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Subject[PATCH 3.16 021/346] tty/serial: atmel: fix RS485 half duplex with DMA
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Alexandre Belloni <alexandre.belloni@free-electrons.com>

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>
---
drivers/tty/serial/atmel_serial.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

--- 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_p
{
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);
}
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