serial: Add Milbeaut serial control

Add Milbeaut serial control including earlycon and console.

Signed-off-by: Sugaya Taichi <sugaya.taichi@socionext.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

4 files changed, 651 insertions, 0 deletions

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 6d0ab0399a72..14768ad0307e 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1580,6 +1580,32 @@ config SERIAL_RDA_CONSOLE
 	  Say 'Y' here if you wish to use the RDA8810PL UART as the system
 	  console. Only earlycon is implemented currently.
 
+config SERIAL_MILBEAUT_USIO
+	tristate "Milbeaut USIO/UART serial port support"
+	depends on ARCH_MILBEAUT || (COMPILE_TEST && OF)
+	default ARCH_MILBEAUT
+	select SERIAL_CORE
+	help
+	  This selects the USIO/UART IP found in Socionext Milbeaut SoCs.
+
+config SERIAL_MILBEAUT_USIO_PORTS
+	int "Maximum number of CSIO/UART ports (1-8)"
+	range 1 8
+	depends on SERIAL_MILBEAUT_USIO
+	default "4"
+
+config SERIAL_MILBEAUT_USIO_CONSOLE
+	bool "Support for console on MILBEAUT USIO/UART serial port"
+	depends on SERIAL_MILBEAUT_USIO=y
+	default y
+	select SERIAL_CORE_CONSOLE
+	select SERIAL_EARLYCON
+	help
+	  Say 'Y' here if you wish to use a USIO/UART of Socionext Milbeaut
+	  SoCs as the system console (the system console is the device which
+	  receives all kernel messages and warnings and which allows logins in
+	  single user mode).
+
 endmenu
 
 config SERIAL_MCTRL_GPIO
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 40b702aaa85e..43ca2d0edde8 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -92,6 +92,7 @@ obj-$(CONFIG_SERIAL_PIC32)	+= pic32_uart.o
 obj-$(CONFIG_SERIAL_MPS2_UART)	+= mps2-uart.o
 obj-$(CONFIG_SERIAL_OWL)	+= owl-uart.o
 obj-$(CONFIG_SERIAL_RDA)	+= rda-uart.o
+obj-$(CONFIG_SERIAL_MILBEAUT_USIO) += milbeaut_usio.o
 
 # GPIOLIB helpers for modem control lines
 obj-$(CONFIG_SERIAL_MCTRL_GPIO)	+= serial_mctrl_gpio.o
diff --git a/drivers/tty/serial/milbeaut_usio.c b/drivers/tty/serial/milbeaut_usio.c
new file mode 100644
index 000000000000..d303b7d4bb20
--- /dev/null
+++ b/drivers/tty/serial/milbeaut_usio.c
@@ -0,0 +1,621 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018 Socionext Inc.
+ */
+
+#if defined(CONFIG_SERIAL_MILBEAUT_USIO_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#define SUPPORT_SYSRQ
+#endif
+
+#include <linux/clk.h>
+#include <linux/console.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/serial_core.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+
+#define USIO_NAME		"mlb-usio-uart"
+#define USIO_UART_DEV_NAME	"ttyUSI"
+
+static struct uart_port mlb_usio_ports[CONFIG_SERIAL_MILBEAUT_USIO_PORTS];
+
+#define RX	0
+#define TX	1
+static int mlb_usio_irq[CONFIG_SERIAL_MILBEAUT_USIO_PORTS][2];
+
+#define MLB_USIO_REG_SMR		0
+#define MLB_USIO_REG_SCR		1
+#define MLB_USIO_REG_ESCR		2
+#define MLB_USIO_REG_SSR		3
+#define MLB_USIO_REG_DR			4
+#define MLB_USIO_REG_BGR		6
+#define MLB_USIO_REG_FCR		12
+#define MLB_USIO_REG_FBYTE		14
+
+#define MLB_USIO_SMR_SOE		BIT(0)
+#define MLB_USIO_SMR_SBL		BIT(3)
+#define MLB_USIO_SCR_TXE		BIT(0)
+#define MLB_USIO_SCR_RXE		BIT(1)
+#define MLB_USIO_SCR_TBIE		BIT(2)
+#define MLB_USIO_SCR_TIE		BIT(3)
+#define MLB_USIO_SCR_RIE		BIT(4)
+#define MLB_USIO_SCR_UPCL		BIT(7)
+#define MLB_USIO_ESCR_L_8BIT		0
+#define MLB_USIO_ESCR_L_5BIT		1
+#define MLB_USIO_ESCR_L_6BIT		2
+#define MLB_USIO_ESCR_L_7BIT		3
+#define MLB_USIO_ESCR_P			BIT(3)
+#define MLB_USIO_ESCR_PEN		BIT(4)
+#define MLB_USIO_ESCR_FLWEN		BIT(7)
+#define MLB_USIO_SSR_TBI		BIT(0)
+#define MLB_USIO_SSR_TDRE		BIT(1)
+#define MLB_USIO_SSR_RDRF		BIT(2)
+#define MLB_USIO_SSR_ORE		BIT(3)
+#define MLB_USIO_SSR_FRE		BIT(4)
+#define MLB_USIO_SSR_PE			BIT(5)
+#define MLB_USIO_SSR_REC		BIT(7)
+#define MLB_USIO_SSR_BRK		BIT(8)
+#define MLB_USIO_FCR_FE1		BIT(0)
+#define MLB_USIO_FCR_FE2		BIT(1)
+#define MLB_USIO_FCR_FCL1		BIT(2)
+#define MLB_USIO_FCR_FCL2		BIT(3)
+#define MLB_USIO_FCR_FSET		BIT(4)
+#define MLB_USIO_FCR_FTIE		BIT(9)
+#define MLB_USIO_FCR_FDRQ		BIT(10)
+#define MLB_USIO_FCR_FRIIE		BIT(11)
+
+static void mlb_usio_stop_tx(struct uart_port *port)
+{
+	writew(readw(port->membase + MLB_USIO_REG_FCR) & ~MLB_USIO_FCR_FTIE,
+	       port->membase + MLB_USIO_REG_FCR);
+	writeb(readb(port->membase + MLB_USIO_REG_SCR) & ~MLB_USIO_SCR_TBIE,
+	       port->membase + MLB_USIO_REG_SCR);
+}
+
+static void mlb_usio_tx_chars(struct uart_port *port)
+{
+	struct circ_buf *xmit = &port->state->xmit;
+	int count;
+
+	writew(readw(port->membase + MLB_USIO_REG_FCR) & ~MLB_USIO_FCR_FTIE,
+	       port->membase + MLB_USIO_REG_FCR);
+	writeb(readb(port->membase + MLB_USIO_REG_SCR) &
+	       ~(MLB_USIO_SCR_TIE | MLB_USIO_SCR_TBIE),
+	       port->membase + MLB_USIO_REG_SCR);
+
+	if (port->x_char) {
+		writew(port->x_char, port->membase + MLB_USIO_REG_DR);
+		port->icount.tx++;
+		port->x_char = 0;
+		return;
+	}
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+		mlb_usio_stop_tx(port);
+		return;
+	}
+
+	count = port->fifosize -
+		(readw(port->membase + MLB_USIO_REG_FBYTE) & 0xff);
+
+	do {
+		writew(xmit->buf[xmit->tail], port->membase + MLB_USIO_REG_DR);
+
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		port->icount.tx++;
+		if (uart_circ_empty(xmit))
+			break;
+
+	} while (--count > 0);
+
+	writew(readw(port->membase + MLB_USIO_REG_FCR) & ~MLB_USIO_FCR_FDRQ,
+	       port->membase + MLB_USIO_REG_FCR);
+
+	writeb(readb(port->membase + MLB_USIO_REG_SCR) | MLB_USIO_SCR_TBIE,
+	       port->membase + MLB_USIO_REG_SCR);
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
+
+	if (uart_circ_empty(xmit))
+		mlb_usio_stop_tx(port);
+}
+
+static void mlb_usio_start_tx(struct uart_port *port)
+{
+	u16 fcr = readw(port->membase + MLB_USIO_REG_FCR);
+
+	writew(fcr | MLB_USIO_FCR_FTIE, port->membase + MLB_USIO_REG_FCR);
+	if (!(fcr & MLB_USIO_FCR_FDRQ))
+		return;
+
+	writeb(readb(port->membase + MLB_USIO_REG_SCR) | MLB_USIO_SCR_TBIE,
+	       port->membase + MLB_USIO_REG_SCR);
+
+	if (readb(port->membase + MLB_USIO_REG_SSR) & MLB_USIO_SSR_TBI)
+		mlb_usio_tx_chars(port);
+}
+
+static void mlb_usio_stop_rx(struct uart_port *port)
+{
+	writeb(readb(port->membase + MLB_USIO_REG_SCR) & ~MLB_USIO_SCR_RIE,
+	       port->membase + MLB_USIO_REG_SCR);
+}
+
+static void mlb_usio_enable_ms(struct uart_port *port)
+{
+	writeb(readb(port->membase + MLB_USIO_REG_SCR) |
+	       MLB_USIO_SCR_RIE | MLB_USIO_SCR_RXE,
+	       port->membase + MLB_USIO_REG_SCR);
+}
+
+static void mlb_usio_rx_chars(struct uart_port *port)
+{
+	struct tty_port *ttyport = &port->state->port;
+	unsigned long flag = 0;
+	char ch = 0;
+	u8 status;
+	int max_count = 2;
+
+	while (max_count--) {
+		status = readb(port->membase + MLB_USIO_REG_SSR);
+
+		if (!(status & MLB_USIO_SSR_RDRF))
+			break;
+
+		if (!(status & (MLB_USIO_SSR_ORE | MLB_USIO_SSR_FRE |
+				MLB_USIO_SSR_PE))) {
+			ch = readw(port->membase + MLB_USIO_REG_DR);
+			flag = TTY_NORMAL;
+			port->icount.rx++;
+			if (uart_handle_sysrq_char(port, ch))
+				continue;
+			uart_insert_char(port, status, MLB_USIO_SSR_ORE,
+					 ch, flag);
+			continue;
+		}
+		if (status & MLB_USIO_SSR_PE)
+			port->icount.parity++;
+		if (status & MLB_USIO_SSR_ORE)
+			port->icount.overrun++;
+		status &= port->read_status_mask;
+		if (status & MLB_USIO_SSR_BRK) {
+			flag = TTY_BREAK;
+			ch = 0;
+		} else
+			if (status & MLB_USIO_SSR_PE) {
+				flag = TTY_PARITY;
+				ch = 0;
+			} else
+				if (status & MLB_USIO_SSR_FRE) {
+					flag = TTY_FRAME;
+					ch = 0;
+				}
+		if (flag)
+			uart_insert_char(port, status, MLB_USIO_SSR_ORE,
+					 ch, flag);
+
+		writeb(readb(port->membase + MLB_USIO_REG_SSR) |
+				MLB_USIO_SSR_REC,
+				port->membase + MLB_USIO_REG_SSR);
+
+		max_count = readw(port->membase + MLB_USIO_REG_FBYTE) >> 8;
+		writew(readw(port->membase + MLB_USIO_REG_FCR) |
+		       MLB_USIO_FCR_FE2 | MLB_USIO_FCR_FRIIE,
+		port->membase + MLB_USIO_REG_FCR);
+	}
+
+	tty_flip_buffer_push(ttyport);
+}
+
+static irqreturn_t mlb_usio_rx_irq(int irq, void *dev_id)
+{
+	struct uart_port *port = dev_id;
+
+	spin_lock(&port->lock);
+	mlb_usio_rx_chars(port);
+	spin_unlock(&port->lock);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t mlb_usio_tx_irq(int irq, void *dev_id)
+{
+	struct uart_port *port = dev_id;
+
+	spin_lock(&port->lock);
+	if (readb(port->membase + MLB_USIO_REG_SSR) & MLB_USIO_SSR_TBI)
+		mlb_usio_tx_chars(port);
+	spin_unlock(&port->lock);
+
+	return IRQ_HANDLED;
+}
+
+static unsigned int mlb_usio_tx_empty(struct uart_port *port)
+{
+	return (readb(port->membase + MLB_USIO_REG_SSR) & MLB_USIO_SSR_TBI) ?
+		TIOCSER_TEMT : 0;
+}
+
+static void mlb_usio_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+}
+
+static unsigned int mlb_usio_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
+
+}
+
+static void mlb_usio_break_ctl(struct uart_port *port, int break_state)
+{
+}
+
+static int mlb_usio_startup(struct uart_port *port)
+{
+	const char *portname = to_platform_device(port->dev)->name;
+	unsigned long flags;
+	int ret, index = port->line;
+	unsigned char  escr;
+
+	ret = request_irq(mlb_usio_irq[index][RX], mlb_usio_rx_irq,
+				0, portname, port);
+	if (ret)
+		return ret;
+	ret = request_irq(mlb_usio_irq[index][TX], mlb_usio_tx_irq,
+				0, portname, port);
+	if (ret) {
+		free_irq(mlb_usio_irq[index][RX], port);
+		return ret;
+	}
+
+	escr = readb(port->membase + MLB_USIO_REG_ESCR);
+	if (of_property_read_bool(port->dev->of_node, "auto-flow-control"))
+		escr |= MLB_USIO_ESCR_FLWEN;
+	spin_lock_irqsave(&port->lock, flags);
+	writeb(0, port->membase + MLB_USIO_REG_SCR);
+	writeb(escr, port->membase + MLB_USIO_REG_ESCR);
+	writeb(MLB_USIO_SCR_UPCL, port->membase + MLB_USIO_REG_SCR);
+	writeb(MLB_USIO_SSR_REC, port->membase + MLB_USIO_REG_SSR);
+	writew(0, port->membase + MLB_USIO_REG_FCR);
+	writew(MLB_USIO_FCR_FCL1 | MLB_USIO_FCR_FCL2,
+	       port->membase + MLB_USIO_REG_FCR);
+	writew(MLB_USIO_FCR_FE1 | MLB_USIO_FCR_FE2 | MLB_USIO_FCR_FRIIE,
+	       port->membase + MLB_USIO_REG_FCR);
+	writew(0, port->membase + MLB_USIO_REG_FBYTE);
+	writew(BIT(12), port->membase + MLB_USIO_REG_FBYTE);
+
+	writeb(MLB_USIO_SCR_TXE  | MLB_USIO_SCR_RIE | MLB_USIO_SCR_TBIE |
+	       MLB_USIO_SCR_RXE, port->membase + MLB_USIO_REG_SCR);
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	return 0;
+}
+
+static void mlb_usio_shutdown(struct uart_port *port)
+{
+	int index = port->line;
+
+	free_irq(mlb_usio_irq[index][RX], port);
+	free_irq(mlb_usio_irq[index][TX], port);
+}
+
+static void mlb_usio_set_termios(struct uart_port *port,
+			struct ktermios *termios, struct ktermios *old)
+{
+	unsigned int escr, smr = MLB_USIO_SMR_SOE;
+	unsigned long flags, baud, quot;
+
+	switch (termios->c_cflag & CSIZE) {
+	case CS5:
+		escr = MLB_USIO_ESCR_L_5BIT;
+		break;
+	case CS6:
+		escr = MLB_USIO_ESCR_L_6BIT;
+		break;
+	case CS7:
+		escr = MLB_USIO_ESCR_L_7BIT;
+		break;
+	case CS8:
+	default:
+		escr = MLB_USIO_ESCR_L_8BIT;
+		break;
+	}
+
+	if (termios->c_cflag & CSTOPB)
+		smr |= MLB_USIO_SMR_SBL;
+
+	if (termios->c_cflag & PARENB) {
+		escr |= MLB_USIO_ESCR_PEN;
+		if (termios->c_cflag & PARODD)
+			escr |= MLB_USIO_ESCR_P;
+	}
+	/* Set hard flow control */
+	if (of_property_read_bool(port->dev->of_node, "auto-flow-control") ||
+			(termios->c_cflag & CRTSCTS))
+		escr |= MLB_USIO_ESCR_FLWEN;
+
+	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk);
+	if (baud > 1)
+		quot = port->uartclk / baud - 1;
+	else
+		quot = 0;
+
+	spin_lock_irqsave(&port->lock, flags);
+	uart_update_timeout(port, termios->c_cflag, baud);
+	port->read_status_mask = MLB_USIO_SSR_ORE | MLB_USIO_SSR_RDRF |
+				 MLB_USIO_SSR_TDRE;
+	if (termios->c_iflag & INPCK)
+		port->read_status_mask |= MLB_USIO_SSR_FRE | MLB_USIO_SSR_PE;
+
+	port->ignore_status_mask = 0;
+	if (termios->c_iflag & IGNPAR)
+		port->ignore_status_mask |= MLB_USIO_SSR_FRE | MLB_USIO_SSR_PE;
+	if ((termios->c_iflag & IGNBRK) && (termios->c_iflag & IGNPAR))
+		port->ignore_status_mask |= MLB_USIO_SSR_ORE;
+	if ((termios->c_cflag & CREAD) == 0)
+		port->ignore_status_mask |= MLB_USIO_SSR_RDRF;
+
+	writeb(0, port->membase + MLB_USIO_REG_SCR);
+	writeb(MLB_USIO_SCR_UPCL, port->membase + MLB_USIO_REG_SCR);
+	writeb(MLB_USIO_SSR_REC, port->membase + MLB_USIO_REG_SSR);
+	writew(0, port->membase + MLB_USIO_REG_FCR);
+	writeb(smr, port->membase + MLB_USIO_REG_SMR);
+	writeb(escr, port->membase + MLB_USIO_REG_ESCR);
+	writew(quot, port->membase + MLB_USIO_REG_BGR);
+	writew(0, port->membase + MLB_USIO_REG_FCR);
+	writew(MLB_USIO_FCR_FCL1 | MLB_USIO_FCR_FCL2 | MLB_USIO_FCR_FE1 |
+	       MLB_USIO_FCR_FE2 | MLB_USIO_FCR_FRIIE,
+	       port->membase + MLB_USIO_REG_FCR);
+	writew(0, port->membase + MLB_USIO_REG_FBYTE);
+	writew(BIT(12), port->membase + MLB_USIO_REG_FBYTE);
+	writeb(MLB_USIO_SCR_RIE | MLB_USIO_SCR_RXE | MLB_USIO_SCR_TBIE |
+	       MLB_USIO_SCR_TXE, port->membase + MLB_USIO_REG_SCR);
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static const char *mlb_usio_type(struct uart_port *port)
+{
+	return ((port->type == PORT_MLB_USIO) ? USIO_NAME : NULL);
+}
+
+static void mlb_usio_config_port(struct uart_port *port, int flags)
+{
+	if (flags & UART_CONFIG_TYPE)
+		port->type = PORT_MLB_USIO;
+}
+
+static const struct uart_ops mlb_usio_ops = {
+	.tx_empty	= mlb_usio_tx_empty,
+	.set_mctrl	= mlb_usio_set_mctrl,
+	.get_mctrl	= mlb_usio_get_mctrl,
+	.stop_tx	= mlb_usio_stop_tx,
+	.start_tx	= mlb_usio_start_tx,
+	.stop_rx	= mlb_usio_stop_rx,
+	.enable_ms	= mlb_usio_enable_ms,
+	.break_ctl	= mlb_usio_break_ctl,
+	.startup	= mlb_usio_startup,
+	.shutdown	= mlb_usio_shutdown,
+	.set_termios	= mlb_usio_set_termios,
+	.type		= mlb_usio_type,
+	.config_port	= mlb_usio_config_port,
+};
+
+#ifdef CONFIG_SERIAL_MILBEAUT_USIO_CONSOLE
+
+static void mlb_usio_console_putchar(struct uart_port *port, int c)
+{
+	while (!(readb(port->membase + MLB_USIO_REG_SSR) & MLB_USIO_SSR_TDRE))
+		cpu_relax();
+
+	writew(c, port->membase + MLB_USIO_REG_DR);
+}
+
+static void mlb_usio_console_write(struct console *co, const char *s,
+			       unsigned int count)
+{
+	struct uart_port *port = &mlb_usio_ports[co->index];
+
+	uart_console_write(port, s, count, mlb_usio_console_putchar);
+}
+
+static int __init mlb_usio_console_setup(struct console *co, char *options)
+{
+	struct uart_port *port;
+	int baud = 115200;
+	int parity = 'n';
+	int flow = 'n';
+	int bits = 8;
+
+	if (co->index >= CONFIG_SERIAL_MILBEAUT_USIO_PORTS)
+		return -ENODEV;
+
+	port = &mlb_usio_ports[co->index];
+	if (!port->membase)
+		return -ENODEV;
+
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	if (of_property_read_bool(port->dev->of_node, "auto-flow-control"))
+		flow = 'r';
+
+	return uart_set_options(port, co, baud, parity, bits, flow);
+}
+
+
+static struct uart_driver mlb_usio_uart_driver;
+static struct console mlb_usio_console = {
+	.name   = USIO_UART_DEV_NAME,
+	.write  = mlb_usio_console_write,
+	.device = uart_console_device,
+	.setup  = mlb_usio_console_setup,
+	.flags  = CON_PRINTBUFFER,
+	.index  = -1,
+	.data   = &mlb_usio_uart_driver,
+};
+
+static int __init mlb_usio_console_init(void)
+{
+	register_console(&mlb_usio_console);
+	return 0;
+}
+console_initcall(mlb_usio_console_init);
+
+
+static void mlb_usio_early_console_write(struct console *co, const char *s,
+					u_int count)
+{
+	struct earlycon_device *dev = co->data;
+
+	uart_console_write(&dev->port, s, count, mlb_usio_console_putchar);
+}
+
+static int __init mlb_usio_early_console_setup(struct earlycon_device *device,
+						const char *opt)
+{
+	if (!device->port.membase)
+		return -ENODEV;
+	device->con->write = mlb_usio_early_console_write;
+	return 0;
+}
+
+OF_EARLYCON_DECLARE(mlb_usio, "socionext,milbeaut-usio-uart",
+			mlb_usio_early_console_setup);
+
+#define USIO_CONSOLE	(&mlb_usio_console)
+#else
+#define USIO_CONSOLE	NULL
+#endif
+
+static struct  uart_driver mlb_usio_uart_driver = {
+	.owner		= THIS_MODULE,
+	.driver_name	= USIO_NAME,
+	.dev_name	= USIO_UART_DEV_NAME,
+	.cons           = USIO_CONSOLE,
+	.nr		= CONFIG_SERIAL_MILBEAUT_USIO_PORTS,
+};
+
+static int mlb_usio_probe(struct platform_device *pdev)
+{
+	struct clk *clk = devm_clk_get(&pdev->dev, 0);
+	struct uart_port *port;
+	struct resource *res;
+	int index = 0;
+	int ret;
+
+	if (IS_ERR(clk)) {
+		dev_err(&pdev->dev, "Missing clock\n");
+		return PTR_ERR(clk);
+	}
+	ret = clk_prepare_enable(clk);
+	if (ret) {
+		dev_err(&pdev->dev, "Clock enable failed: %d\n", ret);
+		return ret;
+	}
+	of_property_read_u32(pdev->dev.of_node, "index", &index);
+	port = &mlb_usio_ports[index];
+
+	port->private_data = (void *)clk;
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (res == NULL) {
+		dev_err(&pdev->dev, "Missing regs\n");
+		ret = -ENODEV;
+		goto failed;
+	}
+	port->mapbase = res->start;
+	port->membase = ioremap(res->start, (res->end - res->start + 1));
+	port->membase = devm_ioremap(&pdev->dev, res->start,
+				resource_size(res));
+
+	ret = platform_get_irq_byname(pdev, "rx");
+	mlb_usio_irq[index][RX] = ret;
+
+	ret = platform_get_irq_byname(pdev, "tx");
+	mlb_usio_irq[index][TX] = ret;
+
+	port->irq = mlb_usio_irq[index][RX];
+	port->uartclk = clk_get_rate(clk);
+	port->fifosize = 128;
+	port->iotype = UPIO_MEM32;
+	port->flags = UPF_BOOT_AUTOCONF | UPF_SPD_VHI;
+	port->line = index;
+	port->ops = &mlb_usio_ops;
+	port->dev = &pdev->dev;
+
+	ret = uart_add_one_port(&mlb_usio_uart_driver, port);
+	if (ret) {
+		dev_err(&pdev->dev, "Adding port failed: %d\n", ret);
+		goto failed1;
+	}
+	return 0;
+
+failed1:
+	iounmap(port->membase);
+
+failed:
+	clk_disable_unprepare(clk);
+	clk_put(clk);
+
+	return ret;
+}
+
+static int mlb_usio_remove(struct platform_device *pdev)
+{
+	struct uart_port *port = &mlb_usio_ports[pdev->id];
+	struct clk *clk = port->private_data;
+
+	uart_remove_one_port(&mlb_usio_uart_driver, port);
+	clk_disable_unprepare(clk);
+	clk_put(clk);
+
+	return 0;
+}
+
+static const struct of_device_id mlb_usio_dt_ids[] = {
+	{ .compatible = "socionext,milbeaut-usio-uart" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mlb_usio_dt_ids);
+
+static struct platform_driver mlb_usio_driver = {
+	.probe          = mlb_usio_probe,
+	.remove         = mlb_usio_remove,
+	.driver         = {
+		.name   = USIO_NAME,
+		.of_match_table = mlb_usio_dt_ids,
+	},
+};
+
+static int __init mlb_usio_init(void)
+{
+	int ret = uart_register_driver(&mlb_usio_uart_driver);
+
+	if (ret) {
+		pr_err("%s: uart registration failed: %d\n", __func__, ret);
+		return ret;
+	}
+	ret = platform_driver_register(&mlb_usio_driver);
+	if (ret) {
+		uart_unregister_driver(&mlb_usio_uart_driver);
+		pr_err("%s: drv registration failed: %d\n", __func__, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit mlb_usio_exit(void)
+{
+	platform_driver_unregister(&mlb_usio_driver);
+	uart_unregister_driver(&mlb_usio_uart_driver);
+}
+
+module_init(mlb_usio_init);
+module_exit(mlb_usio_exit);
+
+MODULE_AUTHOR("SOCIONEXT");
+MODULE_DESCRIPTION("MILBEAUT_USIO/UART Driver");
+MODULE_LICENSE("GPL");
diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h
index 6009ee2c2e99..a51c747b52c5 100644
--- a/include/uapi/linux/serial_core.h
+++ b/include/uapi/linux/serial_core.h
@@ -287,4 +287,7 @@
 /* RDA UART */
 #define PORT_RDA	118
 
+/* Socionext Milbeaut UART */
+#define PORT_MLB_USIO	119
+
 #endif /* _UAPILINUX_SERIAL_CORE_H */