serial: Make retrieval of rs485 properties platform-agnostic

Commit ef838a81 ("serial: Add common rs485 device tree parsing
function") consolidated retrieval of rs485 OF properties in a common
helper function but did not #ifdef it to CONFIG_OF.  The function is
therefore included on ACPI platforms as well even though it's not used.

On the other hand ACPI platforms with rs485 do exist (e.g. Siemens
IOT2040) and they may leverage _DSD to store rs485 properties.  Likewise,
UART platform devices instantiated from an MFD should be able to specify
rs485 properties.  In fact, the tty subsystem maintainer had asked for
a "generic" function during review of commit ef838a81:
https://marc.info/?l=linux-serial&m=150143441725194&w=4

Thus, instead of constraining the helper to OF platforms, make it
platform-agnostic by converting it to device_property_*() functions
and renaming it accordingly.

In imx.c, move the invocation of uart_get_rs485_mode() from
serial_imx_probe_dt() to serial_imx_probe() so that it also gets called
for non-OF devices.

In omap-serial.c, move its invocation further up within
serial_omap_probe_rs485() so that the RTS polarity can be overridden
with the driver-specific "rs485-rts-active-high" property once we
introduce a generic "rs485-rts-active-low" property.

Cc: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Richard Genoud <richard.genoud@gmail.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -2345,7 +2345,7 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
 	atmel_init_property(atmel_port, pdev);
 	atmel_set_ops(port);
 
-	of_get_rs485_mode(pdev->dev.of_node, &port->rs485);
+	uart_get_rs485_mode(&pdev->dev, &port->rs485);
 
 	port->iotype		= UPIO_MEM;
 	port->flags		= UPF_BOOT_AUTOCONF | UPF_IOREMAP;

drivers/tty/serial/fsl_lpuart.c

@@ -2206,7 +2206,7 @@ static int lpuart_probe(struct platform_device *pdev)
 	if (ret)
 		goto failed_attach_port;
 
-	of_get_rs485_mode(np, &sport->port.rs485);
+	uart_get_rs485_mode(&pdev->dev, &sport->port.rs485);
 
 	if (sport->port.rs485.flags & SER_RS485_RX_DURING_TX) {
 		dev_err(&pdev->dev, "driver doesn't support RX during TX\n");

drivers/tty/serial/imx.c

@@ -1999,8 +1999,6 @@ static int serial_imx_probe_dt(struct imx_port *sport,
 	if (of_get_property(np, "rts-gpios", NULL))
 		sport->have_rtsgpio = 1;
 
-	of_get_rs485_mode(np, &sport->port.rs485);
-
 	return 0;
 }
 #else
@@ -2093,6 +2091,8 @@ static int serial_imx_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	uart_get_rs485_mode(&pdev->dev, &sport->port.rs485);
+
 	/* Disable interrupts before requesting them */
 	reg = readl_relaxed(sport->port.membase + UCR1);
 	reg &= ~(UCR1_ADEN | UCR1_TRDYEN | UCR1_IDEN | UCR1_RRDYEN |

drivers/tty/serial/omap-serial.c

@@ -1611,6 +1611,8 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
 	if (!np)
 		return 0;
 
+	uart_get_rs485_mode(up->dev, rs485conf);
+
 	if (of_property_read_bool(np, "rs485-rts-active-high"))
 		rs485conf->flags |= SER_RS485_RTS_ON_SEND;
 	else
@@ -1632,8 +1634,6 @@ static int serial_omap_probe_rs485(struct uart_omap_port *up,
 		up->rts_gpio = -EINVAL;
 	}
 
-	of_get_rs485_mode(np, rs485conf);
-
 	return 0;
 }
 

drivers/tty/serial/serial_core.c

@@ -3013,19 +3013,20 @@ EXPORT_SYMBOL(uart_add_one_port);
 EXPORT_SYMBOL(uart_remove_one_port);
 
 /**
- * of_get_rs485_mode() - Implement parsing rs485 properties
- * @np: uart node
+ * uart_get_rs485_mode() - retrieve rs485 properties for given uart
+ * @dev: uart device
  * @rs485conf: output parameter
  *
  * This function implements the device tree binding described in
  * Documentation/devicetree/bindings/serial/rs485.txt.
  */
-void of_get_rs485_mode(struct device_node *np, struct serial_rs485 *rs485conf)
+void uart_get_rs485_mode(struct device *dev, struct serial_rs485 *rs485conf)
 {
 	u32 rs485_delay[2];
 	int ret;
 
-	ret = of_property_read_u32_array(np, "rs485-rts-delay", rs485_delay, 2);
+	ret = device_property_read_u32_array(dev, "rs485-rts-delay",
+					     rs485_delay, 2);
 	if (!ret) {
 		rs485conf->delay_rts_before_send = rs485_delay[0];
 		rs485conf->delay_rts_after_send = rs485_delay[1];
@@ -3040,13 +3041,13 @@ void of_get_rs485_mode(struct device_node *np, struct serial_rs485 *rs485conf)
 	 */
 	rs485conf->flags &= ~(SER_RS485_RX_DURING_TX | SER_RS485_ENABLED);
 
-	if (of_property_read_bool(np, "rs485-rx-during-tx"))
+	if (device_property_read_bool(dev, "rs485-rx-during-tx"))
 		rs485conf->flags |= SER_RS485_RX_DURING_TX;
 
-	if (of_property_read_bool(np, "linux,rs485-enabled-at-boot-time"))
+	if (device_property_read_bool(dev, "linux,rs485-enabled-at-boot-time"))
 		rs485conf->flags |= SER_RS485_ENABLED;
 }
-EXPORT_SYMBOL_GPL(of_get_rs485_mode);
+EXPORT_SYMBOL_GPL(uart_get_rs485_mode);
 
 MODULE_DESCRIPTION("Serial driver core");
 MODULE_LICENSE("GPL");

include/linux/serial_core.h

@@ -501,9 +501,5 @@ static inline int uart_handle_break(struct uart_port *port)
 					 (cflag) & CRTSCTS || \
 					 !((cflag) & CLOCAL))
 
-/*
- * Common device tree parsing helpers
- */
-void of_get_rs485_mode(struct device_node *np, struct serial_rs485 *rs485conf);
-
+void uart_get_rs485_mode(struct device *dev, struct serial_rs485 *rs485conf);
 #endif /* LINUX_SERIAL_CORE_H */