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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>, Kyösti Mälkki
   <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");

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