i2c-algo-bit.c

/* ------------------------------------------------------------------------- */
/* i2c-algo-bit.c i2c driver algorithms for bit-shift adapters		     */
/* ------------------------------------------------------------------------- */
/*   Copyright (C) 1995-2000 Simon G. Vogl

    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., 675 Mass Ave, Cambridge, MA 02139, USA.		     */
/* ------------------------------------------------------------------------- */

/* With some changes from Frodo Looijaard <frodol@dds.nl>, Kysti Mlkki
   <kmalkki@cc.hut.fi> and Jean Delvare <khali@linux-fr.org> */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>


/* ----- global defines ----------------------------------------------- */

#ifdef DEBUG
#define bit_dbg(level, dev, format, args...) \
	do { \
		if (i2c_debug >= level) \
			dev_dbg(dev, format, ##args); \
	} while (0)
#else
#define bit_dbg(level, dev, format, args...) \
	do {} while (0)
#endif /* DEBUG */

/* ----- global variables ---------------------------------------------	*/

static int bit_test;	/* see if the line-setting functions work	*/
module_param(bit_test, bool, 0);
MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");

#ifdef DEBUG
static int i2c_debug = 1;
module_param(i2c_debug, int, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(i2c_debug,
		 "debug level - 0 off; 1 normal; 2 verbose; 3 very verbose");
#endif

/* --- setting states on the bus with the right timing: ---------------	*/

#define setsda(adap,val) adap->setsda(adap->data, val)
#define setscl(adap,val) adap->setscl(adap->data, val)
#define getsda(adap) adap->getsda(adap->data)
#define getscl(adap) adap->getscl(adap->data)

static inline void sdalo(struct i2c_algo_bit_data *adap)
{
	setsda(adap,0);
	udelay((adap->udelay + 1) / 2);
}

static inline void sdahi(struct i2c_algo_bit_data *adap)
{
	setsda(adap,1);
	udelay((adap->udelay + 1) / 2);
}

static inline void scllo(struct i2c_algo_bit_data *adap)
{
	setscl(adap,0);
	udelay(adap->udelay / 2);
}

/*
 * Raise scl line, and do checking for delays. This is necessary for slower
 * devices.
 */
static int sclhi(struct i2c_algo_bit_data *adap)
{
	unsigned long start;

	setscl(adap,1);

	/* Not all adapters have scl sense line... */
	if (!adap->getscl)
		goto done;

	start=jiffies;
	while (! getscl(adap) ) {	
 		/* the hw knows how to read the clock line,
 		 * so we wait until it actually gets high.
 		 * This is safer as some chips may hold it low
 		 * while they are processing data internally. 
 		 */
		if (time_after_eq(jiffies, start+adap->timeout)) {
			return -ETIMEDOUT;
		}
		cond_resched();
	}
#ifdef DEBUG
	if (jiffies != start && i2c_debug >= 3)
		pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
			 "high\n", jiffies - start);
#endif

done:
	udelay(adap->udelay);
	return 0;
} 


/* --- other auxiliary functions --------------------------------------	*/
static void i2c_start(struct i2c_algo_bit_data *adap) 
{
	/* assert: scl, sda are high */
	setsda(adap, 0);
	udelay(adap->udelay);
	scllo(adap);
}

static void i2c_repstart(struct i2c_algo_bit_data *adap) 
{
	/* assert: scl is low */
	sdahi(adap);
	sclhi(adap);
	setsda(adap, 0);
	udelay(adap->udelay);
	scllo(adap);
}


static void i2c_stop(struct i2c_algo_bit_data *adap) 
{
	/* assert: scl is low */
	sdalo(adap);
	sclhi(adap); 
	setsda(adap, 1);
	udelay(adap->udelay);
}



/* send a byte without start cond., look for arbitration, 
   check ackn. from slave */
/* returns:
 * 1 if the device acknowledged
 * 0 if the device did not ack
 * -ETIMEDOUT if an error occurred (while raising the scl line)
 */
static int i2c_outb(struct i2c_adapter *i2c_adap, unsigned char c)
{
	int i;
	int sb;
	int ack;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: scl is low */
	for ( i=7 ; i>=0 ; i-- ) {
		sb = (c >> i) & 1;
		setsda(adap,sb);
		udelay((adap->udelay + 1) / 2);
		if (sclhi(adap)<0) { /* timed out */
			bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
				"timeout at bit #%d\n", (int)c, i);
			return -ETIMEDOUT;
		};
		/* do arbitration here: 
		 * if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
		 */
		scllo(adap);
	}
	sdahi(adap);
	if (sclhi(adap)<0){ /* timeout */
		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
			"timeout at ack\n", (int)c);
		return -ETIMEDOUT;
	};
	/* read ack: SDA should be pulled down by slave */
	ack = !getsda(adap);    /* ack: sda is pulled low -> success */
	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s\n", (int)c,
		ack ? "A" : "NA");

	scllo(adap);
	return ack;
	/* assert: scl is low (sda undef) */
}


static int i2c_inb(struct i2c_adapter *i2c_adap) 
{
	/* read byte via i2c port, without start/stop sequence	*/
	/* acknowledge is sent in i2c_read.			*/
	int i;
	unsigned char indata=0;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: scl is low */
	sdahi(adap);
	for (i=0;i<8;i++) {
		if (sclhi(adap)<0) { /* timeout */
			bit_dbg(1, &i2c_adap->dev, "i2c_inb: timeout at bit "
				"#%d\n", 7 - i);
			return -ETIMEDOUT;
		};
		indata *= 2;
		if ( getsda(adap) ) 
			indata |= 0x01;
		setscl(adap, 0);
		udelay(i == 7 ? adap->udelay / 2 : adap->udelay);
	}
	/* assert: scl is low */
	return indata;
}

/*
 * Sanity check for the adapter hardware - check the reaction of
 * the bus lines only if it seems to be idle.
 */
static int test_bus(struct i2c_algo_bit_data *adap, char* name) {
	int scl,sda;

	if (adap->getscl==NULL)
		pr_info("%s: Testing SDA only, SCL is not readable\n", name);

	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if (!scl || !sda ) {
		printk(KERN_WARNING "%s: bus seems to be busy\n", name);
		goto bailout;
	}

	sdalo(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if ( 0 != sda ) {
		printk(KERN_WARNING "%s: SDA stuck high!\n", name);
		goto bailout;
	}
	if ( 0 == scl ) {
		printk(KERN_WARNING "%s: SCL unexpected low "
		       "while pulling SDA low!\n", name);
		goto bailout;
	}		

	sdahi(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if ( 0 == sda ) {
		printk(KERN_WARNING "%s: SDA stuck low!\n", name);
		goto bailout;
	}
	if ( 0 == scl ) {
		printk(KERN_WARNING "%s: SCL unexpected low "
		       "while pulling SDA high!\n", name);
		goto bailout;
	}

	scllo(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?0:getscl(adap));
	if ( 0 != scl ) {
		printk(KERN_WARNING "%s: SCL stuck high!\n", name);
		goto bailout;
	}
	if ( 0 == sda ) {
		printk(KERN_WARNING "%s: SDA unexpected low "
		       "while pulling SCL low!\n", name);
		goto bailout;
	}
	
	sclhi(adap);
	sda=getsda(adap);
	scl=(adap->getscl==NULL?1:getscl(adap));
	if ( 0 == scl ) {
		printk(KERN_WARNING "%s: SCL stuck low!\n", name);
		goto bailout;
	}
	if ( 0 == sda ) {
		printk(KERN_WARNING "%s: SDA unexpected low "
		       "while pulling SCL high!\n", name);
		goto bailout;
	}
	pr_info("%s: Test OK\n", name);
	return 0;
bailout:
	sdahi(adap);
	sclhi(adap);
	return -ENODEV;
}

/* ----- Utility functions
 */

/* try_address tries to contact a chip for a number of
 * times before it gives up.
 * return values:
 * 1 chip answered
 * 0 chip did not answer
 * -x transmission error
 */
static int try_address(struct i2c_adapter *i2c_adap,
		       unsigned char addr, int retries)
{
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	int i,ret = -1;
	for (i=0;i<=retries;i++) {
		ret = i2c_outb(i2c_adap,addr);
		if (ret == 1 || i == retries)
			break;
		bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
		i2c_stop(adap);
		udelay(adap->udelay);
		yield();
		bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
		i2c_start(adap);
	}
	if (i && ret)
		bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
			"0x%02x: %s\n", i + 1,
			addr & 1 ? "read from" : "write to", addr >> 1,
			ret == 1 ? "success" : "failed, timeout?");
	return ret;
}

static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	const unsigned char *temp = msg->buf;
	int count = msg->len;
	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 
	int retval;
	int wrcount=0;

	while (count > 0) {
		retval = i2c_outb(i2c_adap, *temp);
		if ((retval>0) || (nak_ok && (retval==0)))  { /* ok or ignored NAK */
			count--; 
			temp++;
			wrcount++;
		} else { /* arbitration or no acknowledge */
			dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");
			return (retval<0)? retval : -EFAULT;
			        /* got a better one ?? */
		}
	}
	return wrcount;
}

static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
{
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: sda is high */
	if (is_ack)		/* send ack */
		setsda(adap, 0);
	udelay((adap->udelay + 1) / 2);
	if (sclhi(adap) < 0) {	/* timeout */
		dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
		return -ETIMEDOUT;
	}
	scllo(adap);
	return 0;
}

static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	int inval;
	int rdcount=0;   	/* counts bytes read */
	unsigned char *temp = msg->buf;
	int count = msg->len;
	const unsigned flags = msg->flags;

	while (count > 0) {
		inval = i2c_inb(i2c_adap);
		if (inval>=0) {
			*temp = inval;
			rdcount++;
		} else {   /* read timed out */
			break;
		}

		temp++;
		count--;

		/* Some SMBus transactions require that we receive the
		   transaction length as the first read byte. */
		if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
			if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
				if (!(flags & I2C_M_NO_RD_ACK))
					acknak(i2c_adap, 0);
				dev_err(&i2c_adap->dev, "readbytes: invalid "
					"block length (%d)\n", inval);
				return -EREMOTEIO;
			}
			/* The original count value accounts for the extra
			   bytes, that is, either 1 for a regular transaction,
			   or 2 for a PEC transaction. */
			count += inval;
			msg->len += inval;
		}

		bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
			inval,
			(flags & I2C_M_NO_RD_ACK)
				? "(no ack/nak)"
				: (count ? "A" : "NA"));

		if (!(flags & I2C_M_NO_RD_ACK)) {
			inval = acknak(i2c_adap, count);
			if (inval < 0)
				return inval;
		}
	}
	return rdcount;
}

/* doAddress initiates the transfer by generating the start condition (in
 * try_address) and transmits the address in the necessary format to handle
 * reads, writes as well as 10bit-addresses.
 * returns:
 *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 *	-ETIMEDOUT, for example if the lines are stuck...) 
 */
static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	unsigned short flags = msg->flags;
	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	unsigned char addr;
	int ret, retries;

	retries = nak_ok ? 0 : i2c_adap->retries;
	
	if ( (flags & I2C_M_TEN)  ) { 
		/* a ten bit address */
		addr = 0xf0 | (( msg->addr >> 7) & 0x03);
		bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
		/* try extended address code...*/
		ret = try_address(i2c_adap, addr, retries);
		if ((ret != 1) && !nak_ok)  {
			dev_err(&i2c_adap->dev,
				"died at extended address code\n");
			return -EREMOTEIO;
		}
		/* the remaining 8 bit address */
		ret = i2c_outb(i2c_adap,msg->addr & 0x7f);
		if ((ret != 1) && !nak_ok) {
			/* the chip did not ack / xmission error occurred */
			dev_err(&i2c_adap->dev, "died at 2nd address code\n");
			return -EREMOTEIO;
		}
		if ( flags & I2C_M_RD ) {
			bit_dbg(3, &i2c_adap->dev, "emitting repeated "
				"start condition\n");
			i2c_repstart(adap);
			/* okay, now switch into reading mode */
			addr |= 0x01;
			ret = try_address(i2c_adap, addr, retries);
			if ((ret!=1) && !nak_ok) {
				dev_err(&i2c_adap->dev,
					"died at repeated address code\n");
				return -EREMOTEIO;
			}
		}
	} else {		/* normal 7bit address	*/
		addr = ( msg->addr << 1 );
		if (flags & I2C_M_RD )
			addr |= 1;
		if (flags & I2C_M_REV_DIR_ADDR )
			addr ^= 1;
		ret = try_address(i2c_adap, addr, retries);
		if ((ret!=1) && !nak_ok)
			return -EREMOTEIO;
	}

	return 0;
}

static int bit_xfer(struct i2c_adapter *i2c_adap,
		    struct i2c_msg msgs[], int num)
{
	struct i2c_msg *pmsg;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	
	int i,ret;
	unsigned short nak_ok;

	bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
	i2c_start(adap);
	for (i=0;i<num;i++) {
		pmsg = &msgs[i];
		nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 
		if (!(pmsg->flags & I2C_M_NOSTART)) {
			if (i) {
				bit_dbg(3, &i2c_adap->dev, "emitting "
					"repeated start condition\n");
				i2c_repstart(adap);
			}
			ret = bit_doAddress(i2c_adap, pmsg);
			if ((ret != 0) && !nak_ok) {
				bit_dbg(1, &i2c_adap->dev, "NAK from "
					"device addr 0x%02x msg #%d\n",
					msgs[i].addr, i);
				goto bailout;
			}
		}
		if (pmsg->flags & I2C_M_RD ) {
			/* read bytes into buffer*/
			ret = readbytes(i2c_adap, pmsg);
			if (ret >= 1)
				bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
					ret, ret == 1 ? "" : "s");
			if (ret < pmsg->len) {
				if (ret >= 0)
					ret = -EREMOTEIO;
				goto bailout;
			}
		} else {
			/* write bytes from buffer */
			ret = sendbytes(i2c_adap, pmsg);
			if (ret >= 1)
				bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
					ret, ret == 1 ? "" : "s");
			if (ret < pmsg->len) {
				if (ret >= 0)
					ret = -EREMOTEIO;
				goto bailout;
			}
		}
	}
	ret = i;

bailout:
	bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
	i2c_stop(adap);
	return ret;
}

static u32 bit_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 
	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |
	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
	       I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
}


/* -----exported algorithm data: -------------------------------------	*/

static const struct i2c_algorithm i2c_bit_algo = {
	.master_xfer	= bit_xfer,
	.functionality	= bit_func,
};

/* 
 * registering functions to load algorithms at runtime 
 */
static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
{
	struct i2c_algo_bit_data *bit_adap = adap->algo_data;

	if (bit_test) {
		int ret = test_bus(bit_adap, adap->name);
		if (ret<0)
			return -ENODEV;
	}

	/* register new adapter to i2c module... */
	adap->algo = &i2c_bit_algo;

	adap->timeout = 100;	/* default values, should	*/
	adap->retries = 3;	/* be replaced by defines	*/

	return 0;
}

int i2c_bit_add_bus(struct i2c_adapter *adap)
{
	int err;

	err = i2c_bit_prepare_bus(adap);
	if (err)
		return err;

	return i2c_add_adapter(adap);
}
EXPORT_SYMBOL(i2c_bit_add_bus);

int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
{
	int err;

	err = i2c_bit_prepare_bus(adap);
	if (err)
		return err;

	return i2c_add_numbered_adapter(adap);
}
EXPORT_SYMBOL(i2c_bit_add_numbered_bus);

MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
MODULE_LICENSE("GPL");