[PATCH 5.11 303/601] serial: omap: dont disable rs485 if rts gpio is missing

Greg Kroah-Hartman
2021-05-12T17:30:59Z

From: Dario Binacchi <dariobin@libero.it>

[ Upstream commit 45f6b6db53c80787b79044629b062dfcf2da71ec ]

There are rs485 transceivers (e.g. MAX13487E/MAX13488E) which
automatically disable or enable the driver and receiver to keep the bus
in the correct state.
In these cases we don't need a GPIO for flow control.

Fixes: 4a0ac0f55b18 ("OMAP: add RS485 support")
Signed-off-by: Dario Binacchi <dariobin@libero.it>
Link: https://lore.kernel.org/r/20210415210945.25863-1-dariobin@libero.it
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/omap-serial.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index 76b94d0ff586..1583e93b2202 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -302,7 +302,8 @@ static void serial_omap_stop_tx(struct uart_port *port)
serial_out(up, UART_OMAP_SCR, up->scr);
res = (port->rs485.flags & SER_RS485_RTS_AFTER_SEND) ?
1 : 0;
- if (gpiod_get_value(up->rts_gpiod) != res) {
+ if (up->rts_gpiod &&
+ gpiod_get_value(up->rts_gpiod) != res) {
if (port->rs485.delay_rts_after_send > 0)
mdelay(
port->rs485.delay_rts_after_send);
@@ -411,7 +412,7 @@ static void serial_omap_start_tx(struct uart_port *port)

/* if rts not already enabled */
res = (port->rs485.flags & SER_RS485_RTS_ON_SEND) ? 1 : 0;
- if (gpiod_get_value(up->rts_gpiod) != res) {
+ if (up->rts_gpiod && gpiod_get_value(up->rts_gpiod) != res) {
gpiod_set_value(up->rts_gpiod, res);
if (port->rs485.delay_rts_before_send > 0)
mdelay(port->rs485.delay_rts_before_send);
@@ -1407,18 +1408,13 @@ serial_omap_config_rs485(struct uart_port *port, struct serial_rs485 *rs485)
/* store new config */
port->rs485 = *rs485;

- /*
- * Just as a precaution, only allow rs485
- * to be enabled if the gpio pin is valid
- */
if (up->rts_gpiod) {
/* enable / disable rts */
val = (port->rs485.flags & SER_RS485_ENABLED) ?
SER_RS485_RTS_AFTER_SEND : SER_RS485_RTS_ON_SEND;
val = (port->rs485.flags & val) ? 1 : 0;
gpiod_set_value(up->rts_gpiod, val);
- } else
- port->rs485.flags &= ~SER_RS485_ENABLED;
+ }

/* Enable interrupts */
up->ier = mode;
--
2.30.2