Dear Linux folks,


Since a while I noticed, output to the serial console with 
`console=ttyS0,115200n8` does not work with the attached configuration 
`defconfig-non-working-serial.txt` created by `make savedefconfig`. 
Only, when with `earlyprintk=ttyS0,115200,keep` the serial console 
starts working. I am able to reproduce it in QEMU. It’s reproducible 
with Linus’ latest master branch.

     $ git log --oneline --no-decorate -1
     8ab2afa23bd19 Merge tag 'for-5.19/fbdev-1' of 
git://git.kernel.org/pub/scm/linux/kernel/git/deller/linux-fbdev
     $ qemu-system-x86_64 --version
     QEMU emulator version 5.1.0
     Copyright (c) 2003-2020 Fabrice Bellard and the QEMU Project developers
     $ qemu-system-x86_64 -kernel arch/x86/boot/bzImage -append 
"console=ttyS0,115200n8" -serial file:/dev/shm/kernel.txt -curses

With `earlyprintk=` it works:

     $ qemu-system-x86_64 -kernel arch/x86/boot/bzImage -append 
"earlyprintk=serial console=ttyS0,115200n8" -serial 
file:/dev/shm/kernel.txt -curses

Strangely, I found a different configuration, where it works, but I 
didn’t see what configuration option makes the difference.

Can you reproduce the problem with `defconfig-no-working-serial.txt`?


Kind regards,

Paul