linux-kernel - [PATCH 3.19.y-ckt 056/251] tty/serial: at91: RS485 mode: 0 is valid for delay_rts_after

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Message-Id: <1437008972-9140-57-git-send-email-kamal@canonical.com>
Date:	Wed, 15 Jul 2015 18:06:17 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 056/251] tty/serial: at91: RS485 mode: 0 is valid for delay_rts_after_send

3.19.8-ckt4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nicolas Ferre <nicolas.ferre@...el.com>

commit 8687634b7908c42eb700e0469e110e02833611d1 upstream.

In RS485 mode, we may want to set the delay_rts_after_send value to 0.
In the datasheet, the 0 value is said to "disable" the Transmitter Timeguard but
this is exactly the expected behavior if we want no delay...

Moreover, if the value was set to non-zero value by device-tree or earlier
ioctl command, it was impossible to change it back to zero.

Reported-by: Sami Pietikäinen <Sami.Pietikainen@...ice.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[ kamal: backport to 3.19-stable: context ]
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/tty/serial/atmel_serial.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index 95f8f64..1ce085a 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -308,8 +308,7 @@ static int atmel_config_rs485(struct uart_port *port,
 	if (rs485conf->flags & SER_RS485_ENABLED) {
 		dev_dbg(port->dev, "Setting UART to RS485\n");
 		atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
-		if ((rs485conf->delay_rts_after_send) > 0)
-			UART_PUT_TTGR(port, rs485conf->delay_rts_after_send);
+		UART_PUT_TTGR(port, rs485conf->delay_rts_after_send);
 		mode |= ATMEL_US_USMODE_RS485;
 	} else {
 		dev_dbg(port->dev, "Setting UART to RS232\n");
@@ -370,8 +369,7 @@ static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
 
 	if (port->rs485.flags & SER_RS485_ENABLED) {
 		dev_dbg(port->dev, "Setting UART to RS485\n");
-		if ((port->rs485.delay_rts_after_send) > 0)
-			UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
+		UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
 		mode |= ATMEL_US_USMODE_RS485;
 	} else {
 		dev_dbg(port->dev, "Setting UART to RS232\n");
@@ -2026,8 +2024,7 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 	mode &= ~ATMEL_US_USMODE;
 
 	if (port->rs485.flags & SER_RS485_ENABLED) {
-		if ((port->rs485.delay_rts_after_send) > 0)
-			UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
+		UART_PUT_TTGR(port, port->rs485.delay_rts_after_send);
 		mode |= ATMEL_US_USMODE_RS485;
 	}
 
-- 
1.9.1

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