kern/59914: DesignWare APB UART: can't break into ddb from serial console

["martin%NetBSD.org@localhost via gnats" <gnats-admin%NetBSD.org@localhost>]

>Number:         59914
>Category:       kern
>Synopsis:       DesignWare APB UART: can't break into ddb from serial console
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 13 11:55:00 +0000 2026
>Originator:     Martin Husemann
>Release:        NetBSD 11.99.4
>Organization:
The NetBSD Foundation, Inc.
>Environment:
System: NetBSD space-truckin.duskware.de 11.99.4 NetBSD 11.99.4 (GENERIC) #438: Tue Jan 13 12:16:32 CET 2026 martin%seven-days-to-the-wolves.aprisoft.de@localhost:/work/src/sys/arch/evbarm/compile/GENERIC evbarm
Architecture: earmv7hfeb
Machine: evbarm
>Description:

I can't break into ddb from my serial console, despite hw.cnmagic being
correct (hw.cnmagic = \x27\x01). The kernel just ignores the BRK input.

Works for me on other com hardware.

com0 at simplebus1: DesignWare APB UART, 64-byte FIFO
com0: console
com0: interrupting on GIC irq 33


>How-To-Repeat:

Boot a cubietruck with serial console, try to break into ddb.

>Fix:
n/a