linux-kernel - [PATCH v7 3/3] tty: 8250_omap: Use software emulated RS485 direction control

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Date:	Tue, 19 Jan 2016 23:33:17 +0300
From:	"Matwey V. Kornilov" <matwey@....msu.ru>
To:	gregkh@...uxfoundation.org, jslaby@...e.com,
	peter@...leysoftware.com, andy.shevchenko@...il.com,
	gnomes@...rguk.ukuu.org.uk
Cc:	"Matwey V. Kornilov" <matwey@....msu.ru>,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: [PATCH v7 3/3] tty: 8250_omap: Use software emulated RS485 direction control

Use software emulated RS485 direction control to provide RS485 API existed in
omap_serial driver. Note that 8250_omap issues interrupt on shift register
empty which is single prerequesite for using software emulated RS485.

Signed-off-by: Matwey V. Kornilov <matwey@....msu.ru>
---
 drivers/tty/serial/8250/8250_omap.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index a2c0734..31f7905 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -697,6 +697,30 @@ static void omap_8250_throttle(struct uart_port *port)
 	pm_runtime_put_autosuspend(port->dev);
 }
 
+static int omap_8250_rs485_config(struct uart_port *port, struct serial_rs485 *rs485)
+{
+	struct uart_8250_port *up = up_to_u8250p(port);
+
+	/* Clamp the delays to [0, 100ms] */
+	rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
+	rs485->delay_rts_after_send  = min(rs485->delay_rts_after_send, 100U);
+
+	port->rs485 = *rs485;
+
+	/* Both serial8250_em485_* functions are idempotent */
+	if (rs485->flags & SER_RS485_ENABLED) {
+		int ret = serial8250_em485_init(up);
+		if (ret) {
+			rs485->flags &= ~SER_RS485_ENABLED;
+			port->rs485.flags &= ~SER_RS485_ENABLED;
+		}
+		return ret;
+	} else
+		serial8250_em485_destroy(up);
+
+	return 0;
+}
+
 static void omap_8250_unthrottle(struct uart_port *port)
 {
 	unsigned long flags;
@@ -1146,6 +1170,7 @@ static int omap8250_probe(struct platform_device *pdev)
 	up.port.shutdown = omap_8250_shutdown;
 	up.port.throttle = omap_8250_throttle;
 	up.port.unthrottle = omap_8250_unthrottle;
+	up.port.rs485_config = omap_8250_rs485_config;
 
 	if (pdev->dev.of_node) {
 		const struct of_device_id *id;
-- 
2.7.0