[PATCH v2] serial: imx: support RS-485 Rx disable on Tx
From: baruch@tkos.co.il (Baruch Siach)
Date: 2016-02-29 12:34:10
Also in:
linux-serial
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
Some RS-232 to RS-485 transceivers require Rx to be disabled on Tx to avoid echo of Tx data into the Rx buffer. Specifically, the XR3160E RS-232/RS-485/RS-422 transceiver behaves this way. This commit disables Rx on active Tx when SER_RS485_ENABLED is active and SER_RS485_RX_DURING_TX is disabled. Note that this is a change in behavior of the driver. Until now SER_RS485_RX_DURING_TX was enabled unconditionally even when disabled in the TIOCSRS485 ioctl serial_rs485 flags field. Cc: Uwe Kleine-K?nig <redacted> Signed-off-by: Baruch Siach <baruch@tkos.co.il> --- v2: * Make Rx enable more robust as Uwe Kleine-K?nig suggested * Expand Cc list --- drivers/tty/serial/imx.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 9362f54c816c..87950c111cbe 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c@@ -361,6 +361,7 @@ static void imx_stop_tx(struct uart_port *port) imx_port_rts_inactive(sport, &temp); else imx_port_rts_active(sport, &temp); + temp |= UCR2_RXEN; writel(temp, port->membase + UCR2); temp = readl(port->membase + UCR4);
@@ -568,6 +569,8 @@ static void imx_start_tx(struct uart_port *port) imx_port_rts_inactive(sport, &temp); else imx_port_rts_active(sport, &temp); + if (!(port->rs485.flags & SER_RS485_RX_DURING_TX)) + temp &= ~UCR2_RXEN; writel(temp, port->membase + UCR2); /* enable transmitter and shifter empty irq */
@@ -1610,19 +1613,17 @@ static int imx_rs485_config(struct uart_port *port, struct serial_rs485 *rs485conf) { struct imx_port *sport = (struct imx_port *)port; + unsigned long temp; /* unimplemented */ rs485conf->delay_rts_before_send = 0; rs485conf->delay_rts_after_send = 0; - rs485conf->flags |= SER_RS485_RX_DURING_TX; /* RTS is required to control the transmitter */ if (!sport->have_rtscts) rs485conf->flags &= ~SER_RS485_ENABLED; if (rs485conf->flags & SER_RS485_ENABLED) { - unsigned long temp; - /* disable transmitter */ temp = readl(sport->port.membase + UCR2); if (rs485conf->flags & SER_RS485_RTS_AFTER_SEND)
@@ -1632,6 +1633,14 @@ static int imx_rs485_config(struct uart_port *port, writel(temp, sport->port.membase + UCR2); } + /* Make sure Rx is enabled in case Tx is active with Rx disabled */ + if (!(rs485conf->flags & SER_RS485_ENABLED) || + rs485conf->flags & SER_RS485_RX_DURING_TX) { + temp = readl(sport->port.membase + UCR2); + temp |= UCR2_RXEN; + writel(temp, sport->port.membase + UCR2); + } + port->rs485 = *rs485conf; return 0;
--
2.7.0