tty/serial/8250: fix RS485 half-duplex RX

When in half-duplex mode RX will be disabled before TX, but not
enabled after deactivating transmitter. This patch enables
UART_IER_RLSI and UART_IER_RDI interrupts after TX is over.

Cc: Matwey V. Kornilov <matwey@sai.msu.ru>
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Fixes: e490c9144cfa ("tty: Add software emulated RS485 support for 8250")
Acked-by: Matwey V. Kornilov <matwey@sai.msu.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 1 deletions

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index e213da01a3d7..00ad2637b08c 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1403,9 +1403,18 @@ static void __do_stop_tx_rs485(struct uart_8250_port *p)
         /*
          * Empty the RX FIFO, we are not interested in anything
          * received during the half-duplex transmission.
+         * Enable previously disabled RX interrupts.
          */
-        if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX))
+        if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
                 serial8250_clear_fifos(p);
+
+                serial8250_rpm_get(p);
+
+                p->ier |= UART_IER_RLSI | UART_IER_RDI;
+                serial_port_out(&p->port, UART_IER, p->ier);
+
+                serial8250_rpm_put(p);
+        }
 }
 
 static void serial8250_em485_handle_stop_tx(unsigned long arg)