flash: stm32l4/g4: force load option bytes after write

[JordanYates]

After writing option bytes, force them to be loaded. Failing to perform this step means the values are never applied and not actually written to non-volatile memory.

This step is documented on the HAL FLASH_OB_RDPConfig function, but nowhere else:

[fouge]

hey

are we sure we wanted to merge that?
Using OBL_LAUNCH when setting RDP OB puts the target into a bad state where a POR is awaited, and i don't think it's the expected behavior most of the time, since we are trying to set RDP at runtime.

the more graceful way is to go into standby mode.

https://www.youtube.com/watch?v=f7vs0NwZPFo&list=PLnMKNibPkDnGxKqGyLbiGygmlrvISIBIT&index=5

[fouge]

update: i've been trying to use the Standby mode without success, the RDP option byte isn't loaded on wake up... any clue? 🤔
OBL_LAUNCH locks the MCU and thus needs a power cycle.

cc @erwango

[erwango]

@fouge Thanks for the update. Would you mind raising an issue to ensure the point doesn't get lost ?

[fouge]

I actually opened a PR #91945

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On Thu, Jun 19, 2025 at 5:17 PM Erwan Gouriou ***@***.***> wrote: *erwango* left a comment (zephyrproject-rtos/zephyr#83561) <#83561 (comment)> @fouge <https://github.com/fouge> Thanks for the update. Would you mind raising an issue to ensure the point doesn't get lost ? — Reply to this email directly, view it on GitHub <#83561 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAJJJ24YKIFJOH2UBIAB72D3ELIADAVCNFSM6AAAAABUTT7AESVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDSOBYGQ3DIMBYGM> . You are receiving this because you were mentioned.Message ID: ***@***.***>

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