start.s

from [e-mail] 电路原理图和详细说明： amd.9966.org或者 arm.9966.org 都是原创,包括boot, loader,u-boot,linu

/*
 * 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]>
 * Copyright Freescale Semiconductor, Inc. 2004, 2006. All rights reserved.
 *
 * 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 MPC83xx PowerPC based Embedded Boards
 */

#include <config.h>
#include <mpc83xx.h>
#include <version.h>

#define CONFIG_83XX	1		/* needed for Linux kernel header files*/
#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 "MPC83XX"
#endif

/* We don't want the  MMU yet.
 */
#undef	MSR_KERNEL

/*
 * Floating Point enable, Machine Check and Recoverable Interr.
 */
#ifdef DEBUG
#define MSR_KERNEL (MSR_FP|MSR_RI)
#else
#define MSR_KERNEL (MSR_FP|MSR_ME|MSR_RI)
#endif

/*
 * 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)
	END_GOT

/*
 * Version string - must be in data segment because MPC83xx uses the
 * first 256 bytes for the Hard Reset Configuration Word table (see
 * below).  Similarly, can't have the U-Boot Magic Number as the first
 * thing in the image - don't know how this will affect the image tools,
 * but I guess I'll find out soon.
 */
	.data
	.globl	version_string
version_string:
	.ascii U_BOOT_VERSION
	.ascii " (", __DATE__, " - ", __TIME__, ")"
	.ascii " ", CONFIG_IDENT_STRING, "\0"

	.text
#define _HRCW_TABLE_ENTRY(w)		\
	.fill	8,1,(((w)>>24)&0xff);	\
	.fill	8,1,(((w)>>16)&0xff);	\
	.fill	8,1,(((w)>> 8)&0xff);	\
	.fill	8,1,(((w)    )&0xff)

	_HRCW_TABLE_ENTRY(CFG_HRCW_LOW)
	_HRCW_TABLE_ENTRY(CFG_HRCW_HIGH)


#ifndef CONFIG_DEFAULT_IMMR
#error CONFIG_DEFAULT_IMMR must be defined
#endif /* CFG_DEFAULT_IMMR */
#ifndef CFG_IMMR
#define CFG_IMMR CONFIG_DEFAULT_IMMR
#endif /* CFG_IMMR */

/*
 * After configuration, a system reset exception is executed using the
 * vector at offset 0x100 relative to the base set by MSR[IP]. If
 * MSR[IP] is 0, the base address is 0x00000000. If MSR[IP] is 1, the
 * base address is 0xfff00000. In the case of a Power On Reset or Hard
 * Reset, the value of MSR[IP] is determined by the CIP field in the
 * HRCW.
 *
 * Other bits in the HRCW set up the Base Address and Port Size in BR0.
 * This determines the location of the boot ROM (flash or EPROM) in the
 * processor's address space at boot time. As long as the HRCW is set up
 * so that we eventually end up executing the code below when the
 * processor executes the reset exception, the actual values used should
 * not matter.
 *
 * Once we have got here, the address mask in OR0 is cleared so that the
 * bottom 32K of the boot ROM is effectively repeated all throughout the
 * processor's address space, after which we can jump to the absolute
 * address at which the boot ROM was linked at compile time, and proceed
 * to initialise the memory controller without worrying if the rug will
 * be pulled out from under us, so to speak (it will be fine as long as
 * we configure BR0 with the same boot ROM link address).
 */
	. = EXC_OFF_SYS_RESET

	.globl	_start
_start: /* time t 0 */
	li	r21, BOOTFLAG_COLD  /* Normal Power-On: Boot from FLASH*/
	nop
	b	boot_cold

	. = EXC_OFF_SYS_RESET + 0x10

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


boot_cold: /* time t 3 */
	lis	r4, CONFIG_DEFAULT_IMMR@h
	nop
boot_warm: /* time t 5 */
	mfmsr	r5			/* save msr contents	*/
	lis	r3, CFG_IMMR@h
	ori	r3, r3, CFG_IMMR@l
	stw	r3, IMMRBAR(r4)

	/* Initialise the E300 processor core		*/
	/*------------------------------------------*/

	bl	init_e300_core

#ifndef CFG_RAMBOOT

	/* Inflate flash location so it appears everywhere, calculate */
	/* the absolute address in final location of the FLASH, jump  */
	/* there and deflate the flash size back to minimal size      */
	/*------------------------------------------------------------*/
	bl map_flash_by_law1
	lis r4, (CFG_MONITOR_BASE)@h
	ori r4, r4, (CFG_MONITOR_BASE)@l
	addi r5, r4, in_flash - _start + EXC_OFF_SYS_RESET
	mtlr r5
	blr
in_flash:
#if 1 /* Remapping flash with LAW0. */
	bl remap_flash_by_law0
#endif
#endif	/* CFG_RAMBOOT */

	/* setup the bats */
	bl	setup_bats
	sync

	/*
	 * Cache must be enabled here for stack-in-cache trick.
	 * This means we need to enable the BATS.
	 * This means:
	 *   1) for the EVB, original gt regs need to be mapped
	 *   2) need to have an IBAT for the 0xf region,
	 *      we are running there!
	 * Cache should be turned on after BATs, since by default
	 * everything is write-through.
	 * The init-mem BAT can be reused after reloc. The old
	 * gt-regs BAT can be reused after board_init_f calls
	 * board_early_init_f (EVB only).
	 */
	/* enable address translation */
	bl	enable_addr_trans
	sync

	/* enable and invalidate the data cache */
	bl	dcache_enable
	sync
#ifdef CFG_INIT_RAM_LOCK
	bl	lock_ram_in_cache
	sync
#endif

	/* set up the stack pointer in our newly created
	 * cache-ram (r1) */
	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 & stack humble   */
	/*------------------------------------------------------*/

	GET_GOT			/* initialize GOT access	*/

	/* r3: IMMR */
	lis	r3, CFG_IMMR@h
	/* run low-level CPU init code (in Flash)*/
	bl	cpu_init_f

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

/*
 * Vector Table
 */

	.globl	_start_of_vectors
_start_of_vectors:

/* Machine check */
	STD_EXCEPTION(0x200, MachineCheck, MachineCheckException)

/* Data Storage exception. */
	STD_EXCEPTION(0x300, DataStorage, UnknownException)

/* Instruction Storage exception. */
	STD_EXCEPTION(0x400, InstStorage, UnknownException)

/* External Interrupt exception. */
#ifndef FIXME
	STD_EXCEPTION(0x500, ExtInterrupt, external_interrupt)
#endif

/* Alignment exception. */
	. = 0x600
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 */
	rlwimi	r20,r23,0,25,25		/* copy IP 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 */
	. = 0x700
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 */
	rlwimi	r20,r23,0,25,25		/* copy IP 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

	STD_EXCEPTION(0x800, FPUnavailable, UnknownException)

	/* I guess we could implement decrementer, and may have
	 * to someday for timekeeping.
	 */
	STD_EXCEPTION(0x900, Decrementer, timer_interrupt)

	STD_EXCEPTION(0xa00, Trap_0a, UnknownException)
	STD_EXCEPTION(0xb00, Trap_0b, UnknownException)
	STD_EXCEPTION(0xc00, SystemCall, UnknownException)
	STD_EXCEPTION(0xd00, SingleStep, UnknownException)

	STD_EXCEPTION(0xe00, Trap_0e, UnknownException)
	STD_EXCEPTION(0xf00, Trap_0f, UnknownException)

	STD_EXCEPTION(0x1000, InstructionTLBMiss, UnknownException)
	STD_EXCEPTION(0x1100, DataLoadTLBMiss, UnknownException)
	STD_EXCEPTION(0x1200, DataStoreTLBMiss, UnknownException)
#ifdef DEBUG
	. = 0x1300
	/*
	 * This exception occurs when the program counter matches the
	 * Instruction Address Breakpoint Register (IABR).
	 *
	 * I want the cpu to halt if this occurs so I can hunt around
	 * with the debugger and look at things.
	 *
	 * When DEBUG is defined, both machine check enable (in the MSR)
	 * and checkstop reset enable (in the reset mode register) are
	 * turned off and so a checkstop condition will result in the cpu
	 * halting.
	 *
	 * I force the cpu into a checkstop condition by putting an illegal
	 * instruction here (at least this is the theory).
	 *
	 * well - that didnt work, so just do an infinite loop!
	 */
1:	b	1b
#else
	STD_EXCEPTION(0x1300, InstructionBreakpoint, DebugException)
#endif
	STD_EXCEPTION(0x1400, SMI, UnknownException)

	STD_EXCEPTION(0x1500, Trap_15, UnknownException)
	STD_EXCEPTION(0x1600, Trap_16, UnknownException)
	STD_EXCEPTION(0x1700, Trap_17, UnknownException)
	STD_EXCEPTION(0x1800, Trap_18, UnknownException)
	STD_EXCEPTION(0x1900, Trap_19, UnknownException)
	STD_EXCEPTION(0x1a00, Trap_1a, UnknownException)
	STD_EXCEPTION(0x1b00, Trap_1b, UnknownException)
	STD_EXCEPTION(0x1c00, Trap_1c, UnknownException)
	STD_EXCEPTION(0x1d00, Trap_1d, UnknownException)
	STD_EXCEPTION(0x1e00, Trap_1e, UnknownException)
	STD_EXCEPTION(0x1f00, Trap_1f, UnknownException)
	STD_EXCEPTION(0x2000, Trap_20, UnknownException)
	STD_EXCEPTION(0x2100, Trap_21, UnknownException)
	STD_EXCEPTION(0x2200, Trap_22, UnknownException)
	STD_EXCEPTION(0x2300, Trap_23, UnknownException)
	STD_EXCEPTION(0x2400, Trap_24, UnknownException)
	STD_EXCEPTION(0x2500, Trap_25, UnknownException)
	STD_EXCEPTION(0x2600, Trap_26, UnknownException)
	STD_EXCEPTION(0x2700, Trap_27, UnknownException)
	STD_EXCEPTION(0x2800, Trap_28, UnknownException)
	STD_EXCEPTION(0x2900, Trap_29, UnknownException)
	STD_EXCEPTION(0x2a00, Trap_2a, UnknownException)
	STD_EXCEPTION(0x2b00, Trap_2b, UnknownException)
	STD_EXCEPTION(0x2c00, Trap_2c, UnknownException)
	STD_EXCEPTION(0x2d00, Trap_2d, UnknownException)
	STD_EXCEPTION(0x2e00, Trap_2e, UnknownException)
	STD_EXCEPTION(0x2f00, Trap_2f, 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)
	mflr	r23
	andi.	r24,r23,0x3f00		/* get vector offset */
	stw	r24,TRAP(r21)
	li	r22,0
	stw	r22,RESULT(r21)
	lwz	r24,0(r23)		/* virtual address of handler */
	lwz	r23,4(r23)		/* where to go when done */
	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