serial: Allow uart_get_rs485_mode() to return errno

We're about to amend uart_get_rs485_mode() to support a GPIO pin for
rs485 bus termination.  Retrieving the GPIO descriptor may fail, so
allow uart_get_rs485_mode() to return an errno and change all callers
to check for failure.

The GPIO descriptor is going to be stored in struct uart_port.  Pass
that struct to uart_get_rs485_mode() in lieu of a struct device and
struct serial_rs485, both of which are directly accessible from struct
uart_port.

A few drivers call uart_get_rs485_mode() before setting the struct
device pointer in struct uart_port.  Shuffle those calls around where
necessary.

[Heiko Stuebner did the ar933x_uart.c portion, hence his Signed-off-by.]

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/271e814af4b0db3bffbbb74abf2b46b75add4516.1589285873.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_core.c

@@ -1026,7 +1026,9 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 
 		if (up->port.dev) {
 			uart->port.dev = up->port.dev;
-			uart_get_rs485_mode(uart->port.dev, &uart->port.rs485);
+			ret = uart_get_rs485_mode(&uart->port);
+			if (ret)
+				goto err;
 		}
 
 		if (up->port.flags & UPF_FIXED_TYPE)

drivers/tty/serial/ar933x_uart.c

@@ -766,8 +766,6 @@ static int ar933x_uart_probe(struct platform_device *pdev)
 		goto err_disable_clk;
 	}
 
-	uart_get_rs485_mode(&pdev->dev, &port->rs485);
-
 	port->mapbase = mem_res->start;
 	port->line = id;
 	port->irq = irq_res->start;
@@ -786,6 +784,10 @@ static int ar933x_uart_probe(struct platform_device *pdev)
 	baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
 	up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
 
+	ret = uart_get_rs485_mode(port);
+	if (ret)
+		goto err_disable_clk;
+
 	up->gpios = mctrl_gpio_init(port, 0);
 	if (IS_ERR(up->gpios) && PTR_ERR(up->gpios) != -ENOSYS)
 		return PTR_ERR(up->gpios);

drivers/tty/serial/atmel_serial.c

@@ -2491,8 +2491,6 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
 	atmel_init_property(atmel_port, pdev);
 	atmel_set_ops(port);
 
-	uart_get_rs485_mode(&mpdev->dev, &port->rs485);
-
 	port->iotype		= UPIO_MEM;
 	port->flags		= UPF_BOOT_AUTOCONF | UPF_IOREMAP;
 	port->ops		= &atmel_pops;
@@ -2506,6 +2504,10 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
 
 	memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring));
 
+	ret = uart_get_rs485_mode(port);
+	if (ret)
+		return ret;
+
 	/* for console, the clock could already be configured */
 	if (!atmel_port->clk) {
 		atmel_port->clk = clk_get(&mpdev->dev, "usart");

drivers/tty/serial/fsl_lpuart.c

@@ -2619,7 +2619,9 @@ static int lpuart_probe(struct platform_device *pdev)
 	if (ret)
 		goto failed_attach_port;
 
-	uart_get_rs485_mode(&pdev->dev, &sport->port.rs485);
+	ret = uart_get_rs485_mode(&sport->port);
+	if (ret)
+		goto failed_get_rs485;
 
 	if (sport->port.rs485.flags & SER_RS485_RX_DURING_TX)
 		dev_err(&pdev->dev, "driver doesn't support RX during TX\n");
@@ -2632,6 +2634,7 @@ static int lpuart_probe(struct platform_device *pdev)
 
 	return 0;
 
+failed_get_rs485:
 failed_attach_port:
 failed_irq_request:
 	lpuart_disable_clks(sport);

drivers/tty/serial/imx.c

@@ -2304,7 +2304,11 @@ static int imx_uart_probe(struct platform_device *pdev)
 	sport->ucr4 = readl(sport->port.membase + UCR4);
 	sport->ufcr = readl(sport->port.membase + UFCR);
 
-	uart_get_rs485_mode(&pdev->dev, &sport->port.rs485);
+	ret = uart_get_rs485_mode(&sport->port);
+	if (ret) {
+		clk_disable_unprepare(sport->clk_ipg);
+		return ret;
+	}
 
 	if (sport->port.rs485.flags & SER_RS485_ENABLED &&
 	    (!sport->have_rtscts && !sport->have_rtsgpio))

drivers/tty/serial/omap-serial.c

@@ -1608,7 +1608,9 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
 	if (!np)
 		return 0;
 
-	uart_get_rs485_mode(up->dev, rs485conf);
+	ret = uart_get_rs485_mode(&up->port);
+	if (ret)
+		return ret;
 
 	if (of_property_read_bool(np, "rs485-rts-active-high")) {
 		rs485conf->flags |= SER_RS485_RTS_ON_SEND;

drivers/tty/serial/serial_core.c

@@ -3295,8 +3295,10 @@ EXPORT_SYMBOL(uart_remove_one_port);
  * This function implements the device tree binding described in
  * Documentation/devicetree/bindings/serial/rs485.txt.
  */
-void uart_get_rs485_mode(struct device *dev, struct serial_rs485 *rs485conf)
+int uart_get_rs485_mode(struct uart_port *port)
 {
+	struct serial_rs485 *rs485conf = &port->rs485;
+	struct device *dev = port->dev;
 	u32 rs485_delay[2];
 	int ret;
 
@@ -3328,6 +3330,8 @@ void uart_get_rs485_mode(struct device *dev, struct serial_rs485 *rs485conf)
 		rs485conf->flags &= ~SER_RS485_RTS_ON_SEND;
 		rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;
 	}
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(uart_get_rs485_mode);
 

drivers/tty/serial/stm32-usart.c

@@ -159,9 +159,7 @@ static int stm32_init_rs485(struct uart_port *port,
 	if (!pdev->dev.of_node)
 		return -ENODEV;
 
-	uart_get_rs485_mode(&pdev->dev, rs485conf);
+	return uart_get_rs485_mode(port);
-
-	return 0;
 }
 
 static int stm32_pending_rx(struct uart_port *port, u32 *sr, int *last_res,
@@ -959,7 +957,9 @@ static int stm32_init_port(struct stm32_port *stm32port,
 
 	port->rs485_config = stm32_config_rs485;
 
-	stm32_init_rs485(port, pdev);
+	ret = stm32_init_rs485(port, pdev);
+	if (ret)
+		return ret;
 
 	if (stm32port->info->cfg.has_wakeup) {
 		stm32port->wakeirq = platform_get_irq(pdev, 1);

include/linux/serial_core.h

@@ -472,5 +472,5 @@ extern int uart_handle_break(struct uart_port *port);
 					 (cflag) & CRTSCTS || \
 					 !((cflag) & CLOCAL))
 
-void uart_get_rs485_mode(struct device *dev, struct serial_rs485 *rs485conf);
+int uart_get_rs485_mode(struct uart_port *port);
 #endif /* LINUX_SERIAL_CORE_H */