From: Heiko Stuebner <heiko.stuebner@xxxxxxxxxxxxxxxxxxxxx>
While in a lot of cases only RTS is needed as DE signal, sometimes the
RE signals is to be controlled separately, as DTR pin.
So add necessary control functions for it.
Signed-off-by: Heiko Stuebner <heiko.stuebner@xxxxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_port.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 3d1d8490bc42..f8e5c096ed51 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -572,6 +572,10 @@ static inline void serial8250_em485_rts_after_send(struct uart_8250_port *p)
mcr &= ~UART_MCR_RTS;
p->port.mctrl &= ~TIOCM_RTS;
}
+
+ mcr |= UART_MCR_DTR;
+ p->port.mctrl |= TIOCM_DTR;
+
serial8250_out_MCR(p, mcr);
}
@@ -1558,6 +1562,13 @@ static inline void start_tx_rs485(struct uart_port *port)
em485->active_timer = NULL;
mcr = serial8250_in_MCR(up);
+
+ /* in rx_during_tx mode keep DTR active, to receive data */
+ if (up->port.rs485.flags & SER_RS485_RX_DURING_TX)
+ mcr |= UART_MCR_DTR;
+ else
+ mcr &= ~UART_MCR_DTR;
+
if (!!(up->port.rs485.flags & SER_RS485_RTS_ON_SEND) !=
!!(mcr & UART_MCR_RTS)) {
if (up->port.rs485.flags & SER_RS485_RTS_ON_SEND)
@@ -1572,6 +1583,8 @@ static inline void start_tx_rs485(struct uart_port *port)
up->port.rs485.delay_rts_before_send);
return;
}
+ } else {
+ serial8250_out_MCR(up, mcr);
}
__start_tx(port);
--
2.24.1
