I have a Board which uses a High-speed UART instead of some legacy hardware thats compiled into the kernel. The serial device only gets detected after loading the kernel module intel_lpss_pci. I am on debian "buster" which uses systemd to manage everything-

This means that enabling output and a getty login is not working as expected.

  • console=ttyS0,115200n8 console=tty0 will not cause systemd to open a getty login
  • kernel messages are delayed as well (and incomplete)
  • systemd will open the getty prompt if I manually add the target
  • That target does not work for rescue mode
  • That target does nothing for the init-ramdisk

Workaround for the normal System

I found that manually telling systemd to open a login via getty works: systemctl enable serial-getty@ttyS0.service This still adds some notable delay to displaying the first kernel messages, but I can atleast login.

Adding the module to initramfs (did not help) I added the intel_lpss_pci module to /etc/initramfs-tools/modules, rebuilt the init-ramfs and verified the module was copied there. This did not make a difference

Required behaviour I want the serial console to work (as I don't have a screen), straight from the Ramdisk - without recompiling a kernel. Is there anyone knowledgeable what I am missing? Do I need to add a script to init-ramfs to load this module as early as possible, and if so - how does this work with the initramfs-tools?

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