It's possible to make work USB-OTG and USART1 in the same device (STM32MP157CAC)?

[areify]

Hi everyone.

I have an already-designed PCB with an STM32MP157 on it. In order to communicate with an external device, I am using USART1. At the same time, I'm using an USB OTG port to connect my device to my PC.

My problem is that USART1 is working with pins PA10 (AF7: USART1 RX), PA12 (AF7: USART1 DE) and PB6 (AF7: USART1 TX). It seems that PA10 is also set up as OTG HS pin:

usbotg_hs_pins_a: usbotg_hs-0 {
				pins {
					pinmux = <STM32_PINMUX('A', 10, ANALOG)>; /* OTG_ID */
				};
			};

(in stm32mp157-pinctrl.dtsi).

I am not sure at all but I think this pin is not referenced at any device tree file in the whole DTS. However, if I disable usb-otg device, USART1 starts working.

But I don't want to do that.

So after reading the usb-otg driver documentation I discovered the following parameter:

dr_mode: shall be one of "host", "peripheral" and "otg"

So I set up my otg as "peripheral" and now my usb otg works when I connect the external device to my USART1. But USART1 still not works.

What am I missing? I also tried deleting node usbotg_hs_pins_a in pinctrl and property pinctrl-0 in usbotg_hs.

My device tree topology is next: I am using a .dts file which includes stm32mp157a-dk1.dts. And I've redefined usbotg_hs node as:

&usbotg_hs {
 /delete-property/ extcon;
	dr_mode = "peripheral";
};

Thank you in advance.

[PatrickF]

Hi,

please see https://wiki.st.com/stm32mpu/wiki/How_to_configure_U-Boot_for_your_board#USB_OTG_node

To disable OTG_ID pin on PA10, at least you miss also the following line:

 	u-boot,force-b-session-valid;

Regards,

[areify]

Hi Patrick

Thank you for your fast reply :)

I've tested that line and it did not worked. Also I tried with

force-b-session-valid;

And USART1 still does not work. Maybe I'm doing something else wrong.

[PatrickF]

Hi,

any log related to USART1 'does not work' ?

Check if USART1 kernel clock is enabled, see https://wiki.st.com/stm32mpu/wiki/STM32MP15_clock_tree

see also https://wiki.st.com/stm32mpu/wiki/Serial_TTY_device_tree_configuration#Activation_of_a_USART_or_UART_instance

if you are trying to use USART1 from Cortex-M4, please see https://wiki.st.com/stm32mpu/wiki/How_to_assign_an_internal_peripheral_to_a_runtime_context

Regards.

[PatrickF]

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