/*
 * Copyright (c) 2014 Linaro Ltd.
 * Copyright (c) 2014 Hisilicon Limited.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Now only support 7 bit address.
 */

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

/* Register Map */
#define HIX5I2C_CTRL		0x00
#define HIX5I2C_COM		0x04
#define HIX5I2C_ICR		0x08
#define HIX5I2C_SR		0x0c
#define HIX5I2C_SCL_H		0x10
#define HIX5I2C_SCL_L		0x14
#define HIX5I2C_TXR		0x18
#define HIX5I2C_RXR		0x1c

/* I2C_CTRL_REG */
#define I2C_ENABLE		BIT(8)
#define I2C_UNMASK_TOTAL	BIT(7)
#define I2C_UNMASK_START	BIT(6)
#define I2C_UNMASK_END		BIT(5)
#define I2C_UNMASK_SEND		BIT(4)
#define I2C_UNMASK_RECEIVE	BIT(3)
#define I2C_UNMASK_ACK		BIT(2)
#define I2C_UNMASK_ARBITRATE	BIT(1)
#define I2C_UNMASK_OVER		BIT(0)
#define I2C_UNMASK_ALL		(I2C_UNMASK_ACK | I2C_UNMASK_OVER)

/* I2C_COM_REG */
#define I2C_NO_ACK		BIT(4)
#define I2C_START		BIT(3)
#define I2C_READ		BIT(2)
#define I2C_WRITE		BIT(1)
#define I2C_STOP		BIT(0)

/* I2C_ICR_REG */
#define I2C_CLEAR_START		BIT(6)
#define I2C_CLEAR_END		BIT(5)
#define I2C_CLEAR_SEND		BIT(4)
#define I2C_CLEAR_RECEIVE	BIT(3)
#define I2C_CLEAR_ACK		BIT(2)
#define I2C_CLEAR_ARBITRATE	BIT(1)
#define I2C_CLEAR_OVER		BIT(0)
#define I2C_CLEAR_ALL		(I2C_CLEAR_START | I2C_CLEAR_END | \
				I2C_CLEAR_SEND | I2C_CLEAR_RECEIVE | \
				I2C_CLEAR_ACK | I2C_CLEAR_ARBITRATE | \
				I2C_CLEAR_OVER)

/* I2C_SR_REG */
#define I2C_BUSY		BIT(7)
#define I2C_START_INTR		BIT(6)
#define I2C_END_INTR		BIT(5)
#define I2C_SEND_INTR		BIT(4)
#define I2C_RECEIVE_INTR	BIT(3)
#define I2C_ACK_INTR		BIT(2)
#define I2C_ARBITRATE_INTR	BIT(1)
#define I2C_OVER_INTR		BIT(0)

#define HIX5I2C_MAX_FREQ	400000		/* 400k */

enum hix5hd2_i2c_state {
	HIX5I2C_STAT_RW_ERR = -1,
	HIX5I2C_STAT_INIT,
	HIX5I2C_STAT_RW,
	HIX5I2C_STAT_SND_STOP,
	HIX5I2C_STAT_RW_SUCCESS,
};

struct hix5hd2_i2c_priv {
	struct i2c_adapter adap;
	struct i2c_msg *msg;
	struct completion msg_complete;
	unsigned int msg_idx;
	unsigned int msg_len;
	int stop;
	void __iomem *regs;
	struct clk *clk;
	struct device *dev;
	spinlock_t lock;	/* IRQ synchronization */
	int err;
	unsigned int freq;
	enum hix5hd2_i2c_state state;
};

static u32 hix5hd2_i2c_clr_pend_irq(struct hix5hd2_i2c_priv *priv)
{
	u32 val = readl_relaxed(priv->regs + HIX5I2C_SR);

	writel_relaxed(val, priv->regs + HIX5I2C_ICR);

	return val;
}

static void hix5hd2_i2c_clr_all_irq(struct hix5hd2_i2c_priv *priv)
{
	writel_relaxed(I2C_CLEAR_ALL, priv->regs + HIX5I2C_ICR);
}

static void hix5hd2_i2c_disable_irq(struct hix5hd2_i2c_priv *priv)
{
	writel_relaxed(0, priv->regs + HIX5I2C_CTRL);
}

static void hix5hd2_i2c_enable_irq(struct hix5hd2_i2c_priv *priv)
{
	writel_relaxed(I2C_ENABLE | I2C_UNMASK_TOTAL | I2C_UNMASK_ALL,
		       priv->regs + HIX5I2C_CTRL);
}

static void hix5hd2_i2c_drv_setrate(struct hix5hd2_i2c_priv *priv)
{
	u32 rate, val;
	u32 scl, sysclock;

	/* close all i2c interrupt */
	val = readl_relaxed(priv->regs + HIX5I2C_CTRL);
	writel_relaxed(val & (~I2C_UNMASK_TOTAL), priv->regs + HIX5I2C_CTRL);

	rate = priv->freq;
	sysclock = clk_get_rate(priv->clk);
	scl = (sysclock / (rate * 2)) / 2 - 1;
	writel_relaxed(scl, priv->regs + HIX5I2C_SCL_H);
	writel_relaxed(scl, priv->regs + HIX5I2C_SCL_L);

	/* restore original interrupt*/
	writel_relaxed(val, priv->regs + HIX5I2C_CTRL);

	dev_dbg(priv->dev, "%s: sysclock=%d, rate=%d, scl=%d\n",
		__func__, sysclock, rate, scl);
}

static void hix5hd2_i2c_init(struct hix5hd2_i2c_priv *priv)
{
	hix5hd2_i2c_disable_irq(priv);
	hix5hd2_i2c_drv_setrate(priv);
	hix5hd2_i2c_clr_all_irq(priv);
	hix5hd2_i2c_enable_irq(priv);
}

static void hix5hd2_i2c_reset(struct hix5hd2_i2c_priv *priv)
{
	clk_disable_unprepare(priv->clk);
	msleep(20);
	clk_prepare_enable(priv->clk);
	hix5hd2_i2c_init(priv);
}

static int hix5hd2_i2c_wait_bus_idle(struct hix5hd2_i2c_priv *priv)
{
	unsigned long stop_time;
	u32 int_status;

	/* wait for 100 milli seconds for the bus to be idle */
	stop_time = jiffies + msecs_to_jiffies(100);
	do {
		int_status = hix5hd2_i2c_clr_pend_irq(priv);
		if (!(int_status & I2C_BUSY))
			return 0;

		usleep_range(50, 200);
	} while (time_before(jiffies, stop_time));

	return -EBUSY;
}

static void hix5hd2_rw_over(struct hix5hd2_i2c_priv *priv)
{
	if (priv->state == HIX5I2C_STAT_SND_STOP)
		dev_dbg(priv->dev, "%s: rw and send stop over\n", __func__);
	else
		dev_dbg(priv->dev, "%s: have not data to send\n", __func__);

	priv->state = HIX5I2C_STAT_RW_SUCCESS;
	priv->err = 0;
}

static void hix5hd2_rw_handle_stop(struct hix5hd2_i2c_priv *priv)
{
	if (priv->stop) {
		priv->state = HIX5I2C_STAT_SND_STOP;
		writel_relaxed(I2C_STOP, priv->regs + HIX5I2C_COM);
	} else {
		hix5hd2_rw_over(priv);
	}
}

static void hix5hd2_read_handle(struct hix5hd2_i2c_priv *priv)
{
	if (priv->msg_len == 1) {
		/* the last byte don't need send ACK */
		writel_relaxed(I2C_READ | I2C_NO_ACK, priv->regs + HIX5I2C_COM);
	} else if (priv->msg_len > 1) {
		/* if i2c master receive data will send ACK */
		writel_relaxed(I2C_READ, priv->regs + HIX5I2C_COM);
	} else {
		hix5hd2_rw_handle_stop(priv);
	}
}

static void hix5hd2_write_handle(struct hix5hd2_i2c_priv *priv)
{
	u8 data;

	if (priv->msg_len > 0) {
		data = priv->msg->buf[priv->msg_idx++];
		writel_relaxed(data, priv->regs + HIX5I2C_TXR);
		writel_relaxed(I2C_WRITE, priv->regs + HIX5I2C_COM);
	} else {
		hix5hd2_rw_handle_stop(priv);
	}
}

static int hix5hd2_rw_preprocess(struct hix5hd2_i2c_priv *priv)
{
	u8 data;

	if (priv->state == HIX5I2C_STAT_INIT) {
		priv->state = HIX5I2C_STAT_RW;
	} else if (priv->state == HIX5I2C_STAT_RW) {
		if (priv->msg->flags & I2C_M_RD) {
			data = readl_relaxed(priv->regs + HIX5I2C_RXR);
			priv->msg->buf[priv->msg_idx++] = data;
		}
		priv->msg_len--;
	} else {
		dev_dbg(priv->dev, "%s: error: priv->state = %d, msg_len = %d\n",
			__func__, priv->state, priv->msg_len);
		return -EAGAIN;
	}
	return 0;
}

static irqreturn_t hix5hd2_i2c_irq(int irqno, void *dev_id)
{
	struct hix5hd2_i2c_priv *priv = dev_id;
	u32 int_status;
	int ret;

	spin_lock(&priv->lock);

	int_status = hix5hd2_i2c_clr_pend_irq(priv);

	/* handle error */
	if (int_status & I2C_ARBITRATE_INTR) {
		/* bus error */
		dev_dbg(priv->dev, "ARB bus loss\n");
		priv->err = -EAGAIN;
		priv->state = HIX5I2C_STAT_RW_ERR;
		goto stop;
	} else if (int_status & I2C_ACK_INTR) {
		/* ack error */
		dev_dbg(priv->dev, "No ACK from device\n");
		priv->err = -ENXIO;
		priv->state = HIX5I2C_STAT_RW_ERR;
		goto stop;
	}

	if (int_status & I2C_OVER_INTR) {
		if (priv->msg_len > 0) {
			ret = hix5hd2_rw_preprocess(priv);
			if (ret) {
				priv->err = ret;
				priv->state = HIX5I2C_STAT_RW_ERR;
				goto stop;
			}
			if (priv->msg->flags & I2C_M_RD)
				hix5hd2_read_handle(priv);
			else
				hix5hd2_write_handle(priv);
		} else {
			hix5hd2_rw_over(priv);
		}
	}

stop:
	if ((priv->state == HIX5I2C_STAT_RW_SUCCESS &&
	     priv->msg->len == priv->msg_idx) ||
	    (priv->state == HIX5I2C_STAT_RW_ERR)) {
		hix5hd2_i2c_disable_irq(priv);
		hix5hd2_i2c_clr_pend_irq(priv);
		complete(&priv->msg_complete);
	}

	spin_unlock(&priv->lock);

	return IRQ_HANDLED;
}

static void hix5hd2_i2c_message_start(struct hix5hd2_i2c_priv *priv, int stop)
{
	unsigned long flags;

	spin_lock_irqsave(&priv->lock, flags);
	hix5hd2_i2c_clr_all_irq(priv);
	hix5hd2_i2c_enable_irq(priv);

	writel_relaxed(i2c_8bit_addr_from_msg(priv->msg),
		       priv->regs + HIX5I2C_TXR);

	writel_relaxed(I2C_WRITE | I2C_START, priv->regs + HIX5I2C_COM);
	spin_unlock_irqrestore(&priv->lock, flags);
}

static int hix5hd2_i2c_xfer_msg(struct hix5hd2_i2c_priv *priv,
				struct i2c_msg *msgs, int stop)
{
	unsigned long timeout;
	int ret;

	priv->msg = msgs;
	priv->msg_idx = 0;
	priv->msg_len = priv->msg->len;
	priv->stop = stop;
	priv->err = 0;
	priv->state = HIX5I2C_STAT_INIT;

	reinit_completion(&priv->msg_complete);
	hix5hd2_i2c_message_start(priv, stop);

	timeout = wait_for_completion_timeout(&priv->msg_complete,
					      priv->adap.timeout);
	if (timeout == 0) {
		priv->state = HIX5I2C_STAT_RW_ERR;
		priv->err = -ETIMEDOUT;
		dev_warn(priv->dev, "%s timeout=%d\n",
			 msgs->flags & I2C_M_RD ? "rx" : "tx",
			 priv->adap.timeout);
	}
	ret = priv->state;

	/*
	 * If this is the last message to be transfered (stop == 1)
	 * Then check if the bus can be brought back to idle.
	 */
	if (priv->state == HIX5I2C_STAT_RW_SUCCESS && stop)
		ret = hix5hd2_i2c_wait_bus_idle(priv);

	if (ret < 0)
		hix5hd2_i2c_reset(priv);

	return priv->err;
}

static int hix5hd2_i2c_xfer(struct i2c_adapter *adap,
			    struct i2c_msg *msgs, int num)
{
	struct hix5hd2_i2c_priv *priv = i2c_get_adapdata(adap);
	int i, ret, stop;

	pm_runtime_get_sync(priv->dev);

	for (i = 0; i < num; i++, msgs++) {
		stop = (i == num - 1);
		ret = hix5hd2_i2c_xfer_msg(priv, msgs, stop);
		if (ret < 0)
			goto out;
	}

	ret = num;

out:
	pm_runtime_mark_last_busy(priv->dev);
	pm_runtime_put_autosuspend(priv->dev);
	return ret;
}

static u32 hix5hd2_i2c_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
}

static const struct i2c_algorithm hix5hd2_i2c_algorithm = {
	.master_xfer		= hix5hd2_i2c_xfer,
	.functionality		= hix5hd2_i2c_func,
};

static int hix5hd2_i2c_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct hix5hd2_i2c_priv *priv;
	struct resource *mem;
	unsigned int freq;
	int irq, ret;

	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	if (of_property_read_u32(np, "clock-frequency", &freq)) {
		/* use 100k as default value */
		priv->freq = 100000;
	} else {
		if (freq > HIX5I2C_MAX_FREQ) {
			priv->freq = HIX5I2C_MAX_FREQ;
			dev_warn(priv->dev, "use max freq %d instead\n",
				 HIX5I2C_MAX_FREQ);
		} else {
			priv->freq = freq;
		}
	}

	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	priv->regs = devm_ioremap_resource(&pdev->dev, mem);
	if (IS_ERR(priv->regs))
		return PTR_ERR(priv->regs);

	irq = platform_get_irq(pdev, 0);
	if (irq <= 0) {
		dev_err(&pdev->dev, "cannot find HS-I2C IRQ\n");
		return irq;
	}

	priv->clk = devm_clk_get(&pdev->dev, NULL);
	if (IS_ERR(priv->clk)) {
		dev_err(&pdev->dev, "cannot get clock\n");
		return PTR_ERR(priv->clk);
	}
	clk_prepare_enable(priv->clk);

	strlcpy(priv->adap.name, "hix5hd2-i2c", sizeof(priv->adap.name));
	priv->dev = &pdev->dev;
	priv->adap.owner = THIS_MODULE;
	priv->adap.algo = &hix5hd2_i2c_algorithm;
	priv->adap.retries = 3;
	priv->adap.dev.of_node = np;
	priv->adap.algo_data = priv;
	priv->adap.dev.parent = &pdev->dev;
	i2c_set_adapdata(&priv->adap, priv);
	platform_set_drvdata(pdev, priv);
	spin_lock_init(&priv->lock);
	init_completion(&priv->msg_complete);

	hix5hd2_i2c_init(priv);

	ret = devm_request_irq(&pdev->dev, irq, hix5hd2_i2c_irq,
			       IRQF_NO_SUSPEND | IRQF_ONESHOT,
			       dev_name(&pdev->dev), priv);
	if (ret != 0) {
		dev_err(&pdev->dev, "cannot request HS-I2C IRQ %d\n", irq);
		goto err_clk;
	}

	pm_runtime_set_autosuspend_delay(priv->dev, MSEC_PER_SEC);
	pm_runtime_use_autosuspend(priv->dev);
	pm_runtime_set_active(priv->dev);
	pm_runtime_enable(priv->dev);

	ret = i2c_add_adapter(&priv->adap);
	if (ret < 0)
		goto err_runtime;

	return ret;

err_runtime:
	pm_runtime_disable(priv->dev);
	pm_runtime_set_suspended(priv->dev);
err_clk:
	clk_disable_unprepare(priv->clk);
	return ret;
}

static int hix5hd2_i2c_remove(struct platform_device *pdev)
{
	struct hix5hd2_i2c_priv *priv = platform_get_drvdata(pdev);

	i2c_del_adapter(&priv->adap);
	pm_runtime_disable(priv->dev);
	pm_runtime_set_suspended(priv->dev);
	clk_disable_unprepare(priv->clk);

	return 0;
}

#ifdef CONFIG_PM
static int hix5hd2_i2c_runtime_suspend(struct device *dev)
{
	struct hix5hd2_i2c_priv *priv = dev_get_drvdata(dev);

	clk_disable_unprepare(priv->clk);

	return 0;
}

static int hix5hd2_i2c_runtime_resume(struct device *dev)
{
	struct hix5hd2_i2c_priv *priv = dev_get_drvdata(dev);

	clk_prepare_enable(priv->clk);
	hix5hd2_i2c_init(priv);

	return 0;
}
#endif

static const struct dev_pm_ops hix5hd2_i2c_pm_ops = {
	SET_RUNTIME_PM_OPS(hix5hd2_i2c_runtime_suspend,
			      hix5hd2_i2c_runtime_resume,
			      NULL)
};

static const struct of_device_id hix5hd2_i2c_match[] = {
	{ .compatible = "hisilicon,hix5hd2-i2c" },
	{},
};
MODULE_DEVICE_TABLE(of, hix5hd2_i2c_match);

static struct platform_driver hix5hd2_i2c_driver = {
	.probe		= hix5hd2_i2c_probe,
	.remove		= hix5hd2_i2c_remove,
	.driver		= {
		.name	= "hix5hd2-i2c",
		.pm	= &hix5hd2_i2c_pm_ops,
		.of_match_table = hix5hd2_i2c_match,
	},
};

module_platform_driver(hix5hd2_i2c_driver);

MODULE_DESCRIPTION("Hix5hd2 I2C Bus driver");
MODULE_AUTHOR("Wei Yan <sledge.yanwei@huawei.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:hix5hd2-i2c");
