Commit 5be605ac authored by Alexandre Belloni's avatar Alexandre Belloni Committed by Greg Kroah-Hartman

tty/serial: atmel: fix hardware handshake selection

Commit 1cf6e8fc ("tty/serial: at91: fix RTS line management when
hardware handshake is enabled") actually allowed to enable hardware
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: default avatarAlexandre Belloni <>
Acked-by: default avatarNicolas Ferre <>
Fixes: 1cf6e8fc ("tty/serial: at91: fix RTS line management when hardware handshake is enabled")
Cc: stable <> # v4.0+
Signed-off-by: default avatarGreg Kroah-Hartman <>
parent d175feca
......@@ -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) */
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 {
} else {
/* RS232 without hadware handshake */
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