %ebp

 	/* stack_limit parameter */
 	pushl	%ecx
 	call	board_init_f	/* Enter, U-boot! */

 	/* indicate (lack of) progress */
 	movw	$0x85, %ax
 	movl	$.progress4a, %ebp
 	jmp	show_boot_progress_asm
 .progress4a:

 die:	hlt
 	jmp	die
 	hlt

 blank_idt_ptr:
 	.word	0		/* limit */
 	.long	0		/* base */

 .align 4
 start_gdt_setup:
 	lgdt	gdt_ptr
 jmp_instr:
 	jmp	*%ebp

 .align 4
 gdt_ptr:
 	.word	0x30		/* limit (48 bytes = 6 GDT entries) */
 gdt_addr:
 	.long	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
 	 */

 .align 4
 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) */
 end_gdt_setup:
	/*
	* 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
	*/


	#include <config.h>
	#include <version.h>


	.section .text
	.code32
	.globl _start
	.type _start, @function
	.globl _i386boot_start
	_i386boot_start:
	/*
	* This is the fail safe 32-bit bootstrap entry point. The
	* following code is not executed from a cold-reset (actually, a
	* lot of it is, but from real-mode after cold reset. It is
	* repeated here to put the board into a state as close to cold
	* reset as necessary)
	*/
	cli
	cld

	/* Turn of cache (this might require a 486-class CPU) */
	movl %cr0, %eax
	orl $0x60000000,%eax
	movl %eax, %cr0
	wbinvd

	/* Tell 32-bit code it is being entered from an in-RAM copy */
	movw $0x0000, %bx
	_start:
	/* This is the 32-bit cold-reset entry point */

	movl $0x18,%eax /* Load our segement registes, the
	* gdt have already been loaded by start16.S */
	movw %ax,%fs
	movw %ax,%ds
	movw %ax,%gs
	movw %ax,%es
	movw %ax,%ss

	/* Clear the interupt vectors */
	lidt blank_idt_ptr

	/*
	* Skip low-level board and memory initialization if not starting
	* from cold-reset. This allows us to do a fail safe boot-strap
	* into a new build of U-Boot from a known-good boot flash
	*/
	movw $0x0001, %ax
	cmpw %ax, %bx
	jne mem_init_ret

	/* We call a few functions in the board support package
	* since we have no stack yet we'll have to use %ebp
	* to store the return address */

	/* Early platform init (setup gpio, etc ) */
	mov $early_board_init_ret, %ebp
	jmp early_board_init
	early_board_init_ret:

	/* The __port80 entry-point should be usabe by now */
	/* so we try to indicate progress */
	movw $0x01, %ax
	movl $.progress0, %ebp
	jmp show_boot_progress_asm
	.progress0:

	/* size memory */
	mov $mem_init_ret, %ebp
	jmp mem_init
	mem_init_ret:

	/* fetch memory size (into %eax) */
	mov $get_mem_size_ret, %ebp
	jmp get_mem_size
	get_mem_size_ret:

	/*
	* We are now in 'Flat Protected Mode' and we know how much memory
	* the board has. The (temporary) Global Descriptor Table is not
	* in a 'Safe' place (it is either in Flash which can be erased or
	* reprogrammed or in a fail-safe boot-strap image which could be
	* over-written).
	*
	* Move the final gdt to a safe place (top of RAM) and load it.
	* This is not a trivial excercise - the lgdt instruction does not
	* have a register operand (memory only) and we may well be
	* running from Flash, so self modifying code will not work here.
	* To overcome this, we copy a stub into upper memory along with
	* the GDT.
	*/

	/* Reduce upper memory limit by (Stub + GDT Pointer + GDT) */
	subl $(end_gdt_setup - start_gdt_setup), %eax

	/* Copy the GDT and Stub */
	movl $start_gdt_setup, %esi
	movl %eax, %edi
	movl $(end_gdt_setup - start_gdt_setup), %ecx
	shrl $2, %ecx
	cld
	rep movsl

	/* write the lgdt 'parameter' */
	subl $(jmp_instr - start_gdt_setup - 4), %ebp
	addl %eax, %ebp
	movl $(gdt_ptr - start_gdt_setup), %ebx
	addl %eax, %ebx
	movl %ebx, (%ebp)

	/* write the gdt address into the pointer */
	movl $(gdt_addr - start_gdt_setup), %ebp
	addl %eax, %ebp
	movl $(gdt - start_gdt_setup), %ebx
	addl %eax, %ebx
	movl %ebx, (%ebp)

	/* Save the return address */
	movl $load_gdt_ret, %ebp

	/* Load the new (safe) Global Descriptor Table */
	jmp *%eax

	load_gdt_ret:
	/* Check we have enough memory for stack */
	movl $CONFIG_SYS_STACK_SIZE, %ecx
	cmpl %ecx, %eax
	jae mem_ok

	/* indicate (lack of) progress */
	movw $0x81, %ax
	movl $.progress0a, %ebp
	jmp show_boot_progress_asm
	.progress0a:
	jmp die
	mem_ok:
	/* Set stack pointer to upper memory limit*/
	movl %eax, %esp

	/* indicate progress */
	movw $0x02, %ax
	movl $.progress1, %ebp
	jmp show_boot_progress_asm
	.progress1:

	/* Test the stack */
	pushl $0
	popl %eax
	cmpl $0, %eax
	jne no_stack
	push $0x55aa55aa
	popl %ebx
	cmpl $0x55aa55aa, %ebx
	je stack_ok

	no_stack:
	/* indicate (lack of) progress */
	movw $0x82, %ax
	movl $.progress1a, %ebp
	jmp show_boot_progress_asm
	.progress1a:
	jmp die


	stack_ok:
	/* indicate progress */
	movw $0x03, %ax
	movl $.progress2, %ebp
	jmp show_boot_progress_asm
	.progress2:

	wbinvd

	/* Get upper memory limit */
	movl %esp, %ecx
	subl $CONFIG_SYS_STACK_SIZE, %ecx

	/* Create a Stack Frame */
	pushl %ebp
	movl %esp, %ebp

	/* stack_limit parameter */
	pushl %ecx
	call board_init_f /* Enter, U-boot! */

	/* indicate (lack of) progress */
	movw $0x85, %ax
	movl $.progress4a, %ebp
	jmp show_boot_progress_asm
	.progress4a:

	die: hlt
	jmp die
	hlt

	blank_idt_ptr:
	.word 0 /* limit */
	.long 0 /* base */

	.align 4
	start_gdt_setup:
	lgdt gdt_ptr
	jmp_instr:
	jmp *%ebp

	.align 4
	gdt_ptr:
	.word 0x30 /* limit (48 bytes = 6 GDT entries) */
	gdt_addr:
	.long 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
	*/

	.align 4
	gdt:
	.word 0, 0, 0, 0 /* NULL */
	.word 0, 0, 0, 0 /* unused */

	.word 0xFFFF /* 4Gb - (0x1000000x1000 = 4Gb) /
	.word 0 /* base address = 0 */
	.word 0x9B00 /* code read/exec */
	.word 0x00CF /* granularity = 4096, 386 (+5th nibble of limit) */

	.word 0xFFFF /* 4Gb - (0x1000000x1000 = 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) */
	end_gdt_setup: