drivers/i2c/s3c24x0_i2c.c - uboot/prism - Git at Google

 /*
  * (C) Copyright 2002
  * David Mueller, ELSOFT AG, d.mueller@elsoft.ch
  *
  * See file CREDITS for list of people who contributed to this
  * project.
  *
  * 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
  */

 /* This code should work for both the S3C2400 and the S3C2410
  * as they seem to have the same I2C controller inside.
  * The different address mapping is handled by the s3c24xx.h files below.
  */

 #include <common.h>
 #if defined(CONFIG_S3C2400)
 #include <s3c2400.h>
 #elif defined(CONFIG_S3C2410)
 #include <s3c2410.h>
 #endif
 #include <i2c.h>

 #ifdef CONFIG_HARD_I2C

 #define	I2C_WRITE	0
 #define I2C_READ	1

 #define I2C_OK		0
 #define I2C_NOK		1
 #define I2C_NACK	2
 #define I2C_NOK_LA	3		/* Lost arbitration */
 #define I2C_NOK_TOUT	4		/* time out */

 #define I2CSTAT_BSY	0x20		/* Busy bit */
 #define I2CSTAT_NACK	0x01		/* Nack bit */
 #define I2CCON_IRPND	0x10		/* Interrupt pending bit */
 #define I2C_MODE_MT	0xC0		/* Master Transmit Mode */
 #define I2C_MODE_MR	0x80		/* Master Receive Mode */
 #define I2C_START_STOP	0x20		/* START / STOP */
 #define I2C_TXRX_ENA	0x10		/* I2C Tx/Rx enable */

 #define I2C_TIMEOUT 1			/* 1 second */


 static int GetI2CSDA(void)
 {
 	S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();

 #ifdef CONFIG_S3C2410
 	return (gpio->GPEDAT & 0x8000) >> 15;
 #endif
 #ifdef CONFIG_S3C2400
 	return (gpio->PGDAT & 0x0020) >> 5;
 #endif
 }

 #if 0
 static void SetI2CSDA(int x)
 {
 	rGPEDAT = (rGPEDAT & ~0x8000) | (x&1) << 15;
 }
 #endif

 static void SetI2CSCL(int x)
 {
 	S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();

 #ifdef CONFIG_S3C2410
 	gpio->GPEDAT = (gpio->GPEDAT & ~0x4000) | (x&1) << 14;
 #endif
 #ifdef CONFIG_S3C2400
 	gpio->PGDAT = (gpio->PGDAT & ~0x0040) | (x&1) << 6;
 #endif
 }


 static int WaitForXfer (void)
 {
 	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();
 	int i, status;

 	i = I2C_TIMEOUT * 10000;
 	status = i2c->IICCON;
 	while ((i > 0) && !(status & I2CCON_IRPND)) {
 		udelay (100);
 		status = i2c->IICCON;
 		i--;
 	}

 	return (status & I2CCON_IRPND) ? I2C_OK : I2C_NOK_TOUT;
 }

 static int IsACK (void)
 {
 	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();

 	return (!(i2c->IICSTAT & I2CSTAT_NACK));
 }

 static void ReadWriteByte (void)
 {
 	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();

 	i2c->IICCON &= ~I2CCON_IRPND;
 }

 void i2c_init (int speed, int slaveadd)
 {
 	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();
 	S3C24X0_GPIO *const gpio = S3C24X0_GetBase_GPIO ();
 	ulong freq, pres = 16, div;
 	int i, status;

 	/* wait for some time to give previous transfer a chance to finish */

 	i = I2C_TIMEOUT * 1000;
 	status = i2c->IICSTAT;
 	while ((i > 0) && (status & I2CSTAT_BSY)) {
 		udelay (1000);
 		status = i2c->IICSTAT;
 		i--;
 	}

 	if ((status & I2CSTAT_BSY) || GetI2CSDA () == 0) {
 #ifdef CONFIG_S3C2410
 		ulong old_gpecon = gpio->GPECON;
 #endif
 #ifdef CONFIG_S3C2400
 		ulong old_gpecon = gpio->PGCON;
 #endif
 		/* bus still busy probably by (most) previously interrupted transfer */

 #ifdef CONFIG_S3C2410
 		/* set I2CSDA and I2CSCL (GPE15, GPE14) to GPIO */
 		gpio->GPECON = (gpio->GPECON & ~0xF0000000) | 0x10000000;
 #endif
 #ifdef CONFIG_S3C2400
 		/* set I2CSDA and I2CSCL (PG5, PG6) to GPIO */
 		gpio->PGCON = (gpio->PGCON & ~0x00003c00) | 0x00001000;
 #endif

 		/* toggle I2CSCL until bus idle */
 		SetI2CSCL (0);
 		udelay (1000);
 		i = 10;
 		while ((i > 0) && (GetI2CSDA () != 1)) {
 			SetI2CSCL (1);
 			udelay (1000);
 			SetI2CSCL (0);
 			udelay (1000);
 			i--;
 		}
 		SetI2CSCL (1);
 		udelay (1000);

 		/* restore pin functions */
 #ifdef CONFIG_S3C2410
 		gpio->GPECON = old_gpecon;
 #endif
 #ifdef CONFIG_S3C2400
 		gpio->PGCON = old_gpecon;
 #endif
 	}

 	/* calculate prescaler and divisor values */
 	freq = get_PCLK ();
 	if ((freq / pres / (16 + 1)) > speed)
 		/* set prescaler to 512 */
 		pres = 512;

 	div = 0;
 	while ((freq / pres / (div + 1)) > speed)
 		div++;

 	/* set prescaler, divisor according to freq, also set
 	 * ACKGEN, IRQ */
 	i2c->IICCON = (div & 0x0F) | 0xA0 | ((pres == 512) ? 0x40 : 0);

 	/* init to SLAVE REVEIVE and set slaveaddr */
 	i2c->IICSTAT = 0;
 	i2c->IICADD = slaveadd;
 	/* program Master Transmit (and implicit STOP) */
 	i2c->IICSTAT = I2C_MODE_MT | I2C_TXRX_ENA;

 }

 /*
  * cmd_type is 0 for write, 1 for read.
  *
  * addr_len can take any value from 0-255, it is only limited
  * by the char, we could make it larger if needed. If it is
  * 0 we skip the address write cycle.
  */
 static
 int i2c_transfer (unsigned char cmd_type,
 		  unsigned char chip,
 		  unsigned char addr[],
 		  unsigned char addr_len,
 		  unsigned char data[], unsigned short data_len)
 {
 	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();
 	int i, status, result;

 	if (data == 0 || data_len == 0) {
 		/*Don't support data transfer of no length or to address 0 */
 		printf ("i2c_transfer: bad call\n");
 		return I2C_NOK;
 	}

 	/* Check I2C bus idle */
 	i = I2C_TIMEOUT * 1000;
 	status = i2c->IICSTAT;
 	while ((i > 0) && (status & I2CSTAT_BSY)) {
 		udelay (1000);
 		status = i2c->IICSTAT;
 		i--;
 	}

 	if (status & I2CSTAT_BSY)
 		return I2C_NOK_TOUT;

 	i2c->IICCON |= 0x80;
 	result = I2C_OK;

 	switch (cmd_type) {
 	case I2C_WRITE:
 		if (addr && addr_len) {
 			i2c->IICDS = chip;
 			/* send START */
 			i2c->IICSTAT = I2C_MODE_MT | I2C_TXRX_ENA | I2C_START_STOP;
 			i = 0;
 			while ((i < addr_len) && (result == I2C_OK)) {
 				result = WaitForXfer ();
 				i2c->IICDS = addr[i];
 				ReadWriteByte ();
 				i++;
 			}
 			i = 0;
 			while ((i < data_len) && (result == I2C_OK)) {
 				result = WaitForXfer ();
 				i2c->IICDS = data[i];
 				ReadWriteByte ();
 				i++;
 			}
 		} else {
 			i2c->IICDS = chip;
 			/* send START */
 			i2c->IICSTAT = I2C_MODE_MT | I2C_TXRX_ENA | I2C_START_STOP;
 			i = 0;
 			while ((i < data_len) && (result = I2C_OK)) {
 				result = WaitForXfer ();
 				i2c->IICDS = data[i];
 				ReadWriteByte ();
 				i++;
 			}
 		}

 		if (result == I2C_OK)
 			result = WaitForXfer ();

 		/* send STOP */
 		i2c->IICSTAT = I2C_MODE_MR | I2C_TXRX_ENA;
 		ReadWriteByte ();
 		break;

 	case I2C_READ:
 		if (addr && addr_len) {
 			i2c->IICSTAT = I2C_MODE_MT | I2C_TXRX_ENA;
 			i2c->IICDS = chip;
 			/* send START */
 			i2c->IICSTAT |= I2C_START_STOP;
 			result = WaitForXfer ();
 			if (IsACK ()) {
 				i = 0;
 				while ((i < addr_len) && (result == I2C_OK)) {
 					i2c->IICDS = addr[i];
 					ReadWriteByte ();
 					result = WaitForXfer ();
 					i++;
 				}

 				i2c->IICDS = chip;
 				/* resend START */
 				i2c->IICSTAT =  I2C_MODE_MR | I2C_TXRX_ENA |
 						I2C_START_STOP;
 				ReadWriteByte ();
 				result = WaitForXfer ();
 				i = 0;
 				while ((i < data_len) && (result == I2C_OK)) {
 					/* disable ACK for final READ */
 					if (i == data_len - 1)
 						i2c->IICCON &= ~0x80;
 					ReadWriteByte ();
 					result = WaitForXfer ();
 					data[i] = i2c->IICDS;
 					i++;
 				}
 			} else {
 				result = I2C_NACK;
 			}

 		} else {
 			i2c->IICSTAT = I2C_MODE_MR | I2C_TXRX_ENA;
 			i2c->IICDS = chip;
 			/* send START */
 			i2c->IICSTAT |= I2C_START_STOP;
 			result = WaitForXfer ();

 			if (IsACK ()) {
 				i = 0;
 				while ((i < data_len) && (result == I2C_OK)) {
 					/* disable ACK for final READ */
 					if (i == data_len - 1)
 						i2c->IICCON &= ~0x80;
 					ReadWriteByte ();
 					result = WaitForXfer ();
 					data[i] = i2c->IICDS;
 					i++;
 				}
 			} else {
 				result = I2C_NACK;
 			}
 		}

 		/* send STOP */
 		i2c->IICSTAT = I2C_MODE_MR | I2C_TXRX_ENA;
 		ReadWriteByte ();
 		break;

 	default:
 		printf ("i2c_transfer: bad call\n");
 		result = I2C_NOK;
 		break;
 	}

 	return (result);
 }

 int i2c_probe (uchar chip)
 {
 	uchar buf[1];

 	buf[0] = 0;

 	/*
 	 * What is needed is to send the chip address and verify that the
 	 * address was <ACK>ed (i.e. there was a chip at that address which
 	 * drove the data line low).
 	 */
 	return (i2c_transfer (I2C_READ, chip << 1, 0, 0, buf, 1) != I2C_OK);
 }

 int i2c_read (uchar chip, uint addr, int alen, uchar * buffer, int len)
 {
 	uchar xaddr[4];
 	int ret;

 	if (alen > 4) {
 		printf ("I2C read: addr len %d not supported\n", alen);
 		return 1;
 	}

 	if (alen > 0) {
 		xaddr[0] = (addr >> 24) & 0xFF;
 		xaddr[1] = (addr >> 16) & 0xFF;
 		xaddr[2] = (addr >> 8) & 0xFF;
 		xaddr[3] = addr & 0xFF;
 	}

 #ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
 	/*
 	 * EEPROM chips that implement "address overflow" are ones
 	 * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 	 * address and the extra bits end up in the "chip address"
 	 * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 	 * four 256 byte chips.
 	 *
 	 * Note that we consider the length of the address field to
 	 * still be one byte because the extra address bits are
 	 * hidden in the chip address.
 	 */
 	if (alen > 0)
 		chip |= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
 #endif
 	if ((ret =
 	     i2c_transfer (I2C_READ, chip << 1, &xaddr[4 - alen], alen,
 			   buffer, len)) != 0) {
 		printf ("I2c read: failed %d\n", ret);
 		return 1;
 	}
 	return 0;
 }

 int i2c_write (uchar chip, uint addr, int alen, uchar * buffer, int len)
 {
 	uchar xaddr[4];

 	if (alen > 4) {
 		printf ("I2C write: addr len %d not supported\n", alen);
 		return 1;
 	}

 	if (alen > 0) {
 		xaddr[0] = (addr >> 24) & 0xFF;
 		xaddr[1] = (addr >> 16) & 0xFF;
 		xaddr[2] = (addr >> 8) & 0xFF;
 		xaddr[3] = addr & 0xFF;
 	}
 #ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
 	/*
 	 * EEPROM chips that implement "address overflow" are ones
 	 * like Catalyst 24WC04/08/16 which has 9/10/11 bits of
 	 * address and the extra bits end up in the "chip address"
 	 * bit slots. This makes a 24WC08 (1Kbyte) chip look like
 	 * four 256 byte chips.
 	 *
 	 * Note that we consider the length of the address field to
 	 * still be one byte because the extra address bits are
 	 * hidden in the chip address.
 	 */
 	if (alen > 0)
 		chip |= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
 #endif
 	return (i2c_transfer
 		(I2C_WRITE, chip << 1, &xaddr[4 - alen], alen, buffer,
 		 len) != 0);
 }
 #endif	/* CONFIG_HARD_I2C */
	/*
	* (C) Copyright 2002
	* David Mueller, ELSOFT AG, d.mueller@elsoft.ch
	*
	* See file CREDITS for list of people who contributed to this
	* project.
	*
	* 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
	*/

	/* This code should work for both the S3C2400 and the S3C2410
	* as they seem to have the same I2C controller inside.
	* The different address mapping is handled by the s3c24xx.h files below.
	*/

	#include <common.h>
	#if defined(CONFIG_S3C2400)
	#include <s3c2400.h>
	#elif defined(CONFIG_S3C2410)
	#include <s3c2410.h>
	#endif
	#include <i2c.h>

	#ifdef CONFIG_HARD_I2C

	#define I2C_WRITE 0
	#define I2C_READ 1

	#define I2C_OK 0
	#define I2C_NOK 1
	#define I2C_NACK 2
	#define I2C_NOK_LA 3 /* Lost arbitration */
	#define I2C_NOK_TOUT 4 /* time out */

	#define I2CSTAT_BSY 0x20 /* Busy bit */
	#define I2CSTAT_NACK 0x01 /* Nack bit */
	#define I2CCON_IRPND 0x10 /* Interrupt pending bit */
	#define I2C_MODE_MT 0xC0 /* Master Transmit Mode */
	#define I2C_MODE_MR 0x80 /* Master Receive Mode */
	#define I2C_START_STOP 0x20 /* START / STOP */
	#define I2C_TXRX_ENA 0x10 /* I2C Tx/Rx enable */

	#define I2C_TIMEOUT 1 /* 1 second */


	static int GetI2CSDA(void)
	{
	S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();

	#ifdef CONFIG_S3C2410
	return (gpio->GPEDAT & 0x8000) >> 15;
	#endif
	#ifdef CONFIG_S3C2400
	return (gpio->PGDAT & 0x0020) >> 5;
	#endif
	}

	#if 0
	static void SetI2CSDA(int x)
	{
	rGPEDAT = (rGPEDAT & ~0x8000) \| (x&1) << 15;
	}
	#endif

	static void SetI2CSCL(int x)
	{
	S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();

	#ifdef CONFIG_S3C2410
	gpio->GPEDAT = (gpio->GPEDAT & ~0x4000) \| (x&1) << 14;
	#endif
	#ifdef CONFIG_S3C2400
	gpio->PGDAT = (gpio->PGDAT & ~0x0040) \| (x&1) << 6;
	#endif
	}


	static int WaitForXfer (void)
	{
	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();
	int i, status;

	i = I2C_TIMEOUT * 10000;
	status = i2c->IICCON;
	while ((i > 0) && !(status & I2CCON_IRPND)) {
	udelay (100);
	status = i2c->IICCON;
	i--;
	}

	return (status & I2CCON_IRPND) ? I2C_OK : I2C_NOK_TOUT;
	}

	static int IsACK (void)
	{
	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();

	return (!(i2c->IICSTAT & I2CSTAT_NACK));
	}

	static void ReadWriteByte (void)
	{
	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();

	i2c->IICCON &= ~I2CCON_IRPND;
	}

	void i2c_init (int speed, int slaveadd)
	{
	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();
	S3C24X0_GPIO *const gpio = S3C24X0_GetBase_GPIO ();
	ulong freq, pres = 16, div;
	int i, status;

	/* wait for some time to give previous transfer a chance to finish */

	i = I2C_TIMEOUT * 1000;
	status = i2c->IICSTAT;
	while ((i > 0) && (status & I2CSTAT_BSY)) {
	udelay (1000);
	status = i2c->IICSTAT;
	i--;
	}

	if ((status & I2CSTAT_BSY) \|\| GetI2CSDA () == 0) {
	#ifdef CONFIG_S3C2410
	ulong old_gpecon = gpio->GPECON;
	#endif
	#ifdef CONFIG_S3C2400
	ulong old_gpecon = gpio->PGCON;
	#endif
	/* bus still busy probably by (most) previously interrupted transfer */

	#ifdef CONFIG_S3C2410
	/* set I2CSDA and I2CSCL (GPE15, GPE14) to GPIO */
	gpio->GPECON = (gpio->GPECON & ~0xF0000000) \| 0x10000000;
	#endif
	#ifdef CONFIG_S3C2400
	/* set I2CSDA and I2CSCL (PG5, PG6) to GPIO */
	gpio->PGCON = (gpio->PGCON & ~0x00003c00) \| 0x00001000;
	#endif

	/* toggle I2CSCL until bus idle */
	SetI2CSCL (0);
	udelay (1000);
	i = 10;
	while ((i > 0) && (GetI2CSDA () != 1)) {
	SetI2CSCL (1);
	udelay (1000);
	SetI2CSCL (0);
	udelay (1000);
	i--;
	}
	SetI2CSCL (1);
	udelay (1000);

	/* restore pin functions */
	#ifdef CONFIG_S3C2410
	gpio->GPECON = old_gpecon;
	#endif
	#ifdef CONFIG_S3C2400
	gpio->PGCON = old_gpecon;
	#endif
	}

	/* calculate prescaler and divisor values */
	freq = get_PCLK ();
	if ((freq / pres / (16 + 1)) > speed)
	/* set prescaler to 512 */
	pres = 512;

	div = 0;
	while ((freq / pres / (div + 1)) > speed)
	div++;

	/* set prescaler, divisor according to freq, also set
	* ACKGEN, IRQ */
	i2c->IICCON = (div & 0x0F) \| 0xA0 \| ((pres == 512) ? 0x40 : 0);

	/* init to SLAVE REVEIVE and set slaveaddr */
	i2c->IICSTAT = 0;
	i2c->IICADD = slaveadd;
	/* program Master Transmit (and implicit STOP) */
	i2c->IICSTAT = I2C_MODE_MT \| I2C_TXRX_ENA;

	}

	/*
	* cmd_type is 0 for write, 1 for read.
	*
	* addr_len can take any value from 0-255, it is only limited
	* by the char, we could make it larger if needed. If it is
	* 0 we skip the address write cycle.
	*/
	static
	int i2c_transfer (unsigned char cmd_type,
	unsigned char chip,
	unsigned char addr[],
	unsigned char addr_len,
	unsigned char data[], unsigned short data_len)
	{
	S3C24X0_I2C *const i2c = S3C24X0_GetBase_I2C ();
	int i, status, result;

	if (data == 0 \|\| data_len == 0) {
	/Don't support data transfer of no length or to address 0 /
	printf ("i2c_transfer: bad call\n");
	return I2C_NOK;
	}

	/* Check I2C bus idle */
	i = I2C_TIMEOUT * 1000;
	status = i2c->IICSTAT;
	while ((i > 0) && (status & I2CSTAT_BSY)) {
	udelay (1000);
	status = i2c->IICSTAT;
	i--;
	}

	if (status & I2CSTAT_BSY)
	return I2C_NOK_TOUT;

	i2c->IICCON \|= 0x80;
	result = I2C_OK;

	switch (cmd_type) {
	case I2C_WRITE:
	if (addr && addr_len) {
	i2c->IICDS = chip;
	/* send START */
	i2c->IICSTAT = I2C_MODE_MT \| I2C_TXRX_ENA \| I2C_START_STOP;
	i = 0;
	while ((i < addr_len) && (result == I2C_OK)) {
	result = WaitForXfer ();
	i2c->IICDS = addr[i];
	ReadWriteByte ();
	i++;
	}
	i = 0;
	while ((i < data_len) && (result == I2C_OK)) {
	result = WaitForXfer ();
	i2c->IICDS = data[i];
	ReadWriteByte ();
	i++;
	}
	} else {
	i2c->IICDS = chip;
	/* send START */
	i2c->IICSTAT = I2C_MODE_MT \| I2C_TXRX_ENA \| I2C_START_STOP;
	i = 0;
	while ((i < data_len) && (result = I2C_OK)) {
	result = WaitForXfer ();
	i2c->IICDS = data[i];
	ReadWriteByte ();
	i++;
	}
	}

	if (result == I2C_OK)
	result = WaitForXfer ();

	/* send STOP */
	i2c->IICSTAT = I2C_MODE_MR \| I2C_TXRX_ENA;
	ReadWriteByte ();
	break;

	case I2C_READ:
	if (addr && addr_len) {
	i2c->IICSTAT = I2C_MODE_MT \| I2C_TXRX_ENA;
	i2c->IICDS = chip;
	/* send START */
	i2c->IICSTAT \|= I2C_START_STOP;
	result = WaitForXfer ();
	if (IsACK ()) {
	i = 0;
	while ((i < addr_len) && (result == I2C_OK)) {
	i2c->IICDS = addr[i];
	ReadWriteByte ();
	result = WaitForXfer ();
	i++;
	}

	i2c->IICDS = chip;
	/* resend START */
	i2c->IICSTAT = I2C_MODE_MR \| I2C_TXRX_ENA \|
	I2C_START_STOP;
	ReadWriteByte ();
	result = WaitForXfer ();
	i = 0;
	while ((i < data_len) && (result == I2C_OK)) {
	/* disable ACK for final READ */
	if (i == data_len - 1)
	i2c->IICCON &= ~0x80;
	ReadWriteByte ();
	result = WaitForXfer ();
	data[i] = i2c->IICDS;
	i++;
	}
	} else {
	result = I2C_NACK;
	}

	} else {
	i2c->IICSTAT = I2C_MODE_MR \| I2C_TXRX_ENA;
	i2c->IICDS = chip;
	/* send START */
	i2c->IICSTAT \|= I2C_START_STOP;
	result = WaitForXfer ();

	if (IsACK ()) {
	i = 0;
	while ((i < data_len) && (result == I2C_OK)) {
	/* disable ACK for final READ */
	if (i == data_len - 1)
	i2c->IICCON &= ~0x80;
	ReadWriteByte ();
	result = WaitForXfer ();
	data[i] = i2c->IICDS;
	i++;
	}
	} else {
	result = I2C_NACK;
	}
	}

	/* send STOP */
	i2c->IICSTAT = I2C_MODE_MR \| I2C_TXRX_ENA;
	ReadWriteByte ();
	break;

	default:
	printf ("i2c_transfer: bad call\n");
	result = I2C_NOK;
	break;
	}

	return (result);
	}

	int i2c_probe (uchar chip)
	{
	uchar buf[1];

	buf[0] = 0;

	/*
	* What is needed is to send the chip address and verify that the
	* address was <ACK>ed (i.e. there was a chip at that address which
	* drove the data line low).
	*/
	return (i2c_transfer (I2C_READ, chip << 1, 0, 0, buf, 1) != I2C_OK);
	}

	int i2c_read (uchar chip, uint addr, int alen, uchar * buffer, int len)
	{
	uchar xaddr[4];
	int ret;

	if (alen > 4) {
	printf ("I2C read: addr len %d not supported\n", alen);
	return 1;
	}

	if (alen > 0) {
	xaddr[0] = (addr >> 24) & 0xFF;
	xaddr[1] = (addr >> 16) & 0xFF;
	xaddr[2] = (addr >> 8) & 0xFF;
	xaddr[3] = addr & 0xFF;
	}

	#ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
	/*
	* EEPROM chips that implement "address overflow" are ones
	* like Catalyst 24WC04/08/16 which has 9/10/11 bits of
	* address and the extra bits end up in the "chip address"
	* bit slots. This makes a 24WC08 (1Kbyte) chip look like
	* four 256 byte chips.
	*
	* Note that we consider the length of the address field to
	* still be one byte because the extra address bits are
	* hidden in the chip address.
	*/
	if (alen > 0)
	chip \|= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
	#endif
	if ((ret =
	i2c_transfer (I2C_READ, chip << 1, &xaddr[4 - alen], alen,
	buffer, len)) != 0) {
	printf ("I2c read: failed %d\n", ret);
	return 1;
	}
	return 0;
	}

	int i2c_write (uchar chip, uint addr, int alen, uchar * buffer, int len)
	{
	uchar xaddr[4];

	if (alen > 4) {
	printf ("I2C write: addr len %d not supported\n", alen);
	return 1;
	}

	if (alen > 0) {
	xaddr[0] = (addr >> 24) & 0xFF;
	xaddr[1] = (addr >> 16) & 0xFF;
	xaddr[2] = (addr >> 8) & 0xFF;
	xaddr[3] = addr & 0xFF;
	}
	#ifdef CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW
	/*
	* EEPROM chips that implement "address overflow" are ones
	* like Catalyst 24WC04/08/16 which has 9/10/11 bits of
	* address and the extra bits end up in the "chip address"
	* bit slots. This makes a 24WC08 (1Kbyte) chip look like
	* four 256 byte chips.
	*
	* Note that we consider the length of the address field to
	* still be one byte because the extra address bits are
	* hidden in the chip address.
	*/
	if (alen > 0)
	chip \|= ((addr >> (alen * 8)) & CONFIG_SYS_I2C_EEPROM_ADDR_OVERFLOW);
	#endif
	return (i2c_transfer
	(I2C_WRITE, chip << 1, &xaddr[4 - alen], alen, buffer,
	len) != 0);
	}
	#endif /* CONFIG_HARD_I2C */