arch: arm: pm_s2ram: fix compatibility with ARMv6-M again #88263
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wearyzen
I took the latest commit as the file's history is quite complicated. Originally (e.g., in 2590c48), there was a I will update the commit message based on your input though. |
The original 'arch_pm_s2ram_resume' implementation saved lr on the stack
using 'push {lr}' and restored it using 'pop {lr}'. However, the Thumb-1
'pop' does not support lr as a target register, so this code would not
compile for ARMv6-M or ARMv8-M Baseline. r0 was added to these push/pop
later in 2590c48.
In 474d4c3, arch_pm_s2ram* functions were
modified to no longer use the stack, which incidentally "fixed" this issue.
b4fb5d3 reverted this commit and brought
back 'pop {r0, lr}' as-is, without taking compatibility into account.
Modify the sequence to use "pop {r0, pc}" which is supported on all
ARM M-profile implementations (v6/v7/v8 Baseline/v8 Mainline), and
add comments to (hopefully) prevent this issue from re-appearing.
Signed-off-by: Mathieu Choplain <[email protected]>
mathieuchopstm
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@wearyzen updated commit message. Let me know what you think 🙂 |
JarmouniA
approved these changes
Apr 8, 2025
wearyzen
approved these changes
Apr 8, 2025
LGTM, Thank you ! |
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Commit b4fb5d3 added a
pop {r0, lr}toarch_pm_s2ram_resumebut this instruction is not valid on ARMv6-M or ARMv8-M Baseline.Modify the sequence to use
pop {r0, pc}which is supported on all ARM M-profile implementations (v6/v7/v8 Baseline/v8 Mainline), and add comments to (hopefully) prevent this issue from re-appearing.