/*
 * Copyright (C) 2014      Panasonic Corporation
 * Copyright (C) 2015-2016 Socionext Inc.
 *   Author: Masahiro Yamada <yamada.masahiro@socionext.com>
 *
 * SPDX-License-Identifier:     GPL-2.0+
 */

#include <linux/errno.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/sizes.h>
#include <linux/types.h>
#include <dm.h>
#include <i2c.h>
#include <fdtdec.h>

struct uniphier_fi2c_regs {
        u32 cr;                         /* control register */
#define I2C_CR_MST      (1 << 3)        /* master mode */
#define I2C_CR_STA      (1 << 2)        /* start condition */
#define I2C_CR_STO      (1 << 1)        /* stop condition */
#define I2C_CR_NACK     (1 << 0)        /* not ACK */
        u32 dttx;                       /* send FIFO (write-only) */
#define dtrx            dttx            /* receive FIFO (read-only) */
#define I2C_DTTX_CMD    (1 << 8)        /* send command (slave addr) */
#define I2C_DTTX_RD     (1 << 0)        /* read */
        u32 __reserved;                 /* no register at offset 0x08 */
        u32 slad;                       /* slave address */
        u32 cyc;                        /* clock cycle control */
        u32 lctl;                       /* clock low period control */
        u32 ssut;                       /* restart/stop setup time control */
        u32 dsut;                       /* data setup time control */
        u32 intr;                       /* interrupt status */
        u32 ie;                         /* interrupt enable */
        u32 ic;                         /* interrupt clear */
#define I2C_INT_TE      (1 << 9)        /* TX FIFO empty */
#define I2C_INT_RB      (1 << 4)        /* received specified bytes */
#define I2C_INT_NA      (1 << 2)        /* no answer */
#define I2C_INT_AL      (1 << 1)        /* arbitration lost */
        u32 sr;                         /* status register */
#define I2C_SR_DB       (1 << 12)       /* device busy */
#define I2C_SR_BB       (1 << 8)        /* bus busy */
#define I2C_SR_RFF      (1 << 3)        /* Rx FIFO full */
#define I2C_SR_RNE      (1 << 2)        /* Rx FIFO not empty */
#define I2C_SR_TNF      (1 << 1)        /* Tx FIFO not full */
#define I2C_SR_TFE      (1 << 0)        /* Tx FIFO empty */
        u32 __reserved2;                /* no register at offset 0x30 */
        u32 rst;                        /* reset control */
#define I2C_RST_TBRST   (1 << 2)        /* clear Tx FIFO */
#define I2C_RST_RBRST   (1 << 1)        /* clear Rx FIFO */
#define I2C_RST_RST     (1 << 0)        /* forcible bus reset */
        u32 bm;                         /* bus monitor */
        u32 noise;                      /* noise filter control */
        u32 tbc;                        /* Tx byte count setting */
        u32 rbc;                        /* Rx byte count setting */
        u32 tbcm;                       /* Tx byte count monitor */
        u32 rbcm;                       /* Rx byte count monitor */
        u32 brst;                       /* bus reset */
#define I2C_BRST_FOEN   (1 << 1)        /* normal operation */
#define I2C_BRST_RSCLO  (1 << 0)        /* release SCL low fixing */
};

#define FIOCLK  50000000

struct uniphier_fi2c_priv {
        struct udevice *dev;
        struct uniphier_fi2c_regs __iomem *regs;        /* register base */
        unsigned long fioclk;                   /* internal operation clock */
        unsigned long timeout;                  /* time out (us) */
};

static void uniphier_fi2c_reset(struct uniphier_fi2c_priv *priv)
{
        writel(I2C_RST_RST, &priv->regs->rst);
}

static int uniphier_fi2c_check_bus_busy(struct uniphier_fi2c_priv *priv)
{
        u32 val;
        int ret;

        ret = readl_poll_timeout(&priv->regs->sr, val, !(val & I2C_SR_DB), 100);
        if (ret < 0) {
                dev_dbg(priv->dev, "error: device busy too long. reset...\n");
                uniphier_fi2c_reset(priv);
        }

        return ret;
}

static int uniphier_fi2c_probe(struct udevice *dev)
{
        fdt_addr_t addr;
        struct uniphier_fi2c_priv *priv = dev_get_priv(dev);

        addr = devfdt_get_addr(dev);
        if (addr == FDT_ADDR_T_NONE)
                return -EINVAL;

        priv->regs = devm_ioremap(dev, addr, SZ_128);
        if (!priv->regs)
                return -ENOMEM;

        priv->fioclk = FIOCLK;

        priv->dev = dev;

        /* bus forcible reset */
        uniphier_fi2c_reset(priv);

        writel(I2C_BRST_FOEN | I2C_BRST_RSCLO, &priv->regs->brst);

        return 0;
}

static int wait_for_irq(struct uniphier_fi2c_priv *priv, u32 flags,
                        bool *stop)
{
        u32 irq;
        int ret;

        ret = readl_poll_timeout(&priv->regs->intr, irq, irq & flags,
                                 priv->timeout);
        if (ret < 0) {
                dev_dbg(priv->dev, "error: time out\n");
                return ret;
        }

        if (irq & I2C_INT_AL) {
                dev_dbg(priv->dev, "error: arbitration lost\n");
                *stop = false;
                return ret;
        }

        if (irq & I2C_INT_NA) {
                dev_dbg(priv->dev, "error: no answer\n");
                return ret;
        }

        return 0;
}

static int issue_stop(struct uniphier_fi2c_priv *priv, int old_ret)
{
        int ret;

        dev_dbg(priv->dev, "stop condition\n");
        writel(I2C_CR_MST | I2C_CR_STO, &priv->regs->cr);

        ret = uniphier_fi2c_check_bus_busy(priv);
        if (ret < 0)
                dev_dbg(priv->dev, "error: device busy after operation\n");

        return old_ret ? old_ret : ret;
}

static int uniphier_fi2c_transmit(struct uniphier_fi2c_priv *priv, uint addr,
                                  uint len, const u8 *buf, bool *stop)
{
        int ret;
        const u32 irq_flags = I2C_INT_TE | I2C_INT_NA | I2C_INT_AL;
        struct uniphier_fi2c_regs __iomem *regs = priv->regs;

        dev_dbg(priv->dev, "%s: addr = %x, len = %d\n", __func__, addr, len);

        writel(I2C_DTTX_CMD | addr << 1, &regs->dttx);

        writel(irq_flags, &regs->ie);
        writel(irq_flags, &regs->ic);

        dev_dbg(priv->dev, "start condition\n");
        writel(I2C_CR_MST | I2C_CR_STA, &regs->cr);

        ret = wait_for_irq(priv, irq_flags, stop);
        if (ret < 0)
                goto error;

        while (len--) {
                dev_dbg(priv->dev, "sending %x\n", *buf);
                writel(*buf++, &regs->dttx);

                writel(irq_flags, &regs->ic);

                ret = wait_for_irq(priv, irq_flags, stop);
                if (ret < 0)
                        goto error;
        }

error:
        writel(irq_flags, &regs->ic);

        if (*stop)
                ret = issue_stop(priv, ret);

        return ret;
}

static int uniphier_fi2c_receive(struct uniphier_fi2c_priv *priv, uint addr,
                                 uint len, u8 *buf, bool *stop)
{
        int ret = 0;
        const u32 irq_flags = I2C_INT_RB | I2C_INT_NA | I2C_INT_AL;
        struct uniphier_fi2c_regs __iomem *regs = priv->regs;

        dev_dbg(priv->dev, "%s: addr = %x, len = %d\n", __func__, addr, len);

        /*
         * In case 'len == 0', only the slave address should be sent
         * for probing, which is covered by the transmit function.
         */
        if (len == 0)
                return uniphier_fi2c_transmit(priv, addr, len, buf, stop);

        writel(I2C_DTTX_CMD | I2C_DTTX_RD | addr << 1, &regs->dttx);

        writel(0, &regs->rbc);
        writel(irq_flags, &regs->ie);
        writel(irq_flags, &regs->ic);

        dev_dbg(priv->dev, "start condition\n");
        writel(I2C_CR_MST | I2C_CR_STA | (len == 1 ? I2C_CR_NACK : 0),
               &regs->cr);

        while (len--) {
                ret = wait_for_irq(priv, irq_flags, stop);
                if (ret < 0)
                        goto error;

                *buf++ = readl(&regs->dtrx);
                dev_dbg(priv->dev, "received %x\n", *(buf - 1));

                if (len == 1)
                        writel(I2C_CR_MST | I2C_CR_NACK, &regs->cr);

                writel(irq_flags, &regs->ic);
        }

error:
        writel(irq_flags, &regs->ic);

        if (*stop)
                ret = issue_stop(priv, ret);

        return ret;
}

static int uniphier_fi2c_xfer(struct udevice *bus, struct i2c_msg *msg,
                             int nmsgs)
{
        int ret;
        struct uniphier_fi2c_priv *priv = dev_get_priv(bus);
        bool stop;

        ret = uniphier_fi2c_check_bus_busy(priv);
        if (ret < 0)
                return ret;

        for (; nmsgs > 0; nmsgs--, msg++) {
                /* If next message is read, skip the stop condition */
                stop = nmsgs > 1 && msg[1].flags & I2C_M_RD ? false : true;

                if (msg->flags & I2C_M_RD)
                        ret = uniphier_fi2c_receive(priv, msg->addr, msg->len,
                                                    msg->buf, &stop);
                else
                        ret = uniphier_fi2c_transmit(priv, msg->addr, msg->len,
                                                     msg->buf, &stop);

                if (ret < 0)
                        break;
        }

        return ret;
}

static int uniphier_fi2c_set_bus_speed(struct udevice *bus, unsigned int speed)
{
        int ret;
        unsigned int clk_count;
        struct uniphier_fi2c_priv *priv = dev_get_priv(bus);
        struct uniphier_fi2c_regs __iomem *regs = priv->regs;

        /* max supported frequency is 400 kHz */
        if (speed > 400000)
                return -EINVAL;

        ret = uniphier_fi2c_check_bus_busy(priv);
        if (ret < 0)
                return ret;

        /* make sure the bus is idle when changing the frequency */
        writel(I2C_BRST_RSCLO, &regs->brst);

        clk_count = priv->fioclk / speed;

        writel(clk_count, &regs->cyc);
        writel(clk_count / 2, &regs->lctl);
        writel(clk_count / 2, &regs->ssut);
        writel(clk_count / 16, &regs->dsut);

        writel(I2C_BRST_FOEN | I2C_BRST_RSCLO, &regs->brst);

        /*
         * Theoretically, each byte can be transferred in
         * 1000000 * 9 / speed usec.
         * This time out value is long enough.
         */
        priv->timeout = 100000000L / speed;

        return 0;
}

static const struct dm_i2c_ops uniphier_fi2c_ops = {
        .xfer = uniphier_fi2c_xfer,
        .set_bus_speed = uniphier_fi2c_set_bus_speed,
};

static const struct udevice_id uniphier_fi2c_of_match[] = {
        { .compatible = "socionext,uniphier-fi2c" },
        { /* sentinel */ }
};

U_BOOT_DRIVER(uniphier_fi2c) = {
        .name = "uniphier-fi2c",
        .id = UCLASS_I2C,
        .of_match = uniphier_fi2c_of_match,
        .probe = uniphier_fi2c_probe,
        .priv_auto_alloc_size = sizeof(struct uniphier_fi2c_priv),
        .ops = &uniphier_fi2c_ops,
};