How to disable the transmit FIFO?

[Michael Haardt <michael@moria.de>]

Hello,

I miss a way to disable the transmit FIFO.

UARTs that don't do hardware handshaking in hardware, but use a transmit
FIFO, can only be used if the peer can deal with the delayed handshaking
response.

If slow peers can not receive at line rate, hardware handshaking will
still cause overruns with Linux as sender, because Linux fills the
transmit FIFO and transmission continues at worst for 16 characters with
a 16550 after CTS was asserted.

So, how can I fix hardware flow control response to the non-delayed
behaviour as it worked with a 8250 or 16450 by disabling the transmit
FIFO?

Michael