/*
   * 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 */
  #define HIX5I2C_READ_OPERATION	0x01
  
  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
  ",
  		__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
  ", __func__);
  	else
  		dev_dbg(priv->dev, "%s: have not data to send
  ", __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
  ",
  			__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
  ");
  		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
  ");
  		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);
  
  	if (priv->msg->flags & I2C_M_RD)
  		writel_relaxed((priv->msg->addr << 1) | HIX5I2C_READ_OPERATION,
  			       priv->regs + HIX5I2C_TXR);
  	else
  		writel_relaxed(priv->msg->addr << 1,
  			       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
  ",
  			 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;
  	}
  
  	if (i == num) {
  		ret = num;
  	} else {
  		/* Only one message, cannot access the device */
  		if (i == 1)
  			ret = -EREMOTEIO;
  		else
  			ret = i;
  
  		dev_warn(priv->dev, "xfer message failed
  ");
  	}
  
  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
  ",
  				 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
  ");
  		return irq;
  	}
  
  	priv->clk = devm_clk_get(&pdev->dev, NULL);
  	if (IS_ERR(priv->clk)) {
  		dev_err(&pdev->dev, "cannot get clock
  ");
  		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
  ", irq);
  		goto err_clk;
  	}
  
  	pm_suspend_ignore_children(&pdev->dev, true);
  	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) {
  		dev_err(&pdev->dev, "failed to add bus to i2c core
  ");
  		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);
  
  	return 0;
  }
  
  #ifdef CONFIG_PM
  static int hix5hd2_i2c_runtime_suspend(struct device *dev)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct hix5hd2_i2c_priv *priv = platform_get_drvdata(pdev);
  
  	clk_disable_unprepare(priv->clk);
  
  	return 0;
  }
  
  static int hix5hd2_i2c_runtime_resume(struct device *dev)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  	struct hix5hd2_i2c_priv *priv = platform_get_drvdata(pdev);
  
  	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");