[RFC][PATCH] serial: spi: add spi-uart driver for Maxim 3110

[Feng Tang <feng.tang@intel.com>]

Hi All,

Here is a driver for Maxim 3110 SPI-UART device, please help to review.

It has been validated with Designware SPI controller (drivers/spi: dw_spi.c &
dw_spi_pci.c). It supports polling and IRQ mode, supports batch read, and
provides a console.

As a RFC, the driver doesn't have a valid UART port type yet, but borrow
PORT_PXA. I would apply one if there is no main objection for it.

Thanks!


Feng

>From 3155eec53d8b1193cae1dce2b0491e86892e6933 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang@intel.com>
Date: Tue, 29 Dec 2009 17:11:17 +0800
Subject: [PATCH] serial: spi: add spi-uart driver for Maxim 3110

This is the driver for Max3110 SPI-UART device, which connect
to host with SPI interface. It supports baud rates from 300 to
230400. It supports both polling and IRQ mode, as well as
providing a console for system use

Its datasheet could be found here:
http://datasheets.maxim-ic.com/en/ds/MAX3110E-MAX3111E.pdf

Signed-off-by: Feng Tang <feng.tang@intel.com>
---
 drivers/serial/Kconfig   |   17 +
 drivers/serial/max3110.c |  842 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/serial/max3110.h |   59 ++++
 3 files changed, 918 insertions(+), 0 deletions(-)
 create mode 100644 drivers/serial/max3110.c
 create mode 100644 drivers/serial/max3110.h

diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 9ff47db..b8d24ae 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -688,6 +688,23 @@ config SERIAL_SA1100_CONSOLE
 	  your boot loader (lilo or loadlin) about how to pass options to the
 	  kernel at boot time.)
 
+config SERIAL_MAX3110
+	tristate "SPI UART driver for Max3110"
+	select SERIAL_CORE
+	select SERIAL_CORE_CONSOLE
+	help
+	  This is the UART protocol driver for MAX3110 device
+
+config MAX3110_DESIGNWARE
+	boolean "Enable Max3110 to work with Designware controller"
+	default y
+	depends on SERIAL_MAX3110
+
+config MAX3110_IRQ
+	boolean "Enable IRQ for Max3110"
+	default n
+	depends on SERIAL_MAX3110
+
 config SERIAL_BFIN
 	tristate "Blackfin serial port support"
 	depends on BLACKFIN
diff --git a/drivers/serial/max3110.c b/drivers/serial/max3110.c
new file mode 100644
index 0000000..1923ade
--- /dev/null
+++ b/drivers/serial/max3110.c
@@ -0,0 +1,842 @@
+/*
+ * max3110.c - spi uart protocol driver for Maxim 3110
+ *
+ * Copyright (c) 2009, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/*
+ * Note:
+ * * From Max3110 spec, the Rx FIFO has 8 words, while the Tx FIFO only has
+ *   1 word. If SPI master controller doesn't support sclk frequency change,
+ *   then the char need be sent out one by one with some delay
+ *
+ * * Currently only RX availabe interrrupt is used
+ */
+
+#include <linux/module.h>
+#include <linux/ioport.h>
+#include <linux/init.h>
+#include <linux/console.h>
+#include <linux/platform_device.h>
+#include <linux/tty.h>
+#include <linux/tty_flip.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+
+#include <linux/kthread.h>
+#include <linux/delay.h>
+#include <asm/atomic.h>
+#include <linux/spi/spi.h>
+#include <linux/spi/dw_spi.h>
+
+#include "max3110.h"
+
+#define PR_FMT	"max3110: "
+
+struct uart_max3110 {
+	struct uart_port port;
+	struct spi_device *spi;
+	char *name;
+
+	wait_queue_head_t wq;
+	struct task_struct *main_thread;
+	struct task_struct *read_thread;
+	int mthread_up;
+	spinlock_t lock;
+
+	u32 baud;
+	u16 cur_conf;
+	u8 clock;
+	u8 parity, word_7bits;
+
+	atomic_t uart_tx_need;
+
+	/* console related */
+	struct circ_buf con_xmit;
+	atomic_t con_tx_need;
+
+	/* irq related */
+	u16 irq;
+	atomic_t irq_pending;
+};
+
+struct uart_max3110 *pmax;
+static void receive_chars(struct uart_max3110 *max,
+				unsigned char *str, int len);
+static int max3110_read_multi(struct uart_max3110 *max, int len, u8 *buf);
+static void max3110_con_receive(struct uart_max3110 *max);
+
+int max3110_write_then_read(struct uart_max3110 *max,
+		const u8 *txbuf, u8 *rxbuf, unsigned len, int always_fast)
+{
+	struct spi_device *spi = max->spi;
+	struct spi_message	message;
+	struct spi_transfer	x;
+	int ret;
+
+	if (!txbuf || !rxbuf)
+		return -EINVAL;
+
+	spi_message_init(&message);
+	memset(&x, 0, sizeof x);
+	x.len = len;
+	x.tx_buf = txbuf;
+	x.rx_buf = rxbuf;
+	spi_message_add_tail(&x, &message);
+
+	if (always_fast)
+		x.speed_hz = spi->max_speed_hz;
+	else if (max->baud)
+		x.speed_hz = max->baud;
+
+	/* Do the i/o */
+	ret = spi_sync(spi, &message);
+	return ret;
+}
+
+/* Write a u16 to the device, and return one u16 read back */
+int max3110_out(struct uart_max3110 *max, const u16 out)
+{
+	u16 tmp;
+	int ret;
+
+	ret = max3110_write_then_read(max, (u8 *)&out, (u8 *)&tmp, 2, 1);
+	if (ret)
+		return ret;
+
+	/* If some valid data is read back */
+	if (tmp & MAX3110_READ_DATA_AVAILABLE) {
+		tmp &= 0xff;
+		receive_chars(max, (unsigned char *)&tmp, 1);
+	}
+
+	return ret;
+}
+
+#define MAX_READ_LEN	20
+/*
+ * This is usually used to read data from SPIC RX FIFO, which doesn't
+ * need any delay like flushing character out.
+ * Returns how many valide bytes are read back
+ */
+static int max3110_read_multi(struct uart_max3110 *max, int len, u8 *buf)
+{
+	u16 out[MAX_READ_LEN], in[MAX_READ_LEN];
+	u8 *pbuf, valid_str[MAX_READ_LEN];
+	int i, j, bytelen;
+
+	if (len > MAX_READ_LEN) {
+		pr_err(PR_FMT "read len %d is too large\n", len);
+		return 0;
+	}
+
+	bytelen = len * 2;
+	memset(out, 0, bytelen);
+	memset(in, 0, bytelen);
+
+	if (max3110_write_then_read(max, (u8 *)out, (u8 *)in, bytelen, 1))
+		return 0;
+
+	/* If caller doesn't provide a buffer, then handle received char */
+	pbuf = buf ? buf : valid_str;
+
+	for (i = 0, j = 0; i < len; i++) {
+		if (in[i] & MAX3110_READ_DATA_AVAILABLE)
+			pbuf[j++] = (u8)(in[i] & 0xff);
+	}
+
+	if (j && (pbuf == valid_str))
+		receive_chars(max, valid_str, j);
+
+	return j;
+}
+
+static void serial_m3110_con_putchar(struct uart_port *port, int ch)
+{
+	struct uart_max3110 *max =
+		container_of(port, struct uart_max3110, port);
+	struct circ_buf *xmit = &max->con_xmit;
+
+	if (uart_circ_chars_free(xmit)) {
+		xmit->buf[xmit->head] = (char)ch;
+		xmit->head = (xmit->head + 1) & (PAGE_SIZE - 1);
+	}
+
+	if (!atomic_read(&max->con_tx_need)) {
+		atomic_set(&max->con_tx_need, 1);
+		wake_up_process(max->main_thread);
+	}
+}
+
+/*
+ * Print a string to the serial port trying not to disturb
+ * any possible real use of the port...
+ *
+ *	The console_lock must be held when we get here.
+ */
+static void serial_m3110_con_write(struct console *co,
+				const char *s, unsigned int count)
+{
+	if (!pmax)
+		return;
+
+	uart_console_write(&pmax->port, s, count, serial_m3110_con_putchar);
+}
+
+static int __init
+serial_m3110_con_setup(struct console *co, char *options)
+{
+	struct uart_max3110 *max = pmax;
+	int baud = 115200;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+
+	pr_info(PR_FMT "setting up console\n");
+
+	if (!max) {
+		pr_err(PR_FMT "pmax is NULL, return");
+		return -ENODEV;
+	}
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+
+	return uart_set_options(&max->port, co, baud, parity, bits, flow);
+}
+
+static struct tty_driver *serial_m3110_con_device(struct console *co,
+							int *index)
+{
+	struct uart_driver *p = co->data;
+	*index = co->index;
+	return p->tty_driver;
+}
+
+static struct uart_driver serial_m3110_reg;
+static struct console serial_m3110_console = {
+	.name		= "ttyS",
+	.write		= serial_m3110_con_write,
+	.device		= serial_m3110_con_device,
+	.setup		= serial_m3110_con_setup,
+	.flags		= CON_PRINTBUFFER,
+	.index		= -1,
+	.data		= &serial_m3110_reg,
+};
+
+#define MRST_CONSOLE	(&serial_m3110_console)
+
+static unsigned int serial_m3110_tx_empty(struct uart_port *port)
+{
+	return 1;
+}
+
+static void serial_m3110_stop_tx(struct uart_port *port)
+{
+	return;
+}
+
+/* stop_rx will be called in spin_lock env */
+static void serial_m3110_stop_rx(struct uart_port *port)
+{
+	return;
+}
+
+#define WORDS_PER_XFER	128
+static inline void send_circ_buf(struct uart_max3110 *max,
+				struct circ_buf *xmit)
+{
+	int len, left = 0;
+	u16 obuf[WORDS_PER_XFER], ibuf[WORDS_PER_XFER];
+	u8 valid_str[WORDS_PER_XFER];
+	int i, j;
+
+	while (!uart_circ_empty(xmit)) {
+		left = uart_circ_chars_pending(xmit);
+		while (left) {
+			len = (left >= WORDS_PER_XFER) ? WORDS_PER_XFER : left;
+
+			memset(obuf, 0, len * 2);
+			memset(ibuf, 0, len * 2);
+			for (i = 0; i < len; i++) {
+				obuf[i] = (u8)xmit->buf[xmit->tail] | WD_TAG;
+				xmit->tail = (xmit->tail + 1) &
+						(UART_XMIT_SIZE - 1);
+			}
+			max3110_write_then_read(max, (u8 *)obuf,
+						(u8 *)ibuf, len * 2, 0);
+
+			for (i = 0, j = 0; i < len; i++) {
+				if (ibuf[i] & MAX3110_READ_DATA_AVAILABLE)
+					valid_str[j++] = (u8)(ibuf[i] & 0xff);
+			}
+
+			if (j)
+				receive_chars(max, valid_str, j);
+
+			max->port.icount.tx += len;
+			left -= len;
+		}
+	}
+}
+
+static void transmit_char(struct uart_max3110 *max)
+{
+	struct uart_port *port = &max->port;
+	struct circ_buf *xmit = &port->state->xmit;
+
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port))
+		return;
+
+	send_circ_buf(max, xmit);
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(port);
+
+	if (uart_circ_empty(xmit))
+		serial_m3110_stop_tx(port);
+}
+
+/*
+ * This will be called by uart_write() and tty_write, can't
+ * go to sleep
+ */
+static void serial_m3110_start_tx(struct uart_port *port)
+{
+	struct uart_max3110 *max =
+		container_of(port, struct uart_max3110, port);
+
+	if (!atomic_read(&max->uart_tx_need)) {
+		atomic_set(&max->uart_tx_need, 1);
+		wake_up_process(max->main_thread);
+	}
+}
+
+static void receive_chars(struct uart_max3110 *max, unsigned char *str, int len)
+{
+	struct uart_port *port = &max->port;
+	struct tty_struct *tty;
+	int usable;
+
+	/* If uart is not opened, just return */
+	if (!port->state)
+		return;
+
+	tty = port->state->port.tty;
+	if (!tty)
+		return;
+
+	while (len) {
+		usable = tty_buffer_request_room(tty, len);
+		if (usable) {
+			tty_insert_flip_string(tty, str, usable);
+			str += usable;
+			port->icount.rx += usable;
+			tty_flip_buffer_push(tty);
+		}
+		len -= usable;
+	}
+}
+
+static void max3110_con_receive(struct uart_max3110 *max)
+{
+	int loop = 1, num, total = 0;
+	u8 recv_buf[512], *pbuf;
+
+	pbuf = recv_buf;
+	do {
+		/* 3110 RX buffer is 8 words */
+		num = max3110_read_multi(max, 8, pbuf);
+
+		if (num) {
+			loop = 5;
+			pbuf += num;
+			total += num;
+
+			if (total >= 500) {
+				receive_chars(max, recv_buf, total);
+				pbuf = recv_buf;
+				total = 0;
+			}
+		}
+	} while (--loop);
+
+	if (total)
+		receive_chars(max, recv_buf, total);
+}
+
+static int max3110_main_thread(void *_max)
+{
+	struct uart_max3110 *max = _max;
+	wait_queue_head_t *wq = &max->wq;
+	int ret = 0;
+	struct circ_buf *xmit = &max->con_xmit;
+
+	init_waitqueue_head(wq);
+	pr_info(PR_FMT "start main thread\n");
+
+	do {
+		wait_event_interruptible(*wq, (atomic_read(&max->irq_pending) ||
+					       atomic_read(&max->con_tx_need) ||
+					     atomic_read(&max->uart_tx_need)) ||
+					     kthread_should_stop());
+		max->mthread_up = 1;
+
+#ifdef CONFIG_MAX3110_IRQ
+		if (atomic_read(&max->irq_pending)) {
+			max3110_con_receive(max);
+			atomic_set(&max->irq_pending, 0);
+		}
+#endif
+
+		/* first handle console output */
+		if (atomic_read(&max->con_tx_need)) {
+			send_circ_buf(max, xmit);
+			atomic_set(&max->con_tx_need, 0);
+		}
+
+		/* handle uart output */
+		if (atomic_read(&max->uart_tx_need)) {
+			transmit_char(max);
+			atomic_set(&max->uart_tx_need, 0);
+		}
+		max->mthread_up = 0;
+	} while (!kthread_should_stop());
+
+	return ret;
+}
+
+#ifdef CONFIG_MAX3110_IRQ
+irqreturn_t static serial_m3110_irq(int irq, void *dev_id)
+{
+	struct uart_max3110 *max = dev_id;
+
+	/* max3110's irq is a falling edge, not level triggered,
+	 * so no need to disable the irq */
+	if (!atomic_read(&max->irq_pending)) {
+		atomic_inc(&max->irq_pending);
+		wake_up_process(max->main_thread);
+	}
+	return IRQ_HANDLED;
+}
+#else
+/* if don't use RX IRQ, then need a thread to polling read */
+static int max3110_read_thread(void *_max)
+{
+	struct uart_max3110 *max = _max;
+
+	pr_info(PR_FMT "start read thread\n");
+	do {
+		if (!max->mthread_up)
+			max3110_con_receive(max);
+
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule_timeout(HZ / 20);
+	} while (!kthread_should_stop());
+
+	return 0;
+}
+#endif
+
+static int serial_m3110_startup(struct uart_port *port)
+{
+	struct uart_max3110 *max =
+		container_of(port, struct uart_max3110, port);
+	u16 config = 0;
+	int ret = 0;
+
+	if (port->line != 0)
+		pr_err(PR_FMT "uart port startup failed\n");
+
+	/* firstly disable all IRQ and config it to 115200, 8n1 */
+	config = WC_TAG | WC_FIFO_ENABLE
+			| WC_1_STOPBITS
+			| WC_8BIT_WORD
+			| WC_BAUD_DR2;
+	ret = max3110_out(max, config);
+
+	/* as we use thread to handle tx/rx, need set low latency */
+	port->state->port.tty->low_latency = 1;
+
+#ifdef CONFIG_MAX3110_IRQ
+	ret = request_irq(max->irq, serial_m3110_irq,
+				IRQ_TYPE_EDGE_FALLING, "max3110", max);
+	if (ret)
+		return ret;
+
+	/* enable RX IRQ only */
+	config |= WC_RXA_IRQ_ENABLE;
+	max3110_out(max, config);
+#else
+	/* if IRQ is disabled, start a read thread for input data */
+	max->read_thread =
+		kthread_run(max3110_read_thread, max, "max3110_read");
+#endif
+
+	max->cur_conf = config;
+	return 0;
+}
+
+static void serial_m3110_shutdown(struct uart_port *port)
+{
+	struct uart_max3110 *max =
+		container_of(port, struct uart_max3110, port);
+	u16 config;
+
+	if (max->read_thread) {
+		kthread_stop(max->read_thread);
+		max->read_thread = NULL;
+	}
+
+#ifdef CONFIG_MAX3110_IRQ
+	free_irq(max->irq, max);
+#endif
+
+	/* Disable interrupts from this port */
+	config = WC_TAG | WC_SW_SHDI;
+	max3110_out(max, config);
+}
+
+static void serial_m3110_release_port(struct uart_port *port)
+{
+}
+
+static int serial_m3110_request_port(struct uart_port *port)
+{
+	return 0;
+}
+
+static void serial_m3110_config_port(struct uart_port *port, int flags)
+{
+	/* Give it fake type */
+	port->type = PORT_PXA;
+}
+
+static int
+serial_m3110_verify_port(struct uart_port *port, struct serial_struct *ser)
+{
+	/* we don't want the core code to modify any port params */
+	return -EINVAL;
+}
+
+
+static const char *serial_m3110_type(struct uart_port *port)
+{
+	struct uart_max3110 *max =
+		container_of(port, struct uart_max3110, port);
+	return max->name;
+}
+
+static void
+serial_m3110_set_termios(struct uart_port *port, struct ktermios *termios,
+		       struct ktermios *old)
+{
+	struct uart_max3110 *max =
+		container_of(port, struct uart_max3110, port);
+	unsigned char cval;
+	unsigned int baud, parity = 0;
+	int clk_div = -1;
+	u16 new_conf = max->cur_conf;
+
+	switch (termios->c_cflag & CSIZE) {
+	case CS7:
+		cval = UART_LCR_WLEN7;
+		new_conf |= WC_7BIT_WORD;
+		break;
+	default:
+	case CS8:
+		cval = UART_LCR_WLEN8;
+		new_conf |= WC_8BIT_WORD;
+		break;
+	}
+
+	baud = uart_get_baud_rate(port, termios, old, 0, 230400);
+
+	/* first calc the div for 1.8MHZ clock case */
+	switch (baud) {
+	case 300:
+		clk_div = WC_BAUD_DR384;
+		break;
+	case 600:
+		clk_div = WC_BAUD_DR192;
+		break;
+	case 1200:
+		clk_div = WC_BAUD_DR96;
+		break;
+	case 2400:
+		clk_div = WC_BAUD_DR48;
+		break;
+	case 4800:
+		clk_div = WC_BAUD_DR24;
+		break;
+	case 9600:
+		clk_div = WC_BAUD_DR12;
+		break;
+	case 19200:
+		clk_div = WC_BAUD_DR6;
+		break;
+	case 38400:
+		clk_div = WC_BAUD_DR3;
+		break;
+	case 57600:
+		clk_div = WC_BAUD_DR2;
+		break;
+	case 115200:
+		clk_div = WC_BAUD_DR1;
+		break;
+	case 230400:
+		if (max->clock & MAX3110_HIGH_CLK)
+			break;
+	default:
+		/* pick the previous baud rate */
+		baud = max->baud;
+		clk_div = max->cur_conf & WC_BAUD_DIV_MASK;
+		tty_termios_encode_baud_rate(termios, baud, baud);
+	}
+
+	if (max->clock & MAX3110_HIGH_CLK) {
+		clk_div += 1;
+		/* high clk version max3110 doesn't support B300 */
+		if (baud == 300)
+			baud = 600;
+		if (baud == 230400)
+			clk_div = WC_BAUD_DR1;
+		tty_termios_encode_baud_rate(termios, baud, baud);
+	}
+
+	new_conf = (new_conf & ~WC_BAUD_DIV_MASK) | clk_div;
+	if (termios->c_cflag & CSTOPB)
+		new_conf |= WC_2_STOPBITS;
+	else
+		new_conf &= ~WC_2_STOPBITS;
+
+	if (termios->c_cflag & PARENB) {
+		new_conf |= WC_PARITY_ENABLE;
+		parity |= UART_LCR_PARITY;
+	} else
+		new_conf &= ~WC_PARITY_ENABLE;
+
+	if (!(termios->c_cflag & PARODD))
+		parity |= UART_LCR_EPAR;
+	max->parity = parity;
+
+	uart_update_timeout(port, termios->c_cflag, baud);
+
+	new_conf |= WC_TAG;
+	if (new_conf != max->cur_conf) {
+		max3110_out(max, new_conf);
+		max->cur_conf = new_conf;
+		max->baud = baud;
+	}
+}
+
+/* don't handle hw handshaking */
+static unsigned int serial_m3110_get_mctrl(struct uart_port *port)
+{
+	return TIOCM_DSR | TIOCM_CAR | TIOCM_DSR;
+}
+
+static void serial_m3110_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+}
+
+static void serial_m3110_break_ctl(struct uart_port *port, int break_state)
+{
+}
+
+static void serial_m3110_pm(struct uart_port *port, unsigned int state,
+			unsigned int oldstate)
+{
+}
+
+static void serial_m3110_enable_ms(struct uart_port *port)
+{
+}
+
+struct uart_ops serial_m3110_ops = {
+	.tx_empty	= serial_m3110_tx_empty,
+	.set_mctrl	= serial_m3110_set_mctrl,
+	.get_mctrl	= serial_m3110_get_mctrl,
+	.stop_tx	= serial_m3110_stop_tx,
+	.start_tx	= serial_m3110_start_tx,
+	.stop_rx	= serial_m3110_stop_rx,
+	.enable_ms	= serial_m3110_enable_ms,
+	.break_ctl	= serial_m3110_break_ctl,
+	.startup	= serial_m3110_startup,
+	.shutdown	= serial_m3110_shutdown,
+	.set_termios	= serial_m3110_set_termios,
+	.pm		= serial_m3110_pm,
+	.type		= serial_m3110_type,
+	.release_port	= serial_m3110_release_port,
+	.request_port	= serial_m3110_request_port,
+	.config_port	= serial_m3110_config_port,
+	.verify_port	= serial_m3110_verify_port,
+};
+
+static struct uart_driver serial_m3110_reg = {
+	.owner		= THIS_MODULE,
+	.driver_name	= "MRST serial",
+	.dev_name	= "ttyS",
+	.major		= TTY_MAJOR,
+	.minor		= 64,
+	.nr		= 1,
+	.cons		= MRST_CONSOLE,
+};
+
+static int serial_m3110_suspend(struct spi_device *spi, pm_message_t state)
+{
+	return 0;
+}
+
+static int serial_m3110_resume(struct spi_device *spi)
+{
+	return 0;
+}
+
+#ifdef CONFIG_MAX3110_DESIGNWARE
+static struct dw_spi_chip spi_uart = {
+	.poll_mode = 1,
+	.enable_dma = 0,
+	.type = SPI_FRF_SPI,
+};
+#endif
+
+static int serial_m3110_probe(struct spi_device *spi)
+{
+	struct uart_max3110 *max;
+	int ret;
+	unsigned char *buffer;
+
+	max = kzalloc(sizeof(*max), GFP_KERNEL);
+	if (!max)
+		return -ENOMEM;
+
+	/* set spi info */
+	spi->mode = SPI_MODE_0;
+	spi->bits_per_word = 16;
+#ifdef CONFIG_MAX3110_DESIGNWARE
+	spi->controller_data = &spi_uart;
+#endif
+	spi_setup(spi);
+
+	max->clock = MAX3110_HIGH_CLK;
+	max->port.type = PORT_PXA;	/* Need apply for a max3110 type */
+	max->port.fifosize = 2;		/* only have 16b buffer */
+	max->port.ops = &serial_m3110_ops;
+	max->port.line = 0;
+	max->port.dev = &spi->dev;
+	max->port.uartclk = 115200;
+
+	max->spi = spi;
+	max->name = spi->modalias;	/* use spi name as the name */
+	max->irq = (u16)spi->irq;
+
+	spin_lock_init(&max->lock);
+
+	max->word_7bits = 0;
+	max->parity = 0;
+	max->baud = 0;
+
+	max->cur_conf = 0;
+	atomic_set(&max->irq_pending, 0);
+
+	buffer = (unsigned char *)__get_free_page(GFP_KERNEL);
+	if (!buffer) {
+		ret = -ENOMEM;
+		goto err_get_page;
+	}
+	max->con_xmit.buf = (unsigned char *)buffer;
+	max->con_xmit.head = max->con_xmit.tail = 0;
+
+	max->main_thread = kthread_run(max3110_main_thread,
+					max, "max3110_main");
+	if (IS_ERR(max->main_thread)) {
+		ret = PTR_ERR(max->main_thread);
+		goto err_kthread;
+	}
+
+	pmax = max;
+	/* Give membase a psudo value to pass serial_core's check */
+	max->port.membase = (void *)0xff110000;
+	uart_add_one_port(&serial_m3110_reg, &max->port);
+
+	return 0;
+
+err_kthread:
+	free_page((unsigned long)buffer);
+err_get_page:
+	pmax = NULL;
+	kfree(max);
+	return ret;
+}
+
+static int max3110_remove(struct spi_device *dev)
+{
+	struct uart_max3110 *max = pmax;
+
+	if (!pmax)
+		return 0;
+
+	pmax = NULL;
+	uart_remove_one_port(&serial_m3110_reg, &max->port);
+
+	free_page((unsigned long)max->con_xmit.buf);
+
+	if (max->main_thread)
+		kthread_stop(max->main_thread);
+
+	kfree(max);
+	return 0;
+}
+
+static struct spi_driver uart_max3110_driver = {
+	.driver = {
+			.name	= "spi_max3111",
+			.bus	= &spi_bus_type,
+			.owner	= THIS_MODULE,
+	},
+	.probe		= serial_m3110_probe,
+	.remove		= __devexit_p(max3110_remove),
+	.suspend	= serial_m3110_suspend,
+	.resume		= serial_m3110_resume,
+};
+
+int __init serial_m3110_init(void)
+{
+	int ret = 0;
+
+	ret = uart_register_driver(&serial_m3110_reg);
+	if (ret)
+		return ret;
+
+	ret = spi_register_driver(&uart_max3110_driver);
+	if (ret)
+		uart_unregister_driver(&serial_m3110_reg);
+
+	return ret;
+}
+
+void __exit serial_m3110_exit(void)
+{
+	spi_unregister_driver(&uart_max3110_driver);
+	uart_unregister_driver(&serial_m3110_reg);
+}
+
+module_init(serial_m3110_init);
+module_exit(serial_m3110_exit);
+
+MODULE_ALIAS("max3110-uart");
+MODULE_AUTHOR("Feng Tang <feng.tang@intel.com>");
diff --git a/drivers/serial/max3110.h b/drivers/serial/max3110.h
new file mode 100644
index 0000000..eae93bd
--- /dev/null
+++ b/drivers/serial/max3110.h
@@ -0,0 +1,59 @@
+#ifndef _MAX3110_HEAD_FILE_
+#define _MAX3110_HEAD_FILE_
+
+#define MAX3110_HIGH_CLK	0x1	/* 3.6864 MHZ */
+#define MAX3110_LOW_CLK		0x0	/* 1.8432 MHZ */
+
+/* status bits for all 4 MAX3110 operate modes */
+#define MAX3110_READ_DATA_AVAILABLE	(1 << 15)
+#define MAX3110_WRITE_BUF_EMPTY		(1 << 14)
+
+#define WC_TAG			(3 << 14)
+#define RC_TAG			(1 << 14)
+#define WD_TAG			(2 << 14)
+#define RD_TAG			(0 << 14)
+
+/* bits def for write configuration */
+#define WC_FIFO_ENABLE_MASK	(1 << 13)
+#define WC_FIFO_ENABLE		(0 << 13)
+
+#define WC_SW_SHDI		(1 << 12)
+
+#define WC_IRQ_MASK		(0xF << 8)
+#define WC_TXE_IRQ_ENABLE	(1 << 11)	/* TX empty irq */
+#define WC_RXA_IRQ_ENABLE	(1 << 10)	/* RX availabe irq */
+#define WC_PAR_HIGH_IRQ_ENABLE	(1 << 9)
+#define WC_REC_ACT_IRQ_ENABLE	(1 << 8)
+
+#define WC_IRDA_ENABLE		(1 << 7)
+
+#define WC_STOPBITS_MASK	(1 << 6)
+#define WC_2_STOPBITS		(1 << 6)
+#define WC_1_STOPBITS		(0 << 6)
+
+#define WC_PARITY_ENABLE_MASK	(1 << 5)
+#define WC_PARITY_ENABLE	(1 << 5)
+
+#define WC_WORDLEN_MASK		(1 << 4)
+#define WC_7BIT_WORD		(1 << 4)
+#define WC_8BIT_WORD		(0 << 4)
+
+#define WC_BAUD_DIV_MASK	(0xF)
+#define WC_BAUD_DR1		(0x0)
+#define WC_BAUD_DR2		(0x1)
+#define WC_BAUD_DR4		(0x2)
+#define WC_BAUD_DR8		(0x3)
+#define WC_BAUD_DR16		(0x4)
+#define WC_BAUD_DR32		(0x5)
+#define WC_BAUD_DR64		(0x6)
+#define WC_BAUD_DR128		(0x7)
+#define WC_BAUD_DR3		(0x8)
+#define WC_BAUD_DR6		(0x9)
+#define WC_BAUD_DR12		(0xA)
+#define WC_BAUD_DR24		(0xB)
+#define WC_BAUD_DR48		(0xC)
+#define WC_BAUD_DR96		(0xD)
+#define WC_BAUD_DR192		(0xE)
+#define WC_BAUD_DR384		(0xF)
+
+#endif
-- 
1.6.0.4