serial: omap: Disallow RS-485 if rts-gpio is not specified

The serial-omap driver requires an rts-gpio for RS-485 to work. Historically it has allowed enabling RS-485 even if no rts-gpio was specified in the device tree. That doesn't make any sense, so disable RS-485 on probe if rts-gpio is missing and disallow user space from enabling it. Three NULL pointer checks for up->rts_gpiod can be dropped as a result, simplifying the driver slightly. Cc: Linus Walleij <[email protected]> Reviewed-by: Ilpo Järvinen <[email protected]> Acked-by: Linus Walleij <[email protected]> Signed-off-by: Lukas Wunner <[email protected]> Link: https://lore.kernel.org/r/f191dcca0d8ea03598c463fc0d3fba8941ff2275.1662888075.git.lukas@wunner.de Signed-off-by: Greg Kroah-Hartman <[email protected]>
josf · Sep 22, 2022 · e2752ae · e2752ae
1 parent ed9f4bb
commit e2752ae
Showing 1 changed file with 13 additions and 14 deletions.
diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
@@ -300,8 +300,7 @@ 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 (up->rts_gpiod &&
-			    gpiod_get_value(up->rts_gpiod) != res) {
+			if (gpiod_get_value(up->rts_gpiod) != res) {
 				if (port->rs485.delay_rts_after_send > 0)
 					mdelay(
 					port->rs485.delay_rts_after_send);
@@ -397,7 +396,7 @@ 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 (up->rts_gpiod && gpiod_get_value(up->rts_gpiod) != res) {
+		if (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);
@@ -1336,13 +1335,11 @@ serial_omap_config_rs485(struct uart_port *port, struct ktermios *termios,
 	up->ier = 0;
 	serial_out(up, UART_IER, 0);
 
-	if (up->rts_gpiod) {
-		/* enable / disable rts */
-		val = (rs485->flags & SER_RS485_ENABLED) ?
-			SER_RS485_RTS_AFTER_SEND : SER_RS485_RTS_ON_SEND;
-		val = (rs485->flags & val) ? 1 : 0;
-		gpiod_set_value(up->rts_gpiod, val);
-	}
+	/* enable / disable rts */
+	val = (rs485->flags & SER_RS485_ENABLED) ?
+	      SER_RS485_RTS_AFTER_SEND : SER_RS485_RTS_ON_SEND;
+	val = (rs485->flags & val) ? 1 : 0;
+	gpiod_set_value(up->rts_gpiod, val);
 
 	/* Enable interrupts */
 	up->ier = mode;
@@ -1547,11 +1544,13 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
 		ret = PTR_ERR(up->rts_gpiod);
 	        if (ret == -EPROBE_DEFER)
 			return ret;
-		/*
-		 * FIXME: the code historically ignored any other error than
-		 * -EPROBE_DEFER and just went on without GPIO.
-		 */
+
 		up->rts_gpiod = NULL;
+		up->port.rs485_supported = (const struct serial_rs485) { };
+		if (rs485conf->flags & SER_RS485_ENABLED) {
+			dev_err(dev, "disabling RS-485 (rts-gpio missing in device tree)\n");
+			memset(rs485conf, 0, sizeof(*rs485conf));
+		}
 	} else {
 		gpiod_set_consumer_name(up->rts_gpiod, "omap-serial");
 	}