Merge tag 'driver-core-4.9-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git...

[cascardo/linux.git] / drivers / tty / serial / atmel_serial.c

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index fd8aa1f..168b10c 100644 (file)
--- 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 */