[riot-notifications] [RIOT-OS/RIOT] cpu/stm32l4/stmclk: fix HSE overwride when MSI is enabled (#11896)

Francisco notifications at github.com
Wed Jul 24 08:55:25 CEST 2019

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For `stm32l4` if `HSE` and `MSI` are enabled, when `MSI` is configured it overrides the `HSE` clock configuration. This causes `stmclk_init_sysclk` to hang since `PLL` is to be setup with `HSE` but it was disabled when setting `MSI`.

### Testing procedure

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Find a `stm32l4` board that has an `HSE` clock (or provide one yourself), enable both `MSI` and `HSE` in `periph_conf.h` for that board. In master flashing whatever application will result in no terminal output since it get stuck at https://github.com/fjmolinas/RIOT/blob/51bc33de973295d6952349a185b5f2bd2f4e3160/cpu/stm32l4/stmclk.c#L152.

With this PR the clk initialization succeeds.

I don't now of any nucleo-board that provides `HSE`, but  #11895 support a `stm32wb` which uses the same `stmclk` function, testing can be performed on that PR and verifying the described behaviour.

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-- Commit Summary --

  * cpu/stm32l4/stmclk: fix HSE overwride when MSI is enabled

-- File Changes --

    M cpu/stm32l4/stmclk.c (2)

-- Patch Links --


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