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| author | Daniel Jedrychowski <avistel@gmail.com> | 2016-12-11 22:18:28 (GMT) |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-01-19 19:18:03 (GMT) |
| commit | eca02f01be96d2ced5b2314dc4462c32e4ad0366 (patch) | |
| tree | 93d6d0ff822a966fb52ba8dbcb72fd174c8bb9b2 | |
| parent | 86820a103f517f8d51a09ceacac30bde355f4e89 (diff) | |
| download | linux-eca02f01be96d2ced5b2314dc4462c32e4ad0366.tar.xz | |
Clearing FIFOs in RS485 emulation mode causes subsequent transmits to break
commit 2bed8a8e70729f996af92042d3ad0f11870acc1f upstream.
When in RS485 emulation mode, __do_stop_tx_rs485() calls
serial8250_clear_fifos(). This not only clears the FIFOs, but also sets
all bits in their control register (UART_FCR) to 0.
One of the effects of this is the disabling of the FIFOs, which turns
them into single-byte holding registers. The rest of the driver doesn't
know this, which results in the lions share of characters passed into a
write call to be dropped.
(I can supply logic analyzer screenshots if necessary)
This fix replaces the serial8250_clear_fifos() call to
serial8250_clear_and_reinit_fifos() - this prevents the "dropped
characters" issue from manifesting again while retaining the requirement
of clearing the RX FIFO after transmission if the SER_RS485_RX_DURING_TX
flag is disabled.
Signed-off-by: Daniel Jedrychowski <avistel@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/8250/8250_port.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 1731b98..080d5a5 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1411,7 +1411,7 @@ static void __do_stop_tx_rs485(struct uart_8250_port *p) * Enable previously disabled RX interrupts. */ if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) { - serial8250_clear_fifos(p); + serial8250_clear_and_reinit_fifos(p); p->ier |= UART_IER_RLSI | UART_IER_RDI; serial_port_out(&p->port, UART_IER, p->ier); |