serial: Do not hold the port lock when setting rx-during-tx GPIO

commit 07c30ea5861fb26a77dade8cdc787252f6122fb1 upstream.

Both the imx and stm32 driver set the rx-during-tx GPIO in rs485_config().
Since this function is called with the port lock held, this can be a
problem in case that setting the GPIO line can sleep (e.g. if a GPIO
expander is used which is connected via SPI or I2C).

Avoid this issue by moving the GPIO setting outside of the port lock into
the serial core and thus making it a generic feature.

Also with commit c54d48543689 ("serial: stm32: Add support for rs485
RX_DURING_TX output GPIO") the SER_RS485_RX_DURING_TX flag is only set if a
rx-during-tx GPIO is _not_ available, which is wrong. Fix this, too.

Furthermore reset old GPIO settings in case that changing the RS485
configuration failed.

Fixes: c54d48543689 ("serial: stm32: Add support for rs485 RX_DURING_TX output GPIO")
Fixes: ca530cfa968c ("serial: imx: Add support for RS485 RX_DURING_TX output GPIO")
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc:  <stable@vger.kernel.org>
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Link: https://lore.kernel.org/r/20240103061818.564-2-l.sanfilippo@kunbus.com
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index cd36251ba1c0253bcc5f3f5f7182cab9c9fef02e..2fbb9b597752b838e904fd5c40d3ce535b52bde6 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1947,10 +1947,6 @@ static int imx_uart_rs485_config(struct uart_port *port, struct ktermios *termio
            rs485conf->flags & SER_RS485_RX_DURING_TX)
                imx_uart_start_rx(port);
 
-       if (port->rs485_rx_during_tx_gpio)
-               gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
-                                        !!(rs485conf->flags & SER_RS485_RX_DURING_TX));
-
        return 0;
 }
 

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index bde5b6015305aca23eeb521a4196026a6dc5e4c0..083ea4de48f9a32093495db64ce5dde3b6177a72 100644 (file)
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -1409,6 +1409,16 @@ static void uart_set_rs485_termination(struct uart_port *port,
                                 !!(rs485->flags & SER_RS485_TERMINATE_BUS));
 }
 
+static void uart_set_rs485_rx_during_tx(struct uart_port *port,
+                                       const struct serial_rs485 *rs485)
+{
+       if (!(rs485->flags & SER_RS485_ENABLED))
+               return;
+
+       gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
+                                !!(rs485->flags & SER_RS485_RX_DURING_TX));
+}
+
 static int uart_rs485_config(struct uart_port *port)
 {
        struct serial_rs485 *rs485 = &port->rs485;
@@ -1420,12 +1430,17 @@ static int uart_rs485_config(struct uart_port *port)
 
        uart_sanitize_serial_rs485(port, rs485);
        uart_set_rs485_termination(port, rs485);
+       uart_set_rs485_rx_during_tx(port, rs485);
 
        spin_lock_irqsave(&port->lock, flags);
        ret = port->rs485_config(port, NULL, rs485);
        spin_unlock_irqrestore(&port->lock, flags);
-       if (ret)
+       if (ret) {
                memset(rs485, 0, sizeof(*rs485));
+               /* unset GPIOs */
+               gpiod_set_value_cansleep(port->rs485_term_gpio, 0);
+               gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio, 0);
+       }
 
        return ret;
 }
@@ -1464,6 +1479,7 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
                return ret;
        uart_sanitize_serial_rs485(port, &rs485);
        uart_set_rs485_termination(port, &rs485);
+       uart_set_rs485_rx_during_tx(port, &rs485);
 
        spin_lock_irqsave(&port->lock, flags);
        ret = port->rs485_config(port, &tty->termios, &rs485);
@@ -1475,8 +1491,14 @@ static int uart_set_rs485_config(struct tty_struct *tty, struct uart_port *port,
                        port->ops->set_mctrl(port, port->mctrl);
        }
        spin_unlock_irqrestore(&port->lock, flags);
-       if (ret)
+       if (ret) {
+               /* restore old GPIO settings */
+               gpiod_set_value_cansleep(port->rs485_term_gpio,
+                       !!(port->rs485.flags & SER_RS485_TERMINATE_BUS));
+               gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
+                       !!(port->rs485.flags & SER_RS485_RX_DURING_TX));
                return ret;
+       }
 
        if (copy_to_user(rs485_user, &port->rs485, sizeof(port->rs485)))
                return -EFAULT;

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 5e9cf0c48813da0d44fc9f31fbb3b625197a46bd..b6f4f436a56532b7b155e88b2e8e58dcbeb9fce9 100644 (file)
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -226,12 +226,6 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
 
        stm32_usart_clr_bits(port, ofs->cr1, BIT(cfg->uart_enable_bit));
 
-       if (port->rs485_rx_during_tx_gpio)
-               gpiod_set_value_cansleep(port->rs485_rx_during_tx_gpio,
-                                        !!(rs485conf->flags & SER_RS485_RX_DURING_TX));
-       else
-               rs485conf->flags |= SER_RS485_RX_DURING_TX;
-
        if (rs485conf->flags & SER_RS485_ENABLED) {
                cr1 = readl_relaxed(port->membase + ofs->cr1);
                cr3 = readl_relaxed(port->membase + ofs->cr3);
@@ -256,6 +250,8 @@ static int stm32_usart_config_rs485(struct uart_port *port, struct ktermios *ter
 
                writel_relaxed(cr3, port->membase + ofs->cr3);
                writel_relaxed(cr1, port->membase + ofs->cr1);
+
+               rs485conf->flags |= SER_RS485_RX_DURING_TX;
        } else {
                stm32_usart_clr_bits(port, ofs->cr3,
                                     USART_CR3_DEM | USART_CR3_DEP);