UART bulk data write leads to Bootloader shell mode on reboot

Robotics & Edge Computing Jetson & Embedded Systems Jetson Xavier NX
1

Hi @JerryChang @WayneWWW

I’m working with the Radar over the ttyTHS1 and ttyTHS2 UART ports provided by the Tegra-High Speed Uart drivers.

I got some basic information on UARTs here :
THS0, THS1, THS4 and TCU0
I’m using THS1 and newly enabled THS2 UART for Radar.

from this I faced the exact error even though the approach is different as described here
Firstly, i’ve disabled the combined-uart provided as :
common/tegra194-p3668-common.dtsi
@@ -247,8 +247,8 @@

    combined-uart {
            console-port;
             combined-uart;
             status = "disabled";
    };

In Linux_for_tegra/Xavier_NX : p3668.conf.common
-CMDLINE_ADD=“console=ttyTCU0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0”;
+CMDLINE_ADD=“console=ttyTHS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0”;

Board booted fine with UARTs: THS0, THS1, THS2, THS4
On command line reboot, I still ended up with BooTloader Sheel Mode

Q1. Is there a document that helps in mapping the Debug-console port, I’m using UART to USB converter to check logs on ttyACM0 port on Host PC ?

Q2. How to rightly switch the Debug console UART port to THS4 or any other unused UART port ?
I still ended up with BooTloader Shell Mode.

Thanks for any help in this.

3

hello yash.j,

here’s discussion thread, NX change console to other uart, you may refer to.
please also refer to Topic 153941, check mappings for serial ports of ttyTHS*, and UART*
thanks

4

Hi @JerryChang

Thanks for pointing to right solution, i missed out on disabling combined-uart at tegra194-mb1-bct-misc-l4t.cfg.

The system turns of gracefully if there is no data being written while trying to reboot the board.

I also found that if I echo 0 > /dev/ttyTHS2 it clears the buffer and solves the issue. But I found that the THSUart driver has support for reset as :
tegra194-soc-uart.dtsi :
serial@c280000 {
…
resets = <&bpmp_resets TEGRA194_RESET_UARTC>;
reset-names = “serial”;
… }

But in the driver : serial-tegra.c :
static struct tegra_uart_chip_data tegra186_uart_chip_data = {
.tx_fifo_full_status = true,
.allow_txfifo_reset_fifo_mode = false,
… }

Is there a chance of providing Reset on this UART to provide a state change ?
As i referred the driver supporting it : serial-tegra.c (line 1188)
reset_control_assert(tup->rst);
udelay(10);
reset_control_deassert(tup->rst);

Thanks and regards,
Yash Jain

5

hello yash.j,

it’s uart driver to lookup and obtain an exclusive reference to a reset controller.
please check if there’s handler for controlling, then you might have implementation to call API for uart reset.
for example,

1811  static int tegra_uart_probe(struct platform_device *pdev)
1812  {
...
1863  	tup->rst = devm_reset_control_get(&pdev->dev, "serial");
1864  	if (IS_ERR(tup->rst)) {
1865  		dev_err(&pdev->dev, "Couldn't get the reset\n");
1866  		return PTR_ERR(tup->rst);
6

Thanks @JerryChang

I had made the /dev/ttyTCU0 disabled and tested a sd-card based image successfully when flashed image using etcher tool.

On using the flash.sh script as suugested in procedure i’m facing error while flashing as : [0005.093] I> Loading kernel-bootctrl from partition[0005.094] I> Loading part - Pastebin.com

I am trying to debug in L4T sources as i want to now is there any more changes required for flash.sh script to work gracefully :
Changes already done :

  1. Disabled TCU0 on common/tegra194-p3668-common.dtsi
  2. L4t sources changes :
    i. Xavier_NX/bootloader/t186ref/BCT/tegra194-mb1-bct-misc-l4t.cfg
    +enable_combined_uart = 0;
    +spe_uart_instance = 0xff;

ii. Xavier_NX/flash.sh : (line 1301)
CMDLINE_ADD=“console=ttyTHS0,115200n8”;

iii. Xavier_NX/p3668.conf.common : (line 100)
CMDLINE_ADD=“console=ttyTHS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0”;

Thanks in advance…