Add function to allow re-init rcc config for stm32

[mickem]

I had a need to configure an external clock generator and then switch to it which means I needed to call init and then configure RCC.
After som input from the matrix chat this is what I came up with.

Not sure if this makes sense, and I did not find any test so I have not added tests.
Might make sense to add an example but as a meaningful example would require a specific external clock generator I am unsure how to proceed but it would be possible to add:

#[embassy_executor::main]
async fn main(_spawner: Spawner) {
    let p = embassy_stm32::init(Default::default());

    // Configure the external clock here

    let mut config = Config::default();
    {
        use embassy_stm32::rcc::*;
        config.rcc.hse = Some(Hse {
            freq: mhz(8),
            mode: HseMode::Bypass,
        });
        config.rcc.pll = Some(Pll {
            src: PllSource::HSE,
            prediv: PllPreDiv::DIV1,
            mul: PllMul::MUL9,
        });
        config.rcc.sys = Sysclk::PLL1_P;
        config.rcc.ahb_pre = AHBPrescaler::DIV1;
        config.rcc.apb1_pre = APBPrescaler::DIV2;
        config.rcc.apb2_pre = APBPrescaler::DIV1;
    }
    embassy_stm32::reinitialize_rcc(config);

    info!("end program");
}

[mickem]

Build fail due to the critical section variable is not used in (I assume here) som configurations. Not sure of a good way to handle this I could rename the variable _cs or I could split the code but since it is a closure it is hard to add feature toggles on it...

[Dirbaio]

Thanks!

• Could you make the function embassy_stm32::rcc:reinit() instead of embassy_stm32::reinitialize_rcc()?
• It should take only the RCC config, not the whole embassy-stm32 config.
• Could you deduplicate the code inside the CS? This way if something gets added there in the future we ensure both init and reinit stay in sync.

[Dirbaio]

could you move this to the RCC module so it's called as embassy_stm32::rcc:reinit() as I said in my last comment and not embassy_stm32::reinit()?

[mickem]

Sorry, I did not see the rcc, please beware that we now have two rcc::init* functions which is somewhat awkward.
Also not 100% sure if the crate::time_driver::init(_cs) should also be moved but given your feedback I assume this is what we want.

One option for the two rcc:init function would be to wrap the old rcc::init inside the new rcc::init_rcc but unsure if this is what we want. I.e. rename or private the existing init and rename the init_rcc function to init.

Feel free to send me a message on matrix (Michael Medin, @mickem:matrix.org) if you want to discuss options here.

[jamesmunns]

bender run

[Dirbaio]

thank you!