I have made a patch that does not enable the loopback when
the RX_DURING_TX flag is disabled. Would you be so kind to
test my patch to see if it also solves your problem.
Regards
Christoph
Commit 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high")
activated the loopback mode for RS485 controlled by UART CTS_B when the
function imx_uart_stop_rx() is called. But through that changes the RS485
flag RX_DURING_TX isn’t able to turn off the receiver anymore. If the flag
RX_DURING_TX is disabled everything that was sent will be received due to
the active loopback. To turn off the receiver in this case the function
imx_uart_stop_rx() is extended by a wrapper function
imx_uart_stop_rx_with_loopback_rs485_ctrl() for the use of RS485 with
disabled flag RX_DURING_TX, where the receiver is turn off. For all other
cases there aren’t a functional change.
When the receiver is turned off the UART CTS_B signal is always high. To
ensure that the RS485 bus won’t blocked by a disabled receiver caused by a
high UART CTS_B signal the function imx_uart_shutdown() is extended. So in
RS485 loopback mode the receiver is always on after shutdown the device.
Fixes: 79d0224f6bf2 ("tty: serial: imx: Handle RS485 DE signal active high")
Signed-off-by: Christoph Niedermaier <cniedermaier@xxxxxxxxxxxxxxxxxx>
---
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jiri Slaby <jirislaby@xxxxxxxxxx>
Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
Cc: Marek Vasut <marex@xxxxxxx>
Cc: Fabio Estevam <festevam@xxxxxxx>
Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
Cc: Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx>
Cc: NXP Linux Team <linux-imx@xxxxxxx>
Cc: Sergey Organov <sorganov@xxxxxxxxx>
Cc: "Uwe Kleine-König" <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Rob Herring <robh@xxxxxxxxxx>
Cc: "Ilpo Järvinen" <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Cc: Tom Rix <trix@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Lukas Wunner <lukas@xxxxxxxxx>
To: linux-serial@xxxxxxxxxxxxxxx
---
drivers/tty/serial/imx.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 4aa72d5aeafb..222e2c929bd7 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -463,7 +463,8 @@ static void imx_uart_stop_tx(struct uart_port *port)
}
/* called with port.lock taken and irqs off */
-static void imx_uart_stop_rx(struct uart_port *port)
+static void imx_uart_stop_rx_with_loopback_rs485_ctrl(struct uart_port *port,
+ bool loopback_rs485_enable)
{
struct imx_port *sport = (struct imx_port *)port;
u32 ucr1, ucr2, ucr4, uts;
@@ -483,7 +484,7 @@ static void imx_uart_stop_rx(struct uart_port *port)
imx_uart_writel(sport, ucr4, UCR4);
/* See SER_RS485_ENABLED/UTS_LOOP comment in imx_uart_probe() */
- if (port->rs485.flags & SER_RS485_ENABLED &&
+ if (port->rs485.flags & SER_RS485_ENABLED && loopback_rs485_enable &&
port->rs485.flags & SER_RS485_RTS_ON_SEND &&
sport->have_rtscts && !sport->have_rtsgpio) {
uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));
@@ -498,6 +499,12 @@ static void imx_uart_stop_rx(struct uart_port *port)
}
/* called with port.lock taken and irqs off */
+static void imx_uart_stop_rx(struct uart_port *port)
+{
+ imx_uart_stop_rx_with_loopback_rs485_ctrl(port, 1);
+}
+
+/* called with port.lock taken and irqs off */
static void imx_uart_enable_ms(struct uart_port *port)
{
struct imx_port *sport = (struct imx_port *)port;
@@ -684,7 +691,7 @@ static void imx_uart_start_tx(struct uart_port *port)
if (!(port->rs485.flags & SER_RS485_RX_DURING_TX) &&
!port->rs485_rx_during_tx_gpio)
- imx_uart_stop_rx(port);
+ imx_uart_stop_rx_with_loopback_rs485_ctrl(port, 0);
sport->tx_state = WAIT_AFTER_RTS;
@@ -1596,6 +1603,9 @@ static void imx_uart_shutdown(struct uart_port *port)
uts = imx_uart_readl(sport, imx_uart_uts_reg(sport));
uts |= UTS_LOOP;
imx_uart_writel(sport, uts, imx_uart_uts_reg(sport));
+ ucr2 = imx_uart_readl(sport, UCR2);
+ ucr2 |= UCR2_RXEN;
+ imx_uart_writel(sport, ucr2, UCR2);
ucr1 |= UCR1_UARTEN;
} else {
ucr1 &= ~UCR1_UARTEN;
--
2.11.0
