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

[ing.mtma]

Hi everyone!

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

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.

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.

[JerryChang]

hello ing.mtma,

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

[ing.mtma]

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!

[JerryChang]

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