/*
 * 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
};