mirror of
https://github.com/buhman/nds.git
synced 2025-06-18 14:35:38 -04:00
62d6a3b2a6
Before this commit, attempting to start the rom on real NDS/DSi hardware would result in the display of a solid white screen, with no apparent evidence of the arm9 program running. After much testing, I found that this issue was directly caused "main mmeory" bus contention. Because arm7 and arm9 are both attempting to read instructions from ewram at the same time, and arm9 bus access stalls completely. I also found that this could not be mitigated with giving arm9 priority in EXMEMCNT. The solution appears to be to relocate arm7 code execution from main/shared memory to an arm7-internal memory. After this commit, the examples now function as intended on real NDS/DSi hardware.
27 lines
527 B
ArmAsm
27 lines
527 B
ArmAsm
.macro COPY_32_BYTE_ALIGNED
|
|
cmp r1, r10
|
|
beq _fill_break.\@
|
|
_fill_loop.\@:
|
|
ldmia r0!, {r2 - r9}
|
|
stmia r1!, {r2 - r9}
|
|
cmp r1, r10
|
|
bne _fill_loop.\@
|
|
_fill_break.\@:
|
|
.endm
|
|
|
|
.section .text.start
|
|
.global _start
|
|
_start:
|
|
// copy .text to internal ram
|
|
ldr r0, =__text_load_start
|
|
ldr r1, =__text_link_start
|
|
ldr r10, =__text_link_end
|
|
COPY_32_BYTE_ALIGNED
|
|
|
|
// jump to internal ram
|
|
ldr r3,=_loop_forever
|
|
bx r3
|
|
|
|
_loop_forever:
|
|
b _loop_forever
|