serial/arc-uart: Add new driver

Driver for non-standard on-chip UART, instantiated in the ARC (Synopsys)
FPGA Boards such as ARCAngel4/ML50x
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/Kconfig

@@ -1423,4 +1423,27 @@ config SERIAL_EFM32_UART_CONSOLE
 	depends on SERIAL_EFM32_UART=y
 	select SERIAL_CORE_CONSOLE
 
+config SERIAL_ARC
+	tristate "ARC UART driver support"
+	select SERIAL_CORE
+	help
+	  Driver for on-chip UART for ARC(Synopsys) for the legacy
+	  FPGA Boards (ML50x/ARCAngel4)
+
+config SERIAL_ARC_CONSOLE
+	bool "Console on ARC UART"
+	depends on SERIAL_ARC=y
+	select SERIAL_CORE_CONSOLE
+	help
+	  Enable system Console on ARC UART
+
+config SERIAL_ARC_NR_PORTS
+	int "Number of ARC UART ports"
+	depends on SERIAL_ARC
+	range 1 3
+	default "1"
+	help
+	  Set this to the number of serial ports you want the driver
+	  to support.
+
 endmenu

drivers/tty/serial/Makefile

@@ -82,3 +82,4 @@ obj-$(CONFIG_SERIAL_XILINX_PS_UART) += xilinx_uartps.o
 obj-$(CONFIG_SERIAL_SIRFSOC) += sirfsoc_uart.o
 obj-$(CONFIG_SERIAL_AR933X)   += ar933x_uart.o
 obj-$(CONFIG_SERIAL_EFM32_UART) += efm32-uart.o
+obj-$(CONFIG_SERIAL_ARC)	+= arc_uart.o

drivers/tty/serial/arc_uart.c

+/*
+ * ARC On-Chip(fpga) UART Driver
+ *
+ * Copyright (C) 2010-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * vineetg: July 10th 2012
+ *  -Decoupled the driver from arch/arc
+ *    +Using platform_get_resource() for irq/membase (thx to bfin_uart.c)
+ *    +Using early_platform_xxx() for early console (thx to mach-shmobile/xxx)
+ *
+ * Vineetg: Aug 21st 2010
+ *  -Is uart_tx_stopped() not done in tty write path as it has already been
+ *   taken care of, in serial core
+ *
+ * Vineetg: Aug 18th 2010
+ *  -New Serial Core based ARC UART driver
+ *  -Derived largely from blackfin driver albiet with some major tweaks
+ *
+ * TODO:
+ *  -check if sysreq works
+ */
+
+#if defined(CONFIG_SERIAL_ARC_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#define SUPPORT_SYSRQ
+#endif
+
+#include <linux/module.h>
+#include <linux/serial.h>
+#include <linux/console.h>
+#include <linux/sysrq.h>
+#include <linux/platform_device.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial_core.h>
+#include <linux/io.h>
+
+/*************************************
+ * ARC UART Hardware Specs
+ ************************************/
+#define ARC_UART_TX_FIFO_SIZE  1
+
+/*
+ * UART Register set (this is not a Standards Compliant IP)
+ * Also each reg is Word aligned, but only 8 bits wide
+ */
+#define R_ID0	0
+#define R_ID1	4
+#define R_ID2	8
+#define R_ID3	12
+#define R_DATA	16
+#define R_STS	20
+#define R_BAUDL	24
+#define R_BAUDH	28
+
+/* Bits for UART Status Reg (R/W) */
+#define RXIENB  0x04	/* Receive Interrupt Enable */
+#define TXIENB  0x40	/* Transmit Interrupt Enable */
+
+#define RXEMPTY 0x20	/* Receive FIFO Empty: No char receivede */
+#define TXEMPTY 0x80	/* Transmit FIFO Empty, thus char can be written into */
+
+#define RXFULL  0x08	/* Receive FIFO full */
+#define RXFULL1 0x10	/* Receive FIFO has space for 1 char (tot space=4) */
+
+#define RXFERR  0x01	/* Frame Error: Stop Bit not detected */
+#define RXOERR  0x02	/* OverFlow Err: Char recv but RXFULL still set */
+
+/* Uart bit fiddling helpers: lowest level */
+#define RBASE(uart, reg)      (uart->port.membase + reg)
+#define UART_REG_SET(u, r, v) writeb((v), RBASE(u, r))
+#define UART_REG_GET(u, r)    readb(RBASE(u, r))
+
+#define UART_REG_OR(u, r, v)  UART_REG_SET(u, r, UART_REG_GET(u, r) | (v))
+#define UART_REG_CLR(u, r, v) UART_REG_SET(u, r, UART_REG_GET(u, r) & ~(v))
+
+/* Uart bit fiddling helpers: API level */
+#define UART_SET_DATA(uart, val)   UART_REG_SET(uart, R_DATA, val)
+#define UART_GET_DATA(uart)        UART_REG_GET(uart, R_DATA)
+
+#define UART_SET_BAUDH(uart, val)  UART_REG_SET(uart, R_BAUDH, val)
+#define UART_SET_BAUDL(uart, val)  UART_REG_SET(uart, R_BAUDL, val)
+
+#define UART_CLR_STATUS(uart, val) UART_REG_CLR(uart, R_STS, val)
+#define UART_GET_STATUS(uart)      UART_REG_GET(uart, R_STS)
+
+#define UART_ALL_IRQ_DISABLE(uart) UART_REG_CLR(uart, R_STS, RXIENB|TXIENB)
+#define UART_RX_IRQ_DISABLE(uart)  UART_REG_CLR(uart, R_STS, RXIENB)
+#define UART_TX_IRQ_DISABLE(uart)  UART_REG_CLR(uart, R_STS, TXIENB)
+
+#define UART_ALL_IRQ_ENABLE(uart)  UART_REG_OR(uart, R_STS, RXIENB|TXIENB)
+#define UART_RX_IRQ_ENABLE(uart)   UART_REG_OR(uart, R_STS, RXIENB)
+#define UART_TX_IRQ_ENABLE(uart)   UART_REG_OR(uart, R_STS, TXIENB)
+
+#define ARC_SERIAL_DEV_NAME	"ttyARC"
+
+struct arc_uart_port {
+	struct uart_port port;
+	unsigned long baud;
+	int is_emulated;	/* H/w vs. Instruction Set Simulator */
+};
+
+#define to_arc_port(uport)  container_of(uport, struct arc_uart_port, port)
+
+static struct arc_uart_port arc_uart_ports[CONFIG_SERIAL_ARC_NR_PORTS];
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+static struct console arc_console;
+#endif
+
+#define DRIVER_NAME	"arc-uart"
+
+static struct uart_driver arc_uart_driver = {
+	.owner		= THIS_MODULE,
+	.driver_name	= DRIVER_NAME,
+	.dev_name	= ARC_SERIAL_DEV_NAME,
+	.major		= 0,
+	.minor		= 0,
+	.nr		= CONFIG_SERIAL_ARC_NR_PORTS,
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+	.cons		= &arc_console,
+#endif
+};
+
+static void arc_serial_stop_rx(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+
+	UART_RX_IRQ_DISABLE(uart);
+}
+
+static void arc_serial_stop_tx(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+
+	while (!(UART_GET_STATUS(uart) & TXEMPTY))
+		cpu_relax();
+
+	UART_TX_IRQ_DISABLE(uart);
+}
+
+/*
+ * Return TIOCSER_TEMT when transmitter is not busy.
+ */
+static unsigned int arc_serial_tx_empty(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+	unsigned int stat;
+
+	stat = UART_GET_STATUS(uart);
+	if (stat & TXEMPTY)
+		return TIOCSER_TEMT;
+
+	return 0;
+}
+
+/*
+ * Driver internal routine, used by both tty(serial core) as well as tx-isr
+ *  -Called under spinlock in either cases
+ *  -also tty->stopped / tty->hw_stopped has already been checked
+ *     = by uart_start( ) before calling us
+ *     = tx_ist checks that too before calling
+ */
+static void arc_serial_tx_chars(struct arc_uart_port *uart)
+{
+	struct circ_buf *xmit = &uart->port.state->xmit;
+	int sent = 0;
+	unsigned char ch;
+
+	if (unlikely(uart->port.x_char)) {
+		UART_SET_DATA(uart, uart->port.x_char);
+		uart->port.icount.tx++;
+		uart->port.x_char = 0;
+		sent = 1;
+	} else if (xmit->tail != xmit->head) {	/* TODO: uart_circ_empty */
+		ch = xmit->buf[xmit->tail];
+		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+		uart->port.icount.tx++;
+		while (!(UART_GET_STATUS(uart) & TXEMPTY))
+			cpu_relax();
+		UART_SET_DATA(uart, ch);
+		sent = 1;
+	}
+
+	/*
+	 * If num chars in xmit buffer are too few, ask tty layer for more.
+	 * By Hard ISR to schedule processing in software interrupt part
+	 */
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&uart->port);
+
+	if (sent)
+		UART_TX_IRQ_ENABLE(uart);
+}
+
+/*
+ * port is locked and interrupts are disabled
+ * uart_start( ) calls us under the port spinlock irqsave
+ */
+static void arc_serial_start_tx(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+
+	arc_serial_tx_chars(uart);
+}
+
+static void arc_serial_rx_chars(struct arc_uart_port *uart)
+{
+	struct tty_struct *tty = tty_port_tty_get(&uart->port.state->port);
+	unsigned int status, ch, flg = 0;
+
+	if (!tty)
+		return;
+
+	/*
+	 * UART has 4 deep RX-FIFO. Driver's recongnition of this fact
+	 * is very subtle. Here's how ...
+	 * Upon getting a RX-Intr, such that RX-EMPTY=0, meaning data available,
+	 * driver reads the DATA Reg and keeps doing that in a loop, until
+	 * RX-EMPTY=1. Multiple chars being avail, with a single Interrupt,
+	 * before RX-EMPTY=0, implies some sort of buffering going on in the
+	 * controller, which is indeed the Rx-FIFO.
+	 */
+	while (!((status = UART_GET_STATUS(uart)) & RXEMPTY)) {
+
+		ch = UART_GET_DATA(uart);
+		uart->port.icount.rx++;
+
+		if (unlikely(status & (RXOERR | RXFERR))) {
+			if (status & RXOERR) {
+				uart->port.icount.overrun++;
+				flg = TTY_OVERRUN;
+				UART_CLR_STATUS(uart, RXOERR);
+			}
+
+			if (status & RXFERR) {
+				uart->port.icount.frame++;
+				flg = TTY_FRAME;
+				UART_CLR_STATUS(uart, RXFERR);
+			}
+		} else
+			flg = TTY_NORMAL;
+
+		if (unlikely(uart_handle_sysrq_char(&uart->port, ch)))
+			goto done;
+
+		uart_insert_char(&uart->port, status, RXOERR, ch, flg);
+
+done:
+		tty_flip_buffer_push(tty);
+	}
+
+	tty_kref_put(tty);
+}
+
+/*
+ * A note on the Interrupt handling state machine of this driver
+ *
+ * kernel printk writes funnel thru the console driver framework and in order
+ * to keep things simple as well as efficient, it writes to UART in polled
+ * mode, in one shot, and exits.
+ *
+ * OTOH, Userland output (via tty layer), uses interrupt based writes as there
+ * can be undeterministic delay between char writes.
+ *
+ * Thus Rx-interrupts are always enabled, while tx-interrupts are by default
+ * disabled.
+ *
+ * When tty has some data to send out, serial core calls driver's start_tx
+ * which
+ *   -checks-if-tty-buffer-has-char-to-send
+ *   -writes-data-to-uart
+ *   -enable-tx-intr
+ *
+ * Once data bits are pushed out, controller raises the Tx-room-avail-Interrupt.
+ * The first thing Tx ISR does is disable further Tx interrupts (as this could
+ * be the last char to send, before settling down into the quiet polled mode).
+ * It then calls the exact routine used by tty layer write to send out any
+ * more char in tty buffer. In case of sending, it re-enables Tx-intr. In case
+ * of no data, it remains disabled.
+ * This is how the transmit state machine is dynamically switched on/off
+ */
+
+static irqreturn_t arc_serial_isr(int irq, void *dev_id)
+{
+	struct arc_uart_port *uart = dev_id;
+	unsigned int status;
+
+	status = UART_GET_STATUS(uart);
+
+	/*
+	 * Single IRQ for both Rx (data available) Tx (room available) Interrupt
+	 * notifications from the UART Controller.
+	 * To demultiplex between the two, we check the relevant bits
+	 */
+	if ((status & RXIENB) && !(status & RXEMPTY)) {
+
+		/* already in ISR, no need of xx_irqsave */
+		spin_lock(&uart->port.lock);
+		arc_serial_rx_chars(uart);
+		spin_unlock(&uart->port.lock);
+	}
+
+	if ((status & TXIENB) && (status & TXEMPTY)) {
+
+		/* Unconditionally disable further Tx-Interrupts.
+		 * will be enabled by tx_chars() if needed.
+		 */
+		UART_TX_IRQ_DISABLE(uart);
+
+		spin_lock(&uart->port.lock);
+
+		if (!uart_tx_stopped(&uart->port))
+			arc_serial_tx_chars(uart);
+
+		spin_unlock(&uart->port.lock);
+	}
+
+	return IRQ_HANDLED;
+}
+
+static unsigned int arc_serial_get_mctrl(struct uart_port *port)
+{
+	/*
+	 * Pretend we have a Modem status reg and following bits are
+	 *  always set, to satify the serial core state machine
+	 *  (DSR) Data Set Ready
+	 *  (CTS) Clear To Send
+	 *  (CAR) Carrier Detect
+	 */
+	return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
+}
+
+static void arc_serial_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	/* MCR not present */
+}
+
+/* Enable Modem Status Interrupts */
+
+static void arc_serial_enable_ms(struct uart_port *port)
+{
+	/* MSR not present */
+}
+
+static void arc_serial_break_ctl(struct uart_port *port, int break_state)
+{
+	/* ARC UART doesn't support sending Break signal */
+}
+
+static int arc_serial_startup(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+
+	/* Before we hook up the ISR, Disable all UART Interrupts */
+	UART_ALL_IRQ_DISABLE(uart);
+
+	if (request_irq(uart->port.irq, arc_serial_isr, 0, "arc uart rx-tx",
+			uart)) {
+		dev_warn(uart->port.dev, "Unable to attach ARC UART intr\n");
+		return -EBUSY;
+	}
+
+	UART_RX_IRQ_ENABLE(uart); /* Only Rx IRQ enabled to begin with */
+
+	return 0;
+}
+
+/* This is not really needed */
+static void arc_serial_shutdown(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+	free_irq(uart->port.irq, uart);
+}
+
+static void
+arc_serial_set_termios(struct uart_port *port, struct ktermios *new,
+		       struct ktermios *old)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+	unsigned int baud, uartl, uarth, hw_val;
+	unsigned long flags;
+
+	/*
+	 * Use the generic handler so that any specially encoded baud rates
+	 * such as SPD_xx flags or "%B0" can be handled
+	 * Max Baud I suppose will not be more than current 115K * 4
+	 * Formula for ARC UART is: hw-val = ((CLK/(BAUD*4)) -1)
+	 * spread over two 8-bit registers
+	 */
+	baud = uart_get_baud_rate(port, new, old, 0, 460800);
+
+	hw_val = port->uartclk / (uart->baud * 4) - 1;
+	uartl = hw_val & 0xFF;
+	uarth = (hw_val >> 8) & 0xFF;
+
+	/*
+	 * UART ISS(Instruction Set simulator) emulation has a subtle bug:
+	 * A existing value of Baudh = 0 is used as a indication to startup
+	 * it's internal state machine.
+	 * Thus if baudh is set to 0, 2 times, it chokes.
+	 * This happens with BAUD=115200 and the formaula above
+	 * Until that is fixed, when running on ISS, we will set baudh to !0
+	 */
+	if (uart->is_emulated)
+		uarth = 1;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	UART_ALL_IRQ_DISABLE(uart);
+
+	UART_SET_BAUDL(uart, uartl);
+	UART_SET_BAUDH(uart, uarth);
+
+	UART_RX_IRQ_ENABLE(uart);
+
+	/*
+	 * UART doesn't support Parity/Hardware Flow Control;
+	 * Only supports 8N1 character size
+	 */
+	new->c_cflag &= ~(CMSPAR|CRTSCTS|CSIZE);
+	new->c_cflag |= CS8;
+
+	if (old)
+		tty_termios_copy_hw(new, old);
+
+	/* Don't rewrite B0 */
+	if (tty_termios_baud_rate(new))
+		tty_termios_encode_baud_rate(new, baud, baud);
+
+	uart_update_timeout(port, new->c_cflag, baud);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static const char *arc_serial_type(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+
+	return uart->port.type == PORT_ARC ? DRIVER_NAME : NULL;
+}
+
+static void arc_serial_release_port(struct uart_port *port)
+{
+}
+
+static int arc_serial_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+/*
+ * Verify the new serial_struct (for TIOCSSERIAL).
+ */
+static int
+arc_serial_verify_port(struct uart_port *port, struct serial_struct *ser)
+{
+	if (port->type != PORT_UNKNOWN && ser->type != PORT_ARC)
+		return -EINVAL;
+
+	return 0;
+}
+
+/*
+ * Configure/autoconfigure the port.
+ */
+static void arc_serial_config_port(struct uart_port *port, int flags)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+
+	if (flags & UART_CONFIG_TYPE)
+		uart->port.type = PORT_ARC;
+}
+
+#if defined(CONFIG_CONSOLE_POLL) || defined(CONFIG_SERIAL_ARC_CONSOLE)
+
+static void arc_serial_poll_putchar(struct uart_port *port, unsigned char chr)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+
+	while (!(UART_GET_STATUS(uart) & TXEMPTY))
+		cpu_relax();
+
+	UART_SET_DATA(uart, chr);
+}
+#endif
+
+#ifdef CONFIG_CONSOLE_POLL
+static int arc_serial_poll_getchar(struct uart_port *port)
+{
+	struct arc_uart_port *uart = to_arc_port(port);
+	unsigned char chr;
+
+	while (!(UART_GET_STATUS(uart) & RXEMPTY))
+		cpu_relax();
+
+	chr = UART_GET_DATA(uart);
+	return chr;
+}
+#endif
+
+static struct uart_ops arc_serial_pops = {
+	.tx_empty	= arc_serial_tx_empty,
+	.set_mctrl	= arc_serial_set_mctrl,
+	.get_mctrl	= arc_serial_get_mctrl,
+	.stop_tx	= arc_serial_stop_tx,
+	.start_tx	= arc_serial_start_tx,
+	.stop_rx	= arc_serial_stop_rx,
+	.enable_ms	= arc_serial_enable_ms,
+	.break_ctl	= arc_serial_break_ctl,
+	.startup	= arc_serial_startup,
+	.shutdown	= arc_serial_shutdown,
+	.set_termios	= arc_serial_set_termios,
+	.type		= arc_serial_type,
+	.release_port	= arc_serial_release_port,
+	.request_port	= arc_serial_request_port,
+	.config_port	= arc_serial_config_port,
+	.verify_port	= arc_serial_verify_port,
+#ifdef CONFIG_CONSOLE_POLL
+	.poll_put_char = arc_serial_poll_putchar,
+	.poll_get_char = arc_serial_poll_getchar,
+#endif
+};
+
+static int __devinit
+arc_uart_init_one(struct platform_device *pdev, struct arc_uart_port *uart)
+{
+	struct resource *res, *res2;
+	unsigned long *plat_data;
+
+	if (pdev->id < 0 || pdev->id >= CONFIG_SERIAL_ARC_NR_PORTS) {
+		dev_err(&pdev->dev, "Wrong uart platform device id.\n");
+		return -ENOENT;
+	}
+
+	plat_data = ((unsigned long *)(pdev->dev.platform_data));
+	uart->baud = plat_data[0];
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!res2)
+		return -ENODEV;
+
+	uart->port.mapbase = res->start;
+	uart->port.membase = ioremap_nocache(res->start, resource_size(res));
+	if (!uart->port.membase)
+		/* No point of dev_err since UART itself is hosed here */
+		return -ENXIO;
+
+	uart->port.irq = res2->start;
+	uart->port.dev = &pdev->dev;
+	uart->port.iotype = UPIO_MEM;
+	uart->port.flags = UPF_BOOT_AUTOCONF;
+	uart->port.line = pdev->id;
+	uart->port.ops = &arc_serial_pops;
+
+	uart->port.uartclk = plat_data[1];
+	uart->port.fifosize = ARC_UART_TX_FIFO_SIZE;
+
+	/*
+	 * uart_insert_char( ) uses it in decideding whether to ignore a
+	 * char or not. Explicitly setting it here, removes the subtelty
+	 */
+	uart->port.ignore_status_mask = 0;
+
+	/* Real Hardware vs. emulated to work around a bug */
+	uart->is_emulated = !!plat_data[2];
+
+	return 0;
+}
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+
+static int __devinit arc_serial_console_setup(struct console *co, char *options)
+{
+	struct uart_port *port;
+	int baud = 115200;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	if (co->index < 0 || co->index >= CONFIG_SERIAL_ARC_NR_PORTS)
+		return -ENODEV;
+
+	/*
+	 * The uart port backing the console (e.g. ttyARC1) might not have been
+	 * init yet. If so, defer the console setup to after the port.
+	 */
+	port = &arc_uart_ports[co->index].port;
+	if (!port->membase)
+		return -ENODEV;
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	/*
+	 * Serial core will call port->ops->set_termios( )
+	 * which will set the baud reg
+	 */
+	return uart_set_options(port, co, baud, parity, bits, flow);
+}
+
+static void arc_serial_console_putchar(struct uart_port *port, int ch)
+{
+	arc_serial_poll_putchar(port, (unsigned char)ch);
+}
+
+/*
+ * Interrupts are disabled on entering
+ */
+static void arc_serial_console_write(struct console *co, const char *s,
+				     unsigned int count)
+{
+	struct uart_port *port = &arc_uart_ports[co->index].port;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+	uart_console_write(port, s, count, arc_serial_console_putchar);
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+static struct console arc_console = {
+	.name	= ARC_SERIAL_DEV_NAME,
+	.write	= arc_serial_console_write,
+	.device	= uart_console_device,
+	.setup	= arc_serial_console_setup,
+	.flags	= CON_PRINTBUFFER,
+	.index	= -1,
+	.data	= &arc_uart_driver
+};
+
+static __init void early_serial_write(struct console *con, const char *s,
+					unsigned int n)
+{
+	struct uart_port *port = &arc_uart_ports[con->index].port;
+	unsigned int i;
+
+	for (i = 0; i < n; i++, s++) {
+		if (*s == '\n')
+			arc_serial_poll_putchar(port, '\r');
+		arc_serial_poll_putchar(port, *s);
+	}
+}
+
+static struct __initdata console arc_early_serial_console = {
+	.name = "early_ARCuart",
+	.write = early_serial_write,
+	.flags = CON_PRINTBUFFER | CON_BOOT,
+	.index = -1
+};
+
+static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
+{
+	arc_early_serial_console.index = pdev->id;
+
+	arc_uart_init_one(pdev, &arc_uart_ports[pdev->id]);
+
+	arc_serial_console_setup(&arc_early_serial_console, NULL);
+
+	register_console(&arc_early_serial_console);
+	return 0;
+}
+#else
+static int __devinit arc_serial_probe_earlyprintk(struct platform_device *pdev)
+{
+	return -ENODEV;
+}
+#endif	/* CONFIG_SERIAL_ARC_CONSOLE */
+
+static int __devinit arc_serial_probe(struct platform_device *pdev)
+{
+	struct arc_uart_port *uart;
+	int rc;
+
+	if (is_early_platform_device(pdev))
+		return arc_serial_probe_earlyprintk(pdev);
+
+	uart = &arc_uart_ports[pdev->id];
+	rc = arc_uart_init_one(pdev, uart);
+	if (rc)
+		return rc;
+
+	return uart_add_one_port(&arc_uart_driver, &uart->port);
+}
+
+static int __devexit arc_serial_remove(struct platform_device *pdev)
+{
+	/* This will never be called */
+	return 0;
+}
+
+static struct platform_driver arc_platform_driver = {
+	.probe = arc_serial_probe,
+	.remove = __devexit_p(arc_serial_remove),
+	.driver = {
+		.name = DRIVER_NAME,
+		.owner = THIS_MODULE,
+	 },
+};
+
+#ifdef CONFIG_SERIAL_ARC_CONSOLE
+/*
+ * Register an early platform driver of "earlyprintk" class.
+ * ARCH platform code installs the driver and probes the early devices
+ * The installation could rely on user specifying earlyprintk=xyx in cmd line
+ * or it could be done independently, for all "earlyprintk" class drivers.
+ * [see arch/arc/plat-arcfpga/platform.c]
+ */
+early_platform_init("earlyprintk", &arc_platform_driver);
+
+#endif  /* CONFIG_SERIAL_ARC_CONSOLE */
+
+static int __init arc_serial_init(void)
+{
+	int ret;
+
+	ret = uart_register_driver(&arc_uart_driver);
+	if (ret)
+		return ret;
+
+	ret = platform_driver_register(&arc_platform_driver);
+	if (ret)
+		uart_unregister_driver(&arc_uart_driver);
+
+	return ret;
+}
+
+static void __exit arc_serial_exit(void)
+{
+	platform_driver_unregister(&arc_platform_driver);
+	uart_unregister_driver(&arc_uart_driver);
+}
+
+module_init(arc_serial_init);
+module_exit(arc_serial_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("plat-arcfpga/uart");
+MODULE_AUTHOR("Vineet Gupta");
+MODULE_DESCRIPTION("ARC(Synopsys) On-Chip(fpga) serial driver");

include/uapi/linux/serial_core.h

@@ -215,5 +215,7 @@
 /* Energy Micro efm32 SoC */
 #define PORT_EFMUART   100
 
+/* ARC (Synopsys) on-chip UART */
+#define PORT_ARC       101
 
 #endif /* _UAPILINUX_SERIAL_CORE_H */