// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (c) 2018 Arm Ltd.
 * Author: Liviu Dudau <liviu.dudau@foss.arm.com>
 *
 */

#include <common.h>
#include <dm.h>
#include <errno.h>
#include <i2c.h>
#include <asm/io.h>
#include <clk.h>
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/io.h>

#define I2C_CONTROL_REG         0x00
#define I2C_SET_REG             0x00
#define I2C_CLEAR_REG           0x04

#define SCL     BIT(0)
#define SDA     BIT(1)

struct versatile_i2c_priv {
        phys_addr_t base;
        u32 delay;
};

static inline void versatile_sda_set(struct versatile_i2c_priv *priv, u8 state)
{
        writel(SDA, priv->base + (state ? I2C_SET_REG : I2C_CLEAR_REG));
        udelay(priv->delay);
}

static inline int versatile_sda_get(struct versatile_i2c_priv *priv)
{
        int v = !!(readl(priv->base + I2C_CONTROL_REG) & SDA);

        udelay(priv->delay);
        return v;
}

static inline void versatile_scl_set(struct versatile_i2c_priv *priv, u8 state)
{
        writel(SCL, priv->base + (state ? I2C_SET_REG : I2C_CLEAR_REG));
        udelay(priv->delay);
}

static inline int versatile_scl_get(struct versatile_i2c_priv *priv)
{
        int v = !!(readl(priv->base + I2C_CONTROL_REG) & SCL);

        udelay(priv->delay);
        return v;
}

/* start: SDA goes from high to low while SCL is high */
static void versatile_i2c_start(struct versatile_i2c_priv *priv)
{
        udelay(priv->delay);
        versatile_sda_set(priv, 1);
        versatile_scl_set(priv, 1);
        versatile_sda_set(priv, 0);
}

/* stop: SDA goes from low to high while SCL is high */
static void versatile_i2c_stop(struct versatile_i2c_priv *priv)
{
        versatile_scl_set(priv, 0);
        versatile_sda_set(priv, 0);
        versatile_scl_set(priv, 1);
        versatile_sda_set(priv, 1);
}

/* read a bit from the SDA line (data or ACK/NACK) */
static u8 versatile_i2c_read_bit(struct versatile_i2c_priv *priv)
{
        versatile_scl_set(priv, 0);
        versatile_sda_set(priv, 1);
        versatile_scl_set(priv, 1);
        udelay(priv->delay);
        return (u8)versatile_sda_get(priv);
}

/* write a bit on the SDA line */
static void versatile_i2c_write_bit(struct versatile_i2c_priv *priv, u8 bit)
{
        versatile_scl_set(priv, 0);
        versatile_sda_set(priv, bit);
        versatile_scl_set(priv, 1);
        udelay(priv->delay);
}

/* send a reset sequence of 9 clocks with SDA high */
static void versatile_i2c_reset_bus(struct versatile_i2c_priv *priv)
{
        int i;

        for (i = 0; i < 9; i++)
                versatile_i2c_write_bit(priv, 1);

        versatile_i2c_stop(priv);
}

/* write byte without start/stop sequence */
static int versatile_i2c_write_byte(struct versatile_i2c_priv *priv, u8 byte)
{
        u8 nak, i;

        for (i = 0; i < 8; i++) {
                versatile_i2c_write_bit(priv, byte & 0x80);
                byte <<= 1;
        }

        /* read ACK */
        nak = versatile_i2c_read_bit(priv);
        versatile_scl_set(priv, 0);

        return nak;     /* not a nack is an ack */
}

static int versatile_i2c_read_byte(struct versatile_i2c_priv *priv,
                                   u8 *byte, u8 ack)
{
        u8 i;

        *byte = 0;
        for (i = 0; i < 8; i++) {
                *byte <<= 1;
                *byte |= versatile_i2c_read_bit(priv);
        }
        /* write the nack */
        versatile_i2c_write_bit(priv, ack);

        return 0;
}

static int versatile_i2c_send_slave_addr(struct versatile_i2c_priv *priv,
                                         struct i2c_msg *msg)
{
        u8 addr;
        int ret;

        if (msg->flags & I2C_M_TEN) {
                /* 10-bit address, send extended address code first */
                addr = 0xf0 | ((msg->addr >> 7) & 0x06);
                ret = versatile_i2c_write_byte(priv, addr);
                if (ret) {
                        versatile_i2c_stop(priv);
                        return -EIO;
                }

                /* remaining bits */
                ret = versatile_i2c_write_byte(priv, msg->addr & 0xff);
                if (ret) {
                        versatile_i2c_stop(priv);
                        return -EIO;
                }
                /* reads need to resend the addr */
                if (msg->flags & I2C_M_RD) {
                        versatile_i2c_start(priv);
                        addr |= 1;
                        ret = versatile_i2c_write_byte(priv, addr);
                        if (ret) {
                                versatile_i2c_stop(priv);
                                return -EIO;
                        }
                }
        } else {
                /* normal 7-bit address */
                addr = msg->addr << 1;
                if (msg->flags & I2C_M_RD)
                        addr |= 1;
                ret = versatile_i2c_write_byte(priv, addr);
                if (ret) {
                        versatile_i2c_stop(priv);
                        return -EIO;
                }
        }

        return 0;
}

static int versatile_i2c_message_xfer(struct versatile_i2c_priv *priv,
                                      struct i2c_msg *msg)
{
        int i, ret;
        u8 ack;

        versatile_i2c_start(priv);
        if (versatile_i2c_send_slave_addr(priv, msg))
                return -EIO;

        for (i = 0; i < msg->len; i++) {
                if (msg->flags & I2C_M_RD) {
                        ack = (msg->len - i - 1) == 0 ? 1 : 0;
                        ret = versatile_i2c_read_byte(priv, &msg->buf[i], ack);
                } else {
                        ret = versatile_i2c_write_byte(priv, msg->buf[i]);
                }

                if (ret)
                        break;
        }

        versatile_i2c_stop(priv);

        return ret;
}

static int versatile_i2c_xfer(struct udevice *bus,
                              struct i2c_msg *msg, int nmsgs)
{
        struct versatile_i2c_priv *priv = dev_get_priv(bus);
        int ret;

        for ( ; nmsgs > 0; nmsgs--, msg++) {
                ret = versatile_i2c_message_xfer(priv, msg);
                if (ret)
                        return -EREMOTEIO;
        }

        return 0;
}

static int versatile_i2c_chip_probe(struct udevice *bus,
                                    uint chip, uint chip_flags)
{
        /* probe the presence of a slave by writing a 0-size message */
        struct i2c_msg msg = { .addr = chip, .flags = chip_flags,
                               .len = 0, .buf = NULL };
        struct versatile_i2c_priv *priv = dev_get_priv(bus);

        return versatile_i2c_message_xfer(priv, &msg);
}

static int versatile_i2c_set_bus_speed(struct udevice *bus, unsigned int speed)
{
        struct versatile_i2c_priv *priv = dev_get_priv(bus);

        priv->delay = 1000000 / (speed << 2);

        versatile_i2c_reset_bus(priv);

        return 0;
}

static int versatile_i2c_probe(struct udevice *dev)
{
        struct versatile_i2c_priv *priv = dev_get_priv(dev);

        priv->base = (phys_addr_t)dev_read_addr(dev);
        priv->delay = 25;       /* 25us * 4 = 100kHz */

        return 0;
}

static const struct dm_i2c_ops versatile_i2c_ops = {
        .xfer = versatile_i2c_xfer,
        .probe_chip = versatile_i2c_chip_probe,
        .set_bus_speed = versatile_i2c_set_bus_speed,
};

static const struct udevice_id versatile_i2c_of_match[] = {
        { .compatible = "arm,versatile-i2c" },
        { }
};

U_BOOT_DRIVER(versatile_i2c) = {
        .name = "i2c-bus-versatile",
        .id = UCLASS_I2C,
        .of_match = versatile_i2c_of_match,
        .probe = versatile_i2c_probe,
        .priv_auto      = sizeof(struct versatile_i2c_priv),
        .ops = &versatile_i2c_ops,
};