drivers: adc: stm32: check ldo ready bit

For STM32H7, U5 and WBA, check the LDORDY bit of the ADC ISR register
after enabling the internal regulator. This method is safer than the
delay.

Signed-off-by: Guillaume Gautier <[email protected]>

Author: gautierg-st

drivers/adc/adc_stm32.c

@@ -1446,7 +1446,28 @@ static int adc_stm32_init(const struct device *dev)
 	!DT_HAS_COMPAT_STATUS_OKAY(st_stm32f1_adc) && \
 	!DT_HAS_COMPAT_STATUS_OKAY(st_stm32f4_adc)
 	LL_ADC_EnableInternalRegulator(adc);
+	/* Wait for Internal regulator stabilisation
+	 * Some series have a dedicated status bit, others relie on a delay
+	 */
+#if defined(CONFIG_SOC_SERIES_STM32H7X) && defined(ADC_VER_V5_V90)
+	/* ADC3 on H72x/H73x doesn't have the LDORDY status bit */
+	if (adc == ADC3) {
+		k_busy_wait(LL_ADC_DELAY_INTERNAL_REGUL_STAB_US);
+	} else {
+		while (LL_ADC_IsActiveFlag_LDORDY(adc) == 0) {
+		}
+	}
+#elif defined(CONFIG_SOC_SERIES_STM32H7X) || \
+	defined(CONFIG_SOC_SERIES_STM32U5X) || \
+	defined(CONFIG_SOC_SERIES_STM32WBAX)
+	/* Don't use LL_ADC_IsActiveFlag_LDORDY since not present in U5 LL (1.5.0)
+	 * (internal issue 185106)
+	 */
+	while ((READ_BIT(adc->ISR, LL_ADC_FLAG_LDORDY) != (LL_ADC_FLAG_LDORDY))) {
+	}
+#else
 	k_busy_wait(LL_ADC_DELAY_INTERNAL_REGUL_STAB_US);
+#endif
 #endif
 
 	if (config->irq_cfg_func) {