linux-kernel - [PATCH 2/3] serial: st-asc: Provide RTS functionality

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Date:   Fri,  2 Dec 2016 14:11:45 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     gregkh@...uxfoundation.org, jslaby@...e.com, patrice.chotard@...com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel@...inux.com, linux-serial@...r.kernel.org,
        Lee Jones <lee.jones@...aro.org>
Subject: [PATCH 2/3] serial: st-asc: Provide RTS functionality

Until this point, it has not been possible for serial applications
to toggle the UART RTS line.  This can be useful with certain
configurations. For example, when using a Mezzanine on a Linaro
96board, RTS line is used to take the the on-board microcontroller
in and out of reset.

Signed-off-by: Lee Jones <lee.jones@...aro.org>
---
 drivers/tty/serial/st-asc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/tty/serial/st-asc.c b/drivers/tty/serial/st-asc.c
index 379e5bd..ce46898 100644
--- a/drivers/tty/serial/st-asc.c
+++ b/drivers/tty/serial/st-asc.c
@@ -30,6 +30,7 @@
 #include <linux/of_platform.h>
 #include <linux/serial_core.h>
 #include <linux/clk.h>
+#include <linux/gpio/consumer.h>
 
 #define DRIVER_NAME "st-asc"
 #define ASC_SERIAL_NAME "ttyAS"
@@ -38,6 +39,7 @@
 
 struct asc_port {
 	struct uart_port port;
+	struct gpio_desc *rts;
 	struct clk *clk;
 	unsigned int hw_flow_control:1;
 	unsigned int force_m1:1;
@@ -381,12 +383,16 @@ static unsigned int asc_tx_empty(struct uart_port *port)
 
 static void asc_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
+	struct asc_port *ascport = to_asc_port(port);
+
 	/*
 	 * This routine is used for seting signals of: DTR, DCD, CTS/RTS
 	 * We use ASC's hardware for CTS/RTS, so don't need any for that.
 	 * Some boards have DTR and DCD implemented using PIO pins,
 	 * code to do this should be hooked in here.
 	 */
+
+	gpiod_set_value(ascport->rts, mctrl & TIOCM_RTS);
 }
 
 static unsigned int asc_get_mctrl(struct uart_port *port)
@@ -731,12 +737,20 @@ MODULE_DEVICE_TABLE(of, asc_match);
 static int asc_serial_probe(struct platform_device *pdev)
 {
 	int ret;
+	struct device_node *np = pdev->dev.of_node;
 	struct asc_port *ascport;
+	struct gpio_desc *gpiod;
 
 	ascport = asc_of_get_asc_port(pdev);
 	if (!ascport)
 		return -ENODEV;
 
+	gpiod = devm_get_gpiod_from_child(&pdev->dev, "rts", &np->fwnode);
+	if (!IS_ERR(gpiod)) {
+		gpiod_direction_output(gpiod, 0);
+		ascport->rts = gpiod;
+	}
+
 	ret = asc_init_port(ascport, pdev);
 	if (ret)
 		return ret;
-- 
2.10.2