/*
   * I2C driver for the Renesas EMEV2 SoC
   *
   * Copyright (C) 2015 Wolfram Sang <wsa@sang-engineering.com>
   * Copyright 2013 Codethink Ltd.
   * Copyright 2010-2015 Renesas Electronics Corporation
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2
   * as published by the Free Software Foundation.
   */
  
  #include <linux/clk.h>
  #include <linux/completion.h>
  #include <linux/device.h>
  #include <linux/i2c.h>
  #include <linux/init.h>
  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/of_device.h>
  #include <linux/platform_device.h>
  #include <linux/sched.h>
  
  /* I2C Registers */
  #define I2C_OFS_IICACT0		0x00	/* start */
  #define I2C_OFS_IIC0		0x04	/* shift */
  #define I2C_OFS_IICC0		0x08	/* control */
  #define I2C_OFS_SVA0		0x0c	/* slave address */
  #define I2C_OFS_IICCL0		0x10	/* clock select */
  #define I2C_OFS_IICX0		0x14	/* extension */
  #define I2C_OFS_IICS0		0x18	/* status */
  #define I2C_OFS_IICSE0		0x1c	/* status For emulation */
  #define I2C_OFS_IICF0		0x20	/* IIC flag */
  
  /* I2C IICACT0 Masks */
  #define I2C_BIT_IICE0		0x0001
  
  /* I2C IICC0 Masks */
  #define I2C_BIT_LREL0		0x0040
  #define I2C_BIT_WREL0		0x0020
  #define I2C_BIT_SPIE0		0x0010
  #define I2C_BIT_WTIM0		0x0008
  #define I2C_BIT_ACKE0		0x0004
  #define I2C_BIT_STT0		0x0002
  #define I2C_BIT_SPT0		0x0001
  
  /* I2C IICCL0 Masks */
  #define I2C_BIT_SMC0		0x0008
  #define I2C_BIT_DFC0		0x0004
  
  /* I2C IICSE0 Masks */
  #define I2C_BIT_MSTS0		0x0080
  #define I2C_BIT_ALD0		0x0040
  #define I2C_BIT_EXC0		0x0020
  #define I2C_BIT_COI0		0x0010
  #define I2C_BIT_TRC0		0x0008
  #define I2C_BIT_ACKD0		0x0004
  #define I2C_BIT_STD0		0x0002
  #define I2C_BIT_SPD0		0x0001
  
  /* I2C IICF0 Masks */
  #define I2C_BIT_STCF		0x0080
  #define I2C_BIT_IICBSY		0x0040
  #define I2C_BIT_STCEN		0x0002
  #define I2C_BIT_IICRSV		0x0001
  
  struct em_i2c_device {
  	void __iomem *base;
  	struct i2c_adapter adap;
  	struct completion msg_done;
  	struct clk *sclk;
  };
  
  static inline void em_clear_set_bit(struct em_i2c_device *priv, u8 clear, u8 set, u8 reg)
  {
  	writeb((readb(priv->base + reg) & ~clear) | set, priv->base + reg);
  }
  
  static int em_i2c_wait_for_event(struct em_i2c_device *priv)
  {
  	unsigned long time_left;
  	int status;
  
  	reinit_completion(&priv->msg_done);
  
  	time_left = wait_for_completion_timeout(&priv->msg_done, priv->adap.timeout);
  
  	if (!time_left)
  		return -ETIMEDOUT;
  
  	status = readb(priv->base + I2C_OFS_IICSE0);
  	return status & I2C_BIT_ALD0 ? -EAGAIN : status;
  }
  
  static void em_i2c_stop(struct em_i2c_device *priv)
  {
  	/* Send Stop condition */
  	em_clear_set_bit(priv, 0, I2C_BIT_SPT0 | I2C_BIT_SPIE0, I2C_OFS_IICC0);
  
  	/* Wait for stop condition */
  	em_i2c_wait_for_event(priv);
  }
  
  static void em_i2c_reset(struct i2c_adapter *adap)
  {
  	struct em_i2c_device *priv = i2c_get_adapdata(adap);
  	int retr;
  
  	/* If I2C active */
  	if (readb(priv->base + I2C_OFS_IICACT0) & I2C_BIT_IICE0) {
  		/* Disable I2C operation */
  		writeb(0, priv->base + I2C_OFS_IICACT0);
  
  		retr = 1000;
  		while (readb(priv->base + I2C_OFS_IICACT0) == 1 && retr)
  			retr--;
  		WARN_ON(retr == 0);
  	}
  
  	/* Transfer mode set */
  	writeb(I2C_BIT_DFC0, priv->base + I2C_OFS_IICCL0);
  
  	/* Can Issue start without detecting a stop, Reservation disabled. */
  	writeb(I2C_BIT_STCEN | I2C_BIT_IICRSV, priv->base + I2C_OFS_IICF0);
  
  	/* I2C enable, 9 bit interrupt mode */
  	writeb(I2C_BIT_WTIM0, priv->base + I2C_OFS_IICC0);
  
  	/* Enable I2C operation */
  	writeb(I2C_BIT_IICE0, priv->base + I2C_OFS_IICACT0);
  
  	retr = 1000;
  	while (readb(priv->base + I2C_OFS_IICACT0) == 0 && retr)
  		retr--;
  	WARN_ON(retr == 0);
  }
  
  static int __em_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
  				int stop)
  {
  	struct em_i2c_device *priv = i2c_get_adapdata(adap);
  	int count, status, read = !!(msg->flags & I2C_M_RD);
  
  	/* Send start condition */
  	em_clear_set_bit(priv, 0, I2C_BIT_ACKE0 | I2C_BIT_WTIM0, I2C_OFS_IICC0);
  	em_clear_set_bit(priv, 0, I2C_BIT_STT0, I2C_OFS_IICC0);
  
  	/* Send slave address and R/W type */
  	writeb((msg->addr << 1) | read, priv->base + I2C_OFS_IIC0);
  
  	/* Wait for transaction */
  	status = em_i2c_wait_for_event(priv);
  	if (status < 0)
  		goto out_reset;
  
  	/* Received NACK (result of setting slave address and R/W) */
  	if (!(status & I2C_BIT_ACKD0)) {
  		em_i2c_stop(priv);
  		goto out;
  	}
  
  	/* Extra setup for read transactions */
  	if (read) {
  		/* 8 bit interrupt mode */
  		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_ACKE0, I2C_OFS_IICC0);
  		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_WREL0, I2C_OFS_IICC0);
  
  		/* Wait for transaction */
  		status = em_i2c_wait_for_event(priv);
  		if (status < 0)
  			goto out_reset;
  	}
  
  	/* Send / receive data */
  	for (count = 0; count < msg->len; count++) {
  		if (read) { /* Read transaction */
  			msg->buf[count] = readb(priv->base + I2C_OFS_IIC0);
  			em_clear_set_bit(priv, 0, I2C_BIT_WREL0, I2C_OFS_IICC0);
  
  		} else { /* Write transaction */
  			/* Received NACK */
  			if (!(status & I2C_BIT_ACKD0)) {
  				em_i2c_stop(priv);
  				goto out;
  			}
  
  			/* Write data */
  			writeb(msg->buf[count], priv->base + I2C_OFS_IIC0);
  		}
  
  		/* Wait for R/W transaction */
  		status = em_i2c_wait_for_event(priv);
  		if (status < 0)
  			goto out_reset;
  	}
  
  	if (stop)
  		em_i2c_stop(priv);
  
  	return count;
  
  out_reset:
  	em_i2c_reset(adap);
  out:
  	return status < 0 ? status : -ENXIO;
  }
  
  static int em_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
  	int num)
  {
  	struct em_i2c_device *priv = i2c_get_adapdata(adap);
  	int ret, i;
  
  	if (readb(priv->base + I2C_OFS_IICF0) & I2C_BIT_IICBSY)
  		return -EAGAIN;
  
  	for (i = 0; i < num; i++) {
  		ret = __em_i2c_xfer(adap, &msgs[i], (i == (num - 1)));
  		if (ret < 0)
  			return ret;
  	}
  
  	/* I2C transfer completed */
  	return num;
  }
  
  static irqreturn_t em_i2c_irq_handler(int this_irq, void *dev_id)
  {
  	struct em_i2c_device *priv = dev_id;
  
  	complete(&priv->msg_done);
  	return IRQ_HANDLED;
  }
  
  static u32 em_i2c_func(struct i2c_adapter *adap)
  {
  	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
  }
  
  static struct i2c_algorithm em_i2c_algo = {
  	.master_xfer = em_i2c_xfer,
  	.functionality = em_i2c_func,
  };
  
  static int em_i2c_probe(struct platform_device *pdev)
  {
  	struct em_i2c_device *priv;
  	struct resource *r;
  	int irq, ret;
  
  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	priv->base = devm_ioremap_resource(&pdev->dev, r);
  	if (IS_ERR(priv->base))
  		return PTR_ERR(priv->base);
  
  	strlcpy(priv->adap.name, "EMEV2 I2C", sizeof(priv->adap.name));
  
  	priv->sclk = devm_clk_get(&pdev->dev, "sclk");
  	if (IS_ERR(priv->sclk))
  		return PTR_ERR(priv->sclk);
  
  	clk_prepare_enable(priv->sclk);
  
  	priv->adap.timeout = msecs_to_jiffies(100);
  	priv->adap.retries = 5;
  	priv->adap.dev.parent = &pdev->dev;
  	priv->adap.algo = &em_i2c_algo;
  	priv->adap.owner = THIS_MODULE;
  	priv->adap.dev.of_node = pdev->dev.of_node;
  
  	init_completion(&priv->msg_done);
  
  	platform_set_drvdata(pdev, priv);
  	i2c_set_adapdata(&priv->adap, priv);
  
  	em_i2c_reset(&priv->adap);
  
  	irq = platform_get_irq(pdev, 0);
  	ret = devm_request_irq(&pdev->dev, irq, em_i2c_irq_handler, 0,
  				"em_i2c", priv);
  	if (ret)
  		goto err_clk;
  
  	ret = i2c_add_adapter(&priv->adap);
  
  	if (ret)
  		goto err_clk;
  
  	dev_info(&pdev->dev, "Added i2c controller %d, irq %d
  ", priv->adap.nr, irq);
  
  	return 0;
  
  err_clk:
  	clk_disable_unprepare(priv->sclk);
  	return ret;
  }
  
  static int em_i2c_remove(struct platform_device *dev)
  {
  	struct em_i2c_device *priv = platform_get_drvdata(dev);
  
  	i2c_del_adapter(&priv->adap);
  	clk_disable_unprepare(priv->sclk);
  
  	return 0;
  }
  
  static const struct of_device_id em_i2c_ids[] = {
  	{ .compatible = "renesas,iic-emev2", },
  	{ }
  };
  
  static struct platform_driver em_i2c_driver = {
  	.probe = em_i2c_probe,
  	.remove = em_i2c_remove,
  	.driver = {
  		.name = "em-i2c",
  		.of_match_table = em_i2c_ids,
  	}
  };
  module_platform_driver(em_i2c_driver);
  
  MODULE_DESCRIPTION("EMEV2 I2C bus driver");
  MODULE_AUTHOR("Ian Molton and Wolfram Sang <wsa@sang-engineering.com>");
  MODULE_LICENSE("GPL v2");
  MODULE_DEVICE_TABLE(of, em_i2c_ids);