bit.c

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/*
 * Copyright 2012 Red Hat Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * 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 COPYRIGHT HOLDER(S) OR AUTHOR(S) 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.
 *
 * Authors: Ben Skeggs
 */

#include "subdev/i2c.h"

#ifdef CONFIG_NOUVEAU_I2C_INTERNAL
#define T_TIMEOUT  2200000
#define T_RISEFALL 1000
#define T_HOLD     5000

static inline void
i2c_drive_scl(struct nouveau_i2c_port *port, int state)
{
    nouveau_i2c_drive_scl(port, state);
}

static inline void
i2c_drive_sda(struct nouveau_i2c_port *port, int state)
{
    nouveau_i2c_drive_sda(port, state);
}

static inline int
i2c_sense_scl(struct nouveau_i2c_port *port)
{
    return nouveau_i2c_sense_scl(port);
}

static inline int
i2c_sense_sda(struct nouveau_i2c_port *port)
{
    return nouveau_i2c_sense_sda(port);
}

static void
i2c_delay(struct nouveau_i2c_port *port, u32 nsec)
{
    udelay((nsec + 500) / 1000);
}

static bool
i2c_raise_scl(struct nouveau_i2c_port *port)
{
    u32 timeout = T_TIMEOUT / T_RISEFALL;

    i2c_drive_scl(port, 1);
    do {
        i2c_delay(port, T_RISEFALL);
    } while (!i2c_sense_scl(port) && --timeout);

    return timeout != 0;
}

static int
i2c_start(struct nouveau_i2c_port *port)
{
    int ret = 0;

    port->state  = i2c_sense_scl(port);
    port->state |= i2c_sense_sda(port) << 1;
    if (port->state != 3) {
        i2c_drive_scl(port, 0);
        i2c_drive_sda(port, 1);
        if (!i2c_raise_scl(port))
            ret = -EBUSY;
    }

    i2c_drive_sda(port, 0);
    i2c_delay(port, T_HOLD);
    i2c_drive_scl(port, 0);
    i2c_delay(port, T_HOLD);
    return ret;
}

static void
i2c_stop(struct nouveau_i2c_port *port)
{
    i2c_drive_scl(port, 0);
    i2c_drive_sda(port, 0);
    i2c_delay(port, T_RISEFALL);

    i2c_drive_scl(port, 1);
    i2c_delay(port, T_HOLD);
    i2c_drive_sda(port, 1);
    i2c_delay(port, T_HOLD);
}

static int
i2c_bitw(struct nouveau_i2c_port *port, int sda)
{
    i2c_drive_sda(port, sda);
    i2c_delay(port, T_RISEFALL);

    if (!i2c_raise_scl(port))
        return -ETIMEDOUT;
    i2c_delay(port, T_HOLD);

    i2c_drive_scl(port, 0);
    i2c_delay(port, T_HOLD);
    return 0;
}

static int
i2c_bitr(struct nouveau_i2c_port *port)
{
    int sda;

    i2c_drive_sda(port, 1);
    i2c_delay(port, T_RISEFALL);

    if (!i2c_raise_scl(port))
        return -ETIMEDOUT;
    i2c_delay(port, T_HOLD);

    sda = i2c_sense_sda(port);

    i2c_drive_scl(port, 0);
    i2c_delay(port, T_HOLD);
    return sda;
}

static int
i2c_get_byte(struct nouveau_i2c_port *port, u8 *byte, bool last)
{
    int i, bit;

    *byte = 0;
    for (i = 7; i >= 0; i--) {
        bit = i2c_bitr(port);
        if (bit < 0)
            return bit;
        *byte |= bit << i;
    }

    return i2c_bitw(port, last ? 1 : 0);
}

static int
i2c_put_byte(struct nouveau_i2c_port *port, u8 byte)
{
    int i, ret;
    for (i = 7; i >= 0; i--) {
        ret = i2c_bitw(port, !!(byte & (1 << i)));
        if (ret < 0)
            return ret;
    }

    ret = i2c_bitr(port);
    if (ret == 1) /* nack */
        ret = -EIO;
    return ret;
}

static int
i2c_addr(struct nouveau_i2c_port *port, struct i2c_msg *msg)
{
    u32 addr = msg->addr << 1;
    if (msg->flags & I2C_M_RD)
        addr |= 1;
    return i2c_put_byte(port, addr);
}

static int
i2c_bit_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
    struct nouveau_i2c_port *port = (struct nouveau_i2c_port *)adap;
    struct i2c_msg *msg = msgs;
    int ret = 0, mcnt = num;

    while (!ret && mcnt--) {
        u8 remaining = msg->len;
        u8 *ptr = msg->buf;

        ret = i2c_start(port);
        if (ret == 0)
            ret = i2c_addr(port, msg);

        if (msg->flags & I2C_M_RD) {
            while (!ret && remaining--)
                ret = i2c_get_byte(port, ptr++, !remaining);
        } else {
            while (!ret && remaining--)
                ret = i2c_put_byte(port, *ptr++);
        }

        msg++;
    }

    i2c_stop(port);
    return (ret < 0) ? ret : num;
}
#else
static int
i2c_bit_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
    return -ENODEV;
}
#endif

static u32
i2c_bit_func(struct i2c_adapter *adap)
{
    return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

const struct i2c_algorithm nouveau_i2c_bit_algo = {
    .master_xfer = i2c_bit_xfer,
    .functionality = i2c_bit_func
};