/*
   * Copyright 2011, Netlogic Microsystems Inc.
   * Copyright 2004, Matt Porter <mporter@kernel.crashing.org>
   *
   * This file is licensed under the terms of the GNU General Public
   * License version 2.  This program is licensed "as is" without any
   * warranty of any kind, whether express or implied.
   */
  
  #include <linux/err.h>
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/ioport.h>
  #include <linux/delay.h>
  #include <linux/errno.h>
  #include <linux/i2c.h>
  #include <linux/io.h>
  #include <linux/platform_device.h>
  
  /* XLR I2C REGISTERS */
  #define XLR_I2C_CFG		0x00
  #define XLR_I2C_CLKDIV		0x01
  #define XLR_I2C_DEVADDR		0x02
  #define XLR_I2C_ADDR		0x03
  #define XLR_I2C_DATAOUT		0x04
  #define XLR_I2C_DATAIN		0x05
  #define XLR_I2C_STATUS		0x06
  #define XLR_I2C_STARTXFR	0x07
  #define XLR_I2C_BYTECNT		0x08
  #define XLR_I2C_HDSTATIM	0x09
  
  /* XLR I2C REGISTERS FLAGS */
  #define XLR_I2C_BUS_BUSY	0x01
  #define XLR_I2C_SDOEMPTY	0x02
  #define XLR_I2C_RXRDY		0x04
  #define XLR_I2C_ACK_ERR		0x08
  #define XLR_I2C_ARB_STARTERR	0x30
  
  /* Register Values */
  #define XLR_I2C_CFG_ADDR	0xF8
  #define XLR_I2C_CFG_NOADDR	0xFA
  #define XLR_I2C_STARTXFR_ND	0x02    /* No Data */
  #define XLR_I2C_STARTXFR_RD	0x01    /* Read */
  #define XLR_I2C_STARTXFR_WR	0x00    /* Write */
  
  #define XLR_I2C_TIMEOUT		10	/* timeout per byte in msec */
  
  /*
   * On XLR/XLS, we need to use __raw_ IO to read the I2C registers
   * because they are in the big-endian MMIO area on the SoC.
   *
   * The readl/writel implementation on XLR/XLS byteswaps, because
   * those are for its little-endian PCI space (see arch/mips/Kconfig).
   */
  static inline void xlr_i2c_wreg(u32 __iomem *base, unsigned int reg, u32 val)
  {
  	__raw_writel(val, base + reg);
  }
  
  static inline u32 xlr_i2c_rdreg(u32 __iomem *base, unsigned int reg)
  {
  	return __raw_readl(base + reg);
  }
  
  struct xlr_i2c_private {
  	struct i2c_adapter adap;
  	u32 __iomem *iobase;
  };
  
  static int xlr_i2c_tx(struct xlr_i2c_private *priv,  u16 len,
  	u8 *buf, u16 addr)
  {
  	struct i2c_adapter *adap = &priv->adap;
  	unsigned long timeout, stoptime, checktime;
  	u32 i2c_status;
  	int pos, timedout;
  	u8 offset, byte;
  
  	offset = buf[0];
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_ADDR, offset);
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_DEVADDR, addr);
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_CFG, XLR_I2C_CFG_ADDR);
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 1);
  
  	timeout = msecs_to_jiffies(XLR_I2C_TIMEOUT);
  	stoptime = jiffies + timeout;
  	timedout = 0;
  	pos = 1;
  retry:
  	if (len == 1) {
  		xlr_i2c_wreg(priv->iobase, XLR_I2C_STARTXFR,
  				XLR_I2C_STARTXFR_ND);
  	} else {
  		xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, buf[pos]);
  		xlr_i2c_wreg(priv->iobase, XLR_I2C_STARTXFR,
  				XLR_I2C_STARTXFR_WR);
  	}
  
  	while (!timedout) {
  		checktime = jiffies;
  		i2c_status = xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS);
  
  		if (i2c_status & XLR_I2C_SDOEMPTY) {
  			pos++;
  			/* need to do a empty dataout after the last byte */
  			byte = (pos < len) ? buf[pos] : 0;
  			xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, byte);
  
  			/* reset timeout on successful xmit */
  			stoptime = jiffies + timeout;
  		}
  		timedout = time_after(checktime, stoptime);
  
  		if (i2c_status & XLR_I2C_ARB_STARTERR) {
  			if (timedout)
  				break;
  			goto retry;
  		}
  
  		if (i2c_status & XLR_I2C_ACK_ERR)
  			return -EIO;
  
  		if ((i2c_status & XLR_I2C_BUS_BUSY) == 0 && pos >= len)
  			return 0;
  	}
  	dev_err(&adap->dev, "I2C transmit timeout
  ");
  	return -ETIMEDOUT;
  }
  
  static int xlr_i2c_rx(struct xlr_i2c_private *priv, u16 len, u8 *buf, u16 addr)
  {
  	struct i2c_adapter *adap = &priv->adap;
  	u32 i2c_status;
  	unsigned long timeout, stoptime, checktime;
  	int nbytes, timedout;
  	u8 byte;
  
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_CFG, XLR_I2C_CFG_NOADDR);
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len);
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_DEVADDR, addr);
  
  	timeout = msecs_to_jiffies(XLR_I2C_TIMEOUT);
  	stoptime = jiffies + timeout;
  	timedout = 0;
  	nbytes = 0;
  retry:
  	xlr_i2c_wreg(priv->iobase, XLR_I2C_STARTXFR, XLR_I2C_STARTXFR_RD);
  
  	while (!timedout) {
  		checktime = jiffies;
  		i2c_status = xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS);
  		if (i2c_status & XLR_I2C_RXRDY) {
  			if (nbytes > len)
  				return -EIO;	/* should not happen */
  
  			/* we need to do a dummy datain when nbytes == len */
  			byte = xlr_i2c_rdreg(priv->iobase, XLR_I2C_DATAIN);
  			if (nbytes < len)
  				buf[nbytes] = byte;
  			nbytes++;
  
  			/* reset timeout on successful read */
  			stoptime = jiffies + timeout;
  		}
  
  		timedout = time_after(checktime, stoptime);
  		if (i2c_status & XLR_I2C_ARB_STARTERR) {
  			if (timedout)
  				break;
  			goto retry;
  		}
  
  		if (i2c_status & XLR_I2C_ACK_ERR)
  			return -EIO;
  
  		if ((i2c_status & XLR_I2C_BUS_BUSY) == 0)
  			return 0;
  	}
  
  	dev_err(&adap->dev, "I2C receive timeout
  ");
  	return -ETIMEDOUT;
  }
  
  static int xlr_i2c_xfer(struct i2c_adapter *adap,
  	struct i2c_msg *msgs, int num)
  {
  	struct i2c_msg *msg;
  	int i;
  	int ret = 0;
  	struct xlr_i2c_private *priv = i2c_get_adapdata(adap);
  
  	for (i = 0; ret == 0 && i < num; i++) {
  		msg = &msgs[i];
  		if (msg->flags & I2C_M_RD)
  			ret = xlr_i2c_rx(priv, msg->len, &msg->buf[0],
  					msg->addr);
  		else
  			ret = xlr_i2c_tx(priv, msg->len, &msg->buf[0],
  					msg->addr);
  	}
  
  	return (ret != 0) ? ret : num;
  }
  
  static u32 xlr_func(struct i2c_adapter *adap)
  {
  	/* Emulate SMBUS over I2C */
  	return I2C_FUNC_SMBUS_EMUL | I2C_FUNC_I2C;
  }
  
  static struct i2c_algorithm xlr_i2c_algo = {
  	.master_xfer	= xlr_i2c_xfer,
  	.functionality	= xlr_func,
  };
  
  static int xlr_i2c_probe(struct platform_device *pdev)
  {
  	struct xlr_i2c_private  *priv;
  	struct resource *res;
  	int ret;
  
  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	priv->iobase = devm_ioremap_resource(&pdev->dev, res);
  	if (IS_ERR(priv->iobase))
  		return PTR_ERR(priv->iobase);
  
  	priv->adap.dev.parent = &pdev->dev;
  	priv->adap.owner	= THIS_MODULE;
  	priv->adap.algo_data	= priv;
  	priv->adap.algo		= &xlr_i2c_algo;
  	priv->adap.nr		= pdev->id;
  	priv->adap.class	= I2C_CLASS_HWMON;
  	snprintf(priv->adap.name, sizeof(priv->adap.name), "xlr-i2c");
  
  	i2c_set_adapdata(&priv->adap, priv);
  	ret = i2c_add_numbered_adapter(&priv->adap);
  	if (ret < 0) {
  		dev_err(&priv->adap.dev, "Failed to add i2c bus.
  ");
  		return ret;
  	}
  
  	platform_set_drvdata(pdev, priv);
  	dev_info(&priv->adap.dev, "Added I2C Bus.
  ");
  	return 0;
  }
  
  static int xlr_i2c_remove(struct platform_device *pdev)
  {
  	struct xlr_i2c_private *priv;
  
  	priv = platform_get_drvdata(pdev);
  	i2c_del_adapter(&priv->adap);
  	return 0;
  }
  
  static struct platform_driver xlr_i2c_driver = {
  	.probe  = xlr_i2c_probe,
  	.remove = xlr_i2c_remove,
  	.driver = {
  		.name   = "xlr-i2cbus",
  	},
  };
  
  module_platform_driver(xlr_i2c_driver);
  
  MODULE_AUTHOR("Ganesan Ramalingam <ganesanr@netlogicmicro.com>");
  MODULE_DESCRIPTION("XLR/XLS SoC I2C Controller driver");
  MODULE_LICENSE("GPL v2");
  MODULE_ALIAS("platform:xlr-i2cbus");