/*
 * I2C bus driver for CSR SiRFprimaII
 *
 * Copyright (c) 2011 Cambridge Silicon Radio Limited, a CSR plc group company.
 *
 * Licensed under GPLv2 or later.
 */

#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>

#define SIRFSOC_I2C_CLK_CTRL            0x00
#define SIRFSOC_I2C_STATUS              0x0C
#define SIRFSOC_I2C_CTRL                0x10
#define SIRFSOC_I2C_IO_CTRL             0x14
#define SIRFSOC_I2C_SDA_DELAY           0x18
#define SIRFSOC_I2C_CMD_START           0x1C
#define SIRFSOC_I2C_CMD_BUF             0x30
#define SIRFSOC_I2C_DATA_BUF            0x80

#define SIRFSOC_I2C_CMD_BUF_MAX         16
#define SIRFSOC_I2C_DATA_BUF_MAX        16

#define SIRFSOC_I2C_CMD(x)              (SIRFSOC_I2C_CMD_BUF + (x)*0x04)
#define SIRFSOC_I2C_DATA_MASK(x)        (0xFF<<(((x)&3)*8))
#define SIRFSOC_I2C_DATA_SHIFT(x)       (((x)&3)*8)

#define SIRFSOC_I2C_DIV_MASK            (0xFFFF)

/* I2C status flags */
#define SIRFSOC_I2C_STAT_BUSY           BIT(0)
#define SIRFSOC_I2C_STAT_TIP            BIT(1)
#define SIRFSOC_I2C_STAT_NACK           BIT(2)
#define SIRFSOC_I2C_STAT_TR_INT         BIT(4)
#define SIRFSOC_I2C_STAT_STOP           BIT(6)
#define SIRFSOC_I2C_STAT_CMD_DONE       BIT(8)
#define SIRFSOC_I2C_STAT_ERR            BIT(9)
#define SIRFSOC_I2C_CMD_INDEX           (0x1F<<16)

/* I2C control flags */
#define SIRFSOC_I2C_RESET               BIT(0)
#define SIRFSOC_I2C_CORE_EN             BIT(1)
#define SIRFSOC_I2C_MASTER_MODE         BIT(2)
#define SIRFSOC_I2C_CMD_DONE_EN         BIT(11)
#define SIRFSOC_I2C_ERR_INT_EN          BIT(12)

#define SIRFSOC_I2C_SDA_DELAY_MASK      (0xFF)
#define SIRFSOC_I2C_SCLF_FILTER         (3<<8)

#define SIRFSOC_I2C_START_CMD           BIT(0)

#define SIRFSOC_I2C_CMD_RP(x)           ((x)&0x7)
#define SIRFSOC_I2C_NACK                BIT(3)
#define SIRFSOC_I2C_WRITE               BIT(4)
#define SIRFSOC_I2C_READ                BIT(5)
#define SIRFSOC_I2C_STOP                BIT(6)
#define SIRFSOC_I2C_START               BIT(7)

#define SIRFSOC_I2C_DEFAULT_SPEED 100000
#define SIRFSOC_I2C_ERR_NOACK      1
#define SIRFSOC_I2C_ERR_TIMEOUT    2

struct sirfsoc_i2c {
        void __iomem *base;
        struct clk *clk;
        u32 cmd_ptr;            /* Current position in CMD buffer */
        u8 *buf;                /* Buffer passed by user */
        u32 msg_len;            /* Message length */
        u32 finished_len;       /* number of bytes read/written */
        u32 read_cmd_len;       /* number of read cmd sent */
        int msg_read;           /* 1 indicates a read message */
        int err_status;         /* 1 indicates an error on bus */

        u32 sda_delay;          /* For suspend/resume */
        u32 clk_div;
        int last;               /* Last message in transfer, STOP cmd can be sent */

        struct completion done; /* indicates completion of message transfer */
        struct i2c_adapter adapter;
};

static void i2c_sirfsoc_read_data(struct sirfsoc_i2c *siic)
{
        u32 data = 0;
        int i;

        for (i = 0; i < siic->read_cmd_len; i++) {
                if (!(i & 0x3))
                        data = readl(siic->base + SIRFSOC_I2C_DATA_BUF + i);
                siic->buf[siic->finished_len++] =
                        (u8)((data & SIRFSOC_I2C_DATA_MASK(i)) >>
                                SIRFSOC_I2C_DATA_SHIFT(i));
        }
}

static void i2c_sirfsoc_queue_cmd(struct sirfsoc_i2c *siic)
{
        u32 regval;
        int i = 0;

        if (siic->msg_read) {
                while (((siic->finished_len + i) < siic->msg_len)
                                && (siic->cmd_ptr < SIRFSOC_I2C_CMD_BUF_MAX)) {
                        regval = SIRFSOC_I2C_READ | SIRFSOC_I2C_CMD_RP(0);
                        if (((siic->finished_len + i) ==
                                        (siic->msg_len - 1)) && siic->last)
                                regval |= SIRFSOC_I2C_STOP | SIRFSOC_I2C_NACK;
                        writel(regval,
                                siic->base + SIRFSOC_I2C_CMD(siic->cmd_ptr++));
                        i++;
                }

                siic->read_cmd_len = i;
        } else {
                while ((siic->cmd_ptr < SIRFSOC_I2C_CMD_BUF_MAX - 1)
                                && (siic->finished_len < siic->msg_len)) {
                        regval = SIRFSOC_I2C_WRITE | SIRFSOC_I2C_CMD_RP(0);
                        if ((siic->finished_len == (siic->msg_len - 1))
                                && siic->last)
                                regval |= SIRFSOC_I2C_STOP;
                        writel(regval,
                                siic->base + SIRFSOC_I2C_CMD(siic->cmd_ptr++));
                        writel(siic->buf[siic->finished_len++],
                                siic->base + SIRFSOC_I2C_CMD(siic->cmd_ptr++));
                }
        }
        siic->cmd_ptr = 0;

        /* Trigger the transfer */
        writel(SIRFSOC_I2C_START_CMD, siic->base + SIRFSOC_I2C_CMD_START);
}

static irqreturn_t i2c_sirfsoc_irq(int irq, void *dev_id)
{
        struct sirfsoc_i2c *siic = (struct sirfsoc_i2c *)dev_id;
        u32 i2c_stat = readl(siic->base + SIRFSOC_I2C_STATUS);

        if (i2c_stat & SIRFSOC_I2C_STAT_ERR) {
                /* Error conditions */
                siic->err_status = SIRFSOC_I2C_ERR_NOACK;
                writel(SIRFSOC_I2C_STAT_ERR, siic->base + SIRFSOC_I2C_STATUS);

                if (i2c_stat & SIRFSOC_I2C_STAT_NACK)
                        dev_dbg(&siic->adapter.dev, "ACK not received\n");
                else
                        dev_err(&siic->adapter.dev, "I2C error\n");

                /*
                 * Due to hardware ANOMALY, we need to reset I2C earlier after
                 * we get NOACK while accessing non-existing clients, otherwise
                 * we will get errors even we access existing clients later
                 */
                writel(readl(siic->base + SIRFSOC_I2C_CTRL) | SIRFSOC_I2C_RESET,
                                siic->base + SIRFSOC_I2C_CTRL);
                while (readl(siic->base + SIRFSOC_I2C_CTRL) & SIRFSOC_I2C_RESET)
                        cpu_relax();

                complete(&siic->done);
        } else if (i2c_stat & SIRFSOC_I2C_STAT_CMD_DONE) {
                /* CMD buffer execution complete */
                if (siic->msg_read)
                        i2c_sirfsoc_read_data(siic);
                if (siic->finished_len == siic->msg_len)
                        complete(&siic->done);
                else /* Fill a new CMD buffer for left data */
                        i2c_sirfsoc_queue_cmd(siic);

                writel(SIRFSOC_I2C_STAT_CMD_DONE, siic->base + SIRFSOC_I2C_STATUS);
        }

        return IRQ_HANDLED;
}

static void i2c_sirfsoc_set_address(struct sirfsoc_i2c *siic,
        struct i2c_msg *msg)
{
        unsigned char addr;
        u32 regval = SIRFSOC_I2C_START | SIRFSOC_I2C_CMD_RP(0) | SIRFSOC_I2C_WRITE;

        /* no data and last message -> add STOP */
        if (siic->last && (msg->len == 0))
                regval |= SIRFSOC_I2C_STOP;

        writel(regval, siic->base + SIRFSOC_I2C_CMD(siic->cmd_ptr++));

        addr = msg->addr << 1;  /* Generate address */
        if (msg->flags & I2C_M_RD)
                addr |= 1;

        /* Reverse direction bit */
        if (msg->flags & I2C_M_REV_DIR_ADDR)
                addr ^= 1;

        writel(addr, siic->base + SIRFSOC_I2C_CMD(siic->cmd_ptr++));
}

static int i2c_sirfsoc_xfer_msg(struct sirfsoc_i2c *siic, struct i2c_msg *msg)
{
        u32 regval = readl(siic->base + SIRFSOC_I2C_CTRL);
        /* timeout waiting for the xfer to finish or fail */
        int timeout = msecs_to_jiffies((msg->len + 1) * 50);

        i2c_sirfsoc_set_address(siic, msg);

        writel(regval | SIRFSOC_I2C_CMD_DONE_EN | SIRFSOC_I2C_ERR_INT_EN,
                siic->base + SIRFSOC_I2C_CTRL);
        i2c_sirfsoc_queue_cmd(siic);

        if (wait_for_completion_timeout(&siic->done, timeout) == 0) {
                siic->err_status = SIRFSOC_I2C_ERR_TIMEOUT;
                dev_err(&siic->adapter.dev, "Transfer timeout\n");
        }

        writel(regval & ~(SIRFSOC_I2C_CMD_DONE_EN | SIRFSOC_I2C_ERR_INT_EN),
                siic->base + SIRFSOC_I2C_CTRL);
        writel(0, siic->base + SIRFSOC_I2C_CMD_START);

        /* i2c control doesn't response, reset it */
        if (siic->err_status == SIRFSOC_I2C_ERR_TIMEOUT) {
                writel(readl(siic->base + SIRFSOC_I2C_CTRL) | SIRFSOC_I2C_RESET,
                        siic->base + SIRFSOC_I2C_CTRL);
                while (readl(siic->base + SIRFSOC_I2C_CTRL) & SIRFSOC_I2C_RESET)
                        cpu_relax();
        }
        return siic->err_status ? -EAGAIN : 0;
}

static u32 i2c_sirfsoc_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static int i2c_sirfsoc_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
        int num)
{
        struct sirfsoc_i2c *siic = adap->algo_data;
        int i, ret;

        clk_enable(siic->clk);

        for (i = 0; i < num; i++) {
                siic->buf = msgs[i].buf;
                siic->msg_len = msgs[i].len;
                siic->msg_read = !!(msgs[i].flags & I2C_M_RD);
                siic->err_status = 0;
                siic->cmd_ptr = 0;
                siic->finished_len = 0;
                siic->last = (i == (num - 1));

                ret = i2c_sirfsoc_xfer_msg(siic, &msgs[i]);
                if (ret) {
                        clk_disable(siic->clk);
                        return ret;
                }
        }

        clk_disable(siic->clk);
        return num;
}

/* I2C algorithms associated with this master controller driver */
static const struct i2c_algorithm i2c_sirfsoc_algo = {
        .master_xfer = i2c_sirfsoc_xfer,
        .functionality = i2c_sirfsoc_func,
};

static int i2c_sirfsoc_probe(struct platform_device *pdev)
{
        struct sirfsoc_i2c *siic;
        struct i2c_adapter *adap;
        struct resource *mem_res;
        struct clk *clk;
        int bitrate;
        int ctrl_speed;
        int irq;

        int err;
        u32 regval;

        clk = clk_get(&pdev->dev, NULL);
        if (IS_ERR(clk)) {
                err = PTR_ERR(clk);
                dev_err(&pdev->dev, "Clock get failed\n");
                goto err_get_clk;
        }

        err = clk_prepare(clk);
        if (err) {
                dev_err(&pdev->dev, "Clock prepare failed\n");
                goto err_clk_prep;
        }

        err = clk_enable(clk);
        if (err) {
                dev_err(&pdev->dev, "Clock enable failed\n");
                goto err_clk_en;
        }

        ctrl_speed = clk_get_rate(clk);

        siic = devm_kzalloc(&pdev->dev, sizeof(*siic), GFP_KERNEL);
        if (!siic) {
                err = -ENOMEM;
                goto out;
        }
        adap = &siic->adapter;
        adap->class = I2C_CLASS_DEPRECATED;

        mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        siic->base = devm_ioremap_resource(&pdev->dev, mem_res);
        if (IS_ERR(siic->base)) {
                err = PTR_ERR(siic->base);
                goto out;
        }

        irq = platform_get_irq(pdev, 0);
        if (irq < 0) {
                err = irq;
                goto out;
        }
        err = devm_request_irq(&pdev->dev, irq, i2c_sirfsoc_irq, 0,
                dev_name(&pdev->dev), siic);
        if (err)
                goto out;

        adap->algo = &i2c_sirfsoc_algo;
        adap->algo_data = siic;
        adap->retries = 3;

        adap->dev.of_node = pdev->dev.of_node;
        adap->dev.parent = &pdev->dev;
        adap->nr = pdev->id;

        strlcpy(adap->name, "sirfsoc-i2c", sizeof(adap->name));

        platform_set_drvdata(pdev, adap);
        init_completion(&siic->done);

        /* Controller Initalisation */

        writel(SIRFSOC_I2C_RESET, siic->base + SIRFSOC_I2C_CTRL);
        while (readl(siic->base + SIRFSOC_I2C_CTRL) & SIRFSOC_I2C_RESET)
                cpu_relax();
        writel(SIRFSOC_I2C_CORE_EN | SIRFSOC_I2C_MASTER_MODE,
                siic->base + SIRFSOC_I2C_CTRL);

        siic->clk = clk;

        err = of_property_read_u32(pdev->dev.of_node,
                "clock-frequency", &bitrate);
        if (err < 0)
                bitrate = SIRFSOC_I2C_DEFAULT_SPEED;

        /*
         * Due to some hardware design issues, we need to tune the formula.
         * Since i2c is open drain interface that allows the slave to
         * stall the transaction by holding the SCL line at '0', the RTL
         * implementation is waiting for SCL feedback from the pin after
         * setting it to High-Z ('1'). This wait adds to the high-time
         * interval counter few cycles of the input synchronization
         * (depending on the SCL_FILTER_REG field), and also the time it
         * takes for the board pull-up resistor to rise the SCL line.
         * For slow SCL settings these additions are negligible,
         * but they start to affect the speed when clock is set to faster
         * frequencies.
         * Through the actual tests, use the different user_div value(which
         * in the divider formular 'Fio / (Fi2c * user_div)') to adapt
         * the different ranges of i2c bus clock frequency, to make the SCL
         * more accurate.
         */
        if (bitrate <= 30000)
                regval = ctrl_speed / (bitrate * 5);
        else if (bitrate > 30000 && bitrate <= 280000)
                regval = (2 * ctrl_speed) / (bitrate * 11);
        else
                regval = ctrl_speed / (bitrate * 6);

        writel(regval, siic->base + SIRFSOC_I2C_CLK_CTRL);
        if (regval > 0xFF)
                writel(0xFF, siic->base + SIRFSOC_I2C_SDA_DELAY);
        else
                writel(regval, siic->base + SIRFSOC_I2C_SDA_DELAY);

        err = i2c_add_numbered_adapter(adap);
        if (err < 0) {
                dev_err(&pdev->dev, "Can't add new i2c adapter\n");
                goto out;
        }

        clk_disable(clk);

        dev_info(&pdev->dev, " I2C adapter ready to operate\n");

        return 0;

out:
        clk_disable(clk);
err_clk_en:
        clk_unprepare(clk);
err_clk_prep:
        clk_put(clk);
err_get_clk:
        return err;
}

static int i2c_sirfsoc_remove(struct platform_device *pdev)
{
        struct i2c_adapter *adapter = platform_get_drvdata(pdev);
        struct sirfsoc_i2c *siic = adapter->algo_data;

        writel(SIRFSOC_I2C_RESET, siic->base + SIRFSOC_I2C_CTRL);
        i2c_del_adapter(adapter);
        clk_unprepare(siic->clk);
        clk_put(siic->clk);
        return 0;
}

#ifdef CONFIG_PM
static int i2c_sirfsoc_suspend(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct i2c_adapter *adapter = platform_get_drvdata(pdev);
        struct sirfsoc_i2c *siic = adapter->algo_data;

        clk_enable(siic->clk);
        siic->sda_delay = readl(siic->base + SIRFSOC_I2C_SDA_DELAY);
        siic->clk_div = readl(siic->base + SIRFSOC_I2C_CLK_CTRL);
        clk_disable(siic->clk);
        return 0;
}

static int i2c_sirfsoc_resume(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct i2c_adapter *adapter = platform_get_drvdata(pdev);
        struct sirfsoc_i2c *siic = adapter->algo_data;

        clk_enable(siic->clk);
        writel(SIRFSOC_I2C_RESET, siic->base + SIRFSOC_I2C_CTRL);
        while (readl(siic->base + SIRFSOC_I2C_CTRL) & SIRFSOC_I2C_RESET)
                cpu_relax();
        writel(SIRFSOC_I2C_CORE_EN | SIRFSOC_I2C_MASTER_MODE,
                siic->base + SIRFSOC_I2C_CTRL);
        writel(siic->clk_div, siic->base + SIRFSOC_I2C_CLK_CTRL);
        writel(siic->sda_delay, siic->base + SIRFSOC_I2C_SDA_DELAY);
        clk_disable(siic->clk);
        return 0;
}

static const struct dev_pm_ops i2c_sirfsoc_pm_ops = {
        .suspend = i2c_sirfsoc_suspend,
        .resume = i2c_sirfsoc_resume,
};
#endif

static const struct of_device_id sirfsoc_i2c_of_match[] = {
        { .compatible = "sirf,prima2-i2c", },
        {},
};
MODULE_DEVICE_TABLE(of, sirfsoc_i2c_of_match);

static struct platform_driver i2c_sirfsoc_driver = {
        .driver = {
                .name = "sirfsoc_i2c",
#ifdef CONFIG_PM
                .pm = &i2c_sirfsoc_pm_ops,
#endif
                .of_match_table = sirfsoc_i2c_of_match,
        },
        .probe = i2c_sirfsoc_probe,
        .remove = i2c_sirfsoc_remove,
};
module_platform_driver(i2c_sirfsoc_driver);

MODULE_DESCRIPTION("SiRF SoC I2C master controller driver");
MODULE_AUTHOR("Zhiwu Song <Zhiwu.Song@csr.com>, "
        "Xiangzhen Ye <Xiangzhen.Ye@csr.com>");
MODULE_LICENSE("GPL v2");