Hello Baruch, On Sun, Feb 28, 2016 at 11:25:51AM +0200, Baruch Siach wrote: > 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 But this change is a good one (assuming it does what it advertises :-). Userspace got informed before that SER_RS485_RX_DURING_TX is enabled, so this is not an incompatible change. Best regards Uwe > SER_RS485_RX_DURING_TX was enabled unconditionally even when disabled in > the TIOCSRS485 ioctl serial_rs485 flags field. > > Cc: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> > Signed-off-by: Baruch Siach <baruch@xxxxxxxxxx> > --- > drivers/tty/serial/imx.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c > index 9362f54c816c..333d34ff358c 100644 > --- a/drivers/tty/serial/imx.c > +++ b/drivers/tty/serial/imx.c > @@ -361,6 +361,8 @@ static void imx_stop_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); > > temp = readl(port->membase + UCR4); > @@ -568,6 +570,8 @@ 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); Can this happen: - SER_RS485_RX_DURING_TX is off - thread A starts sending (and so disables RX) - thread B sets SER_RS485_RX_DURING_TX - thread A finishes sending, and doesn't restore RXEN. ? Even if this cannot happen it might be more robust to restore RXEN unconditionally in imx_stop_tx?! Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
