1 files changed, 22 insertions, 4 deletions

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index fd8aa1f4ba78..168b10cad47b 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2132,11 +2132,29 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
                 mode |= ATMEL_US_USMODE_RS485;
         } else if (termios->c_cflag & CRTSCTS) {
                 /* RS232 with hardware handshake (RTS/CTS) */
-                if (atmel_use_dma_rx(port) && !atmel_use_fifo(port)) {
-                        dev_info(port->dev, "not enabling hardware flow control because DMA is used");
-                        termios->c_cflag &= ~CRTSCTS;
-                } else {
+                if (atmel_use_fifo(port) &&
+                    !mctrl_gpio_to_gpiod(atmel_port->gpios, UART_GPIO_CTS)) {
+                        /*
+                         * with ATMEL_US_USMODE_HWHS set, the controller will
+                         * be able to drive the RTS pin high/low when the RX
+                         * FIFO is above RXFTHRES/below RXFTHRES2.
+                         * It will also disable the transmitter when the CTS
+                         * pin is high.
+                         * This mode is not activated if CTS pin is a GPIO
+                         * because in this case, the transmitter is always
+                         * disabled (there must be an internal pull-up
+                         * responsible for this behaviour).
+                         * If the RTS pin is a GPIO, the controller won't be
+                         * able to drive it according to the FIFO thresholds,
+                         * but it will be handled by the driver.
+                         */
                         mode |= ATMEL_US_USMODE_HWHS;
+                } else {
+                        /*
+                         * For platforms without FIFO, the flow control is
+                         * handled by the driver.
+                         */
+                        mode |= ATMEL_US_USMODE_NORMAL;
                 }
         } else {
                 /* RS232 without hadware handshake */