r220's with serial

Paul Macdonald paul at ifdnrg.com
Tue Jul 21 18:34:04 UTC 2015

On 09/06/2015 20:23, Paul Macdonald wrote:
> has anyone managed to get serial console access working under dell 
> r220's.

This was due to an ACPI bug in r220's

Marcel Moolenaar provided me with a fix which is:


Serial Communication <On with Console Redirection via COM2>
Serial Port Address <Serial Device1=COM2,Serial Device2=COM1>
External Serial Connector <Serial Device 1>


adding the following line to /boot/loader.conf:


 From the looks of it, you have a BIOS bug. In particular a bug in the 
ACPI AML (you can dump the ACPI AML with acpidump -d). If I understand 
it correctly then the first 2 serial devices (UAR1 and UAR2) have the 
same H/W registers. What this boils down to is that the kernel only 
works with 1 serial port (UAR1), which ends up having the H/W 
configuration of the second serial port (UAR2).

With the BIOS redirecting to COM1 (which is H/W address 0x3f8) and 
serial device 1 assigned to COM1 *and* serial device assigned to the 
serial port on the chassis, the kernel had no chance to present a login 

I worked around the problem by reconfiguring the BIOS so that COM2 
(which is H/W address 0x2f8) is assigned to serial port 1 and the BIOS 
redirecting to COM2. What this does is have COM2 connected to the serial 
port on the chassis.

So, even though I suspect that the kernel thinks it’s talking to the 
first serial port, it’s actually talking to the second serial port (due 
to the ACPI/BIOS bus).


Paul Macdonald
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