Re: BeagleBone Black doesn't boot without serial console (10.0 release)

[Martin Husemann <martin%duskware.de@localhost>]

On Sun, Oct 13, 2024 at 04:01:22PM +0200, Dr. Nicola Mingotti wrote:
> I don't see the need to call the debugger when a com is connected, but
> I know nothing of kernel debugging/programming so this may be useful to
> somebody else.

No, you are misunderstanding. There are two points:

 1) The kernel debugger is invoked when the serial port senses a BRK
    condition on the port. This is important for everyone when debugging
    a kernel. The change manuel porposed is one way to change this,
    another (a lot better) change is to use options CNMAGIC to customize
    this signal for your own kernel (e.g. use options CNMAGIC="\"+++++\"").

    This is something we do not want to change for the default kernels.

 2) Some hardware generates a bogus BRK condition when the serial connector
    is removed or pluged in. This can be fixed at the hardware level
    via pull-up resistors, but a lot easier is to (localy) work around
    it by just configuring a different CNMAGIC.

    If you system boots up automatically and you don't need serial console
    untill you reach userland, you can configure this (besides custom
    kernel aproaches from (1)) via setting hw.cnmagic in /etc/sysctl.conf

    This way you do not need a customized kernel and the change is still
    local to your setup.


Martin