linux-kernel - [PATCH 3.2 010/110] tty/serial: at91: RS485 mode: 0 is valid for delay_rts_after

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Message-ID: <lsq.1439201550.413236715@decadent.org.uk>
Date:	Mon, 10 Aug 2015 12:12:30 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Nicolas Ferre" <nicolas.ferre@...el.com>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
	"Sami Pietikäinen" <Sami.Pietikainen@...ice.com>
Subject: [PATCH 3.2 010/110] tty/serial: at91: RS485 mode: 0 is valid for
 delay_rts_after_send

3.2.71-rc1 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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/tty/serial/atmel_serial.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -229,8 +229,7 @@ void atmel_config_rs485(struct uart_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");
@@ -305,9 +304,7 @@ static void atmel_set_mctrl(struct uart_
 
 	if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
 		dev_dbg(port->dev, "Setting UART to RS485\n");
-		if ((atmel_port->rs485.delay_rts_after_send) > 0)
-			UART_PUT_TTGR(port,
-					atmel_port->rs485.delay_rts_after_send);
+		UART_PUT_TTGR(port, atmel_port->rs485.delay_rts_after_send);
 		mode |= ATMEL_US_USMODE_RS485;
 	} else {
 		dev_dbg(port->dev, "Setting UART to RS232\n");
@@ -1229,9 +1226,7 @@ static void atmel_set_termios(struct uar
 
 	if (atmel_port->rs485.flags & SER_RS485_ENABLED) {
 		dev_dbg(port->dev, "Setting UART to RS485\n");
-		if ((atmel_port->rs485.delay_rts_after_send) > 0)
-			UART_PUT_TTGR(port,
-					atmel_port->rs485.delay_rts_after_send);
+		UART_PUT_TTGR(port, atmel_port->rs485.delay_rts_after_send);
 		mode |= ATMEL_US_USMODE_RS485;
 	} else {
 		dev_dbg(port->dev, "Setting UART to RS232\n");

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