// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Actions Semiconductor Owl SoC's I2C driver
 *
 * Copyright (c) 2014 Actions Semi Inc.
 * Author: David Liu <liuwei@actions-semi.com>
 *
 * Copyright (c) 2018 Linaro Ltd.
 * Author: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
 */

#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>

/* I2C registers */
#define OWL_I2C_REG_CTL         0x0000
#define OWL_I2C_REG_CLKDIV      0x0004
#define OWL_I2C_REG_STAT        0x0008
#define OWL_I2C_REG_ADDR        0x000C
#define OWL_I2C_REG_TXDAT       0x0010
#define OWL_I2C_REG_RXDAT       0x0014
#define OWL_I2C_REG_CMD         0x0018
#define OWL_I2C_REG_FIFOCTL     0x001C
#define OWL_I2C_REG_FIFOSTAT    0x0020
#define OWL_I2C_REG_DATCNT      0x0024
#define OWL_I2C_REG_RCNT        0x0028

/* I2Cx_CTL Bit Mask */
#define OWL_I2C_CTL_RB          BIT(1)
#define OWL_I2C_CTL_GBCC(x)     (((x) & 0x3) << 2)
#define OWL_I2C_CTL_GBCC_NONE   OWL_I2C_CTL_GBCC(0)
#define OWL_I2C_CTL_GBCC_START  OWL_I2C_CTL_GBCC(1)
#define OWL_I2C_CTL_GBCC_STOP   OWL_I2C_CTL_GBCC(2)
#define OWL_I2C_CTL_GBCC_RSTART OWL_I2C_CTL_GBCC(3)
#define OWL_I2C_CTL_IRQE        BIT(5)
#define OWL_I2C_CTL_EN          BIT(7)
#define OWL_I2C_CTL_AE          BIT(8)
#define OWL_I2C_CTL_SHSM        BIT(10)

#define OWL_I2C_DIV_FACTOR(x)   ((x) & 0xff)

/* I2Cx_STAT Bit Mask */
#define OWL_I2C_STAT_RACK       BIT(0)
#define OWL_I2C_STAT_BEB        BIT(1)
#define OWL_I2C_STAT_IRQP       BIT(2)
#define OWL_I2C_STAT_LAB        BIT(3)
#define OWL_I2C_STAT_STPD       BIT(4)
#define OWL_I2C_STAT_STAD       BIT(5)
#define OWL_I2C_STAT_BBB        BIT(6)
#define OWL_I2C_STAT_TCB        BIT(7)
#define OWL_I2C_STAT_LBST       BIT(8)
#define OWL_I2C_STAT_SAMB       BIT(9)
#define OWL_I2C_STAT_SRGC       BIT(10)

/* I2Cx_CMD Bit Mask */
#define OWL_I2C_CMD_SBE         BIT(0)
#define OWL_I2C_CMD_RBE         BIT(4)
#define OWL_I2C_CMD_DE          BIT(8)
#define OWL_I2C_CMD_NS          BIT(9)
#define OWL_I2C_CMD_SE          BIT(10)
#define OWL_I2C_CMD_MSS         BIT(11)
#define OWL_I2C_CMD_WRS         BIT(12)
#define OWL_I2C_CMD_SECL        BIT(15)

#define OWL_I2C_CMD_AS(x)       (((x) & 0x7) << 1)
#define OWL_I2C_CMD_SAS(x)      (((x) & 0x7) << 5)

/* I2Cx_FIFOCTL Bit Mask */
#define OWL_I2C_FIFOCTL_NIB     BIT(0)
#define OWL_I2C_FIFOCTL_RFR     BIT(1)
#define OWL_I2C_FIFOCTL_TFR     BIT(2)

/* I2Cc_FIFOSTAT Bit Mask */
#define OWL_I2C_FIFOSTAT_CECB   BIT(0)
#define OWL_I2C_FIFOSTAT_RNB    BIT(1)
#define OWL_I2C_FIFOSTAT_RFE    BIT(2)
#define OWL_I2C_FIFOSTAT_TFF    BIT(5)
#define OWL_I2C_FIFOSTAT_TFD    GENMASK(23, 16)
#define OWL_I2C_FIFOSTAT_RFD    GENMASK(15, 8)

/* I2C bus timeout */
#define OWL_I2C_TIMEOUT_MS      (4 * 1000)
#define OWL_I2C_TIMEOUT         msecs_to_jiffies(OWL_I2C_TIMEOUT_MS)

#define OWL_I2C_MAX_RETRIES     50

struct owl_i2c_dev {
        struct i2c_adapter      adap;
        struct i2c_msg          *msg;
        struct completion       msg_complete;
        struct clk              *clk;
        spinlock_t              lock;
        void __iomem            *base;
        unsigned long           clk_rate;
        u32                     bus_freq;
        u32                     msg_ptr;
        int                     err;
};

static void owl_i2c_update_reg(void __iomem *reg, unsigned int val, bool state)
{
        unsigned int regval;

        regval = readl(reg);

        if (state)
                regval |= val;
        else
                regval &= ~val;

        writel(regval, reg);
}

static void owl_i2c_reset(struct owl_i2c_dev *i2c_dev)
{
        owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
                           OWL_I2C_CTL_EN, false);
        mdelay(1);
        owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
                           OWL_I2C_CTL_EN, true);

        /* Clear status registers */
        writel(0, i2c_dev->base + OWL_I2C_REG_STAT);
}

static int owl_i2c_reset_fifo(struct owl_i2c_dev *i2c_dev)
{
        unsigned int val, timeout = 0;

        /* Reset FIFO */
        owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
                           OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR,
                           true);

        /* Wait 50ms for FIFO reset complete */
        do {
                val = readl(i2c_dev->base + OWL_I2C_REG_FIFOCTL);
                if (!(val & (OWL_I2C_FIFOCTL_RFR | OWL_I2C_FIFOCTL_TFR)))
                        break;
                usleep_range(500, 1000);
        } while (timeout++ < OWL_I2C_MAX_RETRIES);

        if (timeout > OWL_I2C_MAX_RETRIES) {
                dev_err(&i2c_dev->adap.dev, "FIFO reset timeout\n");
                return -ETIMEDOUT;
        }

        return 0;
}

static void owl_i2c_set_freq(struct owl_i2c_dev *i2c_dev)
{
        unsigned int val;

        val = DIV_ROUND_UP(i2c_dev->clk_rate, i2c_dev->bus_freq * 16);

        /* Set clock divider factor */
        writel(OWL_I2C_DIV_FACTOR(val), i2c_dev->base + OWL_I2C_REG_CLKDIV);
}

static void owl_i2c_xfer_data(struct owl_i2c_dev *i2c_dev)
{
        struct i2c_msg *msg = i2c_dev->msg;
        unsigned int stat, fifostat;

        i2c_dev->err = 0;

        /* Handle NACK from target */
        fifostat = readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT);
        if (fifostat & OWL_I2C_FIFOSTAT_RNB) {
                i2c_dev->err = -ENXIO;
                /* Clear NACK error bit by writing "1" */
                owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOSTAT,
                                   OWL_I2C_FIFOSTAT_RNB, true);
                return;
        }

        /* Handle bus error */
        stat = readl(i2c_dev->base + OWL_I2C_REG_STAT);
        if (stat & OWL_I2C_STAT_BEB) {
                i2c_dev->err = -EIO;
                /* Clear BUS error bit by writing "1" */
                owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_STAT,
                                   OWL_I2C_STAT_BEB, true);
                return;
        }

        /* Handle FIFO read */
        if (msg->flags & I2C_M_RD) {
                while ((readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
                        OWL_I2C_FIFOSTAT_RFE) && i2c_dev->msg_ptr < msg->len) {
                        msg->buf[i2c_dev->msg_ptr++] = readl(i2c_dev->base +
                                                             OWL_I2C_REG_RXDAT);
                }
        } else {
                /* Handle the remaining bytes which were not sent */
                while (!(readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
                         OWL_I2C_FIFOSTAT_TFF) && i2c_dev->msg_ptr < msg->len) {
                        writel(msg->buf[i2c_dev->msg_ptr++],
                               i2c_dev->base + OWL_I2C_REG_TXDAT);
                }
        }
}

static irqreturn_t owl_i2c_interrupt(int irq, void *_dev)
{
        struct owl_i2c_dev *i2c_dev = _dev;

        spin_lock(&i2c_dev->lock);

        owl_i2c_xfer_data(i2c_dev);

        /* Clear pending interrupts */
        owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_STAT,
                           OWL_I2C_STAT_IRQP, true);

        complete_all(&i2c_dev->msg_complete);
        spin_unlock(&i2c_dev->lock);

        return IRQ_HANDLED;
}

static u32 owl_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static int owl_i2c_check_bus_busy(struct i2c_adapter *adap)
{
        struct owl_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
        unsigned long timeout;

        /* Check for Bus busy */
        timeout = jiffies + OWL_I2C_TIMEOUT;
        while (readl(i2c_dev->base + OWL_I2C_REG_STAT) & OWL_I2C_STAT_BBB) {
                if (time_after(jiffies, timeout)) {
                        dev_err(&adap->dev, "Bus busy timeout\n");
                        return -ETIMEDOUT;
                }
        }

        return 0;
}

static int owl_i2c_xfer_common(struct i2c_adapter *adap, struct i2c_msg *msgs,
                               int num, bool atomic)
{
        struct owl_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
        struct i2c_msg *msg;
        unsigned long time_left, flags;
        unsigned int i2c_cmd, val;
        unsigned int addr;
        int ret, idx;

        spin_lock_irqsave(&i2c_dev->lock, flags);

        /* Reset I2C controller */
        owl_i2c_reset(i2c_dev);

        /* Set bus frequency */
        owl_i2c_set_freq(i2c_dev);

        /*
         * Spinlock should be released before calling reset FIFO and
         * bus busy check since those functions may sleep
         */
        spin_unlock_irqrestore(&i2c_dev->lock, flags);

        /* Reset FIFO */
        ret = owl_i2c_reset_fifo(i2c_dev);
        if (ret)
                goto unlocked_err_exit;

        /* Check for bus busy */
        ret = owl_i2c_check_bus_busy(adap);
        if (ret)
                goto unlocked_err_exit;

        spin_lock_irqsave(&i2c_dev->lock, flags);

        /* Check for Arbitration lost */
        val = readl(i2c_dev->base + OWL_I2C_REG_STAT);
        if (val & OWL_I2C_STAT_LAB) {
                val &= ~OWL_I2C_STAT_LAB;
                writel(val, i2c_dev->base + OWL_I2C_REG_STAT);
                ret = -EAGAIN;
                goto err_exit;
        }

        if (!atomic)
                reinit_completion(&i2c_dev->msg_complete);

        /* Enable/disable I2C controller interrupt */
        owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
                           OWL_I2C_CTL_IRQE, !atomic);

        /*
         * Select: FIFO enable, controller mode, Stop enable, Data count enable,
         * Send start bit
         */
        i2c_cmd = OWL_I2C_CMD_SECL | OWL_I2C_CMD_MSS | OWL_I2C_CMD_SE |
                  OWL_I2C_CMD_NS | OWL_I2C_CMD_DE | OWL_I2C_CMD_SBE;

        /* Handle repeated start condition */
        if (num > 1) {
                /* Set internal address length and enable repeated start */
                i2c_cmd |= OWL_I2C_CMD_AS(msgs[0].len + 1) |
                           OWL_I2C_CMD_SAS(1) | OWL_I2C_CMD_RBE;

                /* Write target address */
                addr = i2c_8bit_addr_from_msg(&msgs[0]);
                writel(addr, i2c_dev->base + OWL_I2C_REG_TXDAT);

                /* Write internal register address */
                for (idx = 0; idx < msgs[0].len; idx++)
                        writel(msgs[0].buf[idx],
                               i2c_dev->base + OWL_I2C_REG_TXDAT);

                msg = &msgs[1];
        } else {
                /* Set address length */
                i2c_cmd |= OWL_I2C_CMD_AS(1);
                msg = &msgs[0];
        }

        i2c_dev->msg = msg;
        i2c_dev->msg_ptr = 0;

        /* Set data count for the message */
        writel(msg->len, i2c_dev->base + OWL_I2C_REG_DATCNT);

        addr = i2c_8bit_addr_from_msg(msg);
        writel(addr, i2c_dev->base + OWL_I2C_REG_TXDAT);

        if (!(msg->flags & I2C_M_RD)) {
                /* Write data to FIFO */
                for (idx = 0; idx < msg->len; idx++) {
                        /* Check for FIFO full */
                        if (readl(i2c_dev->base + OWL_I2C_REG_FIFOSTAT) &
                            OWL_I2C_FIFOSTAT_TFF)
                                break;

                        writel(msg->buf[idx],
                               i2c_dev->base + OWL_I2C_REG_TXDAT);
                }

                i2c_dev->msg_ptr = idx;
        }

        /* Ignore the NACK if needed */
        if (msg->flags & I2C_M_IGNORE_NAK)
                owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
                                   OWL_I2C_FIFOCTL_NIB, true);
        else
                owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_FIFOCTL,
                                   OWL_I2C_FIFOCTL_NIB, false);

        /* Start the transfer */
        writel(i2c_cmd, i2c_dev->base + OWL_I2C_REG_CMD);

        spin_unlock_irqrestore(&i2c_dev->lock, flags);

        if (atomic) {
                /* Wait for Command Execute Completed or NACK Error bits */
                ret = readl_poll_timeout_atomic(i2c_dev->base + OWL_I2C_REG_FIFOSTAT,
                                                val, val & (OWL_I2C_FIFOSTAT_CECB |
                                                            OWL_I2C_FIFOSTAT_RNB),
                                                10, OWL_I2C_TIMEOUT_MS * 1000);
        } else {
                time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
                                                        adap->timeout);
                if (!time_left)
                        ret = -ETIMEDOUT;
        }

        spin_lock_irqsave(&i2c_dev->lock, flags);

        if (ret) {
                dev_err(&adap->dev, "Transaction timed out\n");
                /* Send stop condition and release the bus */
                owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
                                   OWL_I2C_CTL_GBCC_STOP | OWL_I2C_CTL_RB,
                                   true);
                goto err_exit;
        }

        if (atomic)
                owl_i2c_xfer_data(i2c_dev);

        ret = i2c_dev->err < 0 ? i2c_dev->err : num;

err_exit:
        spin_unlock_irqrestore(&i2c_dev->lock, flags);

unlocked_err_exit:
        /* Disable I2C controller */
        owl_i2c_update_reg(i2c_dev->base + OWL_I2C_REG_CTL,
                           OWL_I2C_CTL_EN, false);

        return ret;
}

static int owl_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                        int num)
{
        return owl_i2c_xfer_common(adap, msgs, num, false);
}

static int owl_i2c_xfer_atomic(struct i2c_adapter *adap,
                               struct i2c_msg *msgs, int num)
{
        return owl_i2c_xfer_common(adap, msgs, num, true);
}

static const struct i2c_algorithm owl_i2c_algorithm = {
        .xfer = owl_i2c_xfer,
        .xfer_atomic = owl_i2c_xfer_atomic,
        .functionality = owl_i2c_func,
};

static const struct i2c_adapter_quirks owl_i2c_quirks = {
        .flags          = I2C_AQ_COMB | I2C_AQ_COMB_WRITE_FIRST,
        .max_read_len   = 240,
        .max_write_len  = 240,
        .max_comb_1st_msg_len = 6,
        .max_comb_2nd_msg_len = 240,
};

static int owl_i2c_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        struct owl_i2c_dev *i2c_dev;
        int ret, irq;

        i2c_dev = devm_kzalloc(dev, sizeof(*i2c_dev), GFP_KERNEL);
        if (!i2c_dev)
                return -ENOMEM;

        i2c_dev->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(i2c_dev->base))
                return PTR_ERR(i2c_dev->base);

        irq = platform_get_irq(pdev, 0);
        if (irq < 0)
                return irq;

        if (of_property_read_u32(dev->of_node, "clock-frequency",
                                 &i2c_dev->bus_freq))
                i2c_dev->bus_freq = I2C_MAX_STANDARD_MODE_FREQ;

        /* We support only frequencies of 100k and 400k for now */
        if (i2c_dev->bus_freq != I2C_MAX_STANDARD_MODE_FREQ &&
            i2c_dev->bus_freq != I2C_MAX_FAST_MODE_FREQ) {
                dev_err(dev, "invalid clock-frequency %d\n", i2c_dev->bus_freq);
                return -EINVAL;
        }

        i2c_dev->clk = devm_clk_get_enabled(dev, NULL);
        if (IS_ERR(i2c_dev->clk)) {
                dev_err(dev, "failed to enable clock\n");
                return PTR_ERR(i2c_dev->clk);
        }

        i2c_dev->clk_rate = clk_get_rate(i2c_dev->clk);
        if (!i2c_dev->clk_rate) {
                dev_err(dev, "input clock rate should not be zero\n");
                return -EINVAL;
        }

        init_completion(&i2c_dev->msg_complete);
        spin_lock_init(&i2c_dev->lock);
        i2c_dev->adap.owner = THIS_MODULE;
        i2c_dev->adap.algo = &owl_i2c_algorithm;
        i2c_dev->adap.timeout = OWL_I2C_TIMEOUT;
        i2c_dev->adap.quirks = &owl_i2c_quirks;
        i2c_dev->adap.dev.parent = dev;
        i2c_dev->adap.dev.of_node = dev->of_node;
        snprintf(i2c_dev->adap.name, sizeof(i2c_dev->adap.name),
                 "%s", "OWL I2C adapter");
        i2c_set_adapdata(&i2c_dev->adap, i2c_dev);

        platform_set_drvdata(pdev, i2c_dev);

        ret = devm_request_irq(dev, irq, owl_i2c_interrupt, 0, pdev->name,
                               i2c_dev);
        if (ret) {
                dev_err(dev, "failed to request irq %d\n", irq);
                return ret;
        }

        return i2c_add_adapter(&i2c_dev->adap);
}

static const struct of_device_id owl_i2c_of_match[] = {
        { .compatible = "actions,s500-i2c" },
        { .compatible = "actions,s700-i2c" },
        { .compatible = "actions,s900-i2c" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, owl_i2c_of_match);

static struct platform_driver owl_i2c_driver = {
        .probe          = owl_i2c_probe,
        .driver         = {
                .name   = "owl-i2c",
                .of_match_table = owl_i2c_of_match,
                .probe_type = PROBE_PREFER_ASYNCHRONOUS,
        },
};
module_platform_driver(owl_i2c_driver);

MODULE_AUTHOR("David Liu <liuwei@actions-semi.com>");
MODULE_AUTHOR("Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>");
MODULE_DESCRIPTION("Actions Semiconductor Owl SoC's I2C driver");
MODULE_LICENSE("GPL");