hello zhangxiaodong ,
you may also refer to Topic 122047,
please modify cfg file as below to do the trick for disabling UART logs.
for example,
enable_combined_uart = 0;
spe_uart_instance = 0xff;
you may looking for kernel init messages, $ dmesg | grep -i THS
and please compare it with $L4T_Sources/r32.5/Linux_for_Tegra/source/public/hardware/nvidia/soc/t19x/kernel-dts/tegra194-soc/tegra194-soc-uart.dtsi
you should program it to output logs to uart3, uartc: serial@c280000 {...}.
there’s also pinmux cfg you should check for reference, uart3_tx_pcc5, and uart3_rx_pcc6.
thanks