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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> */

/* $Id: i2c-algo-bit.c,v 1.52 2004/12/29 10:12:48 khali Exp $ */

#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 "i2c.h"
#include "i2c-algo-bit.h"


/* ----- global defines ----------------------------------------------- */
#define DEB(x) if (i2c_debug>=1) x;
#define DEB2(x) if (i2c_debug>=2) x;
#define DEBSTAT(x) if (i2c_debug>=3) x; /* print several statistical values*/
#define DEBPROTO(x) if (i2c_debug>=9) { x; }
      /* debug the protocol by showing transferred bits */


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

/* module parameters:
 */
static int i2c_debug;
static int bit_test;    /* see if the line-setting functions work */

/* --- 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);
}

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

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

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

      setscl(adap,1);

      /* Not all adapters have scl sense line... */
      if (adap->getscl == NULL ) {
            udelay(adap->udelay);
            return 0;
      }

      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;
            }
#if LINUX_VERSION_CODE < KERNEL_VERSION(2,5,0)
            if (current->need_resched)
                  schedule();
#else
            cond_resched();
#endif
      }
      DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies-start));
      udelay(adap->udelay);
      return 0;
} 


/* --- other auxiliary functions -------------------------------------- */
static void i2c_start(struct i2c_algo_bit_data *adap) 
{
      /* assert: scl, sda are high */
      DEBPROTO(printk("S "));
      sdalo(adap);
      scllo(adap);
}

static void i2c_repstart(struct i2c_algo_bit_data *adap) 
{
      /* scl, sda may not be high */
      DEBPROTO(printk(" Sr "));
      setsda(adap,1);
      sclhi(adap);
      udelay(adap->udelay);
      
      sdalo(adap);
      scllo(adap);
}


static void i2c_stop(struct i2c_algo_bit_data *adap) 
{
      DEBPROTO(printk("P\n"));
      /* assert: scl is low */
      sdalo(adap);
      sclhi(adap); 
      sdahi(adap);
}



/* 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, 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 & ( 1 << i );
            setsda(adap,sb);
            udelay(adap->udelay);
            DEBPROTO(printk(KERN_DEBUG "%d",sb!=0));
            if (sclhi(adap)<0) { /* timed out */
                  sdahi(adap); /* we don't want to block the net */
                  DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at bit #%d\n", c&0xff, i));
                  return -ETIMEDOUT;
            };
            /* do arbitration here: 
             * if ( sb && ! getsda(adap) ) -> ouch! Get out of here.
             */
            setscl(adap, 0 );
            udelay(adap->udelay);
      }
      sdahi(adap);
      if (sclhi(adap)<0){ /* timeout */
            DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x, timeout at ack\n", c&0xff));
            return -ETIMEDOUT;
      };
      /* read ack: SDA should be pulled down by slave */
      ack=getsda(adap); /* ack: sda is pulled low ->success.       */
      DEB2(printk(KERN_DEBUG " i2c_outb: 0x%02x , getsda() = %d\n", c & 0xff, ack));

      DEBPROTO( printk(KERN_DEBUG "[%2.2x]",c&0xff) );
      DEBPROTO(if (0==ack){ printk(KERN_DEBUG " A ");} else printk(KERN_DEBUG " NA ") );
      scllo(adap);
      return 0==ack;          /* return 1 if device acked    */
      /* 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 */
                  DEB2(printk(KERN_DEBUG " i2c_inb: timeout at bit #%d\n", 7-i));
                  return -ETIMEDOUT;
            };
            indata *= 2;
            if ( getsda(adap) ) 
                  indata |= 0x01;
            scllo(adap);
      }
      /* assert: scl is low */
      DEB2(printk(KERN_DEBUG "i2c_inb: 0x%02x\n", indata & 0xff));

      DEBPROTO(printk(KERN_DEBUG " 0x%02x", indata & 0xff));
      return (int) (indata & 0xff);
}

/*
 * 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)
            printk(KERN_INFO "i2c-algo-bit.o: Testing SDA only, "
                  "SCL is not readable.\n");

      sda=getsda(adap);
      scl=(adap->getscl==NULL?1:getscl(adap));
      printk(KERN_DEBUG "i2c-algo-bit.o: (0) scl=%d, sda=%d\n",scl,sda);
      if (!scl || !sda ) {
            printk(KERN_WARNING "i2c-algo-bit.o: %s seems to be busy.\n", name);
            goto bailout;
      }

      sdalo(adap);
      sda=getsda(adap);
      scl=(adap->getscl==NULL?1:getscl(adap));
      printk(KERN_DEBUG "i2c-algo-bit.o: (1) scl=%d, sda=%d\n",scl,sda);
      if ( 0 != sda ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck high!\n");
            goto bailout;
      }
      if ( 0 == scl ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
                  "while pulling SDA low!\n");
            goto bailout;
      }           

      sdahi(adap);
      sda=getsda(adap);
      scl=(adap->getscl==NULL?1:getscl(adap));
      printk(KERN_DEBUG "i2c-algo-bit.o: (2) scl=%d, sda=%d\n",scl,sda);
      if ( 0 == sda ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SDA stuck low!\n");
            goto bailout;
      }
      if ( 0 == scl ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SCL unexpected low "
                  "while pulling SDA high!\n");
            goto bailout;
      }

      scllo(adap);
      sda=getsda(adap);
      scl=(adap->getscl==NULL?0:getscl(adap));
      printk(KERN_DEBUG "i2c-algo-bit.o: (3) scl=%d, sda=%d\n",scl,sda);
      if ( 0 != scl ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck high!\n");
            goto bailout;
      }
      if ( 0 == sda ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
                  "while pulling SCL low!\n");
            goto bailout;
      }
      
      sclhi(adap);
      sda=getsda(adap);
      scl=(adap->getscl==NULL?1:getscl(adap));
      printk(KERN_DEBUG "i2c-algo-bit.o: (4) scl=%d, sda=%d\n",scl,sda);
      if ( 0 == scl ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SCL stuck low!\n");
            goto bailout;
      }
      if ( 0 == sda ) {
            printk(KERN_WARNING "i2c-algo-bit.o: SDA unexpected low "
                  "while pulling SCL high!\n");
            goto bailout;
      }
      printk(KERN_INFO "i2c-algo-bit.o: %s passed test.\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 inline 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)
                  break;      /* success! */
            i2c_stop(adap);
            udelay(5/*adap->udelay*/);
            if (i==retries)  /* no success */
                  break;
            i2c_start(adap);
            udelay(adap->udelay);
      }
      DEB2(if (i)
           printk(KERN_DEBUG "i2c-algo-bit.o: Used %d tries to %s client at 0x%02x : %s\n",
                i+1, addr & 1 ? "read" : "write", addr>>1,
                ret==1 ? "success" : ret==0 ? "no ack" : "failed, timeout?" )
          );
      return ret;
}

static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
      struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
      char c;
      const 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) {
            c = *temp;
            DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: %s sendbytes: writing %2.2X\n",
                      i2c_adap->name, c&0xff));
            retval = i2c_outb(i2c_adap,c);
            if ((retval>0) || (nak_ok && (retval==0)))  { /* ok or ignored NAK */
                  count--; 
                  temp++;
                  wrcount++;
            } else { /* arbitration or no acknowledge */
                  printk(KERN_ERR "i2c-algo-bit.o: %s sendbytes: error - bailout.\n",
                         i2c_adap->name);
                  i2c_stop(adap);
                  return (retval<0)? retval : -EFAULT;
                          /* got a better one ?? */
            }
#if 0
            /* from asm/delay.h */
            __delay(adap->mdelay * (loops_per_sec / 1000) );
#endif
      }
      return wrcount;
}

static inline int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
      int inval;
      int rdcount=0;    /* counts bytes read */
      struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
      char *temp = msg->buf;
      int count = msg->len;
      int recv_len = 0;

      /* Receive [Count] for I2C_SMBUS_BLOCK_DATA or I2C_SMBUS_BLOCK_PROC_CALL protocol */
      if (msg->flags & I2C_M_RECV_LEN)
            recv_len = 1;

      while (count > 0) {
            inval = i2c_inb(i2c_adap);
/*printk("%#02x ",inval); if ( ! (count % 16) ) printk("\n"); */
            if (inval>=0) {
                  *temp = inval;
                  rdcount++;
            } else {   /* read timed out */
                  printk(KERN_ERR "i2c-algo-bit.o: readbytes: i2c_inb timed out.\n");
                  break;
            }

            if (recv_len) {
                  recv_len = 0;
                  /* [Count] should be between 1 and 31 (I2C_SMBUS_BLOCK_MAX - 1). */
                  if (inval > 0 && inval < I2C_SMBUS_BLOCK_MAX) {
                        count = inval + 1;      /* plus one for [Count] itself */
                        msg->len = count;
                        if (msg->flags & I2C_M_RECV_PEC)
                              count++; /* plus one for PEC */
                  } else {
                        printk(KERN_ERR "i2c-algo-bit.o: readbytes: bad block count (%d).\n", inval);
                        break;
                  }
            }
            
            if ( count > 1 ) {            /* send ack */
                  sdalo(adap);
                  DEBPROTO(printk(" Am "));
            } else {
                  sdahi(adap);      /* neg. ack on last byte */
                  DEBPROTO(printk(" NAm "));
            }
            if (sclhi(adap)<0) {    /* timeout */
                  sdahi(adap);
                  printk(KERN_ERR "i2c-algo-bit.o: readbytes: Timeout at ack\n");
                  return -ETIMEDOUT;
            };
            scllo(adap);
            sdahi(adap);
            temp++;
            count--;
      }
      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 inline 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);
            DEB2(printk(KERN_DEBUG "addr0: %d\n",addr));
            /* try extended address code...*/
            ret = try_address(i2c_adap, addr, retries);
            if ((ret != 1) && !nak_ok)  {
                  printk(KERN_ERR "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 */
                  printk(KERN_ERR "died at 2nd address code.\n");
                  return -EREMOTEIO;
            }
            if ( flags & I2C_M_RD ) {
                  i2c_repstart(adap);
                  /* okay, now switch into reading mode */
                  addr |= 0x01;
                  ret = try_address(i2c_adap, addr, retries);
                  if ((ret!=1) && !nak_ok) {
                        printk(KERN_ERR "died at extended 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;

      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) {
                        i2c_repstart(adap);
                  }
                  ret = bit_doAddress(i2c_adap, pmsg);
                  if ((ret != 0) && !nak_ok) {
                        DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: NAK from device addr %2.2x msg #%d\n",
                              msgs[i].addr,i));
                        return (ret<0) ? ret : -EREMOTEIO;
                  }
            }
            if (pmsg->flags & I2C_M_RD ) {
                  /* read bytes into buffer*/
                  ret = readbytes(i2c_adap, pmsg);
                  DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: read %d bytes.\n",ret));
                  if (ret < pmsg->len ) {
                        return (ret<0)? ret : -EREMOTEIO;
                  }
            } else {
                  /* write bytes from buffer */
                  ret = sendbytes(i2c_adap, pmsg);
                  DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: wrote %d bytes.\n",ret));
                  if (ret < pmsg->len ) {
                        return (ret<0) ? ret : -EREMOTEIO;
                  }
            }
      }
      i2c_stop(adap);
      return num;
}

static u32 bit_func(struct i2c_adapter *i2c_adap)
{
      return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
             I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING |
             I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
             I2C_FUNC_SMBUS_READ_BLOCK_DATA |
             I2C_FUNC_SMBUS_BLOCK_PROC_CALL_PEC |
             I2C_FUNC_SMBUS_READ_BLOCK_DATA_PEC;
}


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

static struct i2c_algorithm i2c_bit_algo = {
      .name       = "Bit-shift algorithm",
      .id         = I2C_ALGO_BIT,
      .master_xfer      = bit_xfer,
      .functionality    = bit_func,
};

/* 
 * registering functions to load algorithms at runtime 
 */
int i2c_bit_add_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;
      }

      DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: hw routines for %s registered.\n",
                  adap->name));

      /* register new adapter to i2c module... */

      adap->id |= i2c_bit_algo.id;
      adap->algo = &i2c_bit_algo;

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

      i2c_add_adapter(adap);
      return 0;
}


int i2c_bit_del_bus(struct i2c_adapter *adap)
{
      return i2c_del_adapter(adap);
}

EXPORT_SYMBOL(i2c_bit_add_bus);
EXPORT_SYMBOL(i2c_bit_del_bus);

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

MODULE_PARM(bit_test, "i");
MODULE_PARM(i2c_debug,"i");

MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
MODULE_PARM_DESC(i2c_debug,
            "debug level - 0 off; 1 normal; 2,3 more verbose; 9 bit-protocol");

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