[jetson-nano-B01]: Alternate debug UART port

Hi everyone!

I want to use the UART2(Tegra-side) instead of the UART1(Tegra-side) as debug port:

image

The problem is that I don’t really know how to do so… my first approach was to change u-boot device tree like so:

/* u-boot dev-tree arch/arm/dts/tegra210-p3450-0000.dts */
...
 / {                                                     
     model = "NVIDIA Jetson Nano Developer Kit";
     compatible = "nvidia,p3450-0000", "nvidia,tegra210";
 
     chosen {
         stdout-path = &uartb;
     };

  ...

  // uartb offset tag
 serial@70006040 {
     status = "okay";
 };

/* u-boot include/configs/p3450-0000.h */
 #ifndef _P3450_0000_H
 #define _P3450_0000_H
 
 #include <linux/sizes.h>
         
 #include "tegra210-common.h"
 
 /* Board-specific serial config */
 #define CONFIG_TEGRA_ENABLE_UARTB  

After boot I can see that cboot keeps printing log messages to UART1 (as expected because I didn’t do anything to change this and I don’t really know how to do it) but I stop seeing u-boot messages or prompt from this UART1.

From UART2 I can see u-boot messages from the 40-pin expansion header pins 8&10 but then it complains about “no device found” and then it reboots.
image
Note*: I added those Live tree messages

I’m looking at u-boot:drivers/serial/serial-uclass.c to find out what could be the problem but before digging into this I just wanted to know if it is even possible to configure components like BPMP, CBOOT, etc on t210 platforms.

PS: I already have a look to similar topics, but I didn’t find what I’m looking for
T109102
T110615
T188393

I will really appreciate any clue on the subject, thank you so much for your time.

hello ing.mtma,

you don’t need extra modifications.
Nano using UART2 for sending bootloader and kernel logs by default,

Thanks for the reply Jerry,

Maybe i didn’t explain myself but the Default UART2 debug port pins are connected to Tegra-UART1 pins, but I want to change these to Tegra-UART2. Please let me know if the image of the block diagram is not visible if not you can see it from Jetson_Nano_Product_Design_Guide_DG-09502-001_v2.2.pd Figure 11-5. Jetson Nano UART Connections

BR!

hello ing.mtma,

please check Topic 153941 for the mappings for serial ports of ttyTHS*, and UART*,
you may swap the definition in the device tree for verification.
thanks