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From:   Giulio Benetti <giulio.benetti@micronovasrl.com>
Cc:     matwey.kornilov@gmail.com,
        Giulio Benetti <giulio.benetti@micronovasrl.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>, Ed Blake <ed.blake@sondrel.com>,
        Joshua Scott <joshua.scott@alliedtelesis.co.nz>,
        linux-serial@vger.kernel.org (open list:SERIAL DRIVERS),
        linux-kernel@vger.kernel.org (open list)
Subject: [PATCH 1/4] serial: 8250_dw: add em485 support
Date:   Wed,  6 Jun 2018 11:51:54 +0200
Message-Id: <20180606095156.72628-4-giulio.benetti@micronovasrl.com>
In-Reply-To: <20180606095156.72628-1-giulio.benetti@micronovasrl.com>
References: <CAJs94EZqdQAQG+inWvj89FCQtv06LxhY_J4YgNmK8mtvgDTchQ@mail.gmail.com>
 <20180606095156.72628-1-giulio.benetti@micronovasrl.com>
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Need to use rs485 transceiver so let's use existing em485 485 emulation
layer on top of 8250.

Add rs485_config callback to port.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
---
 drivers/tty/serial/8250/8250_dw.c | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 6fcdb90f616a..45366e6e5411 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -314,6 +314,36 @@ static void dw8250_set_ldisc(struct uart_port *p, struct ktermios *termios)
 	serial8250_do_set_ldisc(p, termios);
 }
 
+static int dw8250_rs485_config(struct uart_port *p,
+			       struct serial_rs485 *rs485)
+{
+	struct uart_8250_port *up = up_to_u8250p(p);
+
+	/* 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);
+
+	p->rs485 = *rs485;
+
+	/*
+	 * Both serial8250_em485_init and serial8250_em485_destroy
+	 * are idempotent
+	 */
+	if (rs485->flags & SER_RS485_ENABLED) {
+		int ret = serial8250_em485_init(up);
+
+		if (ret) {
+			rs485->flags &= ~SER_RS485_ENABLED;
+			p->rs485.flags &= ~SER_RS485_ENABLED;
+		}
+		return ret;
+	}
+
+	serial8250_em485_destroy(up);
+
+	return 0;
+}
+
 /*
  * dw8250_fallback_dma_filter will prevent the UART from getting just any free
  * channel on platforms that have DMA engines, but don't have any channels
@@ -449,6 +479,7 @@ static int dw8250_probe(struct platform_device *pdev)
 	p->serial_out	= dw8250_serial_out;
 	p->set_ldisc	= dw8250_set_ldisc;
 	p->set_termios	= dw8250_set_termios;
+	p->rs485_config = dw8250_rs485_config;
 
 	p->membase = devm_ioremap(dev, regs->start, resource_size(regs));
 	if (!p->membase)
-- 
2.17.1