patch "tty/serial: atmel: fix hardware handshake selection" added to tty-next

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    tty/serial: atmel: fix hardware handshake selection

to my tty git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From 5be605ac9af979265d7b64c160ad9928088a78be Mon Sep 17 00:00:00 2001
From: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Date: Tue, 12 Apr 2016 14:51:40 +0200
Subject: tty/serial: atmel: fix hardware handshake selection

Commit 1cf6e8fc8341 ("tty/serial: at91: fix RTS line management when
hardware handshake is enabled") actually allowed to enable hardware
handshaking.
Before, the CRTSCTS flags was silently ignored.

As the DMA controller can't drive RTS (as explain in the commit message).
Ensure that hardware flow control stays disabled when DMA is used and FIFOs
are not available.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Fixes: 1cf6e8fc8341 ("tty/serial: at91: fix RTS line management when hardware handshake is enabled")
Cc: stable <stable@vger.kernel.org> # v4.0+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tty/serial/atmel_serial.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index d9439e6ab719..954941dd8124 100644
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -274,6 +274,13 @@ static bool atmel_use_dma_rx(struct uart_port *port)
 	return atmel_port->use_dma_rx;
 }
 
+static bool atmel_use_fifo(struct uart_port *port)
+{
+	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
+
+	return atmel_port->fifo_size;
+}
+
 static unsigned int atmel_get_lines_status(struct uart_port *port)
 {
 	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
@@ -2090,7 +2097,12 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
 		mode |= ATMEL_US_USMODE_RS485;
 	} else if (termios->c_cflag & CRTSCTS) {
 		/* RS232 with hardware handshake (RTS/CTS) */
-		mode |= ATMEL_US_USMODE_HWHS;
+		if (atmel_use_dma_rx(port) && !atmel_use_fifo(port)) {
+			dev_info(port->dev, "not enabling hardware flow control because DMA is used");
+			termios->c_cflag &= ~CRTSCTS;
+		} else {
+			mode |= ATMEL_US_USMODE_HWHS;
+		}
 	} else {
 		/* RS232 without hadware handshake */
 		mode |= ATMEL_US_USMODE_NORMAL;
-- 
2.8.0