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arch: arm: cortex_m: pm_s2ram: save system_off before s2ram marking

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The r0 register holds the system_off function pointer. As r0 is a scratch
register, the pointer needs to moved to a preserved register before
branching to a (custom) marker function.

Furthermore, in accordance to rule 6.2.1.2 of aapcs32, the stack pointer
needs to align on 8 bytes. Hence r0 is pushed to the stack in addition to
the lr register, before calling the public interface of checking the
s2ram marker.

Signed-off-by: Hessel van der Molen <hvandermolen@dexels.com>
This commit is contained in:
Hessel van der Molen 2024-08-20 13:15:56 +02:00 committed by Anas Nashif
parent 420ffdd8a8
commit 2590c48d40
1 changed files with 14 additions and 5 deletions
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19
arch/arm/core/cortex_m/pm_s2ram.S
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@ -27,6 +27,11 @@ SECTION_FUNC(TEXT, arch_pm_s2ram_suspend)
* r0: address of the system_off function
*/
push {r4-r12, lr}
/* Move system_off to protected register. */
mov r4, r0
/* Store CPU context */
ldr r1, =_cpu_context
mrs r2, msp
@ -71,7 +76,7 @@ SECTION_FUNC(TEXT, arch_pm_s2ram_suspend)
* Call the system_off function passed as parameter. This should never
* return.
*/
blx r0
blx r4
/*
* The system_off function returns here only when the powering off was
@ -81,9 +86,10 @@ SECTION_FUNC(TEXT, arch_pm_s2ram_suspend)
/*
* Reset the marking of suspend to RAM, return is ignored.
*/
push {r0}
bl pm_s2ram_mark_check_and_clear
pop {r0}
/* Move system_off back to r0 as return value */
mov r0, r4
pop {r4-r12, lr}
bx lr
@ -93,11 +99,14 @@ GTEXT(arch_pm_s2ram_resume)
SECTION_FUNC(TEXT, arch_pm_s2ram_resume)
/*
* Check if reset occurred after suspending to RAM.
* Store LR to ensure we can continue boot when we are not suspended
* to RAM. In addition to LR, R0 is pushed too, to ensure "SP mod 8 = 0",
* as stated by ARM rule 6.2.1.2 for AAPCS32.
*/
push {lr}
push {r0, lr}
bl pm_s2ram_mark_check_and_clear
cmp r0, #0x1
pop {lr}
pop {r0, lr}
beq resume
bx lr