Since commit 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high") RS485 reception no longer works after a transmission. The following scenario shows the problem: 1) Open a port in RS485 mode 2) Receive data from remote (OK) 3) Transmit data to remote (OK) 4) Receive data from remote (Nothing received) In RS485 mode, imx_uart_start_tx() calls imx_uart_stop_rx() and, when the transmission is complete, imx_uart_stop_tx() calls imx_uart_start_rx(). Since the above commit imx_uart_stop_rx() now sets the loopback bit but imx_uart_start_rx() does not clear it causing the hardware to remain in loopback mode and not receive external data. Fix this by moving the existing loopback disable code to a helper function and calling it from imx_uart_start_rx() too. Fixes: 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high") Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group> --- drivers/tty/serial/imx.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index c5e17569c3ad..3fe8ff241522 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -369,6 +369,16 @@ static void imx_uart_soft_reset(struct imx_port *sport) sport->idle_counter = 0; } +static void imx_uart_disable_loopback_rs485(struct imx_port *sport) +{ + unsigned int uts; + + /* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */ + uts = imx_uart_readl(sport, imx_uart_uts_reg(sport)); + uts &= ~UTS_LOOP; + imx_uart_writel(sport, uts, imx_uart_uts_reg(sport)); +} + /* called with port.lock taken and irqs off */ static void imx_uart_start_rx(struct uart_port *port) { @@ -390,6 +400,7 @@ static void imx_uart_start_rx(struct uart_port *port) /* Write UCR2 first as it includes RXEN */ imx_uart_writel(sport, ucr2, UCR2); imx_uart_writel(sport, ucr1, UCR1); + imx_uart_disable_loopback_rs485(sport); } /* called with port.lock taken and irqs off */ @@ -1422,7 +1433,7 @@ static int imx_uart_startup(struct uart_port *port) int retval; unsigned long flags; int dma_is_inited = 0; - u32 ucr1, ucr2, ucr3, ucr4, uts; + u32 ucr1, ucr2, ucr3, ucr4; retval = clk_prepare_enable(sport->clk_per); if (retval) @@ -1521,10 +1532,7 @@ static int imx_uart_startup(struct uart_port *port) imx_uart_writel(sport, ucr2, UCR2); } - /* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */ - uts = imx_uart_readl(sport, imx_uart_uts_reg(sport)); - uts &= ~UTS_LOOP; - imx_uart_writel(sport, uts, imx_uart_uts_reg(sport)); + imx_uart_disable_loopback_rs485(sport); spin_unlock_irqrestore(&sport->port.lock, flags); -- 2.25.1