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> + struct uart_port *port = &p->port; > > if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) > mcr |= UART_MCR_RTS; > @@ -1457,6 +1458,7 @@ void serial8250_em485_stop_tx(struct uart_8250_port *p) > * Enable previously disabled RX interrupts. > */ > if (!(p->port.rs485.flags & SER_RS485_RX_DURING_TX)) { > + gpiod_set_value(port->rs485_re_gpio, 1); > serial8250_clear_and_reinit_fifos(p); > > p->ier |= UART_IER_RLSI | UART_IER_RDI; > @@ -1597,9 +1599,12 @@ static inline void __start_tx(struct uart_port *port) > void serial8250_em485_start_tx(struct uart_8250_port *up) > { > unsigned char mcr = serial8250_in_MCR(up); > + struct uart_port *port = &up->port; > > - if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) > + if (!(up->port.rs485.flags & SER_RS485_RX_DURING_TX)) { > + gpiod_set_value(port->rs485_re_gpio, 0); > serial8250_stop_rx(&up->port); > + } > > if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND) > mcr |= UART_MCR_RTS; > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > index 15ad8737b72b..c0d3ab32b49a 100644 > --- a/drivers/tty/serial/serial_core.c > +++ b/drivers/tty/serial/serial_core.c > @@ -3149,6 +3149,16 @@ int uart_get_rs485_mode(struct uart_port *port) > return ret; > } > > + port->rs485_re_gpio = devm_gpiod_get_optional(dev, "rs485-rx-enable", > + GPIOD_OUT_HIGH); The half duplex emulation can be disabled on-boot or later-on using ioctls in systems that can switch between half and full duplex modes. In that case this gpio should probably be released as it can probably prevent enabling the transceiver-sender mode. I suggest we set the gpio to output active in the em485_init callback and stop driving it in the em485_destroy callback. Regards > + if (IS_ERR(port->rs485_re_gpio)) { > + ret = PTR_ERR(port->rs485_re_gpio); > + port->rs485_re_gpio = NULL; > + if (ret != -EPROBE_DEFER) > + dev_err(dev, "Cannot get rs485-rx-enable-gpios\n"); > + return ret; > + } > + > return 0; > } > EXPORT_SYMBOL_GPL(uart_get_rs485_mode); > diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h > index 108f95411471..dfe18ddb1674 100644 > --- a/include/linux/serial_core.h > +++ b/include/linux/serial_core.h > @@ -253,6 +253,7 @@ struct uart_port { > const struct attribute_group **tty_groups; /* all attributes (serial core use only) */ > struct serial_rs485 rs485; > struct gpio_desc *rs485_term_gpio; /* enable RS485 bus termination */ > + struct gpio_desc *rs485_re_gpio; /* gpio RS485 receive enable */ > struct serial_iso7816 iso7816; > void *private_data; /* generic platform data pointer */ > };