u-boot/arch/arm/cpu/arm720t/start.S

/*
 *  armboot - Startup Code for ARM720 CPU-core
 *
 *  Copyright (c) 2001	Marius Gröger <mag@sysgo.de>
 *  Copyright (c) 2002	Alex Züpke <azu@sysgo.de>
 *
 * SPDX-License-Identifier:	GPL-2.0+
 */

#include <asm-offsets.h>
#include <config.h>
#include <version.h>
#include <asm/hardware.h>

/*
 *************************************************************************
 *
 * Jump vector table as in table 3.1 in [1]
 *
 *************************************************************************
 */


.globl _start
_start: b	reset
	ldr	pc, _undefined_instruction
	ldr	pc, _software_interrupt
	ldr	pc, _prefetch_abort
	ldr	pc, _data_abort
	ldr	pc, _not_used
	ldr	pc, _irq
	ldr	pc, _fiq

#ifdef CONFIG_SPL_BUILD
_undefined_instruction: .word _undefined_instruction
_software_interrupt:	.word _software_interrupt
_prefetch_abort:	.word _prefetch_abort
_data_abort:		.word _data_abort
_not_used:		.word _not_used
_irq:			.word _irq
_fiq:			.word _fiq
_pad:			.word 0x12345678 /* now 16*4=64 */
#else
_undefined_instruction: .word undefined_instruction
_software_interrupt:	.word software_interrupt
_prefetch_abort:	.word prefetch_abort
_data_abort:		.word data_abort
_not_used:		.word not_used
_irq:			.word irq
_fiq:			.word fiq
_pad:			.word 0x12345678 /* now 16*4=64 */
#endif	/* CONFIG_SPL_BUILD */

	.balignl 16,0xdeadbeef


/*
 *************************************************************************
 *
 * Startup Code (reset vector)
 *
 * do important init only if we don't start from RAM!
 * relocate armboot to ram
 * setup stack
 * jump to second stage
 *
 *************************************************************************
 */

#ifdef CONFIG_USE_IRQ
/* IRQ stack memory (calculated at run-time) */
.globl IRQ_STACK_START
IRQ_STACK_START:
	.word	0x0badc0de

/* IRQ stack memory (calculated at run-time) */
.globl FIQ_STACK_START
FIQ_STACK_START:
	.word 0x0badc0de
#endif

/* IRQ stack memory (calculated at run-time) + 8 bytes */
.globl IRQ_STACK_START_IN
IRQ_STACK_START_IN:
	.word	0x0badc0de

/*
 * the actual reset code
 */

reset:
	/*
	 * set the cpu to SVC32 mode
	 */
	mrs	r0,cpsr
	bic	r0,r0,#0x1f
	orr	r0,r0,#0xd3
	msr	cpsr,r0

	/*
	 * we do sys-critical inits only at reboot,
	 * not when booting from ram!
	 */
#ifndef CONFIG_SKIP_LOWLEVEL_INIT
	bl	cpu_init_crit
#endif

	bl	_main

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

	.globl	c_runtime_cpu_setup
c_runtime_cpu_setup:

	mov	pc, lr

/*
 *************************************************************************
 *
 * CPU_init_critical registers
 *
 * setup important registers
 * setup memory timing
 *
 *************************************************************************
 */

#ifndef CONFIG_SKIP_LOWLEVEL_INIT
cpu_init_crit:

	mov	ip, lr
	/*
	 * before relocating, we have to setup RAM timing
	 * because memory timing is board-dependent, you will
	 * find a lowlevel_init.S in your board directory.
	 */
	bl	lowlevel_init
	mov	lr, ip

	mov	pc, lr
#endif /* CONFIG_SKIP_LOWLEVEL_INIT */


#ifndef CONFIG_SPL_BUILD
/*
 *************************************************************************
 *
 * Interrupt handling
 *
 *************************************************************************
 */

@
@ IRQ stack frame.
@
#define S_FRAME_SIZE	72

#define S_OLD_R0	68
#define S_PSR		64
#define S_PC		60
#define S_LR		56
#define S_SP		52

#define S_IP		48
#define S_FP		44
#define S_R10		40
#define S_R9		36
#define S_R8		32
#define S_R7		28
#define S_R6		24
#define S_R5		20
#define S_R4		16
#define S_R3		12
#define S_R2		8
#define S_R1		4
#define S_R0		0

#define MODE_SVC 0x13
#define I_BIT	 0x80

/*
 * use bad_save_user_regs for abort/prefetch/undef/swi ...
 * use irq_save_user_regs / irq_restore_user_regs for IRQ/FIQ handling
 */

	.macro	bad_save_user_regs
	sub	sp, sp, #S_FRAME_SIZE
	stmia	sp, {r0 - r12}			@ Calling r0-r12
	add	r8, sp, #S_PC

	ldr	r2, IRQ_STACK_START_IN
	ldmia	r2, {r2 - r4}			@ get pc, cpsr, old_r0
	add	r0, sp, #S_FRAME_SIZE		@ restore sp_SVC

	add	r5, sp, #S_SP
	mov	r1, lr
	stmia	r5, {r0 - r4}			@ save sp_SVC, lr_SVC, pc, cpsr, old_r
	mov	r0, sp
	.endm

	.macro	irq_save_user_regs
	sub	sp, sp, #S_FRAME_SIZE
	stmia	sp, {r0 - r12}			@ Calling r0-r12
	add	r8, sp, #S_PC
	stmdb	r8, {sp, lr}^			@ Calling SP, LR
	str	lr, [r8, #0]			@ Save calling PC
	mrs	r6, spsr
	str	r6, [r8, #4]			@ Save CPSR
	str	r0, [r8, #8]			@ Save OLD_R0
	mov	r0, sp
	.endm

	.macro	irq_restore_user_regs
	ldmia	sp, {r0 - lr}^			@ Calling r0 - lr
	mov	r0, r0
	ldr	lr, [sp, #S_PC]			@ Get PC
	add	sp, sp, #S_FRAME_SIZE
	subs	pc, lr, #4			@ return & move spsr_svc into cpsr
	.endm

	.macro get_bad_stack
	ldr	r13, IRQ_STACK_START_IN		@ setup our mode stack

	str	lr, [r13]			@ save caller lr / spsr
	mrs	lr, spsr
	str	lr, [r13, #4]

	mov	r13, #MODE_SVC			@ prepare SVC-Mode
	msr	spsr_c, r13
	mov	lr, pc
	movs	pc, lr
	.endm

	.macro get_irq_stack			@ setup IRQ stack
	ldr	sp, IRQ_STACK_START
	.endm

	.macro get_fiq_stack			@ setup FIQ stack
	ldr	sp, FIQ_STACK_START
	.endm

/*
 * exception handlers
 */
	.align	5
undefined_instruction:
	get_bad_stack
	bad_save_user_regs
	bl	do_undefined_instruction

	.align	5
software_interrupt:
	get_bad_stack
	bad_save_user_regs
	bl	do_software_interrupt

	.align	5
prefetch_abort:
	get_bad_stack
	bad_save_user_regs
	bl	do_prefetch_abort

	.align	5
data_abort:
	get_bad_stack
	bad_save_user_regs
	bl	do_data_abort

	.align	5
not_used:
	get_bad_stack
	bad_save_user_regs
	bl	do_not_used

#ifdef CONFIG_USE_IRQ

	.align	5
irq:
	get_irq_stack
	irq_save_user_regs
	bl	do_irq
	irq_restore_user_regs

	.align	5
fiq:
	get_fiq_stack
	/* someone ought to write a more effiction fiq_save_user_regs */
	irq_save_user_regs
	bl	do_fiq
	irq_restore_user_regs

#else

	.align	5
irq:
	get_bad_stack
	bad_save_user_regs
	bl	do_irq

	.align	5
fiq:
	get_bad_stack
	bad_save_user_regs
	bl	do_fiq

#endif
#endif /* CONFIG_SPL_BUILD */