crt0_ram.s

microwindows移植到S3C44B0的源码

/*****************************************************************************/

/*
 *	crt0_ram.S -- startup code for MCF5307 ColdFire based MP3.
 *
 *	(C) Copyright 1999-2001, Greg Ungerer.
 * 	Copyright (C) 2000-2001  Lineo Inc. (www.lineo.com) 
 *
 * 	1999/02/24 Modified for the 5307 processor David W. Miller
 */

/*****************************************************************************/

#include "linux/autoconf.h"
#include "asm/coldfire.h"
#include "asm/mcfsim.h"
#include "asm/nettel.h"

/*****************************************************************************/

/*
 *	Lineo NETtel board memory setup.
 */
#define	MEM_BASE	0x00000000	/* Memory base at address 0 */
#define	VBR_BASE	MEM_BASE	/* Vector address */

#if defined(CONFIG_RAM16MB)
#define	MEM_SIZE	0x01000000	/* Memory size 16Mb */
#else
#define	MEM_SIZE	0x00800000	/* Memory size 8Mb */
#endif

/*****************************************************************************/

.global	_start
.global _rambase
.global _ramvec
.global	_ramstart
.global	_ramend

/*****************************************************************************/

.data

/*
 *	Set up the usable of RAM stuff. Size of RAM is determined then
 *	an initial stack set up at the end.
 */
_rambase:
.long	0
_ramvec:
.long	0
_ramstart:
.long	0
_ramend:
.long	0

/*****************************************************************************/

.text

/*
 *	This is the codes first entry point. This is where it all
 *	begins...
 */

_start:
	nop					/* Filler */
	move.w	#0x2700, %sr			/* No interrupts */

	/*
	 *	Disable watchdog timer.
	 */
	move.l	#MCF_MBAR, %a0			/* Get MBAR address */
	clr.l	%d0				/* Disable SWT */
	move.b	%d0, MCFSIM_SYPCR(%a0)
	move.b	#0x55, %d0			/* Clear SWT as well */
	move.b	%d0, MCFSIM_SWSR(%a0)
	move.b	#0xaa, %d0
	move.b	%d0, MCFSIM_SWSR(%a0)
	move.l	#0xffffffff, %d0		/* Mask out all interrupts */
	move.l	%d0, MCFSIM_IMR(%a0)

	/*
	 * Setup VBR here, otherwise buserror remap will not work.
	 * if dBug was active before (on my SBC with dBug 1.1 of Dec 16 1996)
	 *
	 * [e-mail] 19990306
	 *
	 * Note: this is because dBUG points VBR to ROM, making vectors read
	 * only, so the bus trap can't be changed. (RS)
	 */
	move.l	#VBR_BASE, %a7			/* Note VBR can't be read */
	movec   %a7, %VBR
	move.l	%a7, _ramvec			/* Set up vector addr */
	move.l	%a7, _rambase			/* Set up base RAM addr */


	/*
	 *	Determine size of RAM, then set up initial stack.
	 */
	move.l	#MEM_SIZE, %a0

	move.l	%a0, %d0			/* Mem end addr is in a0 */
	move.l	%d0, %sp			/* Set up initial stack ptr */
	move.l	%d0, _ramend			/* Set end ram addr */

	/*
	 *	Enable CPU internal cache.
	 */
	move.l	#0x01000000, %d0		/* invalidate whole cache */
	movec	%d0,%CACR
	nop

	/* MUST be write-through for DMA to work... */
	/* This also makes this debugger safe */
	move.l	#0x0000c000, %d0		/* Set SDRAM cached only */
	movec	%d0, %ACR0
	move.l	#0x00000000, %d0		/* No other regions cached */
	movec	%d0, %ACR1

	/* Enable cache */
	move.l	#0xa0000200, %d0
	movec	%d0,%CACR
	nop

	/*
	 *	Move ROM filesystem above bss :-)
	 */
	lea.l	_sbss, %a0			/* Get start of bss */
	lea.l	_ebss, %a1			/* Set up destination  */
	move.l	%a0, %a2			/* Copy of bss start */

	move.l	8(%a0), %d0			/* Get size of ROMFS */
	addq.l	#8, %d0				/* Allow for rounding */
	and.l	#0xfffffffc, %d0		/* Whole words */

	add.l	%d0, %a0			/* Copy from end */
	add.l	%d0, %a1			/* Copy from end */
	move.l	%a1, _ramstart			/* Set start of ram */

_copy_romfs:
	move.l	-(%a0), %d0			/* Copy dword */
	move.l	%d0, -(%a1)
	cmp.l	%a0, %a2			/* Check if at end */
	bne	_copy_romfs

	/*
	 *	Zero out the bss region.
	 */
	lea.l	_sbss, %a0			/* Get start of bss */
	lea.l	_ebss, %a1			/* Get end of bss */
	clr.l	%d0				/* Set value */
_clear_bss:
	move.l	%d0, (%a0)+			/* Clear each word */
	cmp.l	%a0, %a1			/* Check if at end */
	bne	_clear_bss

	/*
	 * load the current task pointer and stack
	 */
	lea		init_task_union,%a0
	movel	%a0, _current_task
	lea		0x2000(%a0),%sp
	/*
	 *	Assember start up done, start code proper.
	 */
	jsr	start_kernel			/* Start Linux kernel */

_exit:
	jmp	_exit				/* Should never get here */

/*****************************************************************************/