Commit 45f6b6db authored by Dario Binacchi's avatar Dario Binacchi Committed by Greg Kroah-Hartman
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serial: omap: don't disable rs485 if rts gpio is missing 



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: 4a0ac0f5 ("OMAP: add RS485 support")
Signed-off-by: default avatarDario Binacchi <dariobin@libero.it>
Link: https://lore.kernel.org/r/20210415210945.25863-1-dariobin@libero.it


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cea37afd

drivers/tty/serial/omap-serial.c

+4 −8
Original line number Diff line number Diff line
@@ -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;