On Thu, Jun 02, 2022 at 11:09:15PM +0200, Paul Menzel wrote: > Dear Linux folks, > > > Am 02.06.22 um 18:50 schrieb Paul Menzel: > > > 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`? > > It turns out, the non-working configuration build the serial 8250 driver as > a module (`CONFIG_SERIAL_8250=m`) instead of building it into the Linux > kernel. Building it into the Linux kernel and using > `CONFIG_SERIAL_8250_CONSOLE=y` fixes my issue. That makes sense, you need the console to be able to properly send data out to it :) Was this a Kconfig change somewhere recently that we messed up the defaults for? Any chance you can use 'git bisect' to track down the offending change? thanks, greg k-h
