serial: mxs-auart: use mctrl_gpio helpers for handling modem signals

Dedicated CTS and RTS pins are unusable together with a lot of other
peripherals because they share the same line. Pinctrl is limited.

Moreover, the AUART controller doesn't handle DTR/DSR/DCD/RI signals,
so we have to control them via GPIO.

This patch permits to use GPIOs to control the CTS/RTS/DTR/DSR/DCD/RI
signals.

Signed-off-by: Janusz Uzycki <j.uzycki@elproma.com.pl>
Reviewed-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
index 59a40f18d551..7c408c87e613 100644
--- a/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
+++ b/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
@@ -11,8 +11,13 @@ Required properties:
 - dma-names: "rx" for RX channel, "tx" for TX channel.
 
 Optional properties:
-- fsl,uart-has-rtscts : Indicate the UART has RTS and CTS lines,
+- fsl,uart-has-rtscts : Indicate the UART has RTS and CTS lines
+  for hardware flow control,
         it also means you enable the DMA support for this UART.
+- {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD
+  line respectively. It will use specified PIO instead of the peripheral
+  function pin for the USART feature.
+  If unsure, don't specify this property.
 
 Example:
 auart0: serial@8006a000 {
@@ -21,6 +26,9 @@ auart0: serial@8006a000 {
         interrupts = <112>;
         dmas = <&dma_apbx 8>, <&dma_apbx 9>;
         dma-names = "rx", "tx";
+        cts-gpios = <&gpio1 15 GPIO_ACTIVE_LOW>;
+        dsr-gpios = <&gpio1 16 GPIO_ACTIVE_LOW>;
+        dcd-gpios = <&gpio1 17 GPIO_ACTIVE_LOW>;
 };
 
 Note: Each auart port should have an alias correctly numbered in "aliases"