zephyr/drivers/clock_control/clock_stm32_ll_u3.c

/*
 * Copyright (c) 2025 STMicroelectronics
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <soc.h>
#include <stm32_ll_bus.h>
#include <stm32_ll_pwr.h>
#include <stm32_ll_rcc.h>
#include <stm32_ll_utils.h>
#include <stm32_ll_system.h>
#include <zephyr/arch/cpu.h>
#include <zephyr/drivers/clock_control.h>
#include <zephyr/drivers/clock_control/stm32_clock_control.h>
#include <zephyr/sys/util.h>
#include <stm32_backup_domain.h>

/* Macros to fill up prescaler values */
#define ahb_prescaler(v) CONCAT(LL_RCC_HCLK_SYSCLK_DIV_, v)
#define apb1_prescaler(v) CONCAT(LL_RCC_APB1_HCLK_DIV_, v)
#define apb2_prescaler(v) CONCAT(LL_RCC_APB2_HCLK_DIV_, v)
#define apb3_prescaler(v) CONCAT(LL_RCC_APB3_HCLK_DIV_, v)

static uint32_t get_msis_frequency(void)
{
	uint32_t frequency = MSIRC1_VALUE;

	if (LL_RCC_MSIS_GetClockSource() == LL_RCC_MSIS_CLOCK_SOURCE_RC0) {
		frequency = MSIRC0_VALUE;
	}
	switch (LL_RCC_MSIS_GetClockDivision()) {
	case LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_2:
		return frequency / 2U;
	case LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_4:
		return frequency / 4U;
	case LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_8:
		return frequency / 8U;
	case LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_1:
		return frequency;
	default:
		return 0;
	}
}

static uint32_t get_msik_frequency(void)
{
	uint32_t frequency = MSIRC1_VALUE;

	if (LL_RCC_MSIK_GetClockSource() == LL_RCC_MSIK_CLOCK_SOURCE_RC0) {
		frequency = MSIRC0_VALUE;
	}
	switch (LL_RCC_MSIK_GetClockDivision()) {
	case LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_2:
		return frequency / 2U;
	case LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_4:
		return frequency / 4U;
	case LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_8:
		return frequency / 8U;
	case LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_1:
		return frequency;
	default:
		return 0;
	}
}

static uint32_t get_startup_frequency(void)
{
	switch (LL_RCC_GetSysClkSource()) {
	case LL_RCC_SYS_CLKSOURCE_STATUS_MSIS:
		return get_msis_frequency();
	case LL_RCC_SYS_CLKSOURCE_STATUS_HSI16:
		return STM32_HSI_FREQ;
	case LL_RCC_SYS_CLKSOURCE_STATUS_HSE:
		return STM32_HSE_FREQ;
	default:
		__ASSERT(0, "Unexpected startup freq");
		return 0;
	}
}

static uint32_t get_sysclk_frequency(void)
{
#if defined(STM32_SYSCLK_SRC_MSIS)
	return get_msis_frequency();
#elif defined(STM32_SYSCLK_SRC_HSE)
	return STM32_HSE_FREQ;
#elif defined(STM32_SYSCLK_SRC_HSI)
	return STM32_HSI_FREQ;
#else
	__ASSERT(0, "No SYSCLK Source configured");
	return 0;
#endif

}

/** @brief Verifies clock is part of active clock configuration */
static int enabled_clock(uint32_t src_clk)
{
	if ((src_clk == STM32_SRC_SYSCLK) ||
	    (src_clk == STM32_SRC_HCLK) ||
	    (src_clk == STM32_SRC_PCLK1) ||
	    (src_clk == STM32_SRC_PCLK2) ||
	    (src_clk == STM32_SRC_PCLK3) ||
	    ((src_clk == STM32_SRC_HSE) && IS_ENABLED(STM32_HSE_ENABLED)) ||
	    ((src_clk == STM32_SRC_HSI16) && IS_ENABLED(STM32_HSI_ENABLED)) ||
	    ((src_clk == STM32_SRC_HSI48) && IS_ENABLED(STM32_HSI48_ENABLED)) ||
	    ((src_clk == STM32_SRC_LSE) && IS_ENABLED(STM32_LSE_ENABLED)) ||
	    ((src_clk == STM32_SRC_LSI) && IS_ENABLED(STM32_LSI_ENABLED)) ||
	    ((src_clk == STM32_SRC_MSIS) && IS_ENABLED(STM32_MSIS_ENABLED)) ||
	    ((src_clk == STM32_SRC_MSIK) && IS_ENABLED(STM32_MSIK_ENABLED))) {
		return 0;
	}

	return -ENOTSUP;
}

static int stm32_clock_control_on(const struct device *dev, clock_control_subsys_t sub_system)
{
	struct stm32_pclken *pclken = (struct stm32_pclken *)sub_system;
	volatile int temp;

	ARG_UNUSED(dev);

	if (!IN_RANGE(pclken->bus, STM32_PERIPH_BUS_MIN, STM32_PERIPH_BUS_MAX)) {
		/* Attempt to toggle a wrong periph clock bit */
		return -ENOTSUP;
	}

	sys_set_bits(DT_REG_ADDR(DT_NODELABEL(rcc)) + pclken->bus, pclken->enr);
	/* Delay after enabling the clock, to allow it to become active */
	temp = sys_read32(DT_REG_ADDR(DT_NODELABEL(rcc)) + pclken->bus);
	UNUSED(temp);

	return 0;
}

static int stm32_clock_control_off(const struct device *dev, clock_control_subsys_t sub_system)
{
	struct stm32_pclken *pclken = (struct stm32_pclken *)sub_system;

	ARG_UNUSED(dev);

	if (!IN_RANGE(pclken->bus, STM32_PERIPH_BUS_MIN, STM32_PERIPH_BUS_MAX)) {
		/* Attempt to toggle a wrong periph clock bit */
		return -ENOTSUP;
	}

	sys_clear_bits(DT_REG_ADDR(DT_NODELABEL(rcc)) + pclken->bus, pclken->enr);

	return 0;
}

static int stm32_clock_control_configure(const struct device *dev,
					 clock_control_subsys_t sub_system,
					 void *data)
{
	struct stm32_pclken *pclken = (struct stm32_pclken *)sub_system;
	int err;

	ARG_UNUSED(dev);
	ARG_UNUSED(data);

	err = enabled_clock(pclken->bus);
	if (err < 0) {
		/* Attempt to configure a src clock not available or not valid */
		return err;
	}

	sys_clear_bits(DT_REG_ADDR(DT_NODELABEL(rcc)) + STM32_DT_CLKSEL_REG_GET(pclken->enr),
		       STM32_DT_CLKSEL_MASK_GET(pclken->enr) <<
			STM32_DT_CLKSEL_SHIFT_GET(pclken->enr));
	sys_set_bits(DT_REG_ADDR(DT_NODELABEL(rcc)) + STM32_DT_CLKSEL_REG_GET(pclken->enr),
		     STM32_DT_CLKSEL_VAL_GET(pclken->enr) <<
			STM32_DT_CLKSEL_SHIFT_GET(pclken->enr));

	return 0;
}

static int stm32_clock_control_get_subsys_rate(const struct device *dev,
					       clock_control_subsys_t sys,
					       uint32_t *rate)
{
	struct stm32_pclken *pclken = (struct stm32_pclken *)sys;

	/*
	 * Get AHB Clock (= SystemCoreClock = SYSCLK/prescaler)
	 * SystemCoreClock is preferred to CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC
	 * since it will be updated after clock configuration and hence
	 * more likely to contain actual clock speed
	 */
	uint32_t ahb_clock = SystemCoreClock;
	uint32_t apb1_clock = ahb_clock / STM32_APB1_PRESCALER;
	uint32_t apb2_clock = ahb_clock / STM32_APB2_PRESCALER;
	uint32_t apb3_clock = ahb_clock / STM32_APB3_PRESCALER;

	ARG_UNUSED(dev);

	switch (pclken->bus) {
	case STM32_CLOCK_BUS_AHB1:
	case STM32_CLOCK_BUS_AHB1_2:
	case STM32_CLOCK_BUS_AHB2:
	case STM32_CLOCK_BUS_AHB2_2:
	case STM32_SRC_HCLK:
		*rate = ahb_clock;
		break;
	case STM32_CLOCK_BUS_APB1:
	case STM32_CLOCK_BUS_APB1_2:
	case STM32_SRC_PCLK1:
		*rate = apb1_clock;
		break;
	case STM32_CLOCK_BUS_APB2:
	case STM32_SRC_PCLK2:
		*rate = apb2_clock;
		break;
	case STM32_CLOCK_BUS_APB3:
	case STM32_SRC_PCLK3:
		*rate = apb3_clock;
		break;
	case STM32_SRC_SYSCLK:
		*rate = get_sysclk_frequency();
		break;
#if defined(STM32_HSI_ENABLED)
	case STM32_SRC_HSI16:
		*rate = STM32_HSI_FREQ;
		break;
#endif /* STM32_HSI_ENABLED */
#if defined(STM32_MSIS_ENABLED)
	case STM32_SRC_MSIS:
		*rate = get_msis_frequency();
		break;
#endif /* STM32_MSIS_ENABLED */
#if defined(STM32_MSIK_ENABLED)
	case STM32_SRC_MSIK:
		*rate = get_msik_frequency();
		break;
#endif /* STM32_MSIK_ENABLED */
#if defined(STM32_HSE_ENABLED)
	case STM32_SRC_HSE:
		*rate = STM32_HSE_FREQ;
		break;
#endif /* STM32_HSE_ENABLED */
#if defined(STM32_LSE_ENABLED)
	case STM32_SRC_LSE:
		*rate = STM32_LSE_FREQ;
		break;
#endif /* STM32_LSE_ENABLED */
#if defined(STM32_LSI_ENABLED)
	case STM32_SRC_LSI:
		*rate = STM32_LSI_FREQ;
		break;
#endif /* STM32_LSI_ENABLED */
#if defined(STM32_HSI48_ENABLED)
	case STM32_SRC_HSI48:
		*rate = STM32_HSI48_FREQ;
		break;
#endif /* STM32_HSI48_ENABLED */
	default:
		return -ENOTSUP;
	}

	if (pclken->div) {
		*rate /= pclken->div + 1;
	}

	return 0;
}

static enum clock_control_status stm32_clock_control_get_status(const struct device *dev,
								clock_control_subsys_t sub_system)
{
	struct stm32_pclken *pclken = (struct stm32_pclken *)sub_system;

	ARG_UNUSED(dev);

	if (IN_RANGE(pclken->bus, STM32_PERIPH_BUS_MIN, STM32_PERIPH_BUS_MAX)) {
		/* Gated clocks */
		if ((sys_read32(DT_REG_ADDR(DT_NODELABEL(rcc)) + pclken->bus) & pclken->enr)
		    == pclken->enr) {
			return CLOCK_CONTROL_STATUS_ON;
		} else {
			return CLOCK_CONTROL_STATUS_OFF;
		}
	} else {
		/* Domain clock sources */
		if (enabled_clock(pclken->bus) == 0) {
			return CLOCK_CONTROL_STATUS_ON;
		} else {
			return CLOCK_CONTROL_STATUS_OFF;
		}
	}
}

static DEVICE_API(clock_control, stm32_clock_control_api) = {
	.on = stm32_clock_control_on,
	.off = stm32_clock_control_off,
	.get_rate = stm32_clock_control_get_subsys_rate,
	.get_status = stm32_clock_control_get_status,
	.configure = stm32_clock_control_configure,
};

static void set_regu_voltage(uint32_t hclk_freq)
{
	if (hclk_freq < MHZ(48)) {
		LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE2);
	} else {
		LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
	}
}

static void enable_epod_booster(void)
{
	LL_RCC_SetEPODBoosterClkSource(LL_RCC_EPODBOOSTCLKSRCE_MSIS);
	LL_RCC_SetEPODBoosterClkPrescaler(LL_RCC_EPODBOOSTCLKPRESCAL_1);
	LL_PWR_EnableEPODBooster();
	while (LL_PWR_IsActiveFlag_BOOST() == 0) {
	}
}

static void configure_clock_with_calibration(int range)
{
	LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_MSIS);

	/* Wait till System clock is ready */
	while (LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_MSIS) {
	}

	LL_RCC_SetAHBPrescaler(LL_RCC_HCLK_SYSCLK_DIV_1);
	LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_HCLK_DIV_1);
	LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_HCLK_DIV_1);
	LL_RCC_SetAPB3Prescaler(LL_RCC_APB3_HCLK_DIV_1);

	BUILD_ASSERT(STM32_LSE_ENABLED || !IS_ENABLED(STM32_MSIK_ENABLED),
		"MSIK requires LSE clock to be enabled for auto-calibration");
	BUILD_ASSERT(STM32_LSE_ENABLED || !IS_ENABLED(STM32_MSIS_ENABLED),
		"MSIS requires LSE clock to be enabled for auto-calibration");
	if (IN_RANGE(range, 0, 3)) {
		/*
		 * LSE or HSE must be enabled and ready before selecting
		 * this oscillator as MSIRC0 input clock for Range [0 3]
		 */
		if (LL_RCC_LSE_IsEnabled() != 0U && LL_RCC_LSE_IsReady() != 0U) {
			LL_RCC_MSI_RC0_SetPLLInputClk(LL_RCC_MSIPLL0SEL_LSE);
		} else if (LL_RCC_HSE_IsEnabled() != 0U && LL_RCC_HSE_IsReady() != 0U) {
			LL_RCC_MSI_RC0_SetPLLInputClk(LL_RCC_MSIPLL0SEL_HSE_OR_HSEDIV2);
		}
		LL_RCC_MSI_RC0_PLLmode_Enable();
		while (LL_RCC_MSI_RC0_PLLmode_IsEnabled() == 0U) {
		}
	} else {
		/*
		 * LSE or HSE must be enabled and ready before selecting
		 * this oscillator as MSIRC1 input clock for Range [4 7]
		 */
		if (LL_RCC_LSE_IsEnabled() != 0U && LL_RCC_LSE_IsReady() != 0U) {
			LL_RCC_MSI_RC1_SetPLLInputClk(LL_RCC_MSIPLL1SEL_LSE);
		} else if (LL_RCC_HSE_IsEnabled() != 0U && LL_RCC_HSE_IsReady() != 0U) {
			LL_RCC_MSI_RC1_SetPLLInputClk(LL_RCC_MSIPLL1SEL_HSE_OR_HSEDIV2);
		}
		LL_RCC_MSI_RC1_PLLmode_Enable();
		while (LL_RCC_MSI_RC1_PLLmode_IsEnabled() == 0U) {
		}
	}
}

static void set_up_fixed_clock_sources(void)
{
	if (IS_ENABLED(STM32_HSE_ENABLED)) {
		/* Check if need to enable HSE bypass feature or not */
		if (IS_ENABLED(STM32_HSE_BYPASS)) {
			LL_RCC_HSE_EnableBypass();
		} else {
			LL_RCC_HSE_DisableBypass();
		}

		/* Enable HSE */
		LL_RCC_HSE_Enable();
		while (LL_RCC_HSE_IsReady() == 0) {
			/* Wait for HSE ready */
		}
	}

	if (IS_ENABLED(STM32_HSI_ENABLED)) {
		/* Enable HSI if not enabled */
		if (LL_RCC_HSI_IsReady() == 0) {
			/* Enable HSI */
			LL_RCC_HSI_Enable();
			while (LL_RCC_HSI_IsReady() == 0) {
				/* Wait for HSI ready */
			}
		}
	}

	if (IS_ENABLED(STM32_LSE_ENABLED)) {
		/* N.B.: PWR clock has been enabled by SoC init hook */
		stm32_backup_domain_enable_access();

		/* Configure driving capability */
		LL_RCC_LSE_SetDriveCapability(STM32_LSE_DRIVING << RCC_BDCR_LSEDRV_Pos);

		if (IS_ENABLED(STM32_LSE_BYPASS)) {
			/* Configure LSE bypass */
			LL_RCC_LSE_EnableBypass();
		}

		/* Enable LSE Oscillator */
		LL_RCC_LSE_Enable();
		/* Wait for LSE ready */
		while (LL_RCC_LSE_IsReady() == 0U) {
		}

		/* Enable LSESYS additionally */
		LL_RCC_LSE_EnablePropagation();
		/* Enforce BackUp domain access is disabled after clock initialization */
		while (LL_RCC_LSE_IsPropagationReady() == 0U) {
		}

		stm32_backup_domain_disable_access();
	}

	if (IS_ENABLED(STM32_MSIS_ENABLED)) {
		/* Set MSIS Range */
		LL_FLASH_SetLatency(LL_FLASH_LATENCY_2);
		while (LL_FLASH_GetLatency() != LL_FLASH_LATENCY_2) {
		}

		if (IN_RANGE(STM32_MSIS_RANGE, 0, 3)) {
			LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
		} else {
			LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE2);
		}

		enable_epod_booster();

		if (IN_RANGE(STM32_MSIS_RANGE, 0, 3)) {
			/* Range 0-3 uses RC0 as the clock source */
			LL_RCC_MSIS_SetClockSource(LL_RCC_MSIS_CLOCK_SOURCE_RC0);
			switch (STM32_MSIS_RANGE) {
			case 0:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_1);
				break;
			case 1:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_2);
				break;
			case 2:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_4);
				break;
			case 3:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_8);
				break;
			default:
				break;
			}
		} else {
			/* Range 4-7 uses RC1 as the clock source */
			LL_RCC_MSIS_SetClockSource(LL_RCC_MSIS_CLOCK_SOURCE_RC1);
			switch (STM32_MSIS_RANGE) {
			case 4:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_1);
				break;
			case 5:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_2);
				break;
			case 6:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_4);
				break;
			case 7:
				LL_RCC_MSIS_SetClockDivision(LL_RCC_MSIS_CLOCK_SOURCE_RC_DIV_8);
				break;
			default:
				break;
			}

		}
		LL_RCC_MSI_SetMSIxClockRange();
		/*
		 * For stm32u3 LSE or HSE must be enabled and ready before
		 * selecting this oscillator as MSIRC0/MSIRC1 input clock.
		 */
		/* Enable MSIS */
		LL_RCC_MSIS_Enable();
		while (LL_RCC_MSIS_IsReady() == 0U) {
		}

		configure_clock_with_calibration(STM32_MSIS_RANGE);
	}

	if (IS_ENABLED(STM32_MSIK_ENABLED)) {
		/* Set MSIK Range */
		LL_FLASH_SetLatency(LL_FLASH_LATENCY_2);
		while (LL_FLASH_GetLatency() != LL_FLASH_LATENCY_2) {
		}

		if (IN_RANGE(STM32_MSIK_RANGE, 0, 3)) {
			LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE1);
		} else {
			LL_PWR_SetRegulVoltageScaling(LL_PWR_REGU_VOLTAGE_SCALE2);
		}

		enable_epod_booster();

		if (IN_RANGE(STM32_MSIK_RANGE, 0, 3)) {
			/* Range 0-3 uses RC0 as the clock source */
			LL_RCC_MSIK_SetClockSource(LL_RCC_MSIK_CLOCK_SOURCE_RC0);
			switch (STM32_MSIK_RANGE) {
			case 0:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_1);
				break;
			case 1:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_2);
				break;
			case 2:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_4);
				break;
			case 3:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_8);
				break;
			default:
				break;
			}
		} else {
			/* Range 4-7 uses RC1 as the clock source */
			LL_RCC_MSIK_SetClockSource(LL_RCC_MSIK_CLOCK_SOURCE_RC1);
			switch (STM32_MSIK_RANGE) {
			case 4:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_1);
				break;
			case 5:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_2);
				break;
			case 6:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_4);
				break;
			case 7:
				LL_RCC_MSIK_SetClockDivision(LL_RCC_MSIK_CLOCK_SOURCE_RC_DIV_8);
				break;
			default:
				break;
			}

		}
		LL_RCC_MSI_SetMSIxClockRange();
		/*
		 * For stm32u3 LSE or HSE must be enabled and ready before
		 * selecting this oscillator as MSIRC0/MSIRC1 input clock.
		 */
		LL_RCC_MSIK_Enable();
		while (LL_RCC_MSIK_IsReady() == 0U) {
		}

		configure_clock_with_calibration(STM32_MSIK_RANGE);
	}

	if (IS_ENABLED(STM32_LSI_ENABLED)) {
		stm32_backup_domain_enable_access();

		/* Enable LSI oscillator */
		LL_RCC_LSI_Enable();
		while (LL_RCC_LSI_IsReady() == 0) {
		}

		stm32_backup_domain_disable_access();
	}

	if (IS_ENABLED(STM32_HSI48_ENABLED)) {
		LL_RCC_HSI48_Enable();
		while (LL_RCC_HSI48_IsReady() == 0) {
		}
	}
}

int stm32_clock_control_init(const struct device *dev)
{
	uint32_t old_hclk_freq;

	ARG_UNUSED(dev);

	/* Current hclk value */
	old_hclk_freq = __LL_RCC_CALC_HCLK_FREQ(get_startup_frequency(), LL_RCC_GetAHBPrescaler());

	/* Set voltage regulator to comply with targeted system frequency */
	set_regu_voltage(CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC);

	/* Set flash latency */
	/* If freq increases, set flash latency before any clock setting */
	if (old_hclk_freq < CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC) {
		LL_SetFlashLatency(CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC);
	}

	/* Set up individual enabled clocks */
	set_up_fixed_clock_sources();

	/* Set peripheral buses prescalers */
	LL_RCC_SetAHBPrescaler(ahb_prescaler(STM32_AHB_PRESCALER));
	LL_RCC_SetAPB1Prescaler(apb1_prescaler(STM32_APB1_PRESCALER));
	LL_RCC_SetAPB2Prescaler(apb2_prescaler(STM32_APB2_PRESCALER));
	LL_RCC_SetAPB3Prescaler(apb3_prescaler(STM32_APB3_PRESCALER));

#ifdef STM32_SYSCLK_SRC_HSE
	/* Set HSE as SYSCLCK source */
	LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_HSE);
	while (LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_HSE) {
	}
#elif defined(STM32_SYSCLK_SRC_MSIS)
	/* Set MSIS as SYSCLCK source */
	LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_MSIS);
	while (LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_MSIS) {
	}
#elif defined(STM32_SYSCLK_SRC_HSI)
	/* Set HSI as SYSCLCK source */
	LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_HSI16);
	while (LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_HSI16) {
	}
#else
	return -ENOTSUP;
#endif

	/* Set FLASH latency */
	/* If freq not increased, set flash latency after all clock setting */
	if (old_hclk_freq >= CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC) {
		LL_SetFlashLatency(CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC);
	}

	/* Update CMSIS variable */
	SystemCoreClock = CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC;

	return 0;
}

/**
 * @brief RCC device, note that priority is intentionally set to 1 so
 * that the device init runs just after SOC init
 */
DEVICE_DT_DEFINE(DT_NODELABEL(rcc),
		 stm32_clock_control_init,
		 NULL,
		 NULL, NULL,
		 PRE_KERNEL_1,
		 CONFIG_CLOCK_CONTROL_INIT_PRIORITY,
		 &stm32_clock_control_api);