HAL bug in glass LCD clock init (STM32L0)

[SZano]

in software package STM32L0 1.12.1

in file stm32l0xx_hal_rcc_ex.c

in function

HAL_StatusTypeDef HAL_RCCEx_PeriphCLKConfig(RCC_PeriphCLKInitTypeDef  *PeriphClkInit)

The RTC and LCD have their own settings, though they share the same clock.

These settings are usually handled correctly, e.g.

/*------------------------------- RTC/LCD Configuration ------------------------*/
  if ((((PeriphClkInit->PeriphClockSelection) & RCC_PERIPHCLK_RTC) == RCC_PERIPHCLK_RTC)
#if defined(LCD)
   || (((PeriphClkInit->PeriphClockSelection) & RCC_PERIPHCLK_LCD) == RCC_PERIPHCLK_LCD)
#endif /* LCD */
     )

but they're not correctly handled everywhere; at the end of the block quoted above, there is this initialization:

__HAL_RCC_RTC_CONFIG(PeriphClkInit->RTCClockSelection);

However, if the function was called to initialize the LCD and not the RTC, this is wrong, as it will disable the clock.

This is what that one-line init should actually be:

#if defined(LCD)
	if((((PeriphClkInit->PeriphClockSelection) & RCC_PERIPHCLK_RTC) == RCC_PERIPHCLK_RTC)
		&& (((PeriphClkInit->PeriphClockSelection) & RCC_PERIPHCLK_LCD) == RCC_PERIPHCLK_LCD))
	{
		if(PeriphClkInit->RTCClockSelection != PeriphClkInit->LCDClockSelection) {
			/* RTC and LCD share the same clock; cannot have different settings for the two of them */
			return HAL_ERROR;
		}
	}
	if((((PeriphClkInit->PeriphClockSelection) & RCC_PERIPHCLK_RTC) == RCC_PERIPHCLK_RTC)) {
		__HAL_RCC_RTC_CONFIG(PeriphClkInit->RTCClockSelection);
	} else {
		__HAL_RCC_RTC_CONFIG(PeriphClkInit->LCDClockSelection);
	}
#else
	__HAL_RCC_RTC_CONFIG(PeriphClkInit->RTCClockSelection);
#endif

However, you might probably want to do the RTCClockSelection!=LCDClockSelection check before this point, before touching other registers, to avoid leaving the system in an inconsistent state.

[Amel NASRI · Accepted solution]

Hi @Community member​ ,

Thanks for bringing this limitation to our attention.

I reported it in an internal ticket to development team.

Internal ticket number: 116449 (This is an internal tracking number and is not accessible or usable by customers).

-Amel