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-rw-r--r--libcpu/arm/rm48x50/context_ccs.asm6
1 files changed, 3 insertions, 3 deletions
diff --git a/libcpu/arm/rm48x50/context_ccs.asm b/libcpu/arm/rm48x50/context_ccs.asm
index dad36f8f40..e72f9f0f68 100644
--- a/libcpu/arm/rm48x50/context_ccs.asm
+++ b/libcpu/arm/rm48x50/context_ccs.asm
@@ -127,9 +127,9 @@ rt_hw_context_switch_interrupt_do
STR r1, [r0]
LDMFD sp!, {r0-r12,lr} ; reload saved registers
- STMFD sp!, {r0-r3} ; save r0-r3
- MOV r1, sp
- ADD sp, sp, #16 ; restore sp
+ STMFD sp, {r0-r3} ; save r0-r3. We will restore r0-r3 in the SVC
+ ; mode so there is no need to update SP.
+ SUB r1, sp, #16 ; save the right SP value in r1, so we could restore r0-r3.
SUB r2, lr, #4 ; save old task's pc to r2
MRS r3, spsr ; get cpsr of interrupt thread