How to enable the console in upstream Linux kernel 6.1

jetm · December 12, 2023, 7:31pm

Hi,

I have a RockPi 4 Plus V1.72. How do I enable the console to consequently reach the login prompt?

I am able to boot it in OpenWrt with the upstream Linux kernel 6.1. I get kernel output through a USB <-> Serial port adapter connected to GPIO pins 6/8/10.

This is the inittab configuration:

root@OpenWrt:/# cat /etc/inittab                                                                                               
::sysinit:/etc/init.d/rcS S boot                                                                                               
::shutdown:/etc/init.d/rcS K shutdown                                                                                          
ttyAMA0::askfirst:/usr/libexec/login.sh                                                                                        
ttyS0::askfirst:/usr/libexec/login.sh                                                                                          
tty0::askfirst:/usr/libexec/login.sh                                                                                           
hvc0::askfirst:/usr/libexec/login.sh                                                                                           
ttymxc0::askfirst:/usr/libexec/login.sh                                                                                        
ttymxc1::askfirst:/usr/libexec/login.sh                                                                                        
ttymxc2::askfirst:/usr/libexec/login.sh                                                                                        
ttyPS1::askfirst:/usr/libexec/login.sh                                                                                         
ttyFIQ0::askfirst:/usr/libexec/login.sh

Sharing the kernel output and kernel configuration at

gist.github.com

https://gist.github.com/jetm/91f84baa86db22fe5224afe8d4a4454f

rock-pi-4-rk3399-boot-output.log

EFI stub: Booting Linux Kernel...
EFI stub: EFI_RNG_PROTOCOL unavailable
EFI stub: Using DTB from configuration table
EFI stub: Exiting boot services...
[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd034]
[    0.000000] Linux version 6.1.65 (tiamarin@jetm-rog-x670e-gene) (aarch64-openwrt-linux-musl-gcc (OpenWrt GCC 12.3.0 r24628-
a0effdcb01) 12.3.0, GNU ld (GNU Binutils) 2.40.0) #0 SMP PREEMPT Tue Dec 12 01:39:32 2023
[    0.000000] Machine model: Radxa ROCK Pi 4A
[    0.000000] efi: EFI v2.100 by Das U-Boot
[    0.000000] efi: ESRT=0xf0ed0040 RTPROP=0xf0ed2040 SMBIOS=0xf0ece000 MEMRESERVE=0xf0e94040

This file has been truncated. show original

rock-pi-4-rk3399_defconfig

#
# Automatically generated file; DO NOT EDIT.
# Linux/arm64 6.1.65 Kernel Configuration
#
CONFIG_CC_VERSION_TEXT="aarch64-openwrt-linux-musl-gcc (OpenWrt GCC 12.3.0 r24628-a0effdcb01) 12.3.0"
CONFIG_CC_IS_GCC=y
CONFIG_GCC_VERSION=120300
CONFIG_CLANG_VERSION=0
CONFIG_AS_IS_GNU=y
CONFIG_AS_VERSION=24000

This file has been truncated. show original

I would have submitted the files here, but I am not allowed as I am a new user.

jetm · December 12, 2023, 10:36pm

I am replying to myself for future reference. To enable the console in a Rock Pi 4 serial port, it’s required to add CONFIG_KGDB to the kernel config, which enables CONFIG_KGDB_SERIAL_CONSOLE and then add ttyS2::askfirst:/usr/libexec/login.sh.