drivers/i2c/ppc4xx_i2c.c - u-boot - Git at Google

 /*
  * (C) Copyright 2007-2009
  * Stefan Roese, DENX Software Engineering, sr@denx.de.
  *
  * based on work by Anne Sophie Harnois <anne-sophie.harnois@nextream.fr>
  *
  * (C) Copyright 2001
  * Bill Hunter,  Wave 7 Optics, williamhunter@mediaone.net
  *
  * SPDX-License-Identifier:	GPL-2.0+
  */

 #include <common.h>
 #include <asm/ppc4xx.h>
 #include <asm/ppc4xx-i2c.h>
 #include <i2c.h>
 #include <asm/io.h>

 DECLARE_GLOBAL_DATA_PTR;

 static inline struct ppc4xx_i2c *ppc4xx_get_i2c(int hwadapnr)
 {
 	unsigned long base;

 #if defined(CONFIG_440EP) || defined(CONFIG_440GR) || \
 	defined(CONFIG_440EPX) || defined(CONFIG_440GRX) || \
 	defined(CONFIG_460EX) || defined(CONFIG_460GT)
 	base = CONFIG_SYS_PERIPHERAL_BASE + 0x00000700 + (hwadapnr * 0x100);
 #elif defined(CONFIG_440) || defined(CONFIG_405EX)
 /* all remaining 440 variants */
 	base = CONFIG_SYS_PERIPHERAL_BASE + 0x00000400 + (hwadapnr * 0x100);
 #else
 /* all 405 variants */
 	base = 0xEF600500 + (hwadapnr * 0x100);
 #endif
 	return (struct ppc4xx_i2c *)base;
 }

 static void _i2c_bus_reset(struct i2c_adapter *adap)
 {
 	struct ppc4xx_i2c *i2c = ppc4xx_get_i2c(adap->hwadapnr);
 	int i;
 	u8 dc;

 	/* Reset status register */
 	/* write 1 in SCMP and IRQA to clear these fields */
 	out_8(&i2c->sts, 0x0A);

 	/* write 1 in IRQP IRQD LA ICT XFRA to clear these fields */
 	out_8(&i2c->extsts, 0x8F);

 	/* Place chip in the reset state */
 	out_8(&i2c->xtcntlss, IIC_XTCNTLSS_SRST);

 	/* Check if bus is free */
 	dc = in_8(&i2c->directcntl);
 	if (!DIRCTNL_FREE(dc)){
 		/* Try to set bus free state */
 		out_8(&i2c->directcntl, IIC_DIRCNTL_SDAC | IIC_DIRCNTL_SCC);

 		/* Wait until we regain bus control */
 		for (i = 0; i < 100; ++i) {
 			dc = in_8(&i2c->directcntl);
 			if (DIRCTNL_FREE(dc))
 				break;

 			/* Toggle SCL line */
 			dc ^= IIC_DIRCNTL_SCC;
 			out_8(&i2c->directcntl, dc);
 			udelay(10);
 			dc ^= IIC_DIRCNTL_SCC;
 			out_8(&i2c->directcntl, dc);
 		}
 	}

 	/* Remove reset */
 	out_8(&i2c->xtcntlss, 0);
 }

 static void ppc4xx_i2c_init(struct i2c_adapter *adap, int speed, int slaveaddr)
 {
 	struct ppc4xx_i2c *i2c = ppc4xx_get_i2c(adap->hwadapnr);
 	int val, divisor;

 #ifdef CONFIG_SYS_I2C_INIT_BOARD
 	/*
 	 * Call board specific i2c bus reset routine before accessing the
 	 * environment, which might be in a chip on that bus. For details
 	 * about this problem see doc/I2C_Edge_Conditions.
 	 */
 	i2c_init_board();
 #endif

 	/* Handle possible failed I2C state */
 	/* FIXME: put this into i2c_init_board()? */
 	_i2c_bus_reset(adap);

 	/* clear lo master address */
 	out_8(&i2c->lmadr, 0);

 	/* clear hi master address */
 	out_8(&i2c->hmadr, 0);

 	/* clear lo slave address */
 	out_8(&i2c->lsadr, 0);

 	/* clear hi slave address */
 	out_8(&i2c->hsadr, 0);

 	/* Clock divide Register */
 	/* set divisor according to freq_opb */
 	divisor = (get_OPB_freq() - 1) / 10000000;
 	if (divisor == 0)
 		divisor = 1;
 	out_8(&i2c->clkdiv, divisor);

 	/* no interrupts */
 	out_8(&i2c->intrmsk, 0);

 	/* clear transfer count */
 	out_8(&i2c->xfrcnt, 0);

 	/* clear extended control & stat */
 	/* write 1 in SRC SRS SWC SWS to clear these fields */
 	out_8(&i2c->xtcntlss, 0xF0);

 	/* Mode Control Register
 	   Flush Slave/Master data buffer */
 	out_8(&i2c->mdcntl, IIC_MDCNTL_FSDB | IIC_MDCNTL_FMDB);

 	val = in_8(&i2c->mdcntl);

 	/* Ignore General Call, slave transfers are ignored,
 	 * disable interrupts, exit unknown bus state, enable hold
 	 * SCL 100kHz normaly or FastMode for 400kHz and above
 	 */

 	val |= IIC_MDCNTL_EUBS | IIC_MDCNTL_HSCL;
 	if (speed >= 400000)
 		val |= IIC_MDCNTL_FSM;
 	out_8(&i2c->mdcntl, val);

 	/* clear control reg */
 	out_8(&i2c->cntl, 0x00);
 }

 /*
  * This code tries to use the features of the 405GP i2c
  * controller. It will transfer up to 4 bytes in one pass
  * on the loop. It only does out_8((u8 *)lbz) to the buffer when it
  * is possible to do out16(lhz) transfers.
  *
  * 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.
  *
  * Typical case is a Write of an addr followd by a Read. The
  * IBM FAQ does not cover this. On the last byte of the write
  * we don't set the creg CHT bit but the RPST bit.
  *
  * It does not support address only transfers, there must be
  * a data part. If you want to write the address yourself, put
  * it in the data pointer.
  *
  * It does not support transfer to/from address 0.
  *
  * It does not check XFRCNT.
  */
 static int _i2c_transfer(struct i2c_adapter *adap,
 			unsigned char cmd_type,
 			unsigned char chip,
 			unsigned char addr[],
 			unsigned char addr_len,
 			unsigned char data[],
 			unsigned short data_len)
 {
 	struct ppc4xx_i2c *i2c = ppc4xx_get_i2c(adap->hwadapnr);
 	u8 *ptr;
 	int reading;
 	int tran, cnt;
 	int result;
 	int status;
 	int i;
 	u8 creg;

 	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 IIC_NOK;
 	}
 	if (addr && addr_len) {
 		ptr = addr;
 		cnt = addr_len;
 		reading = 0;
 	} else {
 		ptr = data;
 		cnt = data_len;
 		reading = cmd_type;
 	}

 	/* Clear Stop Complete Bit */
 	out_8(&i2c->sts, IIC_STS_SCMP);

 	/* Check init */
 	i = 10;
 	do {
 		/* Get status */
 		status = in_8(&i2c->sts);
 		i--;
 	} while ((status & IIC_STS_PT) && (i > 0));

 	if (status & IIC_STS_PT) {
 		result = IIC_NOK_TOUT;
 		return(result);
 	}

 	/* flush the Master/Slave Databuffers */
 	out_8(&i2c->mdcntl, in_8(&i2c->mdcntl) |
 	      IIC_MDCNTL_FMDB | IIC_MDCNTL_FSDB);

 	/* need to wait 4 OPB clocks? code below should take that long */

 	/* 7-bit adressing */
 	out_8(&i2c->hmadr, 0);
 	out_8(&i2c->lmadr, chip);

 	tran = 0;
 	result = IIC_OK;
 	creg = 0;

 	while (tran != cnt && (result == IIC_OK)) {
 		int  bc,j;

 		/*
 		 * Control register =
 		 * Normal transfer, 7-bits adressing, Transfer up to
 		 * bc bytes, Normal start, Transfer is a sequence of transfers
 		 */
 		creg |= IIC_CNTL_PT;

 		bc = (cnt - tran) > 4 ? 4 : cnt - tran;
 		creg |= (bc - 1) << 4;
 		/* if the real cmd type is write continue trans */
 		if ((!cmd_type && (ptr == addr)) || ((tran + bc) != cnt))
 			creg |= IIC_CNTL_CHT;

 		/* last part of address, prepare for repeated start on read */
 		if (cmd_type && (ptr == addr) && ((tran + bc) == cnt))
 			creg |= IIC_CNTL_RPST;

 		if (reading) {
 			creg |= IIC_CNTL_READ;
 		} else {
 			for(j = 0; j < bc; j++) {
 				/* Set buffer */
 				out_8(&i2c->mdbuf, ptr[tran + j]);
 			}
 		}
 		out_8(&i2c->cntl, creg);

 		/*
 		 * Transfer is in progress
 		 * we have to wait for upto 5 bytes of data
 		 * 1 byte chip address+r/w bit then bc bytes
 		 * of data.
 		 * udelay(10) is 1 bit time at 100khz
 		 * Doubled for slop. 20 is too small.
 		 */
 		i = 2 * 5 * 8;
 		do {
 			/* Get status */
 			status = in_8(&i2c->sts);
 			udelay(10);
 			i--;
 		} while ((status & IIC_STS_PT) && !(status & IIC_STS_ERR) &&
 			 (i > 0));

 		if (status & IIC_STS_ERR) {
 			result = IIC_NOK;
 			status = in_8(&i2c->extsts);
 			/* Lost arbitration? */
 			if (status & IIC_EXTSTS_LA)
 				result = IIC_NOK_LA;
 			/* Incomplete transfer? */
 			if (status & IIC_EXTSTS_ICT)
 				result = IIC_NOK_ICT;
 			/* Transfer aborted? */
 			if (status & IIC_EXTSTS_XFRA)
 				result = IIC_NOK_XFRA;
 			/* Is bus free?
 			 * If error happened during combined xfer
 			 * IIC interface is usually stuck in some strange
 			 * state without a valid stop condition.
 			 * Brute, but working: generate stop, then soft reset.
 			 */
 			if ((status & IIC_EXTSTS_BCS_MASK)
 			    != IIC_EXTSTS_BCS_FREE){
 				u8 mdcntl = in_8(&i2c->mdcntl);

 				/* Generate valid stop condition */
 				out_8(&i2c->xtcntlss, IIC_XTCNTLSS_SRST);
 				out_8(&i2c->directcntl, IIC_DIRCNTL_SCC);
 				udelay(10);
 				out_8(&i2c->directcntl,
 				      IIC_DIRCNTL_SCC | IIC_DIRCNTL_SDAC);
 				out_8(&i2c->xtcntlss, 0);

 				ppc4xx_i2c_init(adap, (mdcntl & IIC_MDCNTL_FSM)
 						? 400000 : 100000, 0);
 			}
 		} else if ( status & IIC_STS_PT) {
 			result = IIC_NOK_TOUT;
 		}

 		/* Command is reading => get buffer */
 		if ((reading) && (result == IIC_OK)) {
 			/* Are there data in buffer */
 			if (status & IIC_STS_MDBS) {
 				/*
 				 * even if we have data we have to wait 4OPB
 				 * clocks for it to hit the front of the FIFO,
 				 * after that we can just read. We should check
 				 * XFCNT here and if the FIFO is full there is
 				 * no need to wait.
 				 */
 				udelay(1);
 				for (j = 0; j < bc; j++)
 					ptr[tran + j] = in_8(&i2c->mdbuf);
 			} else
 				result = IIC_NOK_DATA;
 		}
 		creg = 0;
 		tran += bc;
 		if (ptr == addr && tran == cnt) {
 			ptr = data;
 			cnt = data_len;
 			tran = 0;
 			reading = cmd_type;
 		}
 	}
 	return result;
 }

 static int ppc4xx_i2c_probe(struct i2c_adapter *adap, 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(adap, 1, chip << 1, 0, 0, buf, 1) != 0);
 }

 static int ppc4xx_i2c_transfer(struct i2c_adapter *adap, uchar chip, uint addr,
 			       int alen, uchar *buffer, int len, int read)
 {
 	uchar xaddr[4];
 	int ret;

 	if (alen > 4) {
 		printf("I2C: 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
 	ret = _i2c_transfer(adap, read, chip << 1, &xaddr[4 - alen], alen,
 			    buffer, len);
 	if (ret) {
 		printf("I2C %s: failed %d\n", read ? "read" : "write", ret);
 		return 1;
 	}

 	return 0;
 }

 static int ppc4xx_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
 			   int alen, uchar *buffer, int len)
 {
 	return ppc4xx_i2c_transfer(adap, chip, addr, alen, buffer, len, 1);
 }

 static int ppc4xx_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
 			    int alen, uchar *buffer, int len)
 {
 	return ppc4xx_i2c_transfer(adap, chip, addr, alen, buffer, len, 0);
 }

 static unsigned int ppc4xx_i2c_set_bus_speed(struct i2c_adapter *adap,
 					     unsigned int speed)
 {
 	if (speed != adap->speed)
 		return -1;
 	return speed;
 }

 /*
  * Register ppc4xx i2c adapters
  */
 #ifdef CONFIG_SYS_I2C_PPC4XX_CH0
 U_BOOT_I2C_ADAP_COMPLETE(ppc4xx_0, ppc4xx_i2c_init, ppc4xx_i2c_probe,
 			 ppc4xx_i2c_read, ppc4xx_i2c_write,
 			 ppc4xx_i2c_set_bus_speed,
 			 CONFIG_SYS_I2C_PPC4XX_SPEED_0,
 			 CONFIG_SYS_I2C_PPC4XX_SLAVE_0, 0)
 #endif
 #ifdef CONFIG_SYS_I2C_PPC4XX_CH1
 U_BOOT_I2C_ADAP_COMPLETE(ppc4xx_1, ppc4xx_i2c_init, ppc4xx_i2c_probe,
 			 ppc4xx_i2c_read, ppc4xx_i2c_write,
 			 ppc4xx_i2c_set_bus_speed,
 			 CONFIG_SYS_I2C_PPC4XX_SPEED_1,
 			 CONFIG_SYS_I2C_PPC4XX_SLAVE_1, 1)
 #endif
	/*
	* (C) Copyright 2007-2009
	* Stefan Roese, DENX Software Engineering, sr@denx.de.
	*
	* based on work by Anne Sophie Harnois <anne-sophie.harnois@nextream.fr>
	*
	* (C) Copyright 2001
	* Bill Hunter, Wave 7 Optics, williamhunter@mediaone.net
	*
	* SPDX-License-Identifier: GPL-2.0+
	*/

	#include <common.h>
	#include <asm/ppc4xx.h>
	#include <asm/ppc4xx-i2c.h>
	#include <i2c.h>
	#include <asm/io.h>

	DECLARE_GLOBAL_DATA_PTR;

	static inline struct ppc4xx_i2c *ppc4xx_get_i2c(int hwadapnr)
	{
	unsigned long base;

	#if defined(CONFIG_440EP) \|\| defined(CONFIG_440GR) \|\| \
	defined(CONFIG_440EPX) \|\| defined(CONFIG_440GRX) \|\| \
	defined(CONFIG_460EX) \|\| defined(CONFIG_460GT)
	base = CONFIG_SYS_PERIPHERAL_BASE + 0x00000700 + (hwadapnr * 0x100);
	#elif defined(CONFIG_440) \|\| defined(CONFIG_405EX)
	/* all remaining 440 variants */
	base = CONFIG_SYS_PERIPHERAL_BASE + 0x00000400 + (hwadapnr * 0x100);
	#else
	/* all 405 variants */
	base = 0xEF600500 + (hwadapnr * 0x100);
	#endif
	return (struct ppc4xx_i2c *)base;
	}

	static void _i2c_bus_reset(struct i2c_adapter *adap)
	{
	struct ppc4xx_i2c *i2c = ppc4xx_get_i2c(adap->hwadapnr);
	int i;
	u8 dc;

	/* Reset status register */
	/* write 1 in SCMP and IRQA to clear these fields */
	out_8(&i2c->sts, 0x0A);

	/* write 1 in IRQP IRQD LA ICT XFRA to clear these fields */
	out_8(&i2c->extsts, 0x8F);

	/* Place chip in the reset state */
	out_8(&i2c->xtcntlss, IIC_XTCNTLSS_SRST);

	/* Check if bus is free */
	dc = in_8(&i2c->directcntl);
	if (!DIRCTNL_FREE(dc)){
	/* Try to set bus free state */
	out_8(&i2c->directcntl, IIC_DIRCNTL_SDAC \| IIC_DIRCNTL_SCC);

	/* Wait until we regain bus control */
	for (i = 0; i < 100; ++i) {
	dc = in_8(&i2c->directcntl);
	if (DIRCTNL_FREE(dc))
	break;

	/* Toggle SCL line */
	dc ^= IIC_DIRCNTL_SCC;
	out_8(&i2c->directcntl, dc);
	udelay(10);
	dc ^= IIC_DIRCNTL_SCC;
	out_8(&i2c->directcntl, dc);
	}
	}

	/* Remove reset */
	out_8(&i2c->xtcntlss, 0);
	}

	static void ppc4xx_i2c_init(struct i2c_adapter *adap, int speed, int slaveaddr)
	{
	struct ppc4xx_i2c *i2c = ppc4xx_get_i2c(adap->hwadapnr);
	int val, divisor;

	#ifdef CONFIG_SYS_I2C_INIT_BOARD
	/*
	* Call board specific i2c bus reset routine before accessing the
	* environment, which might be in a chip on that bus. For details
	* about this problem see doc/I2C_Edge_Conditions.
	*/
	i2c_init_board();
	#endif

	/* Handle possible failed I2C state */
	/* FIXME: put this into i2c_init_board()? */
	_i2c_bus_reset(adap);

	/* clear lo master address */
	out_8(&i2c->lmadr, 0);

	/* clear hi master address */
	out_8(&i2c->hmadr, 0);

	/* clear lo slave address */
	out_8(&i2c->lsadr, 0);

	/* clear hi slave address */
	out_8(&i2c->hsadr, 0);

	/* Clock divide Register */
	/* set divisor according to freq_opb */
	divisor = (get_OPB_freq() - 1) / 10000000;
	if (divisor == 0)
	divisor = 1;
	out_8(&i2c->clkdiv, divisor);

	/* no interrupts */
	out_8(&i2c->intrmsk, 0);

	/* clear transfer count */
	out_8(&i2c->xfrcnt, 0);

	/* clear extended control & stat */
	/* write 1 in SRC SRS SWC SWS to clear these fields */
	out_8(&i2c->xtcntlss, 0xF0);

	/* Mode Control Register
	Flush Slave/Master data buffer */
	out_8(&i2c->mdcntl, IIC_MDCNTL_FSDB \| IIC_MDCNTL_FMDB);

	val = in_8(&i2c->mdcntl);

	/* Ignore General Call, slave transfers are ignored,
	* disable interrupts, exit unknown bus state, enable hold
	* SCL 100kHz normaly or FastMode for 400kHz and above
	*/

	val \|= IIC_MDCNTL_EUBS \| IIC_MDCNTL_HSCL;
	if (speed >= 400000)
	val \|= IIC_MDCNTL_FSM;
	out_8(&i2c->mdcntl, val);

	/* clear control reg */
	out_8(&i2c->cntl, 0x00);
	}

	/*
	* This code tries to use the features of the 405GP i2c
	* controller. It will transfer up to 4 bytes in one pass
	* on the loop. It only does out_8((u8 *)lbz) to the buffer when it
	* is possible to do out16(lhz) transfers.
	*
	* 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.
	*
	* Typical case is a Write of an addr followd by a Read. The
	* IBM FAQ does not cover this. On the last byte of the write
	* we don't set the creg CHT bit but the RPST bit.
	*
	* It does not support address only transfers, there must be
	* a data part. If you want to write the address yourself, put
	* it in the data pointer.
	*
	* It does not support transfer to/from address 0.
	*
	* It does not check XFRCNT.
	*/
	static int _i2c_transfer(struct i2c_adapter *adap,
	unsigned char cmd_type,
	unsigned char chip,
	unsigned char addr[],
	unsigned char addr_len,
	unsigned char data[],
	unsigned short data_len)
	{
	struct ppc4xx_i2c *i2c = ppc4xx_get_i2c(adap->hwadapnr);
	u8 *ptr;
	int reading;
	int tran, cnt;
	int result;
	int status;
	int i;
	u8 creg;

	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 IIC_NOK;
	}
	if (addr && addr_len) {
	ptr = addr;
	cnt = addr_len;
	reading = 0;
	} else {
	ptr = data;
	cnt = data_len;
	reading = cmd_type;
	}

	/* Clear Stop Complete Bit */
	out_8(&i2c->sts, IIC_STS_SCMP);

	/* Check init */
	i = 10;
	do {
	/* Get status */
	status = in_8(&i2c->sts);
	i--;
	} while ((status & IIC_STS_PT) && (i > 0));

	if (status & IIC_STS_PT) {
	result = IIC_NOK_TOUT;
	return(result);
	}

	/* flush the Master/Slave Databuffers */
	out_8(&i2c->mdcntl, in_8(&i2c->mdcntl) \|
	IIC_MDCNTL_FMDB \| IIC_MDCNTL_FSDB);

	/* need to wait 4 OPB clocks? code below should take that long */

	/* 7-bit adressing */
	out_8(&i2c->hmadr, 0);
	out_8(&i2c->lmadr, chip);

	tran = 0;
	result = IIC_OK;
	creg = 0;

	while (tran != cnt && (result == IIC_OK)) {
	int bc,j;

	/*
	* Control register =
	* Normal transfer, 7-bits adressing, Transfer up to
	* bc bytes, Normal start, Transfer is a sequence of transfers
	*/
	creg \|= IIC_CNTL_PT;

	bc = (cnt - tran) > 4 ? 4 : cnt - tran;
	creg \|= (bc - 1) << 4;
	/* if the real cmd type is write continue trans */
	if ((!cmd_type && (ptr == addr)) \|\| ((tran + bc) != cnt))
	creg \|= IIC_CNTL_CHT;

	/* last part of address, prepare for repeated start on read */
	if (cmd_type && (ptr == addr) && ((tran + bc) == cnt))
	creg \|= IIC_CNTL_RPST;

	if (reading) {
	creg \|= IIC_CNTL_READ;
	} else {
	for(j = 0; j < bc; j++) {
	/* Set buffer */
	out_8(&i2c->mdbuf, ptr[tran + j]);
	}
	}
	out_8(&i2c->cntl, creg);

	/*
	* Transfer is in progress
	* we have to wait for upto 5 bytes of data
	* 1 byte chip address+r/w bit then bc bytes
	* of data.
	* udelay(10) is 1 bit time at 100khz
	* Doubled for slop. 20 is too small.
	*/
	i = 2 * 5 * 8;
	do {
	/* Get status */
	status = in_8(&i2c->sts);
	udelay(10);
	i--;
	} while ((status & IIC_STS_PT) && !(status & IIC_STS_ERR) &&
	(i > 0));

	if (status & IIC_STS_ERR) {
	result = IIC_NOK;
	status = in_8(&i2c->extsts);
	/* Lost arbitration? */
	if (status & IIC_EXTSTS_LA)
	result = IIC_NOK_LA;
	/* Incomplete transfer? */
	if (status & IIC_EXTSTS_ICT)
	result = IIC_NOK_ICT;
	/* Transfer aborted? */
	if (status & IIC_EXTSTS_XFRA)
	result = IIC_NOK_XFRA;
	/* Is bus free?
	* If error happened during combined xfer
	* IIC interface is usually stuck in some strange
	* state without a valid stop condition.
	* Brute, but working: generate stop, then soft reset.
	*/
	if ((status & IIC_EXTSTS_BCS_MASK)
	!= IIC_EXTSTS_BCS_FREE){
	u8 mdcntl = in_8(&i2c->mdcntl);

	/* Generate valid stop condition */
	out_8(&i2c->xtcntlss, IIC_XTCNTLSS_SRST);
	out_8(&i2c->directcntl, IIC_DIRCNTL_SCC);
	udelay(10);
	out_8(&i2c->directcntl,
	IIC_DIRCNTL_SCC \| IIC_DIRCNTL_SDAC);
	out_8(&i2c->xtcntlss, 0);

	ppc4xx_i2c_init(adap, (mdcntl & IIC_MDCNTL_FSM)
	? 400000 : 100000, 0);
	}
	} else if ( status & IIC_STS_PT) {
	result = IIC_NOK_TOUT;
	}

	/* Command is reading => get buffer */
	if ((reading) && (result == IIC_OK)) {
	/* Are there data in buffer */
	if (status & IIC_STS_MDBS) {
	/*
	* even if we have data we have to wait 4OPB
	* clocks for it to hit the front of the FIFO,
	* after that we can just read. We should check
	* XFCNT here and if the FIFO is full there is
	* no need to wait.
	*/
	udelay(1);
	for (j = 0; j < bc; j++)
	ptr[tran + j] = in_8(&i2c->mdbuf);
	} else
	result = IIC_NOK_DATA;
	}
	creg = 0;
	tran += bc;
	if (ptr == addr && tran == cnt) {
	ptr = data;
	cnt = data_len;
	tran = 0;
	reading = cmd_type;
	}
	}
	return result;
	}

	static int ppc4xx_i2c_probe(struct i2c_adapter *adap, 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(adap, 1, chip << 1, 0, 0, buf, 1) != 0);
	}

	static int ppc4xx_i2c_transfer(struct i2c_adapter *adap, uchar chip, uint addr,
	int alen, uchar *buffer, int len, int read)
	{
	uchar xaddr[4];
	int ret;

	if (alen > 4) {
	printf("I2C: 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
	ret = _i2c_transfer(adap, read, chip << 1, &xaddr[4 - alen], alen,
	buffer, len);
	if (ret) {
	printf("I2C %s: failed %d\n", read ? "read" : "write", ret);
	return 1;
	}

	return 0;
	}

	static int ppc4xx_i2c_read(struct i2c_adapter *adap, uchar chip, uint addr,
	int alen, uchar *buffer, int len)
	{
	return ppc4xx_i2c_transfer(adap, chip, addr, alen, buffer, len, 1);
	}

	static int ppc4xx_i2c_write(struct i2c_adapter *adap, uchar chip, uint addr,
	int alen, uchar *buffer, int len)
	{
	return ppc4xx_i2c_transfer(adap, chip, addr, alen, buffer, len, 0);
	}

	static unsigned int ppc4xx_i2c_set_bus_speed(struct i2c_adapter *adap,
	unsigned int speed)
	{
	if (speed != adap->speed)
	return -1;
	return speed;
	}

	/*
	* Register ppc4xx i2c adapters
	*/
	#ifdef CONFIG_SYS_I2C_PPC4XX_CH0
	U_BOOT_I2C_ADAP_COMPLETE(ppc4xx_0, ppc4xx_i2c_init, ppc4xx_i2c_probe,
	ppc4xx_i2c_read, ppc4xx_i2c_write,
	ppc4xx_i2c_set_bus_speed,
	CONFIG_SYS_I2C_PPC4XX_SPEED_0,
	CONFIG_SYS_I2C_PPC4XX_SLAVE_0, 0)
	#endif
	#ifdef CONFIG_SYS_I2C_PPC4XX_CH1
	U_BOOT_I2C_ADAP_COMPLETE(ppc4xx_1, ppc4xx_i2c_init, ppc4xx_i2c_probe,
	ppc4xx_i2c_read, ppc4xx_i2c_write,
	ppc4xx_i2c_set_bus_speed,
	CONFIG_SYS_I2C_PPC4XX_SPEED_1,
	CONFIG_SYS_I2C_PPC4XX_SLAVE_1, 1)
	#endif