[PATCH v2 3/9] serial: Add common rs485 device tree parsing function

[Uwe Kleine-König]

From: Sascha Hauer <s.hauer at pengutronix.de>

Several drivers have the same device tree parsing code. Create
a common helper function for it.

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
[ukl: implement default <0 0> for rts-delay, unset unspecified flags]
Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
---
Changed in v2:
 - make rts-delay optional
 - fix prototype of of_get_rs485_mode for the !OF_SERIAL case

 drivers/tty/serial/Kconfig  |  4 ++++
 drivers/tty/serial/Makefile |  2 ++
 drivers/tty/serial/of.c     | 47 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/serial_core.h | 13 +++++++++++++
 4 files changed, 66 insertions(+)
 create mode 100644 drivers/tty/serial/of.c

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 5c8850f7a2a0..8baef5b95bed 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -14,6 +14,10 @@ config SERIAL_EARLYCON
 	  the console before standard serial driver is probed. The console is
 	  enabled when early_param is processed.
 
+config OF_SERIAL
+	depends on SERIAL_CORE
+	def_bool y
+
 source "drivers/tty/serial/8250/Kconfig"
 
 comment "Non-8250 serial port support"
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 53c03e005132..0fee8f4e36cb 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -7,6 +7,8 @@ obj-$(CONFIG_SERIAL_CORE) += serial_core.o
 obj-$(CONFIG_SERIAL_EARLYCON) += earlycon.o
 obj-$(CONFIG_SERIAL_EARLYCON_ARM_SEMIHOST) += earlycon-arm-semihost.o
 
+obj-$(CONFIG_OF_SERIAL) += of.o
+
 # These Sparc drivers have to appear before others such as 8250
 # which share ttySx minor node space.  Otherwise console device
 # names change and other unplesantries.
diff --git a/drivers/tty/serial/of.c b/drivers/tty/serial/of.c
new file mode 100644
index 000000000000..b24e4357661b
--- /dev/null
+++ b/drivers/tty/serial/of.c
@@ -0,0 +1,47 @@
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/of.h>
+#include <linux/serial_core.h>
+
+/**
+ * of_get_rs485_mode() - Implement parsing rs485 properties
+ * @np: uart node
+ * @rs485conf: output parameter
+ *
+ * This function implements the device tree binding described in
+ * Documentation/devicetree/bindings/serial/rs485.txt.
+ *
+ * Return: 0 on success, 1 if the node doesn't contain rs485 stuff.
+ */
+int of_get_rs485_mode(struct device_node *np, struct serial_rs485 *rs485conf)
+{
+	u32 rs485_delay[2];
+	int ret;
+
+	if (!IS_ENABLED(CONFIG_OF) || !np)
+		return 1;
+
+	ret = of_property_read_u32_array(np, "rs485-rts-delay" rs485_delay, 2);
+	if (!ret) {
+		rs485conf->delay_rts_before_send = rs485_delay[0];
+		rs485conf->delay_rts_after_send = rs485_delay[1];
+	} else {
+		rs485conf->delay_rts_before_send = 0;
+		rs485conf->delay_rts_after_send = 0;
+	}
+
+	/*
+	 * clear full-duplex and enabled flags to get to a defined state with
+	 * the two following properties.
+	 */
+	rs485conf->flags &= ~(SER_RS485_RX_DURING_TX | SER_RS485_ENABLED);
+
+	if (of_property_read_bool(np, "rs485-rx-during-tx"))
+		rs485conf->flags |= SER_RS485_RX_DURING_TX;
+
+	if (of_property_read_bool(np, "linux,rs485-enabled-at-boot-time"))
+		rs485conf->flags |= SER_RS485_ENABLED;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_get_rs485_mode);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 64d892f1e5cd..5ba00b1be093 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -500,4 +500,17 @@ static inline int uart_handle_break(struct uart_port *port)
 					 (cflag) & CRTSCTS || \
 					 !((cflag) & CLOCAL))
 
+/*
+ * Common device tree parsing helpers
+ */
+#ifdef CONFIG_OF_SERIAL
+int of_get_rs485_mode(struct device_node *np, struct serial_rs485 *rs485conf);
+#else
+static inline int of_get_rs485_mode(struct device_node *np,
+				    struct serial_rs485 *rs485conf)
+{
+	return 1;
+}
+#endif
+
 #endif /* LINUX_SERIAL_CORE_H */
-- 
2.11.0