/* -------------------------------------------------------------------------
   * 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., 51 Franklin Street, Fifth Floor, Boston,
      MA 02110-1301 USA.
   * ------------------------------------------------------------------------- */
  
  /* With some changes from Frodo Looijaard <frodol@dds.nl>, Kyösti Mälkki
     <kmalkki@cc.hut.fi> and Jean Delvare <jdelvare@suse.de> */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/delay.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, int, S_IRUGO);
  MODULE_PARM_DESC(bit_test, "lines testing - 0 off; 1 report; 2 fail if 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)) {
  		/* This 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 ("clock stretching") while they
  		 * are processing data internally.
  		 */
  		if (time_after(jiffies, start + adap->timeout)) {
  			/* Test one last time, as we may have been preempted
  			 * between last check and timeout test.
  			 */
  			if (getscl(adap))
  				break;
  			return -ETIMEDOUT;
  		}
  		cpu_relax();
  	}
  #ifdef DEBUG
  	if (jiffies != start && i2c_debug >= 3)
  		pr_debug("i2c-algo-bit: needed %ld jiffies for SCL to go "
  			 "high
  ", 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
  ", (int)c, i);
  			return -ETIMEDOUT;
  		}
  		/* FIXME do arbitration here:
  		 * if (sb && !getsda(adap)) -> ouch! Get out of here.
  		 *
  		 * Report a unique code, so higher level code can retry
  		 * the whole (combined) message and *NOT* issue STOP.
  		 */
  		scllo(adap);
  	}
  	sdahi(adap);
  	if (sclhi(adap) < 0) { /* timeout */
  		bit_dbg(1, &i2c_adap->dev, "i2c_outb: 0x%02x, "
  			"timeout at ack
  ", (int)c);
  		return -ETIMEDOUT;
  	}
  
  	/* read ack: SDA should be pulled down by slave, or it may
  	 * NAK (usually to report problems with the data we wrote).
  	 */
  	ack = !getsda(adap);    /* ack: sda is pulled low -> success */
  	bit_dbg(2, &i2c_adap->dev, "i2c_outb: 0x%02x %s
  ", (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
  ", 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_adapter *i2c_adap)
  {
  	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
  	const char *name = i2c_adap->name;
  	int scl, sda, ret;
  
  	if (adap->pre_xfer) {
  		ret = adap->pre_xfer(i2c_adap);
  		if (ret < 0)
  			return -ENODEV;
  	}
  
  	if (adap->getscl == NULL)
  		pr_info("%s: Testing SDA only, SCL is not readable
  ", name);
  
  	sda = getsda(adap);
  	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
  	if (!scl || !sda) {
  		printk(KERN_WARNING
  		       "%s: bus seems to be busy (scl=%d, sda=%d)
  ",
  		       name, scl, sda);
  		goto bailout;
  	}
  
  	sdalo(adap);
  	sda = getsda(adap);
  	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
  	if (sda) {
  		printk(KERN_WARNING "%s: SDA stuck high!
  ", name);
  		goto bailout;
  	}
  	if (!scl) {
  		printk(KERN_WARNING "%s: SCL unexpected low "
  		       "while pulling SDA low!
  ", name);
  		goto bailout;
  	}
  
  	sdahi(adap);
  	sda = getsda(adap);
  	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
  	if (!sda) {
  		printk(KERN_WARNING "%s: SDA stuck low!
  ", name);
  		goto bailout;
  	}
  	if (!scl) {
  		printk(KERN_WARNING "%s: SCL unexpected low "
  		       "while pulling SDA high!
  ", name);
  		goto bailout;
  	}
  
  	scllo(adap);
  	sda = getsda(adap);
  	scl = (adap->getscl == NULL) ? 0 : getscl(adap);
  	if (scl) {
  		printk(KERN_WARNING "%s: SCL stuck high!
  ", name);
  		goto bailout;
  	}
  	if (!sda) {
  		printk(KERN_WARNING "%s: SDA unexpected low "
  		       "while pulling SCL low!
  ", name);
  		goto bailout;
  	}
  
  	sclhi(adap);
  	sda = getsda(adap);
  	scl = (adap->getscl == NULL) ? 1 : getscl(adap);
  	if (!scl) {
  		printk(KERN_WARNING "%s: SCL stuck low!
  ", name);
  		goto bailout;
  	}
  	if (!sda) {
  		printk(KERN_WARNING "%s: SDA unexpected low "
  		       "while pulling SCL high!
  ", name);
  		goto bailout;
  	}
  
  	if (adap->post_xfer)
  		adap->post_xfer(i2c_adap);
  
  	pr_info("%s: Test OK
  ", name);
  	return 0;
  bailout:
  	sdahi(adap);
  	sclhi(adap);
  
  	if (adap->post_xfer)
  		adap->post_xfer(i2c_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 = 0;
  
  	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
  ");
  		i2c_stop(adap);
  		udelay(adap->udelay);
  		yield();
  		bit_dbg(3, &i2c_adap->dev, "emitting start condition
  ");
  		i2c_start(adap);
  	}
  	if (i && ret)
  		bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
  			"0x%02x: %s
  ", 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);
  
  		/* OK/ACK; or ignored NAK */
  		if ((retval > 0) || (nak_ok && (retval == 0))) {
  			count--;
  			temp++;
  			wrcount++;
  
  		/* A slave NAKing the master means the slave didn't like
  		 * something about the data it saw.  For example, maybe
  		 * the SMBus PEC was wrong.
  		 */
  		} else if (retval == 0) {
  			dev_err(&i2c_adap->dev, "sendbytes: NAK bailout.
  ");
  			return -EIO;
  
  		/* Timeout; or (someday) lost arbitration
  		 *
  		 * FIXME Lost ARB implies retrying the transaction from
  		 * the first message, after the "winning" master issues
  		 * its STOP.  As a rule, upper layer code has no reason
  		 * to know or care about this ... it is *NOT* an error.
  		 */
  		} else {
  			dev_err(&i2c_adap->dev, "sendbytes: error %d
  ",
  					retval);
  			return retval;
  		}
  	}
  	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
  ");
  		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)
  ", inval);
  				return -EPROTO;
  			}
  			/* 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
  ",
  			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: -ENXIO 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) & 0x06);
  		bit_dbg(2, &i2c_adap->dev, "addr0: %d
  ", 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
  ");
  			return -ENXIO;
  		}
  		/* the remaining 8 bit address */
  		ret = i2c_outb(i2c_adap, msg->addr & 0xff);
  		if ((ret != 1) && !nak_ok) {
  			/* the chip did not ack / xmission error occurred */
  			dev_err(&i2c_adap->dev, "died at 2nd address code
  ");
  			return -ENXIO;
  		}
  		if (flags & I2C_M_RD) {
  			bit_dbg(3, &i2c_adap->dev, "emitting repeated "
  				"start condition
  ");
  			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
  ");
  				return -EIO;
  			}
  		}
  	} 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 -ENXIO;
  	}
  
  	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;
  
  	if (adap->pre_xfer) {
  		ret = adap->pre_xfer(i2c_adap);
  		if (ret < 0)
  			return ret;
  	}
  
  	bit_dbg(3, &i2c_adap->dev, "emitting start condition
  ");
  	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
  ");
  				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
  ",
  					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
  ",
  					ret, ret == 1 ? "" : "s");
  			if (ret < pmsg->len) {
  				if (ret >= 0)
  					ret = -EIO;
  				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
  ",
  					ret, ret == 1 ? "" : "s");
  			if (ret < pmsg->len) {
  				if (ret >= 0)
  					ret = -EIO;
  				goto bailout;
  			}
  		}
  	}
  	ret = i;
  
  bailout:
  	bit_dbg(3, &i2c_adap->dev, "emitting stop condition
  ");
  	i2c_stop(adap);
  
  	if (adap->post_xfer)
  		adap->post_xfer(i2c_adap);
  	return ret;
  }
  
  static u32 bit_func(struct i2c_adapter *adap)
  {
  	return I2C_FUNC_I2C | I2C_FUNC_NOSTART | 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: -------------------------------------	*/
  
  const struct i2c_algorithm i2c_bit_algo = {
  	.master_xfer	= bit_xfer,
  	.functionality	= bit_func,
  };
  EXPORT_SYMBOL(i2c_bit_algo);
  
  /*
   * registering functions to load algorithms at runtime
   */
  static int __i2c_bit_add_bus(struct i2c_adapter *adap,
  			     int (*add_adapter)(struct i2c_adapter *))
  {
  	struct i2c_algo_bit_data *bit_adap = adap->algo_data;
  	int ret;
  
  	if (bit_test) {
  		ret = test_bus(adap);
  		if (bit_test >= 2 && ret < 0)
  			return -ENODEV;
  	}
  
  	/* register new adapter to i2c module... */
  	adap->algo = &i2c_bit_algo;
  	adap->retries = 3;
  
  	ret = add_adapter(adap);
  	if (ret < 0)
  		return ret;
  
  	/* Complain if SCL can't be read */
  	if (bit_adap->getscl == NULL) {
  		dev_warn(&adap->dev, "Not I2C compliant: can't read SCL
  ");
  		dev_warn(&adap->dev, "Bus may be unreliable
  ");
  	}
  	return 0;
  }
  
  int i2c_bit_add_bus(struct i2c_adapter *adap)
  {
  	return __i2c_bit_add_bus(adap, i2c_add_adapter);
  }
  EXPORT_SYMBOL(i2c_bit_add_bus);
  
  int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
  {
  	return __i2c_bit_add_bus(adap, i2c_add_numbered_adapter);
  }
  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");