Morning,

As Erwan was telling, IMHO the pinmux variant is a good solution. For example if you doing power saving, you might power down parts of you pcb. Just image the case that you have a peripheral communicating via USART. If it is powered down down you should also configure your stm UART pins, to prevent that you stm is powering the IC via the RX, TX lanes. So you need to do this pinmux stuff not only at boot time.

If you image the board startup as just one use case of pin config, because your firmware will have different ones (like production, self test, operational, error state) you can imagine that the generating a static config via dts is not working in most of the cases. For my stm32f4 platform you can perfectly handle pinconfig with the stm32 pinmux port.

for example:

static void uart3_dma_gpio(bool on) {
   const struct pin_config pin_on[] = {
        {STM32_PIN_PC5, STM32F4_PINMUX_FUNC_PC5_USART3_RX},
        {STM32_PIN_PB10, STM32F4_PINMUX_FUNC_PB10_USART3_TX},
        {STM32_PIN_PB13, (STM32_PINMUX_ALT_FUNC_8 | STM32_PUPDR_NO_PULL | STM32_OSPEEDR_LOW_SPEED)},
        {STM32_PIN_PB14, (STM32_PINMUX_ALT_FUNC_7 | STM32_PUPDR_NO_PULL | STM32_OSPEEDR_LOW_SPEED)},
    };

    const struct pin_config pin_off[] = {
        {STM32_PIN_PC5, STM32_MODER_ANALOG_MODE},
        {STM32_PIN_PB10, STM32_MODER_ANALOG_MODE},
        {STM32_PIN_PB13, (STM32_MODER_ANALOG_MODE)},
        {STM32_PIN_PB14, (STM32_MODER_ANALOG_MODE)},
    };
    if (true == on) {
        stm32_setup_pins(pin_on, ARRAY_SIZE(pin_on));
    } else {
        stm32_setup_pins(pin_off, ARRAY_SIZE(pin_off));
    }
}

Stefan