linux-kernel - [PATCH v2] tty/serial/8250: fix RS485 half-duplex RX

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Message-Id: <1458806625-29300-1-git-send-email-yegorslists@googlemail.com>
Date:	Thu, 24 Mar 2016 09:03:45 +0100
From:	yegorslists@...glemail.com
To:	linux-serial@...r.kernel.org
Cc:	gregkh@...uxfoundation.org, peter@...leysoftware.com,
	bigeasy@...utronix.de, linux-kernel@...r.kernel.org,
	u.kleine-koenig@...gutronix.de,
	Yegor Yefremov <yegorslists@...glemail.com>,
	"Matwey V. Kornilov" <matwey@....msu.ru>
Subject: [PATCH v2] tty/serial/8250: fix RS485 half-duplex RX

From: Yegor Yefremov <yegorslists@...glemail.com>

When in half-duplex mode RX will be disabled before TX, but not
enabled after deactivating transmitter. This patch enables
UART_IER_RLSI and UART_IER_RDI interrupts after TX is over.

Cc: Matwey V. Kornilov <matwey@....msu.ru>
Signed-off-by: Yegor Yefremov <yegorslists@...glemail.com>
Fixes: e490c9144cfa ("tty: Add software emulated RS485 support for 8250")
---
Changes:
	v2: change subject and add 'Fixes' tag

 drivers/tty/serial/8250/8250_port.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index e213da0..00ad263 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1403,9 +1403,18 @@ static void __do_stop_tx_rs485(struct uart_8250_port *p)
 	/*
 	 * Empty the RX FIFO, we are not interested in anything
 	 * received during the half-duplex transmission.
+	 * Enable previously disabled RX interrupts.
 	 */
-	if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX))
+	if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) {
 		serial8250_clear_fifos(p);
+
+		serial8250_rpm_get(p);
+
+		p->ier |= UART_IER_RLSI | UART_IER_RDI;
+		serial_port_out(&p->port, UART_IER, p->ier);
+
+		serial8250_rpm_put(p);
+	}
 }
 
 static void serial8250_em485_handle_stop_tx(unsigned long arg)
-- 
2.1.4