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！

/*
 *  Copyright (C) 1998	Dan Malek <[e-mail]>
 *  Copyright (C) 1999	Magnus Damm <kieraypc01.p.y.kie.era.ericsson.se>
 *  Copyright (C) 2000,2001,2002 Wolfgang Denk <[e-mail]>
 *
 * 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
 */

/* U-Boot - Startup Code for PowerPC based Embedded Boards
 *
 *
 * The processor starts at 0x00000100 and the code is executed
 * from flash. The code is organized to be at an other address
 * in memory, but as long we don't jump around before relocating.
 * board_init lies at a quite high address and when the cpu has
 * jumped there, everything is ok.
 * This works because the cpu gives the FLASH (CS0) the whole
 * address space at startup, and board_init lies as a echo of
 * the flash somewhere up there in the memorymap.
 *
 * board_init will change CS0 to be positioned at the correct
 * address and (s)dram will be positioned at address 0
 */
#include <config.h>
#include <mpc824x.h>
#include <version.h>

#define _LINUX_CONFIG_H 1	/* avoid reading Linux autoconf.h file	*/

#include <ppc_asm.tmpl>
#include <ppc_defs.h>

#include <asm/cache.h>
#include <asm/mmu.h>

#ifndef CONFIG_IDENT_STRING
#define CONFIG_IDENT_STRING ""
#endif

/* We don't want the MMU yet.
*/
#undef	MSR_KERNEL
/* FP, Machine Check and Recoverable Interr. */
#define MSR_KERNEL ( MSR_FP | MSR_ME | MSR_RI )

/*
 * Set up GOT: Global Offset Table
 *
 * Use r14 to access the GOT
 */
	START_GOT
	GOT_ENTRY(_GOT2_TABLE_)
	GOT_ENTRY(_FIXUP_TABLE_)

	GOT_ENTRY(_start)
	GOT_ENTRY(_start_of_vectors)
	GOT_ENTRY(_end_of_vectors)
	GOT_ENTRY(transfer_to_handler)

	GOT_ENTRY(__init_end)
	GOT_ENTRY(_end)
	GOT_ENTRY(__bss_start)
#if defined(CONFIG_FADS)
	GOT_ENTRY(environment)
#endif
	END_GOT

/*
 * r3 - 1st arg to board_init(): IMMP pointer
 * r4 - 2nd arg to board_init(): boot flag
 */
	.text
	.long	0x27051956		/* U-Boot Magic Number			*/
	.globl	version_string
version_string:
	.ascii U_BOOT_VERSION
	.ascii " (", __DATE__, " - ", __TIME__, ")"
	.ascii CONFIG_IDENT_STRING, "\0"

	. = EXC_OFF_SYS_RESET
	.globl	_start
_start:
	li	r21, BOOTFLAG_COLD	/* Normal Power-On: Boot from FLASH	*/
	b	boot_cold

	. = EXC_OFF_SYS_RESET + 0x10

	.globl	_start_warm
_start_warm:
	li	r21, BOOTFLAG_WARM	/* Software reboot			*/
	b	boot_warm

boot_cold:
boot_warm:

	/* Initialize machine status; enable machine check interrupt		*/
	/*----------------------------------------------------------------------*/
	li	r3, MSR_KERNEL		/* Set FP, ME, RI flags */
	mtmsr	r3
	mtspr	SRR1, r3		/* Make SRR1 match MSR */

	addis	r0,0,0x0000		/* lets make sure that r0 is really 0 */
	mtspr   HID0, r0		/* disable I and D caches */

	mfspr	r3, ICR			/* clear Interrupt Cause Register */

	mfmsr	r3			/* turn off address translation */
	addis	r4,0,0xffff
	ori	r4,r4,0xffcf
	and	r3,r3,r4
	mtmsr	r3
	isync
	sync				/* the MMU should be off... */


in_flash:
#if defined(CONFIG_BMW)
	bl early_init_f /* Must be ASM: no stack yet! */
#endif
	/*
	 * Setup BATs - cannot be done in C since we don't have a stack yet
	 */
	bl	setup_bats

	/* Enable MMU.
	 */
	mfmsr	r3
	ori	r3, r3, (MSR_IR | MSR_DR)
	mtmsr	r3
#if !defined(CONFIG_BMW)
	/* Enable and invalidate data cache.
	 */
	mfspr	r3, HID0
	mr	r2, r3
	ori	r3, r3, HID0_DCE | HID0_DCI
	ori	r2, r2, HID0_DCE
	sync
	mtspr	HID0, r3
	mtspr	HID0, r2
	sync

	/* Allocate Initial RAM in data cache.
	 */
	lis	r3, CFG_INIT_RAM_ADDR@h
	ori	r3, r3, CFG_INIT_RAM_ADDR@l
	li	r2, 128
	mtctr	r2
1:
	dcbz	r0, r3
	addi	r3, r3, 32
	bdnz	1b

	/* Lock way0 in data cache.
	 */
	mfspr	r3, 1011
	lis	r2, 0xffff
	ori	r2, r2, 0xff1f
	and	r3, r3, r2
	ori	r3, r3, 0x0080
	sync
	mtspr	1011, r3
#endif /* !CONFIG_BMW */
	/*
	 * Thisk the stack pointer *somewhere* sensible. Doesnt
	 * matter much where as we'll move it when we relocate
	 */
	lis	r1, (CFG_INIT_RAM_ADDR + CFG_GBL_DATA_OFFSET)@h
	ori	r1, r1, (CFG_INIT_RAM_ADDR + CFG_GBL_DATA_OFFSET)@l

	li	r0, 0			/* Make room for stack frame header and	*/
	stwu	r0, -4(r1)		/* clear final stack frame so that	*/
	stwu	r0, -4(r1)		/* stack backtraces terminate cleanly	*/

	/* let the C-code set up the rest					*/
	/*									*/
	/* Be careful to keep code relocatable !				*/
	/*----------------------------------------------------------------------*/

	GET_GOT			/* initialize GOT access			*/

	/* r3: IMMR */
	bl	cpu_init_f	/* run low-level CPU init code     (from Flash)	*/

	mr	r3, r21
	/* r3: BOOTFLAG */
	bl	board_init_f	/* run 1st part of board init code (from Flash) */



	.globl	_start_of_vectors
_start_of_vectors:

/* Machine check */
	STD_EXCEPTION(EXC_OFF_MACH_CHCK, MachineCheck, MachineCheckException)

/* Data Storage exception.  "Never" generated on the 860. */
	STD_EXCEPTION(EXC_OFF_DATA_STOR, DataStorage, UnknownException)

/* Instruction Storage exception.  "Never" generated on the 860. */
	STD_EXCEPTION(EXC_OFF_INS_STOR, InstStorage, UnknownException)

/* External Interrupt exception. */
	STD_EXCEPTION(EXC_OFF_EXTERNAL, ExtInterrupt, external_interrupt)

/* Alignment exception. */
	. = EXC_OFF_ALIGN
Alignment:
	EXCEPTION_PROLOG
	mfspr	r4,DAR
	stw	r4,_DAR(r21)
	mfspr	r5,DSISR
	stw	r5,_DSISR(r21)
	addi	r3,r1,STACK_FRAME_OVERHEAD
	li	r20,MSR_KERNEL
	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
	lwz	r6,GOT(transfer_to_handler)
	mtlr	r6
	blrl
.L_Alignment:
	.long	AlignmentException - _start + EXC_OFF_SYS_RESET
	.long	int_return - _start + EXC_OFF_SYS_RESET

/* Program check exception */
	. = EXC_OFF_PROGRAM
ProgramCheck:
	EXCEPTION_PROLOG
	addi	r3,r1,STACK_FRAME_OVERHEAD
	li	r20,MSR_KERNEL
	rlwimi	r20,r23,0,16,16		/* copy EE bit from saved MSR */
	lwz	r6,GOT(transfer_to_handler)
	mtlr	r6
	blrl
.L_ProgramCheck:
	.long	ProgramCheckException - _start + EXC_OFF_SYS_RESET
	.long	int_return - _start + EXC_OFF_SYS_RESET

	/* No FPU on MPC8xx. This exception is not supposed to happen.
	*/
	STD_EXCEPTION(EXC_OFF_FPUNAVAIL, FPUnavailable, UnknownException)

	/* I guess we could implement decrementer, and may have
	 * to someday for timekeeping.
	 */
	STD_EXCEPTION(EXC_OFF_DECR, Decrementer, timer_interrupt)
	STD_EXCEPTION(0xa00, Trap_0a, UnknownException)
	STD_EXCEPTION(0xb00, Trap_0b, UnknownException)

	. = 0xc00
/*
 * r0 - SYSCALL number
 * r3-... arguments
 */
SystemCall:
	addis	r11,r0,0		/* get functions table addr */
	ori	r11,r11,0		/* Note: this code is patched in trap_init */
	addis	r12,r0,0		/* get number of functions */
	ori	r12,r12,0

	cmplw	0, r0, r12
	bge	1f

	rlwinm	r0,r0,2,0,31		/* fn_addr = fn_tbl[r0] */
	add	r11,r11,r0
	lwz	r11,0(r11)

	li	r20,0xd00-4		/* Get stack pointer */
	lwz	r12,0(r20)
	subi	r12,r12,12		/* Adjust stack pointer */
	li	r0,0xc00+_end_back-SystemCall
	cmplw	0, r0, r12		/* Check stack overflow */
	bgt	1f
	stw	r12,0(r20)

	mflr	r0
	stw	r0,0(r12)
	mfspr	r0,SRR0
	stw	r0,4(r12)
	mfspr	r0,SRR1
	stw	r0,8(r12)

	li	r12,0xc00+_back-SystemCall
	mtlr	r12
	mtspr	SRR0,r11

1:	SYNC
	rfi

_back:

	mfmsr	r11			/* Disable interrupts */
	li	r12,0
	ori	r12,r12,MSR_EE
	andc	r11,r11,r12
	SYNC				/* Some chip revs need this... */
	mtmsr	r11
	SYNC

	li	r12,0xd00-4		/* restore regs */
	lwz	r12,0(r12)

	lwz	r11,0(r12)
	mtlr	r11
	lwz	r11,4(r12)
	mtspr	SRR0,r11
	lwz	r11,8(r12)
	mtspr	SRR1,r11

	addi	r12,r12,12		/* Adjust stack pointer */
	li	r20,0xd00-4
	stw	r12,0(r20)

	SYNC
	rfi
_end_back:

	STD_EXCEPTION(EXC_OFF_TRACE, SingleStep, UnknownException)

	STD_EXCEPTION(EXC_OFF_FPUNASSIST, Trap_0e, UnknownException)
	STD_EXCEPTION(EXC_OFF_PMI, Trap_0f, UnknownException)

	STD_EXCEPTION(EXC_OFF_ITME, InstructionTransMiss, UnknownException)
	STD_EXCEPTION(EXC_OFF_DLTME, DataLoadTransMiss, UnknownException)
	STD_EXCEPTION(EXC_OFF_DSTME, DataStoreTransMiss, UnknownException)
	STD_EXCEPTION(EXC_OFF_IABE, InstructionBreakpoint, DebugException)
	STD_EXCEPTION(EXC_OFF_SMIE, SysManageInt, UnknownException)
	STD_EXCEPTION(0x1500, Reserved5, UnknownException)
	STD_EXCEPTION(0x1600, Reserved6, UnknownException)
	STD_EXCEPTION(0x1700, Reserved7, UnknownException)
	STD_EXCEPTION(0x1800, Reserved8, UnknownException)
	STD_EXCEPTION(0x1900, Reserved9, UnknownException)
	STD_EXCEPTION(0x1a00, ReservedA, UnknownException)
	STD_EXCEPTION(0x1b00, ReservedB, UnknownException)
	STD_EXCEPTION(0x1c00, ReservedC, UnknownException)
	STD_EXCEPTION(0x1d00, ReservedD, UnknownException)
	STD_EXCEPTION(0x1e00, ReservedE, UnknownException)
	STD_EXCEPTION(0x1f00, ReservedF, UnknownException)

	STD_EXCEPTION(EXC_OFF_RMTE, RunModeTrace, UnknownException)

	.globl	_end_of_vectors
_end_of_vectors:


	. = 0x3000

/*
 * This code finishes saving the registers to the exception frame
 * and jumps to the appropriate handler for the exception.
 * Register r21 is pointer into trap frame, r1 has new stack pointer.
 */
	.globl	transfer_to_handler
transfer_to_handler:
	stw	r22,_NIP(r21)
	lis	r22,MSR_POW@h
	andc	r23,r23,r22
	stw	r23,_MSR(r21)
	SAVE_GPR(7, r21)
	SAVE_4GPRS(8, r21)
	SAVE_8GPRS(12, r21)
	SAVE_8GPRS(24, r21)
#if 0
	andi.	r23,r23,MSR_PR
	mfspr	r23,SPRG3		/* if from user, fix up tss.regs */
	beq	2f
	addi	r24,r1,STACK_FRAME_OVERHEAD
	stw	r24,PT_REGS(r23)
2:	addi	r2,r23,-TSS		/* set r2 to current */
	tovirt(r2,r2,r23)
#endif
	mflr	r23
	andi.	r24,r23,0x3f00		/* get vector offset */
	stw	r24,TRAP(r21)
	li	r22,0
	stw	r22,RESULT(r21)
	mtspr	SPRG2,r22		/* r1 is now kernel sp */
#if 0
	addi	r24,r2,TASK_STRUCT_SIZE /* check for kernel stack overflow */
	cmplw	0,r1,r2
	cmplw	1,r1,r24
	crand	1,1,4
	bgt	stack_ovf		/* if r2 < r1 < r2+TASK_STRUCT_SIZE */
#endif
	lwz	r24,0(r23)		/* virtual address of handler */
	lwz	r23,4(r23)		/* where to go when done */
	mtspr	SRR0,r24
	ori	r20,r20,0x30		/* enable IR, DR */
	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