qib_twsi.c

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/*
 * Copyright (c) 2012 Intel Corporation. All rights reserved.
 * Copyright (c) 2006 - 2012 QLogic Corporation. All rights reserved.
 * Copyright (c) 2003, 2004, 2005, 2006 PathScale, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <linux/delay.h>
#include <linux/pci.h>
#include <linux/vmalloc.h>

#include "qib.h"

/*
 * QLogic_IB "Two Wire Serial Interface" driver.
 * Originally written for a not-quite-i2c serial eeprom, which is
 * still used on some supported boards. Later boards have added a
 * variety of other uses, most board-specific, so the bit-boffing
 * part has been split off to this file, while the other parts
 * have been moved to chip-specific files.
 *
 * We have also dropped all pretense of fully generic (e.g. pretend
 * we don't know whether '1' is the higher voltage) interface, as
 * the restrictions of the generic i2c interface (e.g. no access from
 * driver itself) make it unsuitable for this use.
 */

#define READ_CMD 1
#define WRITE_CMD 0

static void i2c_wait_for_writes(struct qib_devdata *dd)
{
    /*
     * implicit read of EXTStatus is as good as explicit
     * read of scratch, if all we want to do is flush
     * writes.
     */
    dd->f_gpio_mod(dd, 0, 0, 0);
    rmb(); /* inlined, so prevent compiler reordering */
}

/*
 * QSFP modules are allowed to hold SCL low for 500uSec. Allow twice that
 * for "almost compliant" modules
 */
#define SCL_WAIT_USEC 1000

/* BUF_WAIT is time bus must be free between STOP or ACK and to next START.
 * Should be 20, but some chips need more.
 */
#define TWSI_BUF_WAIT_USEC 60

static void scl_out(struct qib_devdata *dd, u8 bit)
{
    u32 mask;

    udelay(1);

    mask = 1UL << dd->gpio_scl_num;

    /* SCL is meant to be bare-drain, so never set "OUT", just DIR */
    dd->f_gpio_mod(dd, 0, bit ? 0 : mask, mask);

    /*
     * Allow for slow slaves by simple
     * delay for falling edge, sampling on rise.
     */
    if (!bit)
        udelay(2);
    else {
        int rise_usec;
        for (rise_usec = SCL_WAIT_USEC; rise_usec > 0; rise_usec -= 2) {
            if (mask & dd->f_gpio_mod(dd, 0, 0, 0))
                break;
            udelay(2);
        }
        if (rise_usec <= 0)
            qib_dev_err(dd, "SCL interface stuck low > %d uSec\n",
                    SCL_WAIT_USEC);
    }
    i2c_wait_for_writes(dd);
}

static void sda_out(struct qib_devdata *dd, u8 bit)
{
    u32 mask;

    mask = 1UL << dd->gpio_sda_num;

    /* SDA is meant to be bare-drain, so never set "OUT", just DIR */
    dd->f_gpio_mod(dd, 0, bit ? 0 : mask, mask);

    i2c_wait_for_writes(dd);
    udelay(2);
}

static u8 sda_in(struct qib_devdata *dd, int wait)
{
    int bnum;
    u32 read_val, mask;

    bnum = dd->gpio_sda_num;
    mask = (1UL << bnum);
    /* SDA is meant to be bare-drain, so never set "OUT", just DIR */
    dd->f_gpio_mod(dd, 0, 0, mask);
    read_val = dd->f_gpio_mod(dd, 0, 0, 0);
    if (wait)
        i2c_wait_for_writes(dd);
    return (read_val & mask) >> bnum;
}

static int i2c_ackrcv(struct qib_devdata *dd)
{
    u8 ack_received;

    /* AT ENTRY SCL = LOW */
    /* change direction, ignore data */
    ack_received = sda_in(dd, 1);
    scl_out(dd, 1);
    ack_received = sda_in(dd, 1) == 0;
    scl_out(dd, 0);
    return ack_received;
}

static void stop_cmd(struct qib_devdata *dd);

static int rd_byte(struct qib_devdata *dd, int last)
{
    int bit_cntr, data;

    data = 0;

    for (bit_cntr = 7; bit_cntr >= 0; --bit_cntr) {
        data <<= 1;
        scl_out(dd, 1);
        data |= sda_in(dd, 0);
        scl_out(dd, 0);
    }
    if (last) {
        scl_out(dd, 1);
        stop_cmd(dd);
    } else {
        sda_out(dd, 0);
        scl_out(dd, 1);
        scl_out(dd, 0);
        sda_out(dd, 1);
    }
    return data;
}

static int wr_byte(struct qib_devdata *dd, u8 data)
{
    int bit_cntr;
    u8 bit;

    for (bit_cntr = 7; bit_cntr >= 0; bit_cntr--) {
        bit = (data >> bit_cntr) & 1;
        sda_out(dd, bit);
        scl_out(dd, 1);
        scl_out(dd, 0);
    }
    return (!i2c_ackrcv(dd)) ? 1 : 0;
}

/*
 * issue TWSI start sequence:
 * (both clock/data high, clock high, data low while clock is high)
 */
static void start_seq(struct qib_devdata *dd)
{
    sda_out(dd, 1);
    scl_out(dd, 1);
    sda_out(dd, 0);
    udelay(1);
    scl_out(dd, 0);
}

static void stop_seq(struct qib_devdata *dd)
{
    scl_out(dd, 0);
    sda_out(dd, 0);
    scl_out(dd, 1);
    sda_out(dd, 1);
}

static void stop_cmd(struct qib_devdata *dd)
{
    stop_seq(dd);
    udelay(TWSI_BUF_WAIT_USEC);
}

int qib_twsi_reset(struct qib_devdata *dd)
{
    int clock_cycles_left = 9;
    int was_high = 0;
    u32 pins, mask;

    /* Both SCL and SDA should be high. If not, there
     * is something wrong.
     */
    mask = (1UL << dd->gpio_scl_num) | (1UL << dd->gpio_sda_num);

    /*
     * Force pins to desired innocuous state.
     * This is the default power-on state with out=0 and dir=0,
     * So tri-stated and should be floating high (barring HW problems)
     */
    dd->f_gpio_mod(dd, 0, 0, mask);

    /*
     * Clock nine times to get all listeners into a sane state.
     * If SDA does not go high at any point, we are wedged.
     * One vendor recommends then issuing START followed by STOP.
     * we cannot use our "normal" functions to do that, because
     * if SCL drops between them, another vendor's part will
     * wedge, dropping SDA and keeping it low forever, at the end of
     * the next transaction (even if it was not the device addressed).
     * So our START and STOP take place with SCL held high.
     */
    while (clock_cycles_left--) {
        scl_out(dd, 0);
        scl_out(dd, 1);
        /* Note if SDA is high, but keep clocking to sync slave */
        was_high |= sda_in(dd, 0);
    }

    if (was_high) {
        /*
         * We saw a high, which we hope means the slave is sync'd.
         * Issue START, STOP, pause for T_BUF.
         */

        pins = dd->f_gpio_mod(dd, 0, 0, 0);
        if ((pins & mask) != mask)
            qib_dev_err(dd, "GPIO pins not at rest: %d\n",
                    pins & mask);
        /* Drop SDA to issue START */
        udelay(1); /* Guarantee .6 uSec setup */
        sda_out(dd, 0);
        udelay(1); /* Guarantee .6 uSec hold */
        /* At this point, SCL is high, SDA low. Raise SDA for STOP */
        sda_out(dd, 1);
        udelay(TWSI_BUF_WAIT_USEC);
    }

    return !was_high;
}

#define QIB_TWSI_START 0x100
#define QIB_TWSI_STOP 0x200

/* Write byte to TWSI, optionally prefixed with START or suffixed with
 * STOP.
 * returns 0 if OK (ACK received), else != 0
 */
static int qib_twsi_wr(struct qib_devdata *dd, int data, int flags)
{
    int ret = 1;
    if (flags & QIB_TWSI_START)
        start_seq(dd);

    ret = wr_byte(dd, data); /* Leaves SCL low (from i2c_ackrcv()) */

    if (flags & QIB_TWSI_STOP)
        stop_cmd(dd);
    return ret;
}

/* Added functionality for IBA7220-based cards */
#define QIB_TEMP_DEV 0x98

/*
 * qib_twsi_blk_rd
 * Formerly called qib_eeprom_internal_read, and only used for eeprom,
 * but now the general interface for data transfer from twsi devices.
 * One vestige of its former role is that it recognizes a device
 * QIB_TWSI_NO_DEV and does the correct operation for the legacy part,
 * which responded to all TWSI device codes, interpreting them as
 * address within device. On all other devices found on board handled by
 * this driver, the device is followed by a one-byte "address" which selects
 * the "register" or "offset" within the device from which data should
 * be read.
 */
int qib_twsi_blk_rd(struct qib_devdata *dd, int dev, int addr,
            void *buffer, int len)
{
    int ret;
    u8 *bp = buffer;

    ret = 1;

    if (dev == QIB_TWSI_NO_DEV) {
        /* legacy not-really-I2C */
        addr = (addr << 1) | READ_CMD;
        ret = qib_twsi_wr(dd, addr, QIB_TWSI_START);
    } else {
        /* Actual I2C */
        ret = qib_twsi_wr(dd, dev | WRITE_CMD, QIB_TWSI_START);
        if (ret) {
            stop_cmd(dd);
            ret = 1;
            goto bail;
        }
        /*
         * SFF spec claims we do _not_ stop after the addr
         * but simply issue a start with the "read" dev-addr.
         * Since we are implicitely waiting for ACK here,
         * we need t_buf (nominally 20uSec) before that start,
         * and cannot rely on the delay built in to the STOP
         */
        ret = qib_twsi_wr(dd, addr, 0);
        udelay(TWSI_BUF_WAIT_USEC);

        if (ret) {
            qib_dev_err(dd,
                "Failed to write interface read addr %02X\n",
                addr);
            ret = 1;
            goto bail;
        }
        ret = qib_twsi_wr(dd, dev | READ_CMD, QIB_TWSI_START);
    }
    if (ret) {
        stop_cmd(dd);
        ret = 1;
        goto bail;
    }

    /*
     * block devices keeps clocking data out as long as we ack,
     * automatically incrementing the address. Some have "pages"
     * whose boundaries will not be crossed, but the handling
     * of these is left to the caller, who is in a better
     * position to know.
     */
    while (len-- > 0) {
        /*
         * Get and store data, sending ACK if length remaining,
         * else STOP
         */
        *bp++ = rd_byte(dd, !len);
    }

    ret = 0;

bail:
    return ret;
}

/*
 * qib_twsi_blk_wr
 * Formerly called qib_eeprom_internal_write, and only used for eeprom,
 * but now the general interface for data transfer to twsi devices.
 * One vestige of its former role is that it recognizes a device
 * QIB_TWSI_NO_DEV and does the correct operation for the legacy part,
 * which responded to all TWSI device codes, interpreting them as
 * address within device. On all other devices found on board handled by
 * this driver, the device is followed by a one-byte "address" which selects
 * the "register" or "offset" within the device to which data should
 * be written.
 */
int qib_twsi_blk_wr(struct qib_devdata *dd, int dev, int addr,
            const void *buffer, int len)
{
    int sub_len;
    const u8 *bp = buffer;
    int max_wait_time, i;
    int ret;
    ret = 1;

    while (len > 0) {
        if (dev == QIB_TWSI_NO_DEV) {
            if (qib_twsi_wr(dd, (addr << 1) | WRITE_CMD,
                    QIB_TWSI_START)) {
                goto failed_write;
            }
        } else {
            /* Real I2C */
            if (qib_twsi_wr(dd, dev | WRITE_CMD, QIB_TWSI_START))
                goto failed_write;
            ret = qib_twsi_wr(dd, addr, 0);
            if (ret) {
                qib_dev_err(dd,
                    "Failed to write interface write addr %02X\n",
                    addr);
                goto failed_write;
            }
        }

        sub_len = min(len, 4);
        addr += sub_len;
        len -= sub_len;

        for (i = 0; i < sub_len; i++)
            if (qib_twsi_wr(dd, *bp++, 0))
                goto failed_write;

        stop_cmd(dd);

        /*
         * Wait for write complete by waiting for a successful
         * read (the chip replies with a zero after the write
         * cmd completes, and before it writes to the eeprom.
         * The startcmd for the read will fail the ack until
         * the writes have completed.   We do this inline to avoid
         * the debug prints that are in the real read routine
         * if the startcmd fails.
         * We also use the proper device address, so it doesn't matter
         * whether we have real eeprom_dev. Legacy likes any address.
         */
        max_wait_time = 100;
        while (qib_twsi_wr(dd, dev | READ_CMD, QIB_TWSI_START)) {
            stop_cmd(dd);
            if (!--max_wait_time)
                goto failed_write;
        }
        /* now read (and ignore) the resulting byte */
        rd_byte(dd, 1);
    }

    ret = 0;
    goto bail;

failed_write:
    stop_cmd(dd);
    ret = 1;

bail:
    return ret;
}