[Bug 200744] serial driver issue under dell r220

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=200744

--- Comment #3 from paul at ifdnrg.com ---
This was due to an ACPI bug in r220's

Marcel Moolenaar provided me with a fix which is:

 -BIOS-

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

-FreeBSD-

adding the following line to /boot/loader.conf:
    hw.uart.console="io:0x2f8,br:57600"


.....

>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 prompt.

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).

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