imx_uart_set_mctrl() happened to set UCR2_CTSC bit whenever TIOCM_RTS was set, no matter if RTS/CTS handshake is enabled or not. Now fixed by turning handshake on only when CRTSCTS bit for the port is set. Acked-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> Reviewed-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> Tested-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx> Signed-off-by: Sergey Organov <sorganov@xxxxxxxxx> --- drivers/tty/serial/imx.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 32f36d8..059ba35 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -974,10 +974,22 @@ static void imx_uart_set_mctrl(struct uart_port *port, unsigned int mctrl) if (!(port->rs485.flags & SER_RS485_ENABLED)) { u32 ucr2; + /* + * Turn off autoRTS if RTS is lowered and restore autoRTS + * setting if RTS is raised. + */ ucr2 = imx_uart_readl(sport, UCR2); ucr2 &= ~(UCR2_CTS | UCR2_CTSC); - if (mctrl & TIOCM_RTS) - ucr2 |= UCR2_CTS | UCR2_CTSC; + if (mctrl & TIOCM_RTS) { + ucr2 |= UCR2_CTS; + /* + * UCR2_IRTS is unset if and only if the port is + * configured for CRTSCTS, so we use inverted UCR2_IRTS + * to get the state to restore to. + */ + if (!(ucr2 & UCR2_IRTS)) + ucr2 |= UCR2_CTSC; + } imx_uart_writel(sport, ucr2, UCR2); } -- 2.10.0.1.g57b01a3