From 5be605ac9af979265d7b64c160ad9928088a78be Mon Sep 17 00:00:00 2001 From: Alexandre Belloni Date: Tue, 12 Apr 2016 14:51:40 +0200 Subject: [PATCH] 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 Acked-by: Nicolas Ferre Fixes: 1cf6e8fc8341 ("tty/serial: at91: fix RTS line management when hardware handshake is enabled") Cc: stable # v4.0+ Signed-off-by: Greg Kroah-Hartman --- 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 d9439e6..954941d 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; -- 2.7.4