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8250.c: less than 2400 baud fix.

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We noticed that we were loosing data at speed less than 2400 baud.
It turned out our (TI16750 compatible) uart with 64 byte outgoing fifo
was truncated to 16 byte (bit 5 sets fifo len) when modifying the fcr
reg.
The input code still fills the buffer with 64 bytes if I remember
correctly and thus data is lost.
Our fix was to remove whiping of the fcr content and just add the
TRIGGER_1 which we want for latency.
I can't see why this would not work on less than 2400 always, for all
uarts ...
Otherwise one would have to make sure the filling of the fifo re-checks
the current state of available fifo size (urrk).

Signed-off-by: Christian Melki <christian.melki@ericsson.se>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christian Melki 2012-04-30 11:21:26 +02:00 committed by Greg Kroah-Hartman
parent aaa10eb1d0
commit f9a9111b54
1 changed files with 5 additions and 4 deletions
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9
drivers/tty/serial/8250/8250.c
View file

@ -2259,10 +2259,11 @@ serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios,
quot++;
if (up->capabilities & UART_CAP_FIFO && port->fifosize > 1) {
if (baud < 2400)
fcr = UART_FCR_ENABLE_FIFO | UART_FCR_TRIGGER_1;
else
fcr = uart_config[port->type].fcr;
fcr = uart_config[port->type].fcr;
if (baud < 2400) {
fcr &= ~UART_FCR_TRIGGER_MASK;
fcr |= UART_FCR_TRIGGER_1;
}
}
/*