[UART] 8250:RTS/CTS flow control issue.

From: moreau francis
Date: Tue Mar 15 2005 - 11:06:48 EST

I tried to use my serial port with rts/cts flow
control enabled in order to transfer a data file
between 2 DTE. The first one is a PC running Linux
with a 8250 UART and the second one is a developement
board running Linux with a particular UART (I wrote
its driver based on 8250's one).

Actually 8250 UARTs have rts/cts line but they're
managed by software (and then called hw flow control
!!!). Hence when my board's UART (which have a "true"
hw flow control) asserts its RTS line, 8250's UART
sends 8 bytes before stopping TX...
Therefore board's UART fifo have been overrun because
it has only 8 bytes for its fifo.

Does it mean that we can't do any reliable flow
controls with 8250 UART ? In that case a simple
workaround would be to limit tx fifo to 1 byte...



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