start.s

AT91RM9200的完整启动代码：包括loader, boot及U-boot三部分均已编译通过！欢迎下载使用！

	mtspr	SRR0,r24
	mtspr	SRR1,r20
	mtlr	r23
	SYNC
	rfi				/* jump to handler, enable MMU */

int_return:
	mfmsr	r28			/* Disable interrupts */
	li	r4,0
	ori	r4,r4,MSR_EE
	andc	r28,r28,r4
	SYNC				/* Some chip revs need this... */
	mtmsr	r28
	SYNC
	lwz	r2,_CTR(r1)
	lwz	r0,_LINK(r1)
	mtctr	r2
	mtlr	r0
	lwz	r2,_XER(r1)
	lwz	r0,_CCR(r1)
	mtspr	XER,r2
	mtcrf	0xFF,r0
	REST_10GPRS(3, r1)
	REST_10GPRS(13, r1)
	REST_8GPRS(23, r1)
	REST_GPR(31, r1)
	lwz	r2,_NIP(r1)		/* Restore environment */
	lwz	r0,_MSR(r1)
	mtspr	SRR0,r2
	mtspr	SRR1,r0
	lwz	r0,GPR0(r1)
	lwz	r2,GPR2(r1)
	lwz	r1,GPR1(r1)
	SYNC
	rfi

/* Cache functions.
*/
	.globl	icache_enable
icache_enable:
	SYNC
	lis	r3, IDC_INVALL@h
	mtspr	IC_CST, r3
	lis	r3, IDC_ENABLE@h
	mtspr	IC_CST, r3
	blr

	.globl	icache_disable
icache_disable:
	SYNC
	lis	r3, IDC_DISABLE@h
	mtspr	IC_CST, r3
	blr

	.globl	icache_status
icache_status:
	mfspr	r3, IC_CST
	srwi	r3, r3, 31	/* >>31 => select bit 0 */
	blr

	.globl	dcache_enable
dcache_enable:
#if 0
	SYNC
#endif
#if 1
	lis	r3, 0x0400		/* Set cache mode with MMU off */
	mtspr	MD_CTR, r3
#endif

	lis	r3, IDC_INVALL@h
	mtspr	DC_CST, r3
#if 0
	lis	r3, DC_SFWT@h
	mtspr	DC_CST, r3
#endif
	lis	r3, IDC_ENABLE@h
	mtspr	DC_CST, r3
	blr

	.globl	dcache_disable
dcache_disable:
	SYNC
	lis	r3, IDC_DISABLE@h
	mtspr	DC_CST, r3
	lis	r3, IDC_INVALL@h
	mtspr	DC_CST, r3
	blr

	.globl	dcache_status
dcache_status:
	mfspr	r3, DC_CST
	srwi	r3, r3, 31	/* >>31 => select bit 0 */
	blr

	.globl	dc_read
dc_read:
	mtspr	DC_ADR, r3
	mfspr	r3, DC_DAT
	blr

/*
 * unsigned int get_immr (unsigned int mask)
 *
 * return (mask ? (IMMR & mask) : IMMR);
 */
	.globl	get_immr
get_immr:
	mr	r4,r3		/* save mask */
	mfspr	r3, IMMR	/* IMMR */
	cmpwi	0,r4,0		/* mask != 0 ? */
	beq	4f
	and	r3,r3,r4	/* IMMR & mask */
4:
	blr

	.globl get_pvr
get_pvr:
	mfspr	r3, PVR
	blr


	.globl wr_ic_cst
wr_ic_cst:
	mtspr	IC_CST, r3
	blr

	.globl rd_ic_cst
rd_ic_cst:
	mfspr	r3, IC_CST
	blr

	.globl wr_ic_adr
wr_ic_adr:
	mtspr	IC_ADR, r3
	blr


	.globl wr_dc_cst
wr_dc_cst:
	mtspr	DC_CST, r3
	blr

	.globl rd_dc_cst
rd_dc_cst:
	mfspr	r3, DC_CST
	blr

	.globl wr_dc_adr
wr_dc_adr:
	mtspr	DC_ADR, r3
	blr

/*------------------------------------------------------------------------------*/

/*
 * void relocate_code (addr_sp, gd, addr_moni)
 *
 * This "function" does not return, instead it continues in RAM
 * after relocating the monitor code.
 *
 * r3 = dest
 * r4 = src
 * r5 = length in bytes
 * r6 = cachelinesize
 */
	.globl	relocate_code
relocate_code:
	mr	r1,  r3		/* Set new stack pointer		*/
	mr	r9,  r4		/* Save copy of Global Data pointer	*/
	mr	r10, r5		/* Save copy of Destination Address	*/

	mr	r3,  r5				/* Destination Address	*/
	lis	r4, CFG_MONITOR_BASE@h		/* Source      Address	*/
	ori	r4, r4, CFG_MONITOR_BASE@l
	lwz	r5, GOT(__init_end)
	sub	r5, r5, r4
	li	r6, CFG_CACHELINE_SIZE		/* Cache Line Size	*/

	/*
	 * Fix GOT pointer:
	 *
	 * New GOT-PTR = (old GOT-PTR - CFG_MONITOR_BASE) + Destination Address
	 *
	 * Offset:
	 */
	sub	r15, r10, r4

	/* First our own GOT */
	add	r14, r14, r15
	/* then the one used by the C code */
	add	r30, r30, r15

	/*
	 * Now relocate code
	 */

	cmplw	cr1,r3,r4
	addi	r0,r5,3
	srwi.	r0,r0,2
	beq	cr1,4f		/* In place copy is not necessary	*/
	beq	7f		/* Protect against 0 count		*/
	mtctr	r0
	bge	cr1,2f

	la	r8,-4(r4)
	la	r7,-4(r3)
1:	lwzu	r0,4(r8)
	stwu	r0,4(r7)
	bdnz	1b
	b	4f

2:	slwi	r0,r0,2
	add	r8,r4,r0
	add	r7,r3,r0
3:	lwzu	r0,-4(r8)
	stwu	r0,-4(r7)
	bdnz	3b

/*
 * Now flush the cache: note that we must start from a cache aligned
 * address. Otherwise we might miss one cache line.
 */
4:	cmpwi	r6,0
	add	r5,r3,r5
	beq	7f		/* Always flush prefetch queue in any case */
	subi	r0,r6,1
	andc	r3,r3,r0
	mr	r4,r3
5:	dcbst	0,r4
	add	r4,r4,r6
	cmplw	r4,r5
	blt	5b
	sync			/* Wait for all dcbst to complete on bus */
	mr	r4,r3
6:	icbi	0,r4
	add	r4,r4,r6
	cmplw	r4,r5
	blt	6b
7:	sync			/* Wait for all icbi to complete on bus	*/
	isync

/*
 * We are done. Do not return, instead branch to second part of board
 * initialization, now running from RAM.
 */

	addi	r0, r10, in_ram - _start + EXC_OFF_SYS_RESET
	mtlr	r0
	blr

in_ram:

	/*
	 * Relocation Function, r14 point to got2+0x8000
	 *
         * Adjust got2 pointers, no need to check for 0, this code
         * already puts a few entries in the table.
	 */
	li	r0,__got2_entries@sectoff@l
	la	r3,GOT(_GOT2_TABLE_)
	lwz	r11,GOT(_GOT2_TABLE_)
	mtctr	r0
	sub	r11,r3,r11
	addi	r3,r3,-4
1:	lwzu	r0,4(r3)
	add	r0,r0,r11
	stw	r0,0(r3)
	bdnz	1b

	/*
         * Now adjust the fixups and the pointers to the fixups
	 * in case we need to move ourselves again.
	 */
2:	li	r0,__fixup_entries@sectoff@l
	lwz	r3,GOT(_FIXUP_TABLE_)
	cmpwi	r0,0
	mtctr	r0
	addi	r3,r3,-4
	beq	4f
3:	lwzu	r4,4(r3)
	lwzux	r0,r4,r11
	add	r0,r0,r11
	stw	r10,0(r3)
	stw	r0,0(r4)
	bdnz	3b
4:
clear_bss:
	/*
	 * Now clear BSS segment
	 */
	lwz	r3,GOT(__bss_start)
#if defined(CONFIG_FADS) || defined(CONFIG_ICU862)
	/*
	 * For the FADS - the environment is the very last item in flash.
	 * The real .bss stops just before environment starts, so only
	 * clear up to that point.
	 */
	lwz	r4,GOT(environment)
#else
	lwz	r4,GOT(_end)
#endif

	cmplw	0, r3, r4
	beq	6f

	li	r0, 0
5:
	stw	r0, 0(r3)
	addi	r3, r3, 4
	cmplw	0, r3, r4
	bne	5b
6:

	mr	r3, r9		/* Global Data pointer		*/
	mr	r4, r10		/* Destination Address		*/
	bl	board_init_r

	/*
	 * Copy exception vector code to low memory
	 *
	 * r3: dest_addr
	 * r7: source address, r8: end address, r9: target address
	 */
	.globl	trap_init
trap_init:
	lwz	r7, GOT(_start)
	lwz	r8, GOT(_end_of_vectors)

	li	r9, 0x100		/* reset vector always at 0x100 */

	cmplw	0, r7, r8
	bgelr				/* return if r7>=r8 - just in case */

	mflr	r4			/* save link register		*/
1:
	lwz	r0, 0(r7)
	stw	r0, 0(r9)
	addi	r7, r7, 4
	addi	r9, r9, 4
	cmplw	0, r7, r8
	bne	1b

	/*
	 * relocate `hdlr' and `int_return' entries
	 */
	li	r7, .L_MachineCheck - _start + EXC_OFF_SYS_RESET
	li	r8, Alignment - _start + EXC_OFF_SYS_RESET
2:
	bl	trap_reloc
	addi	r7, r7, 0x100		/* next exception vector	*/
	cmplw	0, r7, r8
	blt	2b

	li	r7, .L_Alignment - _start + EXC_OFF_SYS_RESET
	bl	trap_reloc

	li	r7, .L_ProgramCheck - _start + EXC_OFF_SYS_RESET
	bl	trap_reloc

	li	r7, .L_FPUnavailable - _start + EXC_OFF_SYS_RESET
	li	r8, SystemCall - _start + EXC_OFF_SYS_RESET
3:
	bl	trap_reloc
	addi	r7, r7, 0x100		/* next exception vector	*/
	cmplw	0, r7, r8
	blt	3b

	li	r7, .L_SingleStep - _start + EXC_OFF_SYS_RESET
	li	r8, _end_of_vectors - _start + EXC_OFF_SYS_RESET
4:
	bl	trap_reloc
	addi	r7, r7, 0x100		/* next exception vector	*/
	cmplw	0, r7, r8
	blt	4b

	mtlr	r4			/* restore link register	*/
	blr

	/*
	 * Function: relocate entries for one exception vector
	 */
trap_reloc:
	lwz	r0, 0(r7)		/* hdlr ...			*/
	add	r0, r0, r3		/*  ... += dest_addr		*/
	stw	r0, 0(r7)

	lwz	r0, 4(r7)		/* int_return ...		*/
	add	r0, r0, r3		/*  ... += dest_addr		*/
	stw	r0, 4(r7)

	sync
	isync

	blr