Serial console only works after reboot?

[Nate Lawson]

On Sun, 4 Jan 2004, M. Warner Losh wrote:
> In message: <20040103233044.N17367 at root.org>
>             Nate Lawson <nate at root.org> writes:
> : On Sat, 3 Jan 2004, M. Warner Losh wrote:
> : > In message: <20040103184934.V16815 at root.org>
> : >             Nate Lawson <nate at root.org> writes:
> : > : I have a laptop (IBM T23) and use sio0 as my console/gdb port.  One thing
> : > : I noticed is if I power up the laptop and boot -h, I get garbage out the
> : > : serial port.  However, if I boot fully and then just warm reboot, the
> : > : serial console works fine.  I'm only using 9600 bps.  Ideas?
> : >
> : > weird.  Is the garbage data at some different rate?
> :
> : Nope, checked everything from 1200 up to 38400, different garbage but
> : always garbage.  This is with -current as of 2003/12/30, no patches.
>
> Try 115200.

That works.  Now the question is "why".  Note that I have no "options
CONSPEED" so according to /sys/dev/sio/sioreg.h, it should default to 9600
and indeed does, after a reboot.  But not on a cold startup.

-Nate