Hi,
I have a simple startup code for a at91rm9200 processor. The idea was
after the processor setup to restore the processor context saved in
stack pointed by pCurrStack variable.
I don't know where could be a problem becuase it sometimes works but
more often it doesn't work.
This code is downloaded by u-boot so some startup seuences are not
necessary.
I'll be gratefull for comments.
Regards
Jacek
..equ NO_INT, 0xC0
..equ USR_MODE, 0x10
..equ FIQ_MODE, 0x11
..equ IRQ_MODE, 0x12
..equ SVC_MODE, 0x13
..equ ABT_MODE, 0x17
..equ UND_MODE, 0x1B
..equ SYS_MODE, 0x1F
..equ USR_STACK_SIZE, 0x200
..equ FIQ_STACK_SIZE, 0x200
..equ IRQ_STACK_SIZE, 0x200
..equ SVC_STACK_SIZE, 0x200
..equ ABT_STACK_SIZE, 0x200
..equ UND_STACK_SIZE, 0x200
..equ SYS_STACK_SIZE, 0x200
..globl _start
_start:
b reset
ldr pc, ptr_undefined_instruction
ldr pc, ptr_software_interrupt
ldr pc, ptr_prefetch_abort
ldr pc, ptr_data_abort
ldr pc, ptr_not_used
ldr pc, ptr_irq_isr
ldr pc, ptr_fiq_isr
ptr_undefined_instruction:.word undefined_instruction
ptr_software_interrupt: .word software_interrupt
ptr_prefetch_abort: .word prefetch_abort
ptr_data_abort: .word data_abort
ptr_not_used: .word not_used
ptr_irq_isr: .word irq_isr
ptr_fiq_isr: .word fiq_isr
..align 16
reset:
/*
* set the cpu to SVC32 mode
*/
mrs r0,cpsr
bic r0,r0,#0x1f
orr r0,r0,#0x13
msr cpsr,r0
/* Disable "Fast Bus Mode" - set to async */
mrc p15,0,r0,c1,c0,0
orr r0,r0,#0xC0000000
mcr p15,0,r0,c1,c0,0
/*
* After uboot starting memories have been just remapped
*/
ldr r0, =_start
ldr r1, =0x0
mov r2, #16
copy_loop:
subs r2, r2, #1
ldr r3, [r0], #4
str r3, [r1], #4
bne copy_loop
setup_stacks:
/* FIQ mode stack */
msr CPSR_c, #FIQ_MODE|NO_INT
ldr sp, =(fiq_stack - 4)
/* IRQ mode stack */
msr CPSR_c, #IRQ_MODE|NO_INT
ldr sp, =(irq_stack - 4)
/* Undefined mode stack */
msr CPSR_c, #UND_MODE|NO_INT
ldr sp, =(und_stack - 4)
/* Abort mode stack */
msr CPSR_c, #ABT_MODE|NO_INT
ldr sp, =(abt_stack - 4)
/* Supervisor mode stack */
msr CPSR_c, #SVC_MODE|NO_INT
ldr sp, =(svc_stack - 4)
ldr r0, =start @ start()
mov lr, pc
bx r0
LDR R4, =pCurrStack
LDR SP, [R4]
LDR R4, [SP], #4
MSR CPSR_cxsf,R4
LDMFD SP!, {R0-R12,LR,PC}^
undefined_instruction:
b undefined_instruction
software_interrupt:
b software_interrupt
prefetch_abort:
b prefetch_abort
data_abort:
b data_abort
not_used:
b not_used
__bss_start: .word _bss_start
__bss_end: .word _bss_end
..section ".bss"
..align 4
.word 0
.space IRQ_STACK_SIZE
irq_stack:
.word 0
.space FIQ_STACK_SIZE
fiq_stack:
.word 0
.space UND_STACK_SIZE
und_stack:
.word 0
.space ABT_STACK_SIZE
abt_stack:
.word 0
.space SVC_STACK_SIZE
svc_stack:
.word 0
.space SYS_STACK_SIZE
sys_stack:
.word 0
