board/Marvell/common/i2c.c - github/trini/u-boot - Gitiles

 /*
  * (C) Copyright 2000
  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
  *
  * 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
  *
  * Hacked for the DB64360 board by Ingo.Assmus@keymile.com
  * extra improvments by Brain Waite
  */
 #include <common.h>
 #include <mpc8xx.h>
 #include <malloc.h>
 #include "../include/mv_gen_reg.h"
 #include "../include/core.h"

 #define MAX_I2C_RETRYS	    10
 #define I2C_DELAY	    1000	/* Should be at least the # of MHz of Tclk */
 #undef	DEBUG_I2C
 /*#define DEBUG_I2C*/

 #ifdef DEBUG_I2C
 #define DP(x) x
 #else
 #define DP(x)
 #endif

 /* Assuming that there is only one master on the bus (us) */

 static void i2c_init (int speed, int slaveaddr)
 {
 	unsigned int n, m, freq, margin, power;
 	unsigned int actualN = 0, actualM = 0;
 	unsigned int control, status;
 	unsigned int minMargin = 0xffffffff;
 	unsigned int tclk = CONFIG_SYS_TCLK;
 	unsigned int i2cFreq = speed;	/* 100000 max. Fast mode not supported */

 	DP (puts ("i2c_init\n"));
 /* gtI2cMasterInit */
 	for (n = 0; n < 8; n++) {
 		for (m = 0; m < 16; m++) {
 			power = 2 << n;	/* power = 2^(n+1) */
 			freq = tclk / (10 * (m + 1) * power);
 			if (i2cFreq > freq)
 				margin = i2cFreq - freq;
 			else
 				margin = freq - i2cFreq;
 			if (margin < minMargin) {
 				minMargin = margin;
 				actualN = n;
 				actualM = m;
 			}
 		}
 	}

 	DP (puts ("setup i2c bus\n"));

 	/* Setup bus */
 /* gtI2cReset */
 	GT_REG_WRITE (I2C_SOFT_RESET, 0);

 	DP (puts ("udelay...\n"));

 	udelay (I2C_DELAY);

 	DP (puts ("set baudrate\n"));

 	GT_REG_WRITE (I2C_STATUS_BAUDE_RATE, (actualM << 3) | actualN);
 	GT_REG_WRITE (I2C_CONTROL, (0x1 << 2) | (0x1 << 6));

 	udelay (I2C_DELAY * 10);

 	DP (puts ("read control, baudrate\n"));

 	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 	GT_REG_READ (I2C_CONTROL, &control);
 }

 static uchar i2c_start (void)
 {				/* DB64360 checked -> ok */
 	unsigned int control, status;
 	int count = 0;

 	DP (puts ("i2c_start\n"));

 	/* Set the start bit */

 /* gtI2cGenerateStartBit() */

 	GT_REG_READ (I2C_CONTROL, &control);
 	control |= (0x1 << 5);	/* generate the I2C_START_BIT */
 	GT_REG_WRITE (I2C_CONTROL, control);

 	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);

 	count = 0;
 	while ((status & 0xff) != 0x08) {
 		udelay (I2C_DELAY);
 		if (count > 20) {
 			GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));	/*stop */
 			return (status);
 		}
 		GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 		count++;
 	}

 	return (0);
 }

 static uchar i2c_select_device (uchar dev_addr, uchar read, int ten_bit)
 {
 	unsigned int status, data, bits = 7;
 	int count = 0;

 	DP (puts ("i2c_select_device\n"));

 	/* Output slave address */

 	if (ten_bit) {
 		bits = 10;
 	}

 	data = (dev_addr << 1);
 	/* set the read bit */
 	data |= read;
 	GT_REG_WRITE (I2C_DATA, data);
 	/* assert the address */
 	RESET_REG_BITS (I2C_CONTROL, BIT3);

 	udelay (I2C_DELAY);

 	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 	count = 0;
 	while (((status & 0xff) != 0x40) && ((status & 0xff) != 0x18)) {
 		udelay (I2C_DELAY);
 		if (count > 20) {
 			GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));	/*stop */
 			return (status);
 		}
 		GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 		count++;
 	}

 	if (bits == 10) {
 		printf ("10 bit I2C addressing not yet implemented\n");
 		return (0xff);
 	}

 	return (0);
 }

 static uchar i2c_get_data (uchar * return_data, int len)
 {

 	unsigned int data, status = 0;
 	int count = 0;

 	DP (puts ("i2c_get_data\n"));

 	while (len) {

 		/* Get and return the data */

 		RESET_REG_BITS (I2C_CONTROL, (0x1 << 3));

 		udelay (I2C_DELAY * 5);

 		GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 		count++;
 		while ((status & 0xff) != 0x50) {
 			udelay (I2C_DELAY);
 			if (count > 2) {
 				GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));	/*stop */
 				return 0;
 			}
 			GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 			count++;
 		}
 		GT_REG_READ (I2C_DATA, &data);
 		len--;
 		*return_data = (uchar) data;
 		return_data++;
 	}
 	RESET_REG_BITS (I2C_CONTROL, BIT2 | BIT3);
 	while ((status & 0xff) != 0x58) {
 		udelay (I2C_DELAY);
 		if (count > 200) {
 			GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));	/*stop */
 			return (status);
 		}
 		GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 		count++;
 	}
 	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));	/* stop */

 	return (0);
 }

 static uchar i2c_write_data (unsigned int *data, int len)
 {
 	unsigned int status;
 	int count = 0;
 	unsigned int temp;
 	unsigned int *temp_ptr = data;

 	DP (puts ("i2c_write_data\n"));

 	while (len) {
 		temp = (unsigned int) (*temp_ptr);
 		GT_REG_WRITE (I2C_DATA, temp);
 		RESET_REG_BITS (I2C_CONTROL, (0x1 << 3));

 		udelay (I2C_DELAY);

 		GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 		count++;
 		while ((status & 0xff) != 0x28) {
 			udelay (I2C_DELAY);
 			if (count > 20) {
 				GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));	/*stop */
 				return (status);
 			}
 			GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 			count++;
 		}
 		len--;
 		temp_ptr++;
 	}
 /* 11-14-2002 Paul Marchese */
 /* Can't have the write issuing a stop command */
 /* it's wrong to have a stop bit in read stream or write stream */
 /* since we don't know if it's really the end of the command */
 /* or whether we have just send the device address + offset */
 /* we will push issuing the stop command off to the original */
 /* calling function */
 	/* set the interrupt bit in the control register */
 	GT_REG_WRITE (I2C_CONTROL, (0x1 << 3));
 	udelay (I2C_DELAY * 10);
 	return (0);
 }

 /* 11-14-2002 Paul Marchese */
 /* created this function to get the i2c_write() */
 /* function working properly. */
 /* function to write bytes out on the i2c bus */
 /* this is identical to the function i2c_write_data() */
 /* except that it requires a buffer that is an */
 /* unsigned character array.  You can't use */
 /* i2c_write_data() to send an array of unsigned characters */
 /* since the byte of interest ends up on the wrong end of the bus */
 /* aah, the joys of big endian versus little endian! */
 /* */
 /* returns 0 = success */
 /*         anything other than zero is failure */
 static uchar i2c_write_byte (unsigned char *data, int len)
 {
 	unsigned int status;
 	int count = 0;
 	unsigned int temp;
 	unsigned char *temp_ptr = data;

 	DP (puts ("i2c_write_byte\n"));

 	while (len) {
 		/* Set and assert the data */
 		temp = *temp_ptr;
 		GT_REG_WRITE (I2C_DATA, temp);
 		RESET_REG_BITS (I2C_CONTROL, (0x1 << 3));

 		udelay (I2C_DELAY);

 		GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 		count++;
 		while ((status & 0xff) != 0x28) {
 			udelay (I2C_DELAY);
 			if (count > 20) {
 				GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));	/*stop */
 				return (status);
 			}
 			GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
 			count++;
 		}
 		len--;
 		temp_ptr++;
 	}
 /* Can't have the write issuing a stop command */
 /* it's wrong to have a stop bit in read stream or write stream */
 /* since we don't know if it's really the end of the command */
 /* or whether we have just send the device address + offset */
 /* we will push issuing the stop command off to the original */
 /* calling function */
 /*	GT_REG_WRITE(I2C_CONTROL, (0x1 << 3) | (0x1 << 4));
 	GT_REG_WRITE(I2C_CONTROL, (0x1 << 4)); */
 	/* set the interrupt bit in the control register */
 	GT_REG_WRITE (I2C_CONTROL, (0x1 << 3));
 	udelay (I2C_DELAY * 10);

 	return (0);
 }

 static uchar
 i2c_set_dev_offset (uchar dev_addr, unsigned int offset, int ten_bit,
 		    int alen)
 {
 	uchar status;
 	unsigned int table[2];

 /* initialize the table of address offset bytes */
 /* utilized for 2 byte address offsets */
 /* NOTE: the order is high byte first! */
 	table[1] = offset & 0xff;	/* low byte */
 	table[0] = offset / 0x100;	/* high byte */

 	DP (puts ("i2c_set_dev_offset\n"));

 	status = i2c_select_device (dev_addr, 0, ten_bit);
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Failed to select device setting offset: 0x%02x\n",
 			status);
 #endif
 		return status;
 	}
 /* check the address offset length */
 	if (alen == 0)
 		/* no address offset */
 		return (0);
 	else if (alen == 1) {
 		/* 1 byte address offset */
 		status = i2c_write_data (&offset, 1);
 		if (status) {
 #ifdef DEBUG_I2C
 			printf ("Failed to write data: 0x%02x\n", status);
 #endif
 			return status;
 		}
 	} else if (alen == 2) {
 		/* 2 bytes address offset */
 		status = i2c_write_data (table, 2);
 		if (status) {
 #ifdef DEBUG_I2C
 			printf ("Failed to write data: 0x%02x\n", status);
 #endif
 			return status;
 		}
 	} else {
 		/* address offset unknown or not supported */
 		printf ("Address length offset %d is not supported\n", alen);
 		return 1;
 	}
 	return 0;		/* sucessful completion */
 }

 uchar
 i2c_read (uchar dev_addr, unsigned int offset, int alen, uchar * data,
 	  int len)
 {
 	uchar status = 0;
 	unsigned int i2cFreq = CONFIG_SYS_I2C_SPEED;

 	DP (puts ("i2c_read\n"));

 	i2c_init (i2cFreq, 0);	/* set the i2c frequency */

 	status = i2c_start ();

 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Transaction start failed: 0x%02x\n", status);
 #endif
 		return status;
 	}

 	status = i2c_set_dev_offset (dev_addr, offset, 0, alen);	/* send the slave address + offset */
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Failed to set slave address & offset: 0x%02x\n",
 			status);
 #endif
 		return status;
 	}

 	i2c_init (i2cFreq, 0);	/* set the i2c frequency again */

 	status = i2c_start ();
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Transaction restart failed: 0x%02x\n", status);
 #endif
 		return status;
 	}

 	status = i2c_select_device (dev_addr, 1, 0);	/* send the slave address */
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Address not acknowledged: 0x%02x\n", status);
 #endif
 		return status;
 	}

 	status = i2c_get_data (data, len);
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Data not recieved: 0x%02x\n", status);
 #endif
 		return status;
 	}

 	return 0;
 }

 /* 11-14-2002 Paul Marchese */
 /* Function to set the I2C stop bit */
 void i2c_stop (void)
 {
 	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));
 }

 /* 11-14-2002 Paul Marchese */
 /* I2C write function */
 /* dev_addr = device address */
 /* offset = address offset */
 /* alen = length in bytes of the address offset */
 /* data = pointer to buffer to read data into */
 /* len = # of bytes to read */
 /* */
 /* returns 0 = succesful */
 /*         anything but zero is failure */
 uchar
 i2c_write (uchar dev_addr, unsigned int offset, int alen, uchar * data,
 	   int len)
 {
 	uchar status = 0;
 	unsigned int i2cFreq = CONFIG_SYS_I2C_SPEED;

 	DP (puts ("i2c_write\n"));

 	i2c_init (i2cFreq, 0);	/* set the i2c frequency */

 	status = i2c_start ();	/* send a start bit */

 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Transaction start failed: 0x%02x\n", status);
 #endif
 		return status;
 	}

 	status = i2c_set_dev_offset (dev_addr, offset, 0, alen);	/* send the slave address + offset */
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Failed to set slave address & offset: 0x%02x\n",
 			status);
 #endif
 		return status;
 	}


 	status = i2c_write_byte (data, len);	/* write the data */
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Data not written: 0x%02x\n", status);
 #endif
 		return status;
 	}
 	/* issue a stop bit */
 	i2c_stop ();
 	return 0;
 }

 /* 11-14-2002 Paul Marchese */
 /* function to determine if an I2C device is present */
 /* chip = device address of chip to check for */
 /* */
 /* returns 0 = sucessful, the device exists */
 /*         anything other than zero is failure, no device */
 int i2c_probe (uchar chip)
 {

 	/* We are just looking for an <ACK> back. */
 	/* To see if the device/chip is there */

 #ifdef DEBUG_I2C
 	unsigned int i2c_status;
 #endif
 	uchar status = 0;
 	unsigned int i2cFreq = CONFIG_SYS_I2C_SPEED;

 	DP (puts ("i2c_probe\n"));

 	i2c_init (i2cFreq, 0);	/* set the i2c frequency */

 	status = i2c_start ();	/* send a start bit */

 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Transaction start failed: 0x%02x\n", status);
 #endif
 		return (int) status;
 	}

 	status = i2c_set_dev_offset (chip, 0, 0, 0);	/* send the slave address + no offset */
 	if (status) {
 #ifdef DEBUG_I2C
 		printf ("Failed to set slave address: 0x%02x\n", status);
 #endif
 		return (int) status;
 	}
 #ifdef DEBUG_I2C
 	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &i2c_status);
 	printf ("address %#x returned %#x\n", chip, i2c_status);
 #endif
 	/* issue a stop bit */
 	i2c_stop ();
 	return 0;		/* successful completion */
 }
	/*
	* (C) Copyright 2000
	* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
	*
	* 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
	*
	* Hacked for the DB64360 board by Ingo.Assmus@keymile.com
	* extra improvments by Brain Waite
	*/
	#include <common.h>
	#include <mpc8xx.h>
	#include <malloc.h>
	#include "../include/mv_gen_reg.h"
	#include "../include/core.h"

	#define MAX_I2C_RETRYS 10
	#define I2C_DELAY 1000 /* Should be at least the # of MHz of Tclk */
	#undef DEBUG_I2C
	/#define DEBUG_I2C/

	#ifdef DEBUG_I2C
	#define DP(x) x
	#else
	#define DP(x)
	#endif

	/* Assuming that there is only one master on the bus (us) */

	static void i2c_init (int speed, int slaveaddr)
	{
	unsigned int n, m, freq, margin, power;
	unsigned int actualN = 0, actualM = 0;
	unsigned int control, status;
	unsigned int minMargin = 0xffffffff;
	unsigned int tclk = CONFIG_SYS_TCLK;
	unsigned int i2cFreq = speed; /* 100000 max. Fast mode not supported */

	DP (puts ("i2c_init\n"));
	/* gtI2cMasterInit */
	for (n = 0; n < 8; n++) {
	for (m = 0; m < 16; m++) {
	power = 2 << n; /* power = 2^(n+1) */
	freq = tclk / (10 * (m + 1) * power);
	if (i2cFreq > freq)
	margin = i2cFreq - freq;
	else
	margin = freq - i2cFreq;
	if (margin < minMargin) {
	minMargin = margin;
	actualN = n;
	actualM = m;
	}
	}
	}

	DP (puts ("setup i2c bus\n"));

	/* Setup bus */
	/* gtI2cReset */
	GT_REG_WRITE (I2C_SOFT_RESET, 0);

	DP (puts ("udelay...\n"));

	udelay (I2C_DELAY);

	DP (puts ("set baudrate\n"));

	GT_REG_WRITE (I2C_STATUS_BAUDE_RATE, (actualM << 3) \| actualN);
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 2) \| (0x1 << 6));

	udelay (I2C_DELAY * 10);

	DP (puts ("read control, baudrate\n"));

	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	GT_REG_READ (I2C_CONTROL, &control);
	}

	static uchar i2c_start (void)
	{ /* DB64360 checked -> ok */
	unsigned int control, status;
	int count = 0;

	DP (puts ("i2c_start\n"));

	/* Set the start bit */

	/* gtI2cGenerateStartBit() */

	GT_REG_READ (I2C_CONTROL, &control);
	control \|= (0x1 << 5); /* generate the I2C_START_BIT */
	GT_REG_WRITE (I2C_CONTROL, control);

	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);

	count = 0;
	while ((status & 0xff) != 0x08) {
	udelay (I2C_DELAY);
	if (count > 20) {
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4)); /stop /
	return (status);
	}
	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	}

	return (0);
	}

	static uchar i2c_select_device (uchar dev_addr, uchar read, int ten_bit)
	{
	unsigned int status, data, bits = 7;
	int count = 0;

	DP (puts ("i2c_select_device\n"));

	/* Output slave address */

	if (ten_bit) {
	bits = 10;
	}

	data = (dev_addr << 1);
	/* set the read bit */
	data \|= read;
	GT_REG_WRITE (I2C_DATA, data);
	/* assert the address */
	RESET_REG_BITS (I2C_CONTROL, BIT3);

	udelay (I2C_DELAY);

	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count = 0;
	while (((status & 0xff) != 0x40) && ((status & 0xff) != 0x18)) {
	udelay (I2C_DELAY);
	if (count > 20) {
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4)); /stop /
	return (status);
	}
	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	}

	if (bits == 10) {
	printf ("10 bit I2C addressing not yet implemented\n");
	return (0xff);
	}

	return (0);
	}

	static uchar i2c_get_data (uchar * return_data, int len)
	{

	unsigned int data, status = 0;
	int count = 0;

	DP (puts ("i2c_get_data\n"));

	while (len) {

	/* Get and return the data */

	RESET_REG_BITS (I2C_CONTROL, (0x1 << 3));

	udelay (I2C_DELAY * 5);

	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	while ((status & 0xff) != 0x50) {
	udelay (I2C_DELAY);
	if (count > 2) {
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4)); /stop /
	return 0;
	}
	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	}
	GT_REG_READ (I2C_DATA, &data);
	len--;
	*return_data = (uchar) data;
	return_data++;
	}
	RESET_REG_BITS (I2C_CONTROL, BIT2 \| BIT3);
	while ((status & 0xff) != 0x58) {
	udelay (I2C_DELAY);
	if (count > 200) {
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4)); /stop /
	return (status);
	}
	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	}
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4)); /* stop */

	return (0);
	}

	static uchar i2c_write_data (unsigned int *data, int len)
	{
	unsigned int status;
	int count = 0;
	unsigned int temp;
	unsigned int *temp_ptr = data;

	DP (puts ("i2c_write_data\n"));

	while (len) {
	temp = (unsigned int) (*temp_ptr);
	GT_REG_WRITE (I2C_DATA, temp);
	RESET_REG_BITS (I2C_CONTROL, (0x1 << 3));

	udelay (I2C_DELAY);

	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	while ((status & 0xff) != 0x28) {
	udelay (I2C_DELAY);
	if (count > 20) {
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4)); /stop /
	return (status);
	}
	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	}
	len--;
	temp_ptr++;
	}
	/* 11-14-2002 Paul Marchese */
	/* Can't have the write issuing a stop command */
	/* it's wrong to have a stop bit in read stream or write stream */
	/* since we don't know if it's really the end of the command */
	/* or whether we have just send the device address + offset */
	/* we will push issuing the stop command off to the original */
	/* calling function */
	/* set the interrupt bit in the control register */
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 3));
	udelay (I2C_DELAY * 10);
	return (0);
	}

	/* 11-14-2002 Paul Marchese */
	/* created this function to get the i2c_write() */
	/* function working properly. */
	/* function to write bytes out on the i2c bus */
	/* this is identical to the function i2c_write_data() */
	/* except that it requires a buffer that is an */
	/* unsigned character array. You can't use */
	/* i2c_write_data() to send an array of unsigned characters */
	/* since the byte of interest ends up on the wrong end of the bus */
	/* aah, the joys of big endian versus little endian! */
	/* */
	/* returns 0 = success */
	/* anything other than zero is failure */
	static uchar i2c_write_byte (unsigned char *data, int len)
	{
	unsigned int status;
	int count = 0;
	unsigned int temp;
	unsigned char *temp_ptr = data;

	DP (puts ("i2c_write_byte\n"));

	while (len) {
	/* Set and assert the data */
	temp = *temp_ptr;
	GT_REG_WRITE (I2C_DATA, temp);
	RESET_REG_BITS (I2C_CONTROL, (0x1 << 3));

	udelay (I2C_DELAY);

	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	while ((status & 0xff) != 0x28) {
	udelay (I2C_DELAY);
	if (count > 20) {
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4)); /stop /
	return (status);
	}
	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &status);
	count++;
	}
	len--;
	temp_ptr++;
	}
	/* Can't have the write issuing a stop command */
	/* it's wrong to have a stop bit in read stream or write stream */
	/* since we don't know if it's really the end of the command */
	/* or whether we have just send the device address + offset */
	/* we will push issuing the stop command off to the original */
	/* calling function */
	/* GT_REG_WRITE(I2C_CONTROL, (0x1 << 3) \| (0x1 << 4));
	GT_REG_WRITE(I2C_CONTROL, (0x1 << 4)); */
	/* set the interrupt bit in the control register */
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 3));
	udelay (I2C_DELAY * 10);

	return (0);
	}

	static uchar
	i2c_set_dev_offset (uchar dev_addr, unsigned int offset, int ten_bit,
	int alen)
	{
	uchar status;
	unsigned int table[2];

	/* initialize the table of address offset bytes */
	/* utilized for 2 byte address offsets */
	/* NOTE: the order is high byte first! */
	table[1] = offset & 0xff; /* low byte */
	table[0] = offset / 0x100; /* high byte */

	DP (puts ("i2c_set_dev_offset\n"));

	status = i2c_select_device (dev_addr, 0, ten_bit);
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Failed to select device setting offset: 0x%02x\n",
	status);
	#endif
	return status;
	}
	/* check the address offset length */
	if (alen == 0)
	/* no address offset */
	return (0);
	else if (alen == 1) {
	/* 1 byte address offset */
	status = i2c_write_data (&offset, 1);
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Failed to write data: 0x%02x\n", status);
	#endif
	return status;
	}
	} else if (alen == 2) {
	/* 2 bytes address offset */
	status = i2c_write_data (table, 2);
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Failed to write data: 0x%02x\n", status);
	#endif
	return status;
	}
	} else {
	/* address offset unknown or not supported */
	printf ("Address length offset %d is not supported\n", alen);
	return 1;
	}
	return 0; /* sucessful completion */
	}

	uchar
	i2c_read (uchar dev_addr, unsigned int offset, int alen, uchar * data,
	int len)
	{
	uchar status = 0;
	unsigned int i2cFreq = CONFIG_SYS_I2C_SPEED;

	DP (puts ("i2c_read\n"));

	i2c_init (i2cFreq, 0); /* set the i2c frequency */

	status = i2c_start ();

	if (status) {
	#ifdef DEBUG_I2C
	printf ("Transaction start failed: 0x%02x\n", status);
	#endif
	return status;
	}

	status = i2c_set_dev_offset (dev_addr, offset, 0, alen); /* send the slave address + offset */
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Failed to set slave address & offset: 0x%02x\n",
	status);
	#endif
	return status;
	}

	i2c_init (i2cFreq, 0); /* set the i2c frequency again */

	status = i2c_start ();
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Transaction restart failed: 0x%02x\n", status);
	#endif
	return status;
	}

	status = i2c_select_device (dev_addr, 1, 0); /* send the slave address */
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Address not acknowledged: 0x%02x\n", status);
	#endif
	return status;
	}

	status = i2c_get_data (data, len);
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Data not recieved: 0x%02x\n", status);
	#endif
	return status;
	}

	return 0;
	}

	/* 11-14-2002 Paul Marchese */
	/* Function to set the I2C stop bit */
	void i2c_stop (void)
	{
	GT_REG_WRITE (I2C_CONTROL, (0x1 << 4));
	}

	/* 11-14-2002 Paul Marchese */
	/* I2C write function */
	/* dev_addr = device address */
	/* offset = address offset */
	/* alen = length in bytes of the address offset */
	/* data = pointer to buffer to read data into */
	/* len = # of bytes to read */
	/* */
	/* returns 0 = succesful */
	/* anything but zero is failure */
	uchar
	i2c_write (uchar dev_addr, unsigned int offset, int alen, uchar * data,
	int len)
	{
	uchar status = 0;
	unsigned int i2cFreq = CONFIG_SYS_I2C_SPEED;

	DP (puts ("i2c_write\n"));

	i2c_init (i2cFreq, 0); /* set the i2c frequency */

	status = i2c_start (); /* send a start bit */

	if (status) {
	#ifdef DEBUG_I2C
	printf ("Transaction start failed: 0x%02x\n", status);
	#endif
	return status;
	}

	status = i2c_set_dev_offset (dev_addr, offset, 0, alen); /* send the slave address + offset */
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Failed to set slave address & offset: 0x%02x\n",
	status);
	#endif
	return status;
	}


	status = i2c_write_byte (data, len); /* write the data */
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Data not written: 0x%02x\n", status);
	#endif
	return status;
	}
	/* issue a stop bit */
	i2c_stop ();
	return 0;
	}

	/* 11-14-2002 Paul Marchese */
	/* function to determine if an I2C device is present */
	/* chip = device address of chip to check for */
	/* */
	/* returns 0 = sucessful, the device exists */
	/* anything other than zero is failure, no device */
	int i2c_probe (uchar chip)
	{

	/* We are just looking for an <ACK> back. */
	/* To see if the device/chip is there */

	#ifdef DEBUG_I2C
	unsigned int i2c_status;
	#endif
	uchar status = 0;
	unsigned int i2cFreq = CONFIG_SYS_I2C_SPEED;

	DP (puts ("i2c_probe\n"));

	i2c_init (i2cFreq, 0); /* set the i2c frequency */

	status = i2c_start (); /* send a start bit */

	if (status) {
	#ifdef DEBUG_I2C
	printf ("Transaction start failed: 0x%02x\n", status);
	#endif
	return (int) status;
	}

	status = i2c_set_dev_offset (chip, 0, 0, 0); /* send the slave address + no offset */
	if (status) {
	#ifdef DEBUG_I2C
	printf ("Failed to set slave address: 0x%02x\n", status);
	#endif
	return (int) status;
	}
	#ifdef DEBUG_I2C
	GT_REG_READ (I2C_STATUS_BAUDE_RATE, &i2c_status);
	printf ("address %#x returned %#x\n", chip, i2c_status);
	#endif
	/* issue a stop bit */
	i2c_stop ();
	return 0; /* successful completion */
	}