From: satishc@microsoft.com (Satish Chittamuru)
   Date: 25 Aug 92 02:11:42 GMT

    > Does anyone else have problems with Linux not correctly "shutting down"
    > the 16550?  Ever since the kernel has supported a 16550, I have had to
    > hard reset the computer after running linux, or it seems that the
    > computer "forgets" that the port that contains the 16550, exists.

   I have always had this problem. I usually just hard reboot if I need
   to use the modem again. Would be nice if this could be fixed.

If you do a soft reboot back into Linux, does it also lose the 16550?
Or is it only DOS/OS2 which can't find the 16550 after you boot Linux?
If it's the problem I think it is, it would seem to me to be awfully
non-robust of DOS not to be able to deal with a 16550A that has had FIFO
enabled.  You'd either MS-DOS or the BIOS would send the FIFO disable
sequence to a UART before trying to use it.

Once I have time to recover from moving to a new apartment, I'll make
changes to the version of the serial driver I've been working on to
shutdown the 16550A FIFO's upon device close, instead of leaving the
FIFO's enabled the whole time.  I think this should fix the problem.

                                                - Ted