Getting the kernel to let go of my UART!

[Dustin Marquess]

On Sunday, January 22, 2017, Hans Petter Selasky <hps at selasky.org> wrote:

> On 01/22/17 06:07, Dustin Marquess wrote:
>
>> [Sorry if this is somewhat of a dupe, I have yet to find a solution]
>>
>> I've been running FreeBSD on my Pi 3s for a little over a month now,
>> first using gonzo's SMP code + a home cross-compiled kernel, and then
>> I moved to the HardenedBSD images.  All of them work great except one
>> issue that's driving me nuts...
>>
>> The downside to the Pi 3 vs some other boards is that there's really
>> only one UART tied to the GPIO pins.  I'm trying to feed my Pi 3 with
>> a GPS board.
>>
>> 1st issue: The NMEA stream upsets U-boot.  Fine, compiled my own and
>> that's "fixed".
>>
>> 2nd issue: Even with a USB keyboard attached and HDMI output
>> connected, FreeBSD still wants to steal the first uart (ttyu0) as a
>> console port.  I thought that would be fine as long as I use "-m -n
>> -q" in the boot config to disable kernel output and then "conscontrol
>> delete ttyu0".  Well, that KIND of works.  It seems to work fine when
>> using 115200bps, but trying to change the baud rate to match the GPS
>> unit doesn't seem to work at all, I'm guessing because it's still set
>> as an available console?
>>
>> hint.uart.0.flags="0x0" doesn't work, as it still marks it as a
>> console.  console="efi" seems to be the only setting that works,
>> "vidconsole" and "nullconsole" both don't work.
>>
>> Is there a way to stop the kernel from trying to claim the UART as a
>> console?
>>
>
> I think so, have a look in /etc/ttys and comment out the ttyu0 line.
>
> Sadly, I already did that. There's no getty running, but dmesg still shows
the kernel marking it as a console.

-Dustin