[PATCH/RFC 4/5] serial: sh-sci: Add support for GPIO-controlled modem lines

[Geert Uytterhoeven <geert+renesas@glider.be>]

Enhance the Renesas SCI UART driver to add support for GPIO-controlled
modem lines (CTS, DSR, DCD, RNG, RTS, DTR, OUT1, and OUT2), using the
SERIAL_MCTRL_GPIO helpers.

GPIO-controlled modem lines can be used where dedicated modem lines are
not available.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
Testing for regressions on platforms without DT and/or GPIOLIB support
(SuperH) would be appreciated.
Compile-tested on ecovec24_defconfig(GPIOLIB=y) and se7780_defconfig
(GPIOLIB=n).
---
 drivers/tty/serial/Kconfig  |  1 +
 drivers/tty/serial/sh-sci.c | 35 ++++++++++++++++++++++++++++++++++-
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 13d4ed6caac4a78b..ebf91bbfdf0f999d 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -735,6 +735,7 @@ config SERIAL_SH_SCI
 	tristate "SuperH SCI(F) serial port support"
 	depends on SUPERH || ARCH_RENESAS || H8300 || COMPILE_TEST
 	select SERIAL_CORE
+	select SERIAL_MCTRL_GPIO if GPIOLIB
 
 config SERIAL_SH_SCI_NR_UARTS
 	int "Maximum number of SCI(F) serial ports"
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 135f836642ab1c5a..6897100ed5197df3 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -57,6 +57,7 @@
 #include <asm/sh_bios.h>
 #endif
 
+#include "serial_mctrl_gpio.h"
 #include "sh-sci.h"
 
 /* Offsets into the sci_port->irqs array */
@@ -111,6 +112,7 @@ struct sci_port {
 	unsigned int		error_clear;
 	unsigned int		sampling_rate_mask;
 	resource_size_t		reg_size;
+	struct mctrl_gpios	*gpios;
 
 	/* Break timer */
 	struct timer_list	break_timer;
@@ -1829,15 +1831,36 @@ static void sci_set_mctrl(struct uart_port *port, unsigned int mctrl)
 					serial_port_in(port, SCFCR) |
 					SCFCR_LOOP);
 	}
+
+	mctrl_gpio_set(to_sci_port(port)->gpios, mctrl);
 }
 
 static unsigned int sci_get_mctrl(struct uart_port *port)
 {
+	unsigned int mctrl = 0;
+
+	mctrl_gpio_get(to_sci_port(port)->gpios, &mctrl);
+
 	/*
 	 * CTS/RTS is handled in hardware when supported, while nothing
 	 * else is wired up. Keep it simple and simply assert CTS/DSR/CAR.
 	 */
-	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
+	if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(to_sci_port(port)->gpios,
+					       UART_GPIO_CTS)))
+		mctrl |= TIOCM_CTS;
+	if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(to_sci_port(port)->gpios,
+					       UART_GPIO_DSR)))
+		mctrl |= TIOCM_DSR;
+	if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(to_sci_port(port)->gpios,
+					       UART_GPIO_CAR)))
+		mctrl |= TIOCM_CAR;
+
+	return mctrl;
+}
+
+static void sci_enable_ms(struct uart_port *port)
+{
+	mctrl_gpio_enable_ms(to_sci_port(port)->gpios);
 }
 
 static void sci_break_ctl(struct uart_port *port, int break_state)
@@ -1899,6 +1922,8 @@ static void sci_shutdown(struct uart_port *port)
 
 	dev_dbg(port->dev, "%s(%d)\n", __func__, port->line);
 
+	mctrl_gpio_disable_ms(to_sci_port(port)->gpios);
+
 	spin_lock_irqsave(&port->lock, flags);
 	sci_stop_rx(port);
 	sci_stop_tx(port);
@@ -2300,6 +2325,9 @@ done:
 		sci_start_rx(port);
 
 	sci_port_disable(s);
+
+	if (UART_ENABLE_MS(port, termios->c_cflag))
+		sci_enable_ms(port);
 }
 
 static void sci_pm(struct uart_port *port, unsigned int state,
@@ -2425,6 +2453,7 @@ static struct uart_ops sci_uart_ops = {
 	.start_tx	= sci_start_tx,
 	.stop_tx	= sci_stop_tx,
 	.stop_rx	= sci_stop_rx,
+	.enable_ms	= sci_enable_ms,
 	.break_ctl	= sci_break_ctl,
 	.startup	= sci_startup,
 	.shutdown	= sci_shutdown,
@@ -2912,6 +2941,10 @@ static int sci_probe_single(struct platform_device *dev,
 	if (ret)
 		return ret;
 
+	sciport->gpios = mctrl_gpio_init(&sciport->port, 0);
+	if (IS_ERR(sciport->gpios) && PTR_ERR(sciport->gpios) != -ENOSYS)
+		return PTR_ERR(sciport->gpios);
+
 	ret = uart_add_one_port(&sci_uart_driver, &sciport->port);
 	if (ret) {
 		sci_cleanup_single(sciport);
-- 
1.9.1