On Sat, 9 Dec 2023, Lino Sanfilippo wrote:
> 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 an
> 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.
>
> 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@xxxxxxxxxx>
> Cc: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx>
> ---
> drivers/tty/serial/imx.c | 4 ----
> drivers/tty/serial/serial_core.c | 12 ++++++++++++
> drivers/tty/serial/stm32-usart.c | 5 +----
> 3 files changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 708b9852a575..9cffeb23112b 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1943,10 +1943,6 @@ 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 f1348a509552..a0290a5fe8b3 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -1402,6 +1402,16 @@ 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;
> @@ -1413,6 +1423,7 @@ 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);
>
> uart_port_lock_irqsave(port, &flags);
> ret = port->rs485_config(port, NULL, rs485);
> @@ -1457,6 +1468,7 @@ 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);
>
> uart_port_lock_irqsave(port, &flags);
> ret = port->rs485_config(port, &tty->termios, &rs485);
Also a nice simplification of driver-side code.
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
Just noting since this is now in core that if ->rs485_config() fails,
I suppose it's just normal to not rollback gpiod_set_value_cansleep()
(skimming through existing users in tree, it looks it's practically
never touched on the error rollback paths so I guess it's the normal
practice)?
Anyway, since neither of the users currently don't fail in their
->rs485_config() so it doesn't seem a critical issue.
--
i.
