i2c-algo-bit.c

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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., 51 Franklin Street, Fifth Floor, Boston,
    MA 02110-1301 USA.
 * ------------------------------------------------------------------------- */

/* With some changes from Frodo Looijaard <[email protected]>, Kyösti Mälkki
   <[email protected]> and Jean Delvare <[email protected]> */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.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, 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\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;
        }
        /* 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\n", (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\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_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\n", 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)\n",
               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!\n", name);
        goto bailout;
    }
    if (!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 (!sda) {
        printk(KERN_WARNING "%s: SDA stuck low!\n", name);
        goto bailout;
    }
    if (!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 (scl) {
        printk(KERN_WARNING "%s: SCL stuck high!\n", name);
        goto bailout;
    }
    if (!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 (!scl) {
        printk(KERN_WARNING "%s: SCL stuck low!\n", name);
        goto bailout;
    }
    if (!sda) {
        printk(KERN_WARNING "%s: SDA unexpected low "
               "while pulling SCL high!\n", name);
        goto bailout;
    }

    if (adap->post_xfer)
        adap->post_xfer(i2c_adap);

    pr_info("%s: Test OK\n", 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\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);

        /* 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.\n");
            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\n",
                    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\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 -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\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: -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\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 -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\n");
            return -ENXIO;
        }
        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 -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\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 = -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\n",
                    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\n");
    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\n");
        dev_warn(&adap->dev, "Bus may be unreliable\n");
    }
    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 <[email protected]>");
MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
MODULE_LICENSE("GPL");