drivers: adc: stm32: get prescaler value from dts

Get the STM32 ADC prescaler data from dts to create the appropriate LL
macro to use for the ADC clock.

(cherry picked from commit e8c4990)

Original-Signed-off-by: Guillaume Gautier <guillaume.gautier-ext@st.com>
GitOrigin-RevId: e8c4990
Change-Id: Ie52cbfc369af36b2100be28e382f4e0b149a522a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/zephyr/+/4822198
Commit-Queue: Yuval Peress <peress@google.com>
Tested-by: Yuval Peress <peress@google.com>
Reviewed-by: Yuval Peress <peress@google.com>
Tested-by: ChromeOS Prod (Robot) <chromeos-ci-prod@chromeos-bot.iam.gserviceaccount.com>

drivers/adc/adc_stm32.c

@@ -160,6 +160,7 @@ struct adc_stm32_cfg {
 	ADC_TypeDef *base;
 	void (*irq_cfg_func)(void);
 	struct stm32_pclken pclken;
+	uint32_t clk_prescaler;
 	const struct pinctrl_dev_config *pcfg;
 	const uint16_t sampling_time_table[STM32_NB_SAMPLING_TIME];
 	int8_t num_sampling_time_common_channels;
@@ -1388,6 +1389,29 @@ static const struct adc_driver_api api_stm32_driver_api = {
 	.ref_internal = STM32_ADC_VREF_MV, /* VREF is usually connected to VDD */
 };
 
+#if defined(CONFIG_SOC_SERIES_STM32F0X)
+/* LL_ADC_CLOCK_ASYNC_DIV1 doesn't exist in F0 LL. Define it here. */
+#define LL_ADC_CLOCK_ASYNC_DIV1 LL_ADC_CLOCK_ASYNC
+#endif
+
+/* st_prescaler property requires 2 elements : clock ASYNC/SYNC and DIV */
+#define ADC_STM32_CLOCK(x)	DT_INST_PROP(x, st_adc_clock_source)
+#define ADC_STM32_DIV(x)	DT_INST_PROP(x, st_adc_prescaler)
+
+/* Macro to set the prefix depending on the 1st element: check if it is SYNC or ASYNC */
+#define ADC_STM32_CLOCK_PREFIX(x)			\
+	COND_CODE_1(IS_EQ(ADC_STM32_CLOCK(x), SYNC),	\
+		(LL_ADC_CLOCK_SYNC_PCLK_DIV),		\
+		(LL_ADC_CLOCK_ASYNC_DIV))
+
+/* Concat prefix (1st element) and DIV value (2nd element) of st,adc-prescaler */
+#if DT_HAS_COMPAT_STATUS_OKAY(st_stm32f1_adc)
+#define ADC_STM32_DT_PRESC(x)	0
+#else
+#define ADC_STM32_DT_PRESC(x)	\
+	_CONCAT(ADC_STM32_CLOCK_PREFIX(x), ADC_STM32_DIV(x))
+#endif
+
 #ifdef CONFIG_ADC_STM32_SHARED_IRQS
 
 bool adc_stm32_is_irq_active(ADC_TypeDef *adc)
@@ -1500,6 +1524,7 @@ static const struct adc_stm32_cfg adc_stm32_cfg_##index = {		\
 		.enr = DT_INST_CLOCKS_CELL(index, bits),		\
 		.bus = DT_INST_CLOCKS_CELL(index, bus),			\
 	},								\
+	.clk_prescaler = ADC_STM32_DT_PRESC(index),			\
 	.pcfg = PINCTRL_DT_INST_DEV_CONFIG_GET(index),			\
 	.temp_channel = DT_INST_PROP_OR(index, temp_channel, 0xFF),	\
 	.vref_channel = DT_INST_PROP_OR(index, vref_channel, 0xFF),	\