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/* ------------------------------------------------------------------------- */

/* 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 Kyösti Mälkki <kmalkki@cc.hut.fi> and even

   Frodo Looijaard <frodol@dds.nl> */

/* $Id: i2c-algo-bit.c,v 1.2 2004-03-20 12:22:37 giacomo Exp $ */

/* #define DEBUG 1 */

#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 ----------------------------------------------- */

#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)

{

        unsigned long start;

        setscl(adap,1);

        /* Not all adapters have scl sense line... */

        if (adap->getscl == NULL )

                return 0;

        start=jiffies26;

        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(jiffies26, start+adap->timeout)) {

                        return -ETIMEDOUT;

                }

                //cond_resched();

        }

        DEBSTAT(printk(KERN_DEBUG "needed %ld jiffies\n", jiffies26-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;

        sda=getsda(adap);

        if (adap->getscl==NULL) {

                printk(KERN_WARNING "i2c-algo-bit.o: Warning: Adapter can't read from clock line - skipping test.\n");

                return 0;              

        }

        scl=getscl(adap);

        printk(KERN_INFO "i2c-algo-bit.o: Adapter: %s scl: %d  sda: %d -- testing...\n",

               name,getscl(adap),getsda(adap));

        if (!scl || !sda ) {

                printk(KERN_INFO " i2c-algo-bit.o: %s seems to be busy.\n",name);

                goto bailout;

        }

        sdalo(adap);

        printk(KERN_DEBUG "i2c-algo-bit.o:1 scl: %d  sda: %d \n",getscl(adap),

               getsda(adap));

        if ( 0 != getsda(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SDA stuck high!\n",name);

                sdahi(adap);

                goto bailout;

        }

        if ( 0 == getscl(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SCL unexpected low while pulling SDA low!\n",

                        name);

                goto bailout;

        }              

        sdahi(adap);

        printk(KERN_DEBUG "i2c-algo-bit.o:2 scl: %d  sda: %d \n",getscl(adap),

               getsda(adap));

        if ( 0 == getsda(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SDA stuck low!\n",name);

                sdahi(adap);

                goto bailout;

        }

        if ( 0 == getscl(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SCL unexpected low while SDA high!\n",

                       name);

        goto bailout;

        }

        scllo(adap);

        printk(KERN_DEBUG "i2c-algo-bit.o:3 scl: %d  sda: %d \n",getscl(adap),

               getsda(adap));

        if ( 0 != getscl(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SCL stuck high!\n",name);

                sclhi(adap);

                goto bailout;

        }

        if ( 0 == getsda(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SDA unexpected low while pulling SCL low!\n",

                        name);

                goto bailout;

        }

        sclhi(adap);

        printk(KERN_DEBUG "i2c-algo-bit.o:4 scl: %d  sda: %d \n",getscl(adap),

               getsda(adap));

        if ( 0 == getscl(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SCL stuck low!\n",name);

                sclhi(adap);

                goto bailout;

        }

        if ( 0 == getsda(adap) ) {

                printk(KERN_WARNING "i2c-algo-bit.o: %s SDA unexpected low while SCL high!\n",

                        name);

                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(dev_dbg(&i2c_adap->dev, "sendbytes: writing %2.2X\n", 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 */

                        dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");

                        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;

        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 ( 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 *adap)

{

        return I2C_FUNC_SMBUS_EMUL | I2C_FUNC_10BIT_ADDR |

               I2C_FUNC_PROTOCOL_MANGLING;

}

/* -----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(dev_dbg(&adap->dev, "hw routines registered.\n"));

        /* 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");