i2c: Blackfin Two Wire Interface driver

The i2c linux driver for blackfin architecture which supports blackfin
on-chip TWI controller i2c operation.

Signed-off-by: Bryan Wu <bryan.wu@analog.com>
Reviewed-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 644 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-bfin-twi.c b/drivers/i2c/busses/i2c-bfin-twi.c
new file mode 100644
index 00000000000..6311039dfe6
--- /dev/null
+++ b/drivers/i2c/busses/i2c-bfin-twi.c
@@ -0,0 +1,644 @@
+/*
+ * drivers/i2c/busses/i2c-bfin-twi.c
+ *
+ * Description: Driver for Blackfin Two Wire Interface
+ *
+ * Author:      sonicz  <sonic.zhang@analog.com>
+ *
+ * Copyright (c) 2005-2007 Analog Devices, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/i2c.h>
+#include <linux/mm.h>
+#include <linux/timer.h>
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+
+#include <asm/blackfin.h>
+#include <asm/irq.h>
+
+#define POLL_TIMEOUT       (2 * HZ)
+
+/* SMBus mode*/
+#define TWI_I2C_MODE_STANDARD		0x01
+#define TWI_I2C_MODE_STANDARDSUB	0x02
+#define TWI_I2C_MODE_COMBINED		0x04
+
+struct bfin_twi_iface {
+	struct mutex		twi_lock;
+	int			irq;
+	spinlock_t		lock;
+	char			read_write;
+	u8			command;
+	u8			*transPtr;
+	int			readNum;
+	int			writeNum;
+	int			cur_mode;
+	int			manual_stop;
+	int			result;
+	int			timeout_count;
+	struct timer_list	timeout_timer;
+	struct i2c_adapter	adap;
+	struct completion	complete;
+};
+
+static struct bfin_twi_iface twi_iface;
+
+static void bfin_twi_handle_interrupt(struct bfin_twi_iface *iface)
+{
+	unsigned short twi_int_status = bfin_read_TWI_INT_STAT();
+	unsigned short mast_stat = bfin_read_TWI_MASTER_STAT();
+
+	if (twi_int_status & XMTSERV) {
+		/* Transmit next data */
+		if (iface->writeNum > 0) {
+			bfin_write_TWI_XMT_DATA8(*(iface->transPtr++));
+			iface->writeNum--;
+		}
+		/* start receive immediately after complete sending in
+		 * combine mode.
+		 */
+		else if (iface->cur_mode == TWI_I2C_MODE_COMBINED) {
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
+				| MDIR | RSTART);
+		} else if (iface->manual_stop)
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
+				| STOP);
+		SSYNC();
+		/* Clear status */
+		bfin_write_TWI_INT_STAT(XMTSERV);
+		SSYNC();
+	}
+	if (twi_int_status & RCVSERV) {
+		if (iface->readNum > 0) {
+			/* Receive next data */
+			*(iface->transPtr) = bfin_read_TWI_RCV_DATA8();
+			if (iface->cur_mode == TWI_I2C_MODE_COMBINED) {
+				/* Change combine mode into sub mode after
+				 * read first data.
+				 */
+				iface->cur_mode = TWI_I2C_MODE_STANDARDSUB;
+				/* Get read number from first byte in block
+				 * combine mode.
+				 */
+				if (iface->readNum == 1 && iface->manual_stop)
+					iface->readNum = *iface->transPtr + 1;
+			}
+			iface->transPtr++;
+			iface->readNum--;
+		} else if (iface->manual_stop) {
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL()
+				| STOP);
+			SSYNC();
+		}
+		/* Clear interrupt source */
+		bfin_write_TWI_INT_STAT(RCVSERV);
+		SSYNC();
+	}
+	if (twi_int_status & MERR) {
+		bfin_write_TWI_INT_STAT(MERR);
+		bfin_write_TWI_INT_MASK(0);
+		bfin_write_TWI_MASTER_STAT(0x3e);
+		bfin_write_TWI_MASTER_CTL(0);
+		SSYNC();
+		iface->result = -1;
+		/* if both err and complete int stats are set, return proper
+		 * results.
+		 */
+		if (twi_int_status & MCOMP) {
+			bfin_write_TWI_INT_STAT(MCOMP);
+			bfin_write_TWI_INT_MASK(0);
+			bfin_write_TWI_MASTER_CTL(0);
+			SSYNC();
+			/* If it is a quick transfer, only address bug no data,
+			 * not an err, return 1.
+			 */
+			if (iface->writeNum == 0 && (mast_stat & BUFRDERR))
+				iface->result = 1;
+			/* If address not acknowledged return -1,
+			 * else return 0.
+			 */
+			else if (!(mast_stat & ANAK))
+				iface->result = 0;
+		}
+		complete(&iface->complete);
+		return;
+	}
+	if (twi_int_status & MCOMP) {
+		bfin_write_TWI_INT_STAT(MCOMP);
+		SSYNC();
+		if (iface->cur_mode == TWI_I2C_MODE_COMBINED) {
+			if (iface->readNum == 0) {
+				/* set the read number to 1 and ask for manual
+				 * stop in block combine mode
+				 */
+				iface->readNum = 1;
+				iface->manual_stop = 1;
+				bfin_write_TWI_MASTER_CTL(
+					bfin_read_TWI_MASTER_CTL()
+					| (0xff << 6));
+			} else {
+				/* set the readd number in other
+				 * combine mode.
+				 */
+				bfin_write_TWI_MASTER_CTL(
+					(bfin_read_TWI_MASTER_CTL() &
+					(~(0xff << 6))) |
+					( iface->readNum << 6));
+			}
+			/* remove restart bit and enable master receive */
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() &
+				~RSTART);
+			bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() |
+				MEN | MDIR);
+			SSYNC();
+		} else {
+			iface->result = 1;
+			bfin_write_TWI_INT_MASK(0);
+			bfin_write_TWI_MASTER_CTL(0);
+			SSYNC();
+			complete(&iface->complete);
+		}
+	}
+}
+
+/* Interrupt handler */
+static irqreturn_t bfin_twi_interrupt_entry(int irq, void *dev_id)
+{
+	struct bfin_twi_iface *iface = dev_id;
+	unsigned long flags;
+
+	spin_lock_irqsave(&iface->lock, flags);
+	del_timer(&iface->timeout_timer);
+	bfin_twi_handle_interrupt(iface);
+	spin_unlock_irqrestore(&iface->lock, flags);
+	return IRQ_HANDLED;
+}
+
+static void bfin_twi_timeout(unsigned long data)
+{
+	struct bfin_twi_iface *iface = (struct bfin_twi_iface *)data;
+	unsigned long flags;
+
+	spin_lock_irqsave(&iface->lock, flags);
+	bfin_twi_handle_interrupt(iface);
+	if (iface->result == 0) {
+		iface->timeout_count--;
+		if (iface->timeout_count > 0) {
+			iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
+			add_timer(&iface->timeout_timer);
+		} else {
+			iface->result = -1;
+			complete(&iface->complete);
+		}
+	}
+	spin_unlock_irqrestore(&iface->lock, flags);
+}
+
+/*
+ * Generic i2c master transfer entrypoint
+ */
+static int bfin_twi_master_xfer(struct i2c_adapter *adap,
+				struct i2c_msg *msgs, int num)
+{
+	struct bfin_twi_iface *iface = adap->algo_data;
+	struct i2c_msg *pmsg;
+	int i, ret;
+	int rc = 0;
+
+	if (!(bfin_read_TWI_CONTROL() & TWI_ENA))
+		return -ENXIO;
+
+	mutex_lock(&iface->twi_lock);
+
+	while (bfin_read_TWI_MASTER_STAT() & BUSBUSY) {
+		mutex_unlock(&iface->twi_lock);
+		yield();
+		mutex_lock(&iface->twi_lock);
+	}
+
+	ret = 0;
+	for (i = 0; rc >= 0 && i < num; i++) {
+		pmsg = &msgs[i];
+		if (pmsg->flags & I2C_M_TEN) {
+			dev_err(&(adap->dev), "i2c-bfin-twi: 10 bits addr "
+				"not supported !\n");
+			rc = -EINVAL;
+			break;
+		}
+
+		iface->cur_mode = TWI_I2C_MODE_STANDARD;
+		iface->manual_stop = 0;
+		iface->transPtr = pmsg->buf;
+		iface->writeNum = iface->readNum = pmsg->len;
+		iface->result = 0;
+		iface->timeout_count = 10;
+		/* Set Transmit device address */
+		bfin_write_TWI_MASTER_ADDR(pmsg->addr);
+
+		/* FIFO Initiation. Data in FIFO should be
+		 *  discarded before start a new operation.
+		 */
+		bfin_write_TWI_FIFO_CTL(0x3);
+		SSYNC();
+		bfin_write_TWI_FIFO_CTL(0);
+		SSYNC();
+
+		if (pmsg->flags & I2C_M_RD)
+			iface->read_write = I2C_SMBUS_READ;
+		else {
+			iface->read_write = I2C_SMBUS_WRITE;
+			/* Transmit first data */
+			if (iface->writeNum > 0) {
+				bfin_write_TWI_XMT_DATA8(*(iface->transPtr++));
+				iface->writeNum--;
+				SSYNC();
+			}
+		}
+
+		/* clear int stat */
+		bfin_write_TWI_INT_STAT(MERR|MCOMP|XMTSERV|RCVSERV);
+
+		/* Interrupt mask . Enable XMT, RCV interrupt */
+		bfin_write_TWI_INT_MASK(MCOMP | MERR |
+			((iface->read_write == I2C_SMBUS_READ)?
+			RCVSERV : XMTSERV));
+		SSYNC();
+
+		if (pmsg->len > 0 && pmsg->len <= 255)
+			bfin_write_TWI_MASTER_CTL(pmsg->len << 6);
+		else if (pmsg->len > 255) {
+			bfin_write_TWI_MASTER_CTL(0xff << 6);
+			iface->manual_stop = 1;
+		} else
+			break;
+
+		iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
+		add_timer(&iface->timeout_timer);
+
+		/* Master enable */
+		bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() | MEN |
+			((iface->read_write == I2C_SMBUS_READ) ? MDIR : 0) |
+			((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ>100) ? FAST : 0));
+		SSYNC();
+
+		wait_for_completion(&iface->complete);
+
+		rc = iface->result;
+		if (rc == 1)
+			ret++;
+		else if (rc == -1)
+			break;
+	}
+
+	/* Release mutex */
+	mutex_unlock(&iface->twi_lock);
+
+	return ret;
+}
+
+/*
+ * SMBus type transfer entrypoint
+ */
+
+int bfin_twi_smbus_xfer(struct i2c_adapter *adap, u16 addr,
+			unsigned short flags, char read_write,
+			u8 command, int size, union i2c_smbus_data *data)
+{
+	struct bfin_twi_iface *iface = adap->algo_data;
+	int rc = 0;
+
+	if (!(bfin_read_TWI_CONTROL() & TWI_ENA))
+		return -ENXIO;
+
+	mutex_lock(&iface->twi_lock);
+
+	while (bfin_read_TWI_MASTER_STAT() & BUSBUSY) {
+		mutex_unlock(&iface->twi_lock);
+		yield();
+		mutex_lock(&iface->twi_lock);
+	}
+
+	iface->writeNum = 0;
+	iface->readNum = 0;
+
+	/* Prepare datas & select mode */
+	switch (size) {
+	case I2C_SMBUS_QUICK:
+		iface->transPtr = NULL;
+		iface->cur_mode = TWI_I2C_MODE_STANDARD;
+		break;
+	case I2C_SMBUS_BYTE:
+		if (data == NULL)
+			iface->transPtr = NULL;
+		else {
+			if (read_write == I2C_SMBUS_READ)
+				iface->readNum = 1;
+			else
+				iface->writeNum = 1;
+			iface->transPtr = &data->byte;
+		}
+		iface->cur_mode = TWI_I2C_MODE_STANDARD;
+		break;
+	case I2C_SMBUS_BYTE_DATA:
+		if (read_write == I2C_SMBUS_READ) {
+			iface->readNum = 1;
+			iface->cur_mode = TWI_I2C_MODE_COMBINED;
+		} else {
+			iface->writeNum = 1;
+			iface->cur_mode = TWI_I2C_MODE_STANDARDSUB;
+		}
+		iface->transPtr = &data->byte;
+		break;
+	case I2C_SMBUS_WORD_DATA:
+		if (read_write == I2C_SMBUS_READ) {
+			iface->readNum = 2;
+			iface->cur_mode = TWI_I2C_MODE_COMBINED;
+		} else {
+			iface->writeNum = 2;
+			iface->cur_mode = TWI_I2C_MODE_STANDARDSUB;
+		}
+		iface->transPtr = (u8 *)&data->word;
+		break;
+	case I2C_SMBUS_PROC_CALL:
+		iface->writeNum = 2;
+		iface->readNum = 2;
+		iface->cur_mode = TWI_I2C_MODE_COMBINED;
+		iface->transPtr = (u8 *)&data->word;
+		break;
+	case I2C_SMBUS_BLOCK_DATA:
+		if (read_write == I2C_SMBUS_READ) {
+			iface->readNum = 0;
+			iface->cur_mode = TWI_I2C_MODE_COMBINED;
+		} else {
+			iface->writeNum = data->block[0] + 1;
+			iface->cur_mode = TWI_I2C_MODE_STANDARDSUB;
+		}
+		iface->transPtr = data->block;
+		break;
+	default:
+		return -1;
+	}
+
+	iface->result = 0;
+	iface->manual_stop = 0;
+	iface->read_write = read_write;
+	iface->command = command;
+	iface->timeout_count = 10;
+
+	/* FIFO Initiation. Data in FIFO should be discarded before
+	 * start a new operation.
+	 */
+	bfin_write_TWI_FIFO_CTL(0x3);
+	SSYNC();
+	bfin_write_TWI_FIFO_CTL(0);
+
+	/* clear int stat */
+	bfin_write_TWI_INT_STAT(MERR|MCOMP|XMTSERV|RCVSERV);
+
+	/* Set Transmit device address */
+	bfin_write_TWI_MASTER_ADDR(addr);
+	SSYNC();
+
+	iface->timeout_timer.expires = jiffies + POLL_TIMEOUT;
+	add_timer(&iface->timeout_timer);
+
+	switch (iface->cur_mode) {
+	case TWI_I2C_MODE_STANDARDSUB:
+		bfin_write_TWI_XMT_DATA8(iface->command);
+		bfin_write_TWI_INT_MASK(MCOMP | MERR |
+			((iface->read_write == I2C_SMBUS_READ) ?
+			RCVSERV : XMTSERV));
+		SSYNC();
+
+		if (iface->writeNum + 1 <= 255)
+			bfin_write_TWI_MASTER_CTL((iface->writeNum + 1) << 6);
+		else {
+			bfin_write_TWI_MASTER_CTL(0xff << 6);
+			iface->manual_stop = 1;
+		}
+		/* Master enable */
+		bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() | MEN |
+			((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ>100) ? FAST : 0));
+		break;
+	case TWI_I2C_MODE_COMBINED:
+		bfin_write_TWI_XMT_DATA8(iface->command);
+		bfin_write_TWI_INT_MASK(MCOMP | MERR | RCVSERV | XMTSERV);
+		SSYNC();
+
+		if (iface->writeNum > 0)
+			bfin_write_TWI_MASTER_CTL((iface->writeNum + 1) << 6);
+		else
+			bfin_write_TWI_MASTER_CTL(0x1 << 6);
+		/* Master enable */
+		bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() | MEN |
+			((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ>100) ? FAST : 0));
+		break;
+	default:
+		bfin_write_TWI_MASTER_CTL(0);
+		if (size != I2C_SMBUS_QUICK) {
+			/* Don't access xmit data register when this is a
+			 * read operation.
+			 */
+			if (iface->read_write != I2C_SMBUS_READ) {
+				if (iface->writeNum > 0) {
+					bfin_write_TWI_XMT_DATA8(*(iface->transPtr++));
+					if (iface->writeNum <= 255)
+						bfin_write_TWI_MASTER_CTL(iface->writeNum << 6);
+					else {
+						bfin_write_TWI_MASTER_CTL(0xff << 6);
+						iface->manual_stop = 1;
+					}
+					iface->writeNum--;
+				} else {
+					bfin_write_TWI_XMT_DATA8(iface->command);
+					bfin_write_TWI_MASTER_CTL(1 << 6);
+				}
+			} else {
+				if (iface->readNum > 0 && iface->readNum <= 255)
+					bfin_write_TWI_MASTER_CTL(iface->readNum << 6);
+				else if (iface->readNum > 255) {
+					bfin_write_TWI_MASTER_CTL(0xff << 6);
+					iface->manual_stop = 1;
+				} else {
+					del_timer(&iface->timeout_timer);
+					break;
+				}
+			}
+		}
+		bfin_write_TWI_INT_MASK(MCOMP | MERR |
+			((iface->read_write == I2C_SMBUS_READ) ?
+			RCVSERV : XMTSERV));
+		SSYNC();
+
+		/* Master enable */
+		bfin_write_TWI_MASTER_CTL(bfin_read_TWI_MASTER_CTL() | MEN |
+			((iface->read_write == I2C_SMBUS_READ) ? MDIR : 0) |
+			((CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ > 100) ? FAST : 0));
+		break;
+	}
+	SSYNC();
+
+	wait_for_completion(&iface->complete);
+
+	rc = (iface->result >= 0) ? 0 : -1;
+
+	/* Release mutex */
+	mutex_unlock(&iface->twi_lock);
+
+	return rc;
+}
+
+/*
+ * Return what the adapter supports
+ */
+static u32 bfin_twi_functionality(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
+	       I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
+	       I2C_FUNC_SMBUS_BLOCK_DATA | I2C_FUNC_SMBUS_PROC_CALL |
+	       I2C_FUNC_I2C;
+}
+
+
+static struct i2c_algorithm bfin_twi_algorithm = {
+	.master_xfer   = bfin_twi_master_xfer,
+	.smbus_xfer    = bfin_twi_smbus_xfer,
+	.functionality = bfin_twi_functionality,
+};
+
+
+static int i2c_bfin_twi_suspend(struct platform_device *dev, pm_message_t state)
+{
+/*	struct bfin_twi_iface *iface = platform_get_drvdata(dev);*/
+
+	/* Disable TWI */
+	bfin_write_TWI_CONTROL(bfin_read_TWI_CONTROL() & ~TWI_ENA);
+	SSYNC();
+
+	return 0;
+}
+
+static int i2c_bfin_twi_resume(struct platform_device *dev)
+{
+/*	struct bfin_twi_iface *iface = platform_get_drvdata(dev);*/
+
+	/* Enable TWI */
+	bfin_write_TWI_CONTROL(bfin_read_TWI_CONTROL() | TWI_ENA);
+	SSYNC();
+
+	return 0;
+}
+
+static int i2c_bfin_twi_probe(struct platform_device *dev)
+{
+	struct bfin_twi_iface *iface = &twi_iface;
+	struct i2c_adapter *p_adap;
+	int rc;
+
+	mutex_init(&(iface->twi_lock));
+	spin_lock_init(&(iface->lock));
+	init_completion(&(iface->complete));
+	iface->irq = IRQ_TWI;
+
+	init_timer(&(iface->timeout_timer));
+	iface->timeout_timer.function = bfin_twi_timeout;
+	iface->timeout_timer.data = (unsigned long)iface;
+
+	p_adap = &iface->adap;
+	p_adap->id = I2C_HW_BLACKFIN;
+	strlcpy(p_adap->name, dev->name, sizeof(p_adap->name));
+	p_adap->algo = &bfin_twi_algorithm;
+	p_adap->algo_data = iface;
+	p_adap->class = I2C_CLASS_ALL;
+	p_adap->dev.parent = &dev->dev;
+
+	rc = request_irq(iface->irq, bfin_twi_interrupt_entry,
+		IRQF_DISABLED, dev->name, iface);
+	if (rc) {
+		dev_err(&(p_adap->dev), "i2c-bfin-twi: can't get IRQ %d !\n",
+			iface->irq);
+		return -ENODEV;
+	}
+
+	/* Set TWI internal clock as 10MHz */
+	bfin_write_TWI_CONTROL(((get_sclk() / 1024 / 1024 + 5) / 10) & 0x7F);
+
+	/* Set Twi interface clock as specified */
+	bfin_write_TWI_CLKDIV((( 5*1024 / CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ )
+			<< 8) | (( 5*1024 / CONFIG_I2C_BLACKFIN_TWI_CLK_KHZ )
+			& 0xFF));
+
+	/* Enable TWI */
+	bfin_write_TWI_CONTROL(bfin_read_TWI_CONTROL() | TWI_ENA);
+	SSYNC();
+
+	rc = i2c_add_adapter(p_adap);
+	if (rc < 0)
+		free_irq(iface->irq, iface);
+	else
+		platform_set_drvdata(dev, iface);
+
+	return rc;
+}
+
+static int i2c_bfin_twi_remove(struct platform_device *pdev)
+{
+	struct bfin_twi_iface *iface = platform_get_drvdata(pdev);
+
+	platform_set_drvdata(pdev, NULL);
+
+	i2c_del_adapter(&(iface->adap));
+	free_irq(iface->irq, iface);
+
+	return 0;
+}
+
+static struct platform_driver i2c_bfin_twi_driver = {
+	.probe		= i2c_bfin_twi_probe,
+	.remove		= i2c_bfin_twi_remove,
+	.suspend	= i2c_bfin_twi_suspend,
+	.resume		= i2c_bfin_twi_resume,
+	.driver		= {
+		.name	= "i2c-bfin-twi",
+		.owner	= THIS_MODULE,
+	},
+};
+
+static int __init i2c_bfin_twi_init(void)
+{
+	pr_info("I2C: Blackfin I2C TWI driver\n");
+
+	return platform_driver_register(&i2c_bfin_twi_driver);
+}
+
+static void __exit i2c_bfin_twi_exit(void)
+{
+	platform_driver_unregister(&i2c_bfin_twi_driver);
+}
+
+MODULE_AUTHOR("Sonic Zhang <sonic.zhang@analog.com>");
+MODULE_DESCRIPTION("I2C-Bus adapter routines for Blackfin TWI");
+MODULE_LICENSE("GPL");
+
+module_init(i2c_bfin_twi_init);
+module_exit(i2c_bfin_twi_exit);