/*
 * 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>
#include <linux/of_device.h>
#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/wait.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

/* Sigma Designs additional registers */
#define XLR_I2C_INT_EN		0x09
#define XLR_I2C_INT_STAT	0x0a

/* 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);
}

#define XLR_I2C_FLAG_IRQ	1

struct xlr_i2c_config {
	u32 flags;		/* optional feature support */
	u32 status_busy;	/* value of STATUS[0] when busy */
	u32 cfg_extra;		/* extra CFG bits to set */
};

struct xlr_i2c_private {
	struct i2c_adapter adap;
	u32 __iomem *iobase;
	int irq;
	int pos;
	struct i2c_msg *msg;
	const struct xlr_i2c_config *cfg;
	wait_queue_head_t wait;
	struct clk *clk;
};

static int xlr_i2c_busy(struct xlr_i2c_private *priv, u32 status)
{
	return (status & XLR_I2C_BUS_BUSY) == priv->cfg->status_busy;
}

static int xlr_i2c_idle(struct xlr_i2c_private *priv)
{
	return !xlr_i2c_busy(priv, xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS));
}

static int xlr_i2c_wait(struct xlr_i2c_private *priv, unsigned long timeout)
{
	int status;
	int t;

	t = wait_event_timeout(priv->wait, xlr_i2c_idle(priv),
				msecs_to_jiffies(timeout));
	if (!t)
		return -ETIMEDOUT;

	status = xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS);

	return status & XLR_I2C_ACK_ERR ? -EIO : 0;
}

static void xlr_i2c_tx_irq(struct xlr_i2c_private *priv, u32 status)
{
	struct i2c_msg *msg = priv->msg;

	if (status & XLR_I2C_SDOEMPTY)
		xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT,
				msg->buf[priv->pos++]);
}

static void xlr_i2c_rx_irq(struct xlr_i2c_private *priv, u32 status)
{
	struct i2c_msg *msg = priv->msg;

	if (status & XLR_I2C_RXRDY)
		msg->buf[priv->pos++] =
			xlr_i2c_rdreg(priv->iobase, XLR_I2C_DATAIN);
}

static irqreturn_t xlr_i2c_irq(int irq, void *dev_id)
{
	struct xlr_i2c_private *priv = dev_id;
	struct i2c_msg *msg = priv->msg;
	u32 int_stat, status;

	int_stat = xlr_i2c_rdreg(priv->iobase, XLR_I2C_INT_STAT);
	if (!int_stat)
		return IRQ_NONE;

	xlr_i2c_wreg(priv->iobase, XLR_I2C_INT_STAT, int_stat);

	if (!msg)
		return IRQ_HANDLED;

	status = xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS);

	if (priv->pos < msg->len) {
		if (msg->flags & I2C_M_RD)
			xlr_i2c_rx_irq(priv, status);
		else
			xlr_i2c_tx_irq(priv, status);
	}

	if (!xlr_i2c_busy(priv, status))
		wake_up(&priv->wait);

	return IRQ_HANDLED;
}

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;
	u32 xfer;

	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 | priv->cfg->cfg_extra);

	timeout = msecs_to_jiffies(XLR_I2C_TIMEOUT);
	stoptime = jiffies + timeout;
	timedout = 0;

	if (len == 1) {
		xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 1);
		xfer = XLR_I2C_STARTXFR_ND;
		pos = 1;
	} else {
		xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 2);
		xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, buf[1]);
		xfer = XLR_I2C_STARTXFR_WR;
		pos = 2;
	}

	priv->pos = pos;

retry:
	/* retry can only happen on the first byte */
	xlr_i2c_wreg(priv->iobase, XLR_I2C_STARTXFR, xfer);

	if (priv->irq > 0)
		return xlr_i2c_wait(priv, XLR_I2C_TIMEOUT * len);

	while (!timedout) {
		checktime = jiffies;
		i2c_status = xlr_i2c_rdreg(priv->iobase, XLR_I2C_STATUS);

		if ((i2c_status & XLR_I2C_SDOEMPTY) && pos < len) {
			xlr_i2c_wreg(priv->iobase, XLR_I2C_DATAOUT, buf[pos++]);

			/* 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 (!xlr_i2c_busy(priv, i2c_status) && pos >= len)
			return 0;
	}
	dev_err(&adap->dev, "I2C transmit timeout\n");
	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;

	xlr_i2c_wreg(priv->iobase, XLR_I2C_CFG,
			XLR_I2C_CFG_NOADDR | priv->cfg->cfg_extra);
	xlr_i2c_wreg(priv->iobase, XLR_I2C_BYTECNT, len - 1);
	xlr_i2c_wreg(priv->iobase, XLR_I2C_DEVADDR, addr);

	priv->pos = 0;

	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);

	if (priv->irq > 0)
		return xlr_i2c_wait(priv, XLR_I2C_TIMEOUT * len);

	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 */

			buf[nbytes++] =
				xlr_i2c_rdreg(priv->iobase, XLR_I2C_DATAIN);

			/* 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 (!xlr_i2c_busy(priv, i2c_status))
			return 0;
	}

	dev_err(&adap->dev, "I2C receive timeout\n");
	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);

	ret = clk_enable(priv->clk);
	if (ret)
		return ret;

	if (priv->irq)
		xlr_i2c_wreg(priv->iobase, XLR_I2C_INT_EN, 0xf);


	for (i = 0; ret == 0 && i < num; i++) {
		msg = &msgs[i];
		priv->msg = msg;
		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);
	}

	if (priv->irq)
		xlr_i2c_wreg(priv->iobase, XLR_I2C_INT_EN, 0);

	clk_disable(priv->clk);
	priv->msg = NULL;

	return (ret != 0) ? ret : num;
}

static u32 xlr_func(struct i2c_adapter *adap)
{
	/* Emulate SMBUS over I2C */
	return (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK) | I2C_FUNC_I2C;
}

static const struct i2c_algorithm xlr_i2c_algo = {
	.master_xfer	= xlr_i2c_xfer,
	.functionality	= xlr_func,
};

static const struct i2c_adapter_quirks xlr_i2c_quirks = {
	.flags = I2C_AQ_NO_ZERO_LEN,
};

static const struct xlr_i2c_config xlr_i2c_config_default = {
	.status_busy	= XLR_I2C_BUS_BUSY,
	.cfg_extra	= 0,
};

static const struct xlr_i2c_config xlr_i2c_config_tangox = {
	.flags		= XLR_I2C_FLAG_IRQ,
	.status_busy	= 0,
	.cfg_extra	= 1 << 8,
};

static const struct of_device_id xlr_i2c_dt_ids[] = {
	{
		.compatible	= "sigma,smp8642-i2c",
		.data		= &xlr_i2c_config_tangox,
	},
	{ }
};
MODULE_DEVICE_TABLE(of, xlr_i2c_dt_ids);

static int xlr_i2c_probe(struct platform_device *pdev)
{
	const struct of_device_id *match;
	struct xlr_i2c_private  *priv;
	struct resource *res;
	struct clk *clk;
	unsigned long clk_rate;
	unsigned long clk_div;
	u32 busfreq;
	int irq;
	int ret;

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

	match = of_match_device(xlr_i2c_dt_ids, &pdev->dev);
	if (match)
		priv->cfg = match->data;
	else
		priv->cfg = &xlr_i2c_config_default;

	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);

	irq = platform_get_irq(pdev, 0);

	if (irq > 0 && (priv->cfg->flags & XLR_I2C_FLAG_IRQ)) {
		priv->irq = irq;

		xlr_i2c_wreg(priv->iobase, XLR_I2C_INT_EN, 0);
		xlr_i2c_wreg(priv->iobase, XLR_I2C_INT_STAT, 0xf);

		ret = devm_request_irq(&pdev->dev, priv->irq, xlr_i2c_irq,
					IRQF_SHARED, dev_name(&pdev->dev),
					priv);
		if (ret)
			return ret;

		init_waitqueue_head(&priv->wait);
	}

	if (of_property_read_u32(pdev->dev.of_node, "clock-frequency",
				 &busfreq))
		busfreq = 100000;

	clk = devm_clk_get(&pdev->dev, NULL);
	if (!IS_ERR(clk)) {
		ret = clk_prepare_enable(clk);
		if (ret)
			return ret;

		clk_rate = clk_get_rate(clk);
		clk_div = DIV_ROUND_UP(clk_rate, 2 * busfreq);
		xlr_i2c_wreg(priv->iobase, XLR_I2C_CLKDIV, clk_div);

		clk_disable(clk);
		priv->clk = clk;
	}

	priv->adap.dev.parent = &pdev->dev;
	priv->adap.dev.of_node	= pdev->dev.of_node;
	priv->adap.owner	= THIS_MODULE;
	priv->adap.algo_data	= priv;
	priv->adap.algo		= &xlr_i2c_algo;
	priv->adap.quirks	= &xlr_i2c_quirks;
	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)
		return ret;

	platform_set_drvdata(pdev, priv);
	dev_info(&priv->adap.dev, "Added I2C Bus.\n");
	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);
	clk_unprepare(priv->clk);

	return 0;
}

static struct platform_driver xlr_i2c_driver = {
	.probe  = xlr_i2c_probe,
	.remove = xlr_i2c_remove,
	.driver = {
		.name   = "xlr-i2cbus",
		.of_match_table	= xlr_i2c_dt_ids,
	},
};

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");