/*
 * 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 busions 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 "bus.h"

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

static inline void
nvkm_i2c_drive_scl(struct nvkm_i2c_bus *bus, int state)
{
        bus->func->drive_scl(bus, state);
}

static inline void
nvkm_i2c_drive_sda(struct nvkm_i2c_bus *bus, int state)
{
        bus->func->drive_sda(bus, state);
}

static inline int
nvkm_i2c_sense_scl(struct nvkm_i2c_bus *bus)
{
        return bus->func->sense_scl(bus);
}

static inline int
nvkm_i2c_sense_sda(struct nvkm_i2c_bus *bus)
{
        return bus->func->sense_sda(bus);
}

static void
nvkm_i2c_delay(struct nvkm_i2c_bus *bus, u32 nsec)
{
        udelay((nsec + 500) / 1000);
}

static bool
nvkm_i2c_raise_scl(struct nvkm_i2c_bus *bus)
{
        u32 timeout = T_TIMEOUT / T_RISEFALL;

        nvkm_i2c_drive_scl(bus, 1);
        do {
                nvkm_i2c_delay(bus, T_RISEFALL);
        } while (!nvkm_i2c_sense_scl(bus) && --timeout);

        return timeout != 0;
}

static int
i2c_start(struct nvkm_i2c_bus *bus)
{
        int ret = 0;

        if (!nvkm_i2c_sense_scl(bus) ||
            !nvkm_i2c_sense_sda(bus)) {
                nvkm_i2c_drive_scl(bus, 0);
                nvkm_i2c_drive_sda(bus, 1);
                if (!nvkm_i2c_raise_scl(bus))
                        ret = -EBUSY;
        }

        nvkm_i2c_drive_sda(bus, 0);
        nvkm_i2c_delay(bus, T_HOLD);
        nvkm_i2c_drive_scl(bus, 0);
        nvkm_i2c_delay(bus, T_HOLD);
        return ret;
}

static void
i2c_stop(struct nvkm_i2c_bus *bus)
{
        nvkm_i2c_drive_scl(bus, 0);
        nvkm_i2c_drive_sda(bus, 0);
        nvkm_i2c_delay(bus, T_RISEFALL);

        nvkm_i2c_drive_scl(bus, 1);
        nvkm_i2c_delay(bus, T_HOLD);
        nvkm_i2c_drive_sda(bus, 1);
        nvkm_i2c_delay(bus, T_HOLD);
}

static int
i2c_bitw(struct nvkm_i2c_bus *bus, int sda)
{
        nvkm_i2c_drive_sda(bus, sda);
        nvkm_i2c_delay(bus, T_RISEFALL);

        if (!nvkm_i2c_raise_scl(bus))
                return -ETIMEDOUT;
        nvkm_i2c_delay(bus, T_HOLD);

        nvkm_i2c_drive_scl(bus, 0);
        nvkm_i2c_delay(bus, T_HOLD);
        return 0;
}

static int
i2c_bitr(struct nvkm_i2c_bus *bus)
{
        int sda;

        nvkm_i2c_drive_sda(bus, 1);
        nvkm_i2c_delay(bus, T_RISEFALL);

        if (!nvkm_i2c_raise_scl(bus))
                return -ETIMEDOUT;
        nvkm_i2c_delay(bus, T_HOLD);

        sda = nvkm_i2c_sense_sda(bus);

        nvkm_i2c_drive_scl(bus, 0);
        nvkm_i2c_delay(bus, T_HOLD);
        return sda;
}

static int
nvkm_i2c_get_byte(struct nvkm_i2c_bus *bus, u8 *byte, bool last)
{
        int i, bit;

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

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

static int
nvkm_i2c_put_byte(struct nvkm_i2c_bus *bus, u8 byte)
{
        int i, ret;
        for (i = 7; i >= 0; i--) {
                ret = i2c_bitw(bus, !!(byte & (1 << i)));
                if (ret < 0)
                        return ret;
        }

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

static int
i2c_addr(struct nvkm_i2c_bus *bus, struct i2c_msg *msg)
{
        u32 addr = msg->addr << 1;
        if (msg->flags & I2C_M_RD)
                addr |= 1;
        return nvkm_i2c_put_byte(bus, addr);
}

int
nvkm_i2c_bit_xfer(struct nvkm_i2c_bus *bus, struct i2c_msg *msgs, int num)
{
        struct i2c_msg *msg = msgs;
        int ret = 0, mcnt = num;

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

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

                if (msg->flags & I2C_M_RD) {
                        while (!ret && remaining--)
                                ret = nvkm_i2c_get_byte(bus, ptr++, !remaining);
                } else {
                        while (!ret && remaining--)
                                ret = nvkm_i2c_put_byte(bus, *ptr++);
                }

                msg++;
        }

        i2c_stop(bus);
        return (ret < 0) ? ret : num;
}
#else
int
nvkm_i2c_bit_xfer(struct nvkm_i2c_bus *bus, struct i2c_msg *msgs, int num)
{
        return -ENODEV;
}
#endif