tty/serial: atmel: fix RS485 half duplex with DMA

commit 0058f0871efe7b01c6f2b3046c68196ab73e96da upstream.

When using DMA, half duplex doesn't work properly because rx is not stopped
before starting tx. Ensure we call atmel_stop_rx() in the DMA case.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16:
 - Adjust context
 - Keep using UART_GET_PTSR()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 0d39ae4ff533201e4050bbedde0e657b14900d33..d806657ca53e4a7b117257b02e1ee5bbce66f2c1 100644 (file)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -434,19 +434,21 @@ static void atmel_start_tx(struct uart_port *port)
 {
        struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
 
-       if (atmel_use_pdc_tx(port)) {
-               if (UART_GET_PTSR(port) & ATMEL_PDC_TXTEN)
-                       /* The transmitter is already running.  Yes, we
-                          really need this.*/
-                       return;
+       if (atmel_use_pdc_tx(port) && (UART_GET_PTSR(port)
+                                      & ATMEL_PDC_TXTEN))
+               /* The transmitter is already running.  Yes, we
+                  really need this.*/
+               return;
 
+       if (atmel_use_pdc_tx(port) || atmel_use_dma_tx(port))
                if ((atmel_port->rs485.flags & SER_RS485_ENABLED) &&
                    !(atmel_port->rs485.flags & SER_RS485_RX_DURING_TX))
                        atmel_stop_rx(port);
 
+       if (atmel_use_pdc_tx(port))
                /* re-enable PDC transmit */
                UART_PUT_PTCR(port, ATMEL_PDC_TXTEN);
-       }
+
        /* Enable interrupts */
        UART_PUT_IER(port, atmel_port->tx_done_mask);
 }