I recently experienced some trouble with setting up an encrypted-root
system, my Chromebook Plus (rk3399-gru-kevin, ARM64) would appear to
hang where it should have asked for an encryption passphrase; and I
eventually figured out that the kernel preferred the serial port
(inaccessible to me) over the built-in working display/keyboard and was
probably asking there.
Running plymouth in the initramfs solves that specific problem, but
both the documentation and tty-related kconfig descriptions imply that
/dev/console should be tty0 if graphics are working, CONFIG_VT_CONSOLE
is enabled and no explicit console argument is given in the kernel
commandline.
However, I'm seeing different behaviour on systems with SPCR (as in QEMU
aarch64 virtual machines) and/or a device-tree chosen stdout-path node
(as in most arm/arm64 devices). On these machines, depending on the
console argument, the contents of the /proc/consoles file are:
| "console=tty0" | (no console arg) |
------------------+-----------------------+-----------------------+
QEMU VM | tty0 -WU (EC p ) | ttyAMA0 -W- (EC a) |
(w/ SPCR) | ttyAMA0 -W- (E a) | |
------------------+-----------------------+-----------------------+
Chromebook Plus | tty0 -WU (EC p ) | ttyS2 -W- (EC p a) |
(w/ stdout-path) | | tty0 -WU (E ) |
------------------+-----------------------+-----------------------+
Chromebook Plus | tty0 -WU (EC p ) | tty0 -WU (EC p ) |
(w/o either) | | |
------------------+-----------------------+-----------------------+
This patchset tries to ensure that VT is preferred in those conditions
even in the presence of firmware-mandated serial consoles. These should
cleanly apply onto next-20200430.
More discussion due to or about the console confusion on ARM64:
- My Debian bug report about the initramfs prompts [0]
- Fedora test issue arising from ARM64 QEMU machines having SPCR [1]
- Debian-installer discussion on what to do with multiple consoles [2]
[0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=952452
[1] https://bugzilla.redhat.com/show_bug.cgi?id=1661288
[2] https://lists.debian.org/debian-boot/2019/01/msg00184.html
Changes in v2:
- Fix #elif to #else (Reported-by: kbuild test robot <lkp@xxxxxxxxx>)
- Refresh dmesg outputs with/without earlycon for next-20200430
- Use the correct format when referencing a commit
Alper Nebi Yasak (3):
printk: Add function to set console to preferred console's driver
vt: Set as preferred console when a non-dummy backend is bound
printk: Preset tty0 as a pseudo-preferred console
drivers/tty/vt/vt.c | 7 +++++
include/linux/console.h | 1 +
kernel/printk/printk.c | 68 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 76 insertions(+)
--
2.26.2
