Add support for HSE bypass on STM32.

[liampwll]

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[KevinOConnor]

I'm not sure what this does, or why one would want it. Can you elaborate?

Thanks, -Kevin

[liampwll]

HSE bypass mode only uses a single pin as an input for a clock signal rather than connecting the two pins to a crystal driver. It's required when using a clock generation IC rather than a crystal.

On Thu, 24 Oct 2024, 11:16 pm KevinOConnor, @.***> wrote:

I'm not sure what this does, or why one would want it. Can you elaborate?

Thanks, -Kevin

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[KevinOConnor]

Okay, thanks. How about we change the "clock reference" menu so that it lists: 8Mhz crystal, 12Mhz crystal, ..., 12Mhz external clock, ..., Internal clock. That is, add options for external clocks to the menu instead of adding a new "HSE bypass" config option (which I suspect may confuse many people).

Cheers, -Kevin

[liampwll]

Doing so would likely involve breaking existing configs as we would likely want to change STM32_CLOCK_REF_8M to STM32_CLOCK_REF_CRYSTAL_8M etc..

I'm not sure if it makes sense to do that given that the HSE bypass options is hidden away in the low level options.

[KevinOConnor]

Okay, thanks. However, I think maintaining the single clock reference menu would be desirable, and I think we should avoid using cryptic terms like "HSE" in the user facing Kconfig menus. There's quite a bit of flexibility in the Kconfig files to introduce non user-facing symbols to achieve what we want while maintaining a unified menu interface.

Cheers, -Kevin