diff options
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/8250/8250_port.c | 3 | ||||
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 16 |
2 files changed, 19 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index bf2722e5e3aa..1632f7d25acc 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -681,6 +681,9 @@ int serial8250_em485_config(struct uart_port *port, struct serial_rs485 *rs485) memset(rs485->padding, 0, sizeof(rs485->padding)); port->rs485 = *rs485; + gpiod_set_value(port->rs485_term_gpio, + rs485->flags & SER_RS485_TERMINATE_BUS); + /* * Both serial8250_em485_init() and serial8250_em485_destroy() * are idempotent. diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 43b6682877d5..57840cf90388 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -3317,6 +3317,7 @@ int uart_get_rs485_mode(struct uart_port *port) * to get to a defined state with the following properties: */ rs485conf->flags &= ~(SER_RS485_RX_DURING_TX | SER_RS485_ENABLED | + SER_RS485_TERMINATE_BUS | SER_RS485_RTS_AFTER_SEND); rs485conf->flags |= SER_RS485_RTS_ON_SEND; @@ -3331,6 +3332,21 @@ int uart_get_rs485_mode(struct uart_port *port) rs485conf->flags |= SER_RS485_RTS_AFTER_SEND; } + /* + * Disabling termination by default is the safe choice: Else if many + * bus participants enable it, no communication is possible at all. + * Works fine for short cables and users may enable for longer cables. + */ + port->rs485_term_gpio = devm_gpiod_get_optional(dev, "rs485-term", + GPIOD_OUT_LOW); + if (IS_ERR(port->rs485_term_gpio)) { + ret = PTR_ERR(port->rs485_term_gpio); + port->rs485_term_gpio = NULL; + if (ret != -EPROBE_DEFER) + dev_err(dev, "Cannot get rs485-term-gpios\n"); + return ret; + } + return 0; } EXPORT_SYMBOL_GPL(uart_get_rs485_mode); |