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@xxxxxxxxx>
---
drivers/tty/serial/8250/8250_port.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
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);
--
2.7.4
--
To unsubscribe from this list: send the line "unsubscribe linux-serial" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
