操作步骤如下： bootloader/t186ref/BCT/tegra194-mb1-bct-misc-flash.cfg
-enable_combined_uart = 1; -spe_uart_instance = 2; +enable_combined_uart = 0; +spe_uart_instance = 0xff;bootloader/t186ref/BCT/tegra194-mb1-bct-misc-l4t.cfg
-enable_combined_uart = 1; -spe_uart_instance = 0x2; +enable_combined_uart = 0; +spe_uart_instance = 0xff;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″;flash.sh
– CMDLINE_ADD=”console=ttyTCU0,115200n8″; + CMDLINE_ADD=”console=ttyTHS0,115200n8″;common/tegra194-p3668-common.dtsi
– bootargs =”console=ttyTCU0,115200″; + bootargs =”console=ttyTHS0,115200″; combined-uart { console-port; combined-uart; – status = “okay”; + status = “disabled”; };修改完后使用 jetson-disk-image-creator.sh和flash开发SoM创建一个sdcard映像 板子就会启动并正常工作 但如果我尝试flash生产SoM，在刷机阶段会出现以下问题
[ 13.0009 ] Sending bootloader and pre-requisite binaries [ 13.0022 ] tegrarcm_v2 –download blob blob.bin [ 13.0033 ] Applet version 01.00.0000 [ 13.0183 ] Sending blob [ 13.0185 ] […………………………………………] 100% [ 13.7927 ] [ 13.7960 ] tegrarcm_v2 –boot recovery [ 13.7983 ] Applet version 01.00.0000 [ 13.8223 ] [ 14.8264 ] tegrarcm_v2 –isapplet如果我试图恢复 bootloader/t186ref/BCT/tegra194-mb1-bct-misc-flash.cfg中的更改 并在bootloader/t186ref/BCT/tegra194-mb1-bct-misc-flash.cfg 中保留以下更改并恢复其他更改
-enable_combined_uart = 1; +enable_combined_uart = 0;可以flash，但在引导期间出现以下问题
[0001.165] I> EKB detected (length: 0x410) @ VA:0x52714400 ipc-unittest-main: 1519: Welcome to IPC unittest!!! ipc-unittest-main: 1531: waiting forever ipc-unittest-srv: 329: Init unittest services!!! hwkey-agent: 40: hwkey-agent is running!! hwkey-agent: 182: key_mgnt_processing ……. hwkey-agent: 157: Init hweky-agent services!! platform_bootstrap_epilog: trusty bootstrap complete 2. 参考Xavier上禁用组合uart修改方法（1）更新misc配置文件
diff –git a/misc/tegra194-mb1-bct-misc.cfg b/misc/tegra194-mb1-bct-misc.cfg @@ -105,8 +105,8 @@ aocluster.evp_reset_addr = 0xc480000; enable_sce = 0; enable_rce = 1; enable_ape = 1; -enable_combined_uart = 1; -spe_uart_instance = 2; +enable_combined_uart = 0; +spe_uart_instance = 0xff;（2）更新设备树禁用组合UART
+ serial@c280000 { + compatible = “nvidia,tegra20-uart”; + clock-frequency = <0x18519600>; + console-port; + status = “okay”; + /delete-property/ resets; + /delete-property/ reset-names; + }; + serial@3140000 { compatible = “nvidia,tegra186-hsuart”; status = “okay”; diff –git a/common/tegra194-p2888-0001-p2822-0000-common.dtsi b/common/tegra194-p2888-0001-p2822-0000-common.dtsi @@ -34,7 +34,8 @@ compatible = “nvidia,galen”, “nvidia,jetson-xavier”, “nvidia,p2822-0000+p2888-0001”, “nvidia,tegra194″; chosen { – bootargs =”console=ttyTCU0,115200″; + bootargs =”console=ttyS2,115200 earlycon=uart8250,mmio32,0x0c280000”; + stdout-path = &uartc; board-has-eeprom; };（3）内核命令行禁用组合UART
diff –git a/scripts/board_config/p2972-0000.conf.common b/scripts/board_config/p2972-0000.conf.common ROOTFSSIZE=28GiB; – CMDLINE_ADD=”console=ttyTCU0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 rootfstype=ext4″; + CMDLINE_ADD=”console=ttyS2,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 rootfstype=ext4″;（4）将bpmp-dtb文件反汇编为文本进行修改
diff –git a/include/platforms/bpmp-p2888-a01.dtsi b/include/platforms/bpmp-p2888-a01.dtsi @@ -6,7 +6,7 @@ #include “parts/uphy/tegra194-bpmp-p2888-uphy.dtsi” #include “parts/emc-strap/emc-p2888.dtsi” #include “parts/i2c/cvm-i2c-common.dtsi” -#include “parts/policy/serial-3-comb-uart.dtsi” +#include “parts/policy/serial-2-input.dtsi” #include “parts/policy/mail-common.dtsi” diff –git a/include/platforms/bpmp-p2888-a02.dtsi b/include/platforms/bpmp-p2888-a02.dtsi @@ -6,7 +6,7 @@ #include “parts/uphy/tegra194-bpmp-p2888-uphy.dtsi” #include “parts/emc-strap/emc-p2888.dtsi” #include “parts/i2c/cvm-i2c-common.dtsi” -#include “parts/policy/serial-3-comb-uart.dtsi” +#include “parts/policy/serial-2-input.dtsi” #include “parts/policy/mail-common.dtsi” diff –git a/include/platforms/bpmp-p2888-a04.dtsi b/include/platforms/bpmp-p2888-a04.dtsi @@ -6,7 +6,7 @@ #include “parts/uphy/tegra194-bpmp-p2888-uphy.dtsi” #include “parts/emc-strap/emc-p2888.dtsi” #include “parts/i2c/cvm-i2c-common.dtsi” -#include “parts/policy/serial-3-comb-uart.dtsi” +#include “parts/policy/serial-2-input.dtsi” #include “parts/policy/mail-common.dtsi”这个解决方案是为Xavier 试图将上述解决方案合并到Xavier NX (tegra194-p3509-0000-a00.dtsi, tegra194-p3668-common.dtsi, tegra194-mb1-bct-misc-l4t.cfg, tegra194-mb1-bct-misc-flash.cfg)
3. bpmp-dtb文件修改这是配置BPMP固件禁用联合UART， 下面是将DTB文件反汇编为文本文件的命令， 例如
$ dtc -I dtb -O dts -o temp.dts tegra.dtb可以从bpmp-dtb blob中排除下面的内容来禁用它
serial { port = <0x3>; has_input; combined-uart { enabled; }; };可以包括下面的添加串行2输入
/ { serial { port = <2>; has_input; };执行命令将其转换为另一个新的DTB文件进行验证， 例如,
$ dtc -I dts -O dtb -o new-output.dtb temp.dts按照上述流程执行 但Xavier Nx仍然卡在Init内核中
[ 0.000000] Booting Linux on physical CPU 0x0 [ 0.000000] Linux version 4.9.140 (user@user-HP-EliteDesk-800-G4-TWR) (gcc v0 [ 0.000000] Boot CPU: AArch64 Processor [4e0f0040] [ 0.000000] OF: fdt:memory scan node memory, reg size 48, [ 0.000000] OF: fdt: – 80000000 , 2c000000 [ 0.000000] OF: fdt: – ac200000 , 44600000 [ 0.000000] OF: fdt: – 100000000 , 180000000 [ 0.000000] earlycon: uart8250 at MMIO32 0x000000000c280000 (options ‘’) [ 0.000000] bootconsole [uart8250] enabled [ 0.000000] Found tegra_fbmem: 00140000@a069c000 [ 0.000000] Found lut_mem: 00002008@a0696000卡住地方与添加到设备树地址0x000000000c280000的UART相关。
4. 修改p3668.conf.common更新NX平台配置文件p3668.conf.common 可以参考jetson-xavier-nx-devkit.conf获取其配置文件 例如,
source “${LDK_DIR}/p3668.conf.common”; 5. 总结Jetson Xavier NX将三个uart带出主连接器; 有3个uart可用，UART0到M2;UART1 40-PIN;UART2调试。 可以访问NX产品设计指南，并检查Xavier NX uart引脚描述。 修改misc配置文件，告诉引导加载程序不要使用调试UART， 如果使用其他uart#作为调试UART 应该更改内核dts中的值也为bootparam和串行节点作为当前UART0。
