Since upgrading from STM32Cube MCU Package for STM32L4 from 1.17.1 to 1.17.2 (or 1.18.0), when disabling the PLL, HAL_RCC_OscConfig() will fail with HAL_TIMEOUT.
I reconfigure the oscillators and PLL to run at 4 different speeds, depending on mode: 2MHz MSI (idle), 16MHz HSI (startup), and either 48MHz or 72MHz HSE (run) depending on state. The PLL is only enabled in run mode.
The issue appears to be that HAL_RCC_OscConfig() will stop the clock feeding the PLL before the PLL is disabled. When that happens, PLLRDY does not change after setting PLLON to 0. This results in what is shown below, where PLLON is 0, PLLRDY remains 1, and HAL_RCC_OscConfig() fails with HAL_TIMEOUT.
The work-around I have in place is to call __HAL_RCC_PLL_DISABLE() before calling HAL_RCC_OscConfig() where the PLL will being disabled. I am not sure what exactly changed in the HAL to trigger this problem. There are changes in 1.17.2 in the section of code that disables the PLL.
The fix would seem to be to change the function to disable PLLs, if so requested, before any oscillators are changed and enable PLLs only after the oscillators are configured.
Minimal reproducer is available here: https://github.com/mobilinkd/HAL_RCC_OscConfig_TIMEOUT
This requires a STM32L432KC Nucleo32 board with SB17 shorted to provide HSE.
The requirements to trigger the bug are:
- Have an oscillator configured and feeding the PLL, and the PLL enabled.
- Create a configuration which will disable both the PLL and the oscillator.
- Call `HAL_RCC_OscConfig()`
