UART4 Pins H13 and H14 not working as expected.

[SRaic.1]

I am trying to use the UART4 TX: H13 and RX: H14 pins for the tty console access.

The TX from the MPU works fine as I can see the kernel boot logs, but cannot access the kernel command line. No prompt shows up on hitting ENTER.

Here are my stm32mp15-pinctrl.dtsi UART4 configurations:

   uart4_pins_a: uart4-0 {

    pins1 {

      //pinmux = <STM32_PINMUX('G', 11, AF6)>; /* UART4_TX */

      pinmux = <STM32_PINMUX('H', 13, AF8)>;  /* UART4_TX */

      bias-disable;

      drive-push-pull;

      slew-rate = <0>;

    };

    pins2 {

      //pinmux = <STM32_PINMUX('B', 2, AF8)>; /* UART4_RX */

      pinmux = <STM32_PINMUX('H', 14, AF8)>; /* UART4_RX */

      bias-disable;

    };

  };

  uart4_idle_pins_a: uart4-idle-0 {

    pins1 {

      //pinmux = <STM32_PINMUX('G', 11, ANALOG)>; /* UART4_TX */

      pinmux = <STM32_PINMUX('H', 13, ANALOG)>;  /* UART4_TX */

    };

    pins2 {

      //pinmux = <STM32_PINMUX('B', 2, AF8)>; /* UART4_RX */

      pinmux = <STM32_PINMUX('H', 14, AF8)>; /* UART4_RX */

      bias-disable;

    };

  };

  uart4_sleep_pins_a: uart4-sleep-0 {

    pins {

      //pinmux = <STM32_PINMUX('G', 11, ANALOG)>, /* UART4_TX */

      //  <STM32_PINMUX('B', 2, ANALOG)>; /* UART4_RX */

      pinmux = <STM32_PINMUX('H', 13, ANALOG)>, /* UART4_TX */

         <STM32_PINMUX('H', 14, ANALOG)>; /* UART4_RX */

    };

  };

And the stm32mp15xx-evx.dtsi configurations:

&uart4 {

  pinctrl-names = "default", "sleep", "idle";

  pinctrl-0 = <&uart4_pins_a>;

  pinctrl-1 = <&uart4_sleep_pins_a>;

  pinctrl-2 = <&uart4_idle_pins_a>;

  //uart-has-rtscts;

  //status = "disabled";

  status = "okay";

};

Have also added chosen path as:

   chosen {

    stdout-path = "serial0:115200n8";

  };

  aliases {

    serial0 = &uart4;

  };

What is missing for the configurations?

[Kevin HUBER]

Hello @SRaic.1​ ,

Please can you share the complete boot log.

Does it was working previously with the default UART4 config?

Does it work under U-Boot?

Best Regards,

Kevin

[SRaic.1]

Hi @Kevin HUBER​ 

Attaching boot logs after enabling the UART 4 as console uart.

Yes, when using the default uart4 config, uart4 TX and RX worked fine as kernel console.

Not made changes for U-boot uart4 yet.

Regards,

Swapnil.

[Kevin HUBER]

Hello @SRaic.1​ ,

You are using an ecosystem v2.1 that is no longer supported by ST (deprecated version), it is recommended to switch to the latest environment release which is the v4.1:

https://wiki.st.com/stm32mpu/wiki/STM32_MPU_OpenSTLinux_release_note_-_v4.1.0

Otherwise, regarding your problem I tried on my 157F-EV1 board with the ecosystem v4.1.0 and I was able to use H13 and H14 without issue.

It is possible to verify which pins are used with the command:

root@stm32mp1:~# cat /sys/kernel/debug/pinctrl/soc:pinctrl@50002000/pinmux-pins
 
pin 125 (PH13): device 40010000.serial function af8 group PH13
pin 126 (PH14): device 40010000.serial function af8 group PH14

For doing that I only modified (for test purpose) the file stm32mp15-pinctrl.dtsi

where I replaced every

• "('G', 11, AF6)" by "('H', 13, AF8)"
• "('B', 2, AF8)" by "('H', 14, AF8)"

In uart4_pins_a,  uart4_idle_pins_a, uart4_sleep_pins_a.

I didn't changed anything else.

My uart4 node looks like this:

&uart4 {
	pinctrl-names = "default", "sleep", "idle";
	pinctrl-0 = <&uart4_pins_a>;
	pinctrl-1 = <&uart4_sleep_pins_a>;
	pinctrl-2 = <&uart4_idle_pins_a>;
	/delete-property/dmas;
	/delete-property/dma-names;
	status = "okay";
};

Best Regards,

Kevin

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