drivers/i2c/omap24xx_i2c.c - platform/external/u-boot - Gitiles

 /*
  * Basic I2C functions
  *
  * Copyright (c) 2004 Texas Instruments
  *
  * This package is free software;  you can redistribute it and/or
  * modify it under the terms of the license found in the file
  * named COPYING that should have accompanied this file.
  *
  * THIS PACKAGE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  *
  * Author: Jian Zhang jzhang@ti.com, Texas Instruments
  *
  * Copyright (c) 2003 Wolfgang Denk, wd@denx.de
  * Rewritten to fit into the current U-Boot framework
  *
  * Adapted for OMAP2420 I2C, r-woodruff2@ti.com
  *
  */

 #include <common.h>

 #include <asm/arch/i2c.h>
 #include <asm/io.h>

 #include "omap24xx_i2c.h"

 DECLARE_GLOBAL_DATA_PTR;

 #define I2C_TIMEOUT	1000

 static void wait_for_bb(void);
 static u16 wait_for_pin(void);
 static void flush_fifo(void);

 /*
  * For SPL boot some boards need i2c before SDRAM is initialised so force
  * variables to live in SRAM
  */
 static struct i2c __attribute__((section (".data"))) *i2c_base =
 					(struct i2c *)I2C_DEFAULT_BASE;
 static unsigned int __attribute__((section (".data"))) bus_initialized[I2C_BUS_MAX] =
 					{ [0 ... (I2C_BUS_MAX-1)] = 0 };
 static unsigned int __attribute__((section (".data"))) current_bus = 0;

 void i2c_init(int speed, int slaveadd)
 {
 	int psc, fsscll, fssclh;
 	int hsscll = 0, hssclh = 0;
 	u32 scll, sclh;
 	int timeout = I2C_TIMEOUT;

 	/* Only handle standard, fast and high speeds */
 	if ((speed != OMAP_I2C_STANDARD) &&
 	    (speed != OMAP_I2C_FAST_MODE) &&
 	    (speed != OMAP_I2C_HIGH_SPEED)) {
 		printf("Error : I2C unsupported speed %d\n", speed);
 		return;
 	}

 	psc = I2C_IP_CLK / I2C_INTERNAL_SAMPLING_CLK;
 	psc -= 1;
 	if (psc < I2C_PSC_MIN) {
 		printf("Error : I2C unsupported prescalar %d\n", psc);
 		return;
 	}

 	if (speed == OMAP_I2C_HIGH_SPEED) {
 		/* High speed */

 		/* For first phase of HS mode */
 		fsscll = fssclh = I2C_INTERNAL_SAMPLING_CLK /
 			(2 * OMAP_I2C_FAST_MODE);

 		fsscll -= I2C_HIGHSPEED_PHASE_ONE_SCLL_TRIM;
 		fssclh -= I2C_HIGHSPEED_PHASE_ONE_SCLH_TRIM;
 		if (((fsscll < 0) || (fssclh < 0)) ||
 		    ((fsscll > 255) || (fssclh > 255))) {
 			puts("Error : I2C initializing first phase clock\n");
 			return;
 		}

 		/* For second phase of HS mode */
 		hsscll = hssclh = I2C_INTERNAL_SAMPLING_CLK / (2 * speed);

 		hsscll -= I2C_HIGHSPEED_PHASE_TWO_SCLL_TRIM;
 		hssclh -= I2C_HIGHSPEED_PHASE_TWO_SCLH_TRIM;
 		if (((fsscll < 0) || (fssclh < 0)) ||
 		    ((fsscll > 255) || (fssclh > 255))) {
 			puts("Error : I2C initializing second phase clock\n");
 			return;
 		}

 		scll = (unsigned int)hsscll << 8 | (unsigned int)fsscll;
 		sclh = (unsigned int)hssclh << 8 | (unsigned int)fssclh;

 	} else {
 		/* Standard and fast speed */
 		fsscll = fssclh = I2C_INTERNAL_SAMPLING_CLK / (2 * speed);

 		fsscll -= I2C_FASTSPEED_SCLL_TRIM;
 		fssclh -= I2C_FASTSPEED_SCLH_TRIM;
 		if (((fsscll < 0) || (fssclh < 0)) ||
 		    ((fsscll > 255) || (fssclh > 255))) {
 			puts("Error : I2C initializing clock\n");
 			return;
 		}

 		scll = (unsigned int)fsscll;
 		sclh = (unsigned int)fssclh;
 	}

 	if (readw(&i2c_base->con) & I2C_CON_EN) {
 		writew(0, &i2c_base->con);
 		udelay(50000);
 	}

 	writew(0x2, &i2c_base->sysc); /* for ES2 after soft reset */
 	udelay(1000);

 	writew(I2C_CON_EN, &i2c_base->con);
 	while (!(readw(&i2c_base->syss) & I2C_SYSS_RDONE) && timeout--) {
 		if (timeout <= 0) {
 			puts("ERROR: Timeout in soft-reset\n");
 			return;
 		}
 		udelay(1000);
 	}

 	writew(0, &i2c_base->con);
 	writew(psc, &i2c_base->psc);
 	writew(scll, &i2c_base->scll);
 	writew(sclh, &i2c_base->sclh);

 	/* own address */
 	writew(slaveadd, &i2c_base->oa);
 	writew(I2C_CON_EN, &i2c_base->con);

 	/* have to enable intrrupts or OMAP i2c module doesn't work */
 	writew(I2C_IE_XRDY_IE | I2C_IE_RRDY_IE | I2C_IE_ARDY_IE |
 		I2C_IE_NACK_IE | I2C_IE_AL_IE, &i2c_base->ie);
 	udelay(1000);
 	flush_fifo();
 	writew(0xFFFF, &i2c_base->stat);
 	writew(0, &i2c_base->cnt);

 	if (gd->flags & GD_FLG_RELOC)
 		bus_initialized[current_bus] = 1;
 }

 static int i2c_read_byte(u8 devaddr, u8 regoffset, u8 *value)
 {
 	int i2c_error = 0;
 	u16 status;

 	/* wait until bus not busy */
 	wait_for_bb();

 	/* one byte only */
 	writew(1, &i2c_base->cnt);
 	/* set slave address */
 	writew(devaddr, &i2c_base->sa);
 	/* no stop bit needed here */
 	writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT |
 	      I2C_CON_TRX, &i2c_base->con);

 	/* send register offset */
 	while (1) {
 		status = wait_for_pin();
 		if (status == 0 || status & I2C_STAT_NACK) {
 			i2c_error = 1;
 			goto read_exit;
 		}
 		if (status & I2C_STAT_XRDY) {
 			/* Important: have to use byte access */
 			writeb(regoffset, &i2c_base->data);
 			writew(I2C_STAT_XRDY, &i2c_base->stat);
 		}
 		if (status & I2C_STAT_ARDY) {
 			writew(I2C_STAT_ARDY, &i2c_base->stat);
 			break;
 		}
 	}

 	/* set slave address */
 	writew(devaddr, &i2c_base->sa);
 	/* read one byte from slave */
 	writew(1, &i2c_base->cnt);
 	/* need stop bit here */
 	writew(I2C_CON_EN | I2C_CON_MST |
 		I2C_CON_STT | I2C_CON_STP,
 		&i2c_base->con);

 	/* receive data */
 	while (1) {
 		status = wait_for_pin();
 		if (status == 0 || status & I2C_STAT_NACK) {
 			i2c_error = 1;
 			goto read_exit;
 		}
 		if (status & I2C_STAT_RRDY) {
 #if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
 	defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX)
 			*value = readb(&i2c_base->data);
 #else
 			*value = readw(&i2c_base->data);
 #endif
 			writew(I2C_STAT_RRDY, &i2c_base->stat);
 		}
 		if (status & I2C_STAT_ARDY) {
 			writew(I2C_STAT_ARDY, &i2c_base->stat);
 			break;
 		}
 	}

 read_exit:
 	flush_fifo();
 	writew(0xFFFF, &i2c_base->stat);
 	writew(0, &i2c_base->cnt);
 	return i2c_error;
 }

 static void flush_fifo(void)
 {	u16 stat;

 	/* note: if you try and read data when its not there or ready
 	 * you get a bus error
 	 */
 	while (1) {
 		stat = readw(&i2c_base->stat);
 		if (stat == I2C_STAT_RRDY) {
 #if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
 	defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX)
 			readb(&i2c_base->data);
 #else
 			readw(&i2c_base->data);
 #endif
 			writew(I2C_STAT_RRDY, &i2c_base->stat);
 			udelay(1000);
 		} else
 			break;
 	}
 }

 int i2c_probe(uchar chip)
 {
 	u16 status;
 	int res = 1; /* default = fail */

 	if (chip == readw(&i2c_base->oa))
 		return res;

 	/* wait until bus not busy */
 	wait_for_bb();

 	/* try to read one byte */
 	writew(1, &i2c_base->cnt);
 	/* set slave address */
 	writew(chip, &i2c_base->sa);
 	/* stop bit needed here */
 	writew (I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_STP, &i2c_base->con);

 	while (1) {
 		status = wait_for_pin();
 		if (status == 0 || status & I2C_STAT_AL) {
 			res = 1;
 			goto probe_exit;
 		}
 		if (status & I2C_STAT_NACK) {
 			res = 1;
 			writew(0xff, &i2c_base->stat);
 			writew (readw (&i2c_base->con) | I2C_CON_STP, &i2c_base->con);
 			wait_for_bb ();
 			break;
 		}
 		if (status & I2C_STAT_ARDY) {
 			writew(I2C_STAT_ARDY, &i2c_base->stat);
 			break;
 		}
 		if (status & I2C_STAT_RRDY) {
 			res = 0;
 #if defined(CONFIG_OMAP243X) || defined(CONFIG_OMAP34XX) || \
     defined(CONFIG_OMAP44XX) || defined(CONFIG_AM33XX)
 			readb(&i2c_base->data);
 #else
 			readw(&i2c_base->data);
 #endif
 			writew(I2C_STAT_RRDY, &i2c_base->stat);
 		}
 	}

 probe_exit:
 	flush_fifo();
 	/* don't allow any more data in... we don't want it. */
 	writew(0, &i2c_base->cnt);
 	writew(0xFFFF, &i2c_base->stat);
 	return res;
 }

 int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
 {
 	int i;

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

 	if (addr + len > 256) {
 		puts("I2C read: address out of range\n");
 		return 1;
 	}

 	for (i = 0; i < len; i++) {
 		if (i2c_read_byte(chip, addr + i, &buffer[i])) {
 			puts("I2C read: I/O error\n");
 			i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
 			return 1;
 		}
 	}

 	return 0;
 }

 int i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
 {
 	int i;
 	u16 status;
 	int i2c_error = 0;

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

 	if (addr + len > 256) {
 		printf("I2C write: address 0x%x + 0x%x out of range\n",
 				addr, len);
 		return 1;
 	}

 	/* wait until bus not busy */
 	wait_for_bb();

 	/* start address phase - will write regoffset + len bytes data */
 	/* TODO consider case when !CONFIG_OMAP243X/34XX/44XX */
 	writew(alen + len, &i2c_base->cnt);
 	/* set slave address */
 	writew(chip, &i2c_base->sa);
 	/* stop bit needed here */
 	writew(I2C_CON_EN | I2C_CON_MST | I2C_CON_STT | I2C_CON_TRX |
 		I2C_CON_STP, &i2c_base->con);

 	/* Send address byte */
 	status = wait_for_pin();

 	if (status == 0 || status & I2C_STAT_NACK) {
 		i2c_error = 1;
 		printf("error waiting for i2c address ACK (status=0x%x)\n",
 		      status);
 		goto write_exit;
 	}

 	if (status & I2C_STAT_XRDY) {
 		writeb(addr & 0xFF, &i2c_base->data);
 		writew(I2C_STAT_XRDY, &i2c_base->stat);
 	} else {
 		i2c_error = 1;
 		printf("i2c bus not ready for transmit (status=0x%x)\n",
 		      status);
 		goto write_exit;
 	}

 	/* address phase is over, now write data */
 	for (i = 0; i < len; i++) {
 		status = wait_for_pin();

 		if (status == 0 || status & I2C_STAT_NACK) {
 			i2c_error = 1;
 			printf("i2c error waiting for data ACK (status=0x%x)\n",
 					status);
 			goto write_exit;
 		}

 		if (status & I2C_STAT_XRDY) {
 			writeb(buffer[i], &i2c_base->data);
 			writew(I2C_STAT_XRDY, &i2c_base->stat);
 		} else {
 			i2c_error = 1;
 			printf("i2c bus not ready for Tx (i=%d)\n", i);
 			goto write_exit;
 		}
 	}

 write_exit:
 	flush_fifo();
 	writew(0xFFFF, &i2c_base->stat);
 	return i2c_error;
 }

 static void wait_for_bb(void)
 {
 	int timeout = I2C_TIMEOUT;
 	u16 stat;

 	writew(0xFFFF, &i2c_base->stat);	/* clear current interrupts...*/
 	while ((stat = readw(&i2c_base->stat) & I2C_STAT_BB) && timeout--) {
 		writew(stat, &i2c_base->stat);
 		udelay(1000);
 	}

 	if (timeout <= 0) {
 		printf("timed out in wait_for_bb: I2C_STAT=%x\n",
 			readw(&i2c_base->stat));
 	}
 	writew(0xFFFF, &i2c_base->stat);	 /* clear delayed stuff*/
 }

 static u16 wait_for_pin(void)
 {
 	u16 status;
 	int timeout = I2C_TIMEOUT;

 	do {
 		udelay(1000);
 		status = readw(&i2c_base->stat);
 	} while (!(status &
 		   (I2C_STAT_ROVR | I2C_STAT_XUDF | I2C_STAT_XRDY |
 		    I2C_STAT_RRDY | I2C_STAT_ARDY | I2C_STAT_NACK |
 		    I2C_STAT_AL)) && timeout--);

 	if (timeout <= 0) {
 		printf("timed out in wait_for_pin: I2C_STAT=%x\n",
 			readw(&i2c_base->stat));
 		writew(0xFFFF, &i2c_base->stat);
 		status = 0;
 	}

 	return status;
 }

 int i2c_set_bus_num(unsigned int bus)
 {
 	if ((bus < 0) || (bus >= I2C_BUS_MAX)) {
 		printf("Bad bus: %d\n", bus);
 		return -1;
 	}

 #if I2C_BUS_MAX == 3
 	if (bus == 2)
 		i2c_base = (struct i2c *)I2C_BASE3;
 	else
 #endif
 	if (bus == 1)
 		i2c_base = (struct i2c *)I2C_BASE2;
 	else
 		i2c_base = (struct i2c *)I2C_BASE1;

 	current_bus = bus;

 	if (!bus_initialized[current_bus])
 		i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);

 	return 0;
 }

 int i2c_get_bus_num(void)
 {
 	return (int) current_bus;
 }
	/*
	* Basic I2C functions
	*
	* Copyright (c) 2004 Texas Instruments
	*
	* This package is free software; you can redistribute it and/or
	* modify it under the terms of the license found in the file
	* named COPYING that should have accompanied this file.
	*
	* THIS PACKAGE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
	* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
	*
	* Author: Jian Zhang jzhang@ti.com, Texas Instruments
	*
	* Copyright (c) 2003 Wolfgang Denk, wd@denx.de
	* Rewritten to fit into the current U-Boot framework
	*
	* Adapted for OMAP2420 I2C, r-woodruff2@ti.com
	*
	*/

	#include <common.h>

	#include <asm/arch/i2c.h>
	#include <asm/io.h>

	#include "omap24xx_i2c.h"

	DECLARE_GLOBAL_DATA_PTR;

	#define I2C_TIMEOUT 1000

	static void wait_for_bb(void);
	static u16 wait_for_pin(void);
	static void flush_fifo(void);

	/*
	* For SPL boot some boards need i2c before SDRAM is initialised so force
	* variables to live in SRAM
	*/
	static struct i2c __attribute__((section (".data"))) *i2c_base =
	(struct i2c *)I2C_DEFAULT_BASE;
	static unsigned int __attribute__((section (".data"))) bus_initialized[I2C_BUS_MAX] =
	{ [0 ... (I2C_BUS_MAX-1)] = 0 };
	static unsigned int __attribute__((section (".data"))) current_bus = 0;

	void i2c_init(int speed, int slaveadd)
	{
	int psc, fsscll, fssclh;
	int hsscll = 0, hssclh = 0;
	u32 scll, sclh;
	int timeout = I2C_TIMEOUT;

	/* Only handle standard, fast and high speeds */
	if ((speed != OMAP_I2C_STANDARD) &&
	(speed != OMAP_I2C_FAST_MODE) &&
	(speed != OMAP_I2C_HIGH_SPEED)) {
	printf("Error : I2C unsupported speed %d\n", speed);
	return;
	}

	psc = I2C_IP_CLK / I2C_INTERNAL_SAMPLING_CLK;
	psc -= 1;
	if (psc < I2C_PSC_MIN) {
	printf("Error : I2C unsupported prescalar %d\n", psc);
	return;
	}

	if (speed == OMAP_I2C_HIGH_SPEED) {
	/* High speed */

	/* For first phase of HS mode */
	fsscll = fssclh = I2C_INTERNAL_SAMPLING_CLK /
	(2 * OMAP_I2C_FAST_MODE);

	fsscll -= I2C_HIGHSPEED_PHASE_ONE_SCLL_TRIM;
	fssclh -= I2C_HIGHSPEED_PHASE_ONE_SCLH_TRIM;
	if (((fsscll < 0) \|\| (fssclh < 0)) \|\|
	((fsscll > 255) \|\| (fssclh > 255))) {
	puts("Error : I2C initializing first phase clock\n");
	return;
	}

	/* For second phase of HS mode */
	hsscll = hssclh = I2C_INTERNAL_SAMPLING_CLK / (2 * speed);

	hsscll -= I2C_HIGHSPEED_PHASE_TWO_SCLL_TRIM;
	hssclh -= I2C_HIGHSPEED_PHASE_TWO_SCLH_TRIM;
	if (((fsscll < 0) \|\| (fssclh < 0)) \|\|
	((fsscll > 255) \|\| (fssclh > 255))) {
	puts("Error : I2C initializing second phase clock\n");
	return;
	}

	scll = (unsigned int)hsscll << 8 \| (unsigned int)fsscll;
	sclh = (unsigned int)hssclh << 8 \| (unsigned int)fssclh;

	} else {
	/* Standard and fast speed */
	fsscll = fssclh = I2C_INTERNAL_SAMPLING_CLK / (2 * speed);

	fsscll -= I2C_FASTSPEED_SCLL_TRIM;
	fssclh -= I2C_FASTSPEED_SCLH_TRIM;
	if (((fsscll < 0) \|\| (fssclh < 0)) \|\|
	((fsscll > 255) \|\| (fssclh > 255))) {
	puts("Error : I2C initializing clock\n");
	return;
	}

	scll = (unsigned int)fsscll;
	sclh = (unsigned int)fssclh;
	}

	if (readw(&i2c_base->con) & I2C_CON_EN) {
	writew(0, &i2c_base->con);
	udelay(50000);
	}

	writew(0x2, &i2c_base->sysc); /* for ES2 after soft reset */
	udelay(1000);

	writew(I2C_CON_EN, &i2c_base->con);
	while (!(readw(&i2c_base->syss) & I2C_SYSS_RDONE) && timeout--) {
	if (timeout <= 0) {
	puts("ERROR: Timeout in soft-reset\n");
	return;
	}
	udelay(1000);
	}

	writew(0, &i2c_base->con);
	writew(psc, &i2c_base->psc);
	writew(scll, &i2c_base->scll);
	writew(sclh, &i2c_base->sclh);

	/* own address */
	writew(slaveadd, &i2c_base->oa);
	writew(I2C_CON_EN, &i2c_base->con);

	/* have to enable intrrupts or OMAP i2c module doesn't work */
	writew(I2C_IE_XRDY_IE \| I2C_IE_RRDY_IE \| I2C_IE_ARDY_IE \|
	I2C_IE_NACK_IE \| I2C_IE_AL_IE, &i2c_base->ie);
	udelay(1000);
	flush_fifo();
	writew(0xFFFF, &i2c_base->stat);
	writew(0, &i2c_base->cnt);

	if (gd->flags & GD_FLG_RELOC)
	bus_initialized[current_bus] = 1;
	}

	static int i2c_read_byte(u8 devaddr, u8 regoffset, u8 *value)
	{
	int i2c_error = 0;
	u16 status;

	/* wait until bus not busy */
	wait_for_bb();

	/* one byte only */
	writew(1, &i2c_base->cnt);
	/* set slave address */
	writew(devaddr, &i2c_base->sa);
	/* no stop bit needed here */
	writew(I2C_CON_EN \| I2C_CON_MST \| I2C_CON_STT \|
	I2C_CON_TRX, &i2c_base->con);

	/* send register offset */
	while (1) {
	status = wait_for_pin();
	if (status == 0 \|\| status & I2C_STAT_NACK) {
	i2c_error = 1;
	goto read_exit;
	}
	if (status & I2C_STAT_XRDY) {
	/* Important: have to use byte access */
	writeb(regoffset, &i2c_base->data);
	writew(I2C_STAT_XRDY, &i2c_base->stat);
	}
	if (status & I2C_STAT_ARDY) {
	writew(I2C_STAT_ARDY, &i2c_base->stat);
	break;
	}
	}

	/* set slave address */
	writew(devaddr, &i2c_base->sa);
	/* read one byte from slave */
	writew(1, &i2c_base->cnt);
	/* need stop bit here */
	writew(I2C_CON_EN \| I2C_CON_MST \|
	I2C_CON_STT \| I2C_CON_STP,
	&i2c_base->con);

	/* receive data */
	while (1) {
	status = wait_for_pin();
	if (status == 0 \|\| status & I2C_STAT_NACK) {
	i2c_error = 1;
	goto read_exit;
	}
	if (status & I2C_STAT_RRDY) {
	#if defined(CONFIG_OMAP243X) \|\| defined(CONFIG_OMAP34XX) \|\| \
	defined(CONFIG_OMAP44XX) \|\| defined(CONFIG_AM33XX)
	*value = readb(&i2c_base->data);
	#else
	*value = readw(&i2c_base->data);
	#endif
	writew(I2C_STAT_RRDY, &i2c_base->stat);
	}
	if (status & I2C_STAT_ARDY) {
	writew(I2C_STAT_ARDY, &i2c_base->stat);
	break;
	}
	}

	read_exit:
	flush_fifo();
	writew(0xFFFF, &i2c_base->stat);
	writew(0, &i2c_base->cnt);
	return i2c_error;
	}

	static void flush_fifo(void)
	{ u16 stat;

	/* note: if you try and read data when its not there or ready
	* you get a bus error
	*/
	while (1) {
	stat = readw(&i2c_base->stat);
	if (stat == I2C_STAT_RRDY) {
	#if defined(CONFIG_OMAP243X) \|\| defined(CONFIG_OMAP34XX) \|\| \
	defined(CONFIG_OMAP44XX) \|\| defined(CONFIG_AM33XX)
	readb(&i2c_base->data);
	#else
	readw(&i2c_base->data);
	#endif
	writew(I2C_STAT_RRDY, &i2c_base->stat);
	udelay(1000);
	} else
	break;
	}
	}

	int i2c_probe(uchar chip)
	{
	u16 status;
	int res = 1; /* default = fail */

	if (chip == readw(&i2c_base->oa))
	return res;

	/* wait until bus not busy */
	wait_for_bb();

	/* try to read one byte */
	writew(1, &i2c_base->cnt);
	/* set slave address */
	writew(chip, &i2c_base->sa);
	/* stop bit needed here */
	writew (I2C_CON_EN \| I2C_CON_MST \| I2C_CON_STT \| I2C_CON_STP, &i2c_base->con);

	while (1) {
	status = wait_for_pin();
	if (status == 0 \|\| status & I2C_STAT_AL) {
	res = 1;
	goto probe_exit;
	}
	if (status & I2C_STAT_NACK) {
	res = 1;
	writew(0xff, &i2c_base->stat);
	writew (readw (&i2c_base->con) \| I2C_CON_STP, &i2c_base->con);
	wait_for_bb ();
	break;
	}
	if (status & I2C_STAT_ARDY) {
	writew(I2C_STAT_ARDY, &i2c_base->stat);
	break;
	}
	if (status & I2C_STAT_RRDY) {
	res = 0;
	#if defined(CONFIG_OMAP243X) \|\| defined(CONFIG_OMAP34XX) \|\| \
	defined(CONFIG_OMAP44XX) \|\| defined(CONFIG_AM33XX)
	readb(&i2c_base->data);
	#else
	readw(&i2c_base->data);
	#endif
	writew(I2C_STAT_RRDY, &i2c_base->stat);
	}
	}

	probe_exit:
	flush_fifo();
	/* don't allow any more data in... we don't want it. */
	writew(0, &i2c_base->cnt);
	writew(0xFFFF, &i2c_base->stat);
	return res;
	}

	int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len)
	{
	int i;

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

	if (addr + len > 256) {
	puts("I2C read: address out of range\n");
	return 1;
	}

	for (i = 0; i < len; i++) {
	if (i2c_read_byte(chip, addr + i, &buffer[i])) {
	puts("I2C read: I/O error\n");
	i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);
	return 1;
	}
	}

	return 0;
	}

	int i2c_write(uchar chip, uint addr, int alen, uchar *buffer, int len)
	{
	int i;
	u16 status;
	int i2c_error = 0;

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

	if (addr + len > 256) {
	printf("I2C write: address 0x%x + 0x%x out of range\n",
	addr, len);
	return 1;
	}

	/* wait until bus not busy */
	wait_for_bb();

	/* start address phase - will write regoffset + len bytes data */
	/* TODO consider case when !CONFIG_OMAP243X/34XX/44XX */
	writew(alen + len, &i2c_base->cnt);
	/* set slave address */
	writew(chip, &i2c_base->sa);
	/* stop bit needed here */
	writew(I2C_CON_EN \| I2C_CON_MST \| I2C_CON_STT \| I2C_CON_TRX \|
	I2C_CON_STP, &i2c_base->con);

	/* Send address byte */
	status = wait_for_pin();

	if (status == 0 \|\| status & I2C_STAT_NACK) {
	i2c_error = 1;
	printf("error waiting for i2c address ACK (status=0x%x)\n",
	status);
	goto write_exit;
	}

	if (status & I2C_STAT_XRDY) {
	writeb(addr & 0xFF, &i2c_base->data);
	writew(I2C_STAT_XRDY, &i2c_base->stat);
	} else {
	i2c_error = 1;
	printf("i2c bus not ready for transmit (status=0x%x)\n",
	status);
	goto write_exit;
	}

	/* address phase is over, now write data */
	for (i = 0; i < len; i++) {
	status = wait_for_pin();

	if (status == 0 \|\| status & I2C_STAT_NACK) {
	i2c_error = 1;
	printf("i2c error waiting for data ACK (status=0x%x)\n",
	status);
	goto write_exit;
	}

	if (status & I2C_STAT_XRDY) {
	writeb(buffer[i], &i2c_base->data);
	writew(I2C_STAT_XRDY, &i2c_base->stat);
	} else {
	i2c_error = 1;
	printf("i2c bus not ready for Tx (i=%d)\n", i);
	goto write_exit;
	}
	}

	write_exit:
	flush_fifo();
	writew(0xFFFF, &i2c_base->stat);
	return i2c_error;
	}

	static void wait_for_bb(void)
	{
	int timeout = I2C_TIMEOUT;
	u16 stat;

	writew(0xFFFF, &i2c_base->stat); /* clear current interrupts...*/
	while ((stat = readw(&i2c_base->stat) & I2C_STAT_BB) && timeout--) {
	writew(stat, &i2c_base->stat);
	udelay(1000);
	}

	if (timeout <= 0) {
	printf("timed out in wait_for_bb: I2C_STAT=%x\n",
	readw(&i2c_base->stat));
	}
	writew(0xFFFF, &i2c_base->stat); /* clear delayed stuff*/
	}

	static u16 wait_for_pin(void)
	{
	u16 status;
	int timeout = I2C_TIMEOUT;

	do {
	udelay(1000);
	status = readw(&i2c_base->stat);
	} while (!(status &
	(I2C_STAT_ROVR \| I2C_STAT_XUDF \| I2C_STAT_XRDY \|
	I2C_STAT_RRDY \| I2C_STAT_ARDY \| I2C_STAT_NACK \|
	I2C_STAT_AL)) && timeout--);

	if (timeout <= 0) {
	printf("timed out in wait_for_pin: I2C_STAT=%x\n",
	readw(&i2c_base->stat));
	writew(0xFFFF, &i2c_base->stat);
	status = 0;
	}

	return status;
	}

	int i2c_set_bus_num(unsigned int bus)
	{
	if ((bus < 0) \|\| (bus >= I2C_BUS_MAX)) {
	printf("Bad bus: %d\n", bus);
	return -1;
	}

	#if I2C_BUS_MAX == 3
	if (bus == 2)
	i2c_base = (struct i2c *)I2C_BASE3;
	else
	#endif
	if (bus == 1)
	i2c_base = (struct i2c *)I2C_BASE2;
	else
	i2c_base = (struct i2c *)I2C_BASE1;

	current_bus = bus;

	if (!bus_initialized[current_bus])
	i2c_init(CONFIG_SYS_I2C_SPEED, CONFIG_SYS_I2C_SLAVE);

	return 0;
	}

	int i2c_get_bus_num(void)
	{
	return (int) current_bus;
	}