/*
   * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
   *
   * 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.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #include <linux/clk.h>
  #include <linux/i2c.h>
  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  
  #define UNIPHIER_I2C_DTRM	0x00	/* TX register */
  #define     UNIPHIER_I2C_DTRM_IRQEN	BIT(11)	/* enable interrupt */
  #define     UNIPHIER_I2C_DTRM_STA	BIT(10)	/* start condition */
  #define     UNIPHIER_I2C_DTRM_STO	BIT(9)	/* stop condition */
  #define     UNIPHIER_I2C_DTRM_NACK	BIT(8)	/* do not return ACK */
  #define     UNIPHIER_I2C_DTRM_RD	BIT(0)	/* read transaction */
  #define UNIPHIER_I2C_DREC	0x04	/* RX register */
  #define     UNIPHIER_I2C_DREC_MST	BIT(14)	/* 1 = master, 0 = slave */
  #define     UNIPHIER_I2C_DREC_TX	BIT(13)	/* 1 = transmit, 0 = receive */
  #define     UNIPHIER_I2C_DREC_STS	BIT(12)	/* stop condition detected */
  #define     UNIPHIER_I2C_DREC_LRB	BIT(11)	/* no ACK */
  #define     UNIPHIER_I2C_DREC_LAB	BIT(9)	/* arbitration lost */
  #define     UNIPHIER_I2C_DREC_BBN	BIT(8)	/* bus not busy */
  #define UNIPHIER_I2C_MYAD	0x08	/* slave address */
  #define UNIPHIER_I2C_CLK	0x0c	/* clock frequency control */
  #define UNIPHIER_I2C_BRST	0x10	/* bus reset */
  #define     UNIPHIER_I2C_BRST_FOEN	BIT(1)	/* normal operation */
  #define     UNIPHIER_I2C_BRST_RSCL	BIT(0)	/* release SCL */
  #define UNIPHIER_I2C_HOLD	0x14	/* hold time control */
  #define UNIPHIER_I2C_BSTS	0x18	/* bus status monitor */
  #define     UNIPHIER_I2C_BSTS_SDA	BIT(1)	/* readback of SDA line */
  #define     UNIPHIER_I2C_BSTS_SCL	BIT(0)	/* readback of SCL line */
  #define UNIPHIER_I2C_NOISE	0x1c	/* noise filter control */
  #define UNIPHIER_I2C_SETUP	0x20	/* setup time control */
  
  #define UNIPHIER_I2C_DEFAULT_SPEED	100000
  #define UNIPHIER_I2C_MAX_SPEED		400000
  
  struct uniphier_i2c_priv {
  	struct completion comp;
  	struct i2c_adapter adap;
  	void __iomem *membase;
  	struct clk *clk;
  	unsigned int busy_cnt;
  };
  
  static irqreturn_t uniphier_i2c_interrupt(int irq, void *dev_id)
  {
  	struct uniphier_i2c_priv *priv = dev_id;
  
  	/*
  	 * This hardware uses edge triggered interrupt.  Do not touch the
  	 * hardware registers in this handler to make sure to catch the next
  	 * interrupt edge.  Just send a complete signal and return.
  	 */
  	complete(&priv->comp);
  
  	return IRQ_HANDLED;
  }
  
  static int uniphier_i2c_xfer_byte(struct i2c_adapter *adap, u32 txdata,
  				  u32 *rxdatap)
  {
  	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
  	unsigned long time_left;
  	u32 rxdata;
  
  	reinit_completion(&priv->comp);
  
  	txdata |= UNIPHIER_I2C_DTRM_IRQEN;
  	dev_dbg(&adap->dev, "write data: 0x%04x
  ", txdata);
  	writel(txdata, priv->membase + UNIPHIER_I2C_DTRM);
  
  	time_left = wait_for_completion_timeout(&priv->comp, adap->timeout);
  	if (unlikely(!time_left)) {
  		dev_err(&adap->dev, "transaction timeout
  ");
  		return -ETIMEDOUT;
  	}
  
  	rxdata = readl(priv->membase + UNIPHIER_I2C_DREC);
  	dev_dbg(&adap->dev, "read data: 0x%04x
  ", rxdata);
  
  	if (rxdatap)
  		*rxdatap = rxdata;
  
  	return 0;
  }
  
  static int uniphier_i2c_send_byte(struct i2c_adapter *adap, u32 txdata)
  {
  	u32 rxdata;
  	int ret;
  
  	ret = uniphier_i2c_xfer_byte(adap, txdata, &rxdata);
  	if (ret)
  		return ret;
  
  	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LAB)) {
  		dev_dbg(&adap->dev, "arbitration lost
  ");
  		return -EAGAIN;
  	}
  	if (unlikely(rxdata & UNIPHIER_I2C_DREC_LRB)) {
  		dev_dbg(&adap->dev, "could not get ACK
  ");
  		return -ENXIO;
  	}
  
  	return 0;
  }
  
  static int uniphier_i2c_tx(struct i2c_adapter *adap, u16 addr, u16 len,
  			   const u8 *buf)
  {
  	int ret;
  
  	dev_dbg(&adap->dev, "start condition
  ");
  	ret = uniphier_i2c_send_byte(adap, addr << 1 |
  				     UNIPHIER_I2C_DTRM_STA |
  				     UNIPHIER_I2C_DTRM_NACK);
  	if (ret)
  		return ret;
  
  	while (len--) {
  		ret = uniphier_i2c_send_byte(adap,
  					     UNIPHIER_I2C_DTRM_NACK | *buf++);
  		if (ret)
  			return ret;
  	}
  
  	return 0;
  }
  
  static int uniphier_i2c_rx(struct i2c_adapter *adap, u16 addr, u16 len,
  			   u8 *buf)
  {
  	int ret;
  
  	dev_dbg(&adap->dev, "start condition
  ");
  	ret = uniphier_i2c_send_byte(adap, addr << 1 |
  				     UNIPHIER_I2C_DTRM_STA |
  				     UNIPHIER_I2C_DTRM_NACK |
  				     UNIPHIER_I2C_DTRM_RD);
  	if (ret)
  		return ret;
  
  	while (len--) {
  		u32 rxdata;
  
  		ret = uniphier_i2c_xfer_byte(adap,
  					     len ? 0 : UNIPHIER_I2C_DTRM_NACK,
  					     &rxdata);
  		if (ret)
  			return ret;
  		*buf++ = rxdata;
  	}
  
  	return 0;
  }
  
  static int uniphier_i2c_stop(struct i2c_adapter *adap)
  {
  	dev_dbg(&adap->dev, "stop condition
  ");
  	return uniphier_i2c_send_byte(adap, UNIPHIER_I2C_DTRM_STO |
  				      UNIPHIER_I2C_DTRM_NACK);
  }
  
  static int uniphier_i2c_master_xfer_one(struct i2c_adapter *adap,
  					struct i2c_msg *msg, bool stop)
  {
  	bool is_read = msg->flags & I2C_M_RD;
  	bool recovery = false;
  	int ret;
  
  	dev_dbg(&adap->dev, "%s: addr=0x%02x, len=%d, stop=%d
  ",
  		is_read ? "receive" : "transmit", msg->addr, msg->len, stop);
  
  	if (is_read)
  		ret = uniphier_i2c_rx(adap, msg->addr, msg->len, msg->buf);
  	else
  		ret = uniphier_i2c_tx(adap, msg->addr, msg->len, msg->buf);
  
  	if (ret == -EAGAIN) /* could not acquire bus. bail out without STOP */
  		return ret;
  
  	if (ret == -ETIMEDOUT) {
  		/* This error is fatal.  Needs recovery. */
  		stop = false;
  		recovery = true;
  	}
  
  	if (stop) {
  		int ret2 = uniphier_i2c_stop(adap);
  
  		if (ret2) {
  			/* Failed to issue STOP.  The bus needs recovery. */
  			recovery = true;
  			ret = ret ?: ret2;
  		}
  	}
  
  	if (recovery)
  		i2c_recover_bus(adap);
  
  	return ret;
  }
  
  static int uniphier_i2c_check_bus_busy(struct i2c_adapter *adap)
  {
  	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
  
  	if (!(readl(priv->membase + UNIPHIER_I2C_DREC) &
  						UNIPHIER_I2C_DREC_BBN)) {
  		if (priv->busy_cnt++ > 3) {
  			/*
  			 * If bus busy continues too long, it is probably
  			 * in a wrong state.  Try bus recovery.
  			 */
  			i2c_recover_bus(adap);
  			priv->busy_cnt = 0;
  		}
  
  		return -EAGAIN;
  	}
  
  	priv->busy_cnt = 0;
  	return 0;
  }
  
  static int uniphier_i2c_master_xfer(struct i2c_adapter *adap,
  				    struct i2c_msg *msgs, int num)
  {
  	struct i2c_msg *msg, *emsg = msgs + num;
  	int ret;
  
  	ret = uniphier_i2c_check_bus_busy(adap);
  	if (ret)
  		return ret;
  
  	for (msg = msgs; msg < emsg; msg++) {
  		/* If next message is read, skip the stop condition */
  		bool stop = !(msg + 1 < emsg && msg[1].flags & I2C_M_RD);
  		/* but, force it if I2C_M_STOP is set */
  		if (msg->flags & I2C_M_STOP)
  			stop = true;
  
  		ret = uniphier_i2c_master_xfer_one(adap, msg, stop);
  		if (ret)
  			return ret;
  	}
  
  	return num;
  }
  
  static u32 uniphier_i2c_functionality(struct i2c_adapter *adap)
  {
  	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
  }
  
  static const struct i2c_algorithm uniphier_i2c_algo = {
  	.master_xfer = uniphier_i2c_master_xfer,
  	.functionality = uniphier_i2c_functionality,
  };
  
  static void uniphier_i2c_reset(struct uniphier_i2c_priv *priv, bool reset_on)
  {
  	u32 val = UNIPHIER_I2C_BRST_RSCL;
  
  	val |= reset_on ? 0 : UNIPHIER_I2C_BRST_FOEN;
  	writel(val, priv->membase + UNIPHIER_I2C_BRST);
  }
  
  static int uniphier_i2c_get_scl(struct i2c_adapter *adap)
  {
  	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
  
  	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
  							UNIPHIER_I2C_BSTS_SCL);
  }
  
  static void uniphier_i2c_set_scl(struct i2c_adapter *adap, int val)
  {
  	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
  
  	writel(val ? UNIPHIER_I2C_BRST_RSCL : 0,
  	       priv->membase + UNIPHIER_I2C_BRST);
  }
  
  static int uniphier_i2c_get_sda(struct i2c_adapter *adap)
  {
  	struct uniphier_i2c_priv *priv = i2c_get_adapdata(adap);
  
  	return !!(readl(priv->membase + UNIPHIER_I2C_BSTS) &
  							UNIPHIER_I2C_BSTS_SDA);
  }
  
  static void uniphier_i2c_unprepare_recovery(struct i2c_adapter *adap)
  {
  	uniphier_i2c_reset(i2c_get_adapdata(adap), false);
  }
  
  static struct i2c_bus_recovery_info uniphier_i2c_bus_recovery_info = {
  	.recover_bus = i2c_generic_scl_recovery,
  	.get_scl = uniphier_i2c_get_scl,
  	.set_scl = uniphier_i2c_set_scl,
  	.get_sda = uniphier_i2c_get_sda,
  	.unprepare_recovery = uniphier_i2c_unprepare_recovery,
  };
  
  static int uniphier_i2c_clk_init(struct device *dev,
  				 struct uniphier_i2c_priv *priv)
  {
  	struct device_node *np = dev->of_node;
  	unsigned long clk_rate;
  	u32 bus_speed;
  	int ret;
  
  	if (of_property_read_u32(np, "clock-frequency", &bus_speed))
  		bus_speed = UNIPHIER_I2C_DEFAULT_SPEED;
  
  	if (bus_speed > UNIPHIER_I2C_MAX_SPEED)
  		bus_speed = UNIPHIER_I2C_MAX_SPEED;
  
  	/* Get input clk rate through clk driver */
  	priv->clk = devm_clk_get(dev, NULL);
  	if (IS_ERR(priv->clk)) {
  		dev_err(dev, "failed to get clock
  ");
  		return PTR_ERR(priv->clk);
  	}
  
  	ret = clk_prepare_enable(priv->clk);
  	if (ret)
  		return ret;
  
  	clk_rate = clk_get_rate(priv->clk);
  
  	uniphier_i2c_reset(priv, true);
  
  	writel((clk_rate / bus_speed / 2 << 16) | (clk_rate / bus_speed),
  	       priv->membase + UNIPHIER_I2C_CLK);
  
  	uniphier_i2c_reset(priv, false);
  
  	return 0;
  }
  
  static int uniphier_i2c_probe(struct platform_device *pdev)
  {
  	struct device *dev = &pdev->dev;
  	struct uniphier_i2c_priv *priv;
  	struct resource *regs;
  	int irq;
  	int ret;
  
  	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	priv->membase = devm_ioremap_resource(dev, regs);
  	if (IS_ERR(priv->membase))
  		return PTR_ERR(priv->membase);
  
  	irq = platform_get_irq(pdev, 0);
  	if (irq < 0) {
  		dev_err(dev, "failed to get IRQ number");
  		return irq;
  	}
  
  	init_completion(&priv->comp);
  	priv->adap.owner = THIS_MODULE;
  	priv->adap.algo = &uniphier_i2c_algo;
  	priv->adap.dev.parent = dev;
  	priv->adap.dev.of_node = dev->of_node;
  	strlcpy(priv->adap.name, "UniPhier I2C", sizeof(priv->adap.name));
  	priv->adap.bus_recovery_info = &uniphier_i2c_bus_recovery_info;
  	i2c_set_adapdata(&priv->adap, priv);
  	platform_set_drvdata(pdev, priv);
  
  	ret = uniphier_i2c_clk_init(dev, priv);
  	if (ret)
  		return ret;
  
  	ret = devm_request_irq(dev, irq, uniphier_i2c_interrupt, 0, pdev->name,
  			       priv);
  	if (ret) {
  		dev_err(dev, "failed to request irq %d
  ", irq);
  		goto err;
  	}
  
  	ret = i2c_add_adapter(&priv->adap);
  	if (ret) {
  		dev_err(dev, "failed to add I2C adapter
  ");
  		goto err;
  	}
  
  err:
  	if (ret)
  		clk_disable_unprepare(priv->clk);
  
  	return ret;
  }
  
  static int uniphier_i2c_remove(struct platform_device *pdev)
  {
  	struct uniphier_i2c_priv *priv = platform_get_drvdata(pdev);
  
  	i2c_del_adapter(&priv->adap);
  	clk_disable_unprepare(priv->clk);
  
  	return 0;
  }
  
  static const struct of_device_id uniphier_i2c_match[] = {
  	{ .compatible = "socionext,uniphier-i2c" },
  	{ /* sentinel */ }
  };
  MODULE_DEVICE_TABLE(of, uniphier_i2c_match);
  
  static struct platform_driver uniphier_i2c_drv = {
  	.probe  = uniphier_i2c_probe,
  	.remove = uniphier_i2c_remove,
  	.driver = {
  		.name  = "uniphier-i2c",
  		.of_match_table = uniphier_i2c_match,
  	},
  };
  module_platform_driver(uniphier_i2c_drv);
  
  MODULE_AUTHOR("Masahiro Yamada <yamada.masahiro@socionext.com>");
  MODULE_DESCRIPTION("UniPhier I2C bus driver");
  MODULE_LICENSE("GPL");