/*
 * 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;
	struct i2c_client *slave;
};

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 bool em_i2c_slave_irq(struct em_i2c_device *priv)
{
	u8 status, value;
	enum i2c_slave_event event;
	int ret;

	if (!priv->slave)
		return false;

	status = readb(priv->base + I2C_OFS_IICSE0);

	/* Extension code, do not participate */
	if (status & I2C_BIT_EXC0) {
		em_clear_set_bit(priv, 0, I2C_BIT_LREL0, I2C_OFS_IICC0);
		return true;
	}

	/* Stop detected, we don't know if it's for slave or master */
	if (status & I2C_BIT_SPD0) {
		/* Notify slave device */
		i2c_slave_event(priv->slave, I2C_SLAVE_STOP, &value);
		/* Pretend we did not handle the interrupt */
		return false;
	}

	/* Only handle interrupts addressed to us */
	if (!(status & I2C_BIT_COI0))
		return false;

	/* Enable stop interrupts */
	em_clear_set_bit(priv, 0, I2C_BIT_SPIE0, I2C_OFS_IICC0);

	/* Transmission or Reception */
	if (status & I2C_BIT_TRC0) {
		if (status & I2C_BIT_ACKD0) {
			/* 9 bit interrupt mode */
			em_clear_set_bit(priv, 0, I2C_BIT_WTIM0, I2C_OFS_IICC0);

			/* Send data */
			event = status & I2C_BIT_STD0 ?
				I2C_SLAVE_READ_REQUESTED :
				I2C_SLAVE_READ_PROCESSED;
			i2c_slave_event(priv->slave, event, &value);
			writeb(value, priv->base + I2C_OFS_IIC0);
		} else {
			/* NACK, stop transmitting */
			em_clear_set_bit(priv, 0, I2C_BIT_LREL0, I2C_OFS_IICC0);
		}
	} else {
		/* 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);

		if (status & I2C_BIT_STD0) {
			i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_REQUESTED,
					&value);
		} else {
			/* Recv data */
			value = readb(priv->base + I2C_OFS_IIC0);
			ret = i2c_slave_event(priv->slave,
					I2C_SLAVE_WRITE_RECEIVED, &value);
			if (ret < 0)
				em_clear_set_bit(priv, I2C_BIT_ACKE0, 0,
						I2C_OFS_IICC0);
		}
	}

	return true;
}

static irqreturn_t em_i2c_irq_handler(int this_irq, void *dev_id)
{
	struct em_i2c_device *priv = dev_id;

	if (em_i2c_slave_irq(priv))
		return IRQ_HANDLED;

	complete(&priv->msg_done);

	return IRQ_HANDLED;
}

static u32 em_i2c_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SLAVE;
}

static int em_i2c_reg_slave(struct i2c_client *slave)
{
	struct em_i2c_device *priv = i2c_get_adapdata(slave->adapter);

	if (priv->slave)
		return -EBUSY;

	if (slave->flags & I2C_CLIENT_TEN)
		return -EAFNOSUPPORT;

	priv->slave = slave;

	/* Set slave address */
	writeb(slave->addr << 1, priv->base + I2C_OFS_SVA0);

	return 0;
}

static int em_i2c_unreg_slave(struct i2c_client *slave)
{
	struct em_i2c_device *priv = i2c_get_adapdata(slave->adapter);

	WARN_ON(!priv->slave);

	writeb(0, priv->base + I2C_OFS_SVA0);

	priv->slave = NULL;

	return 0;
}

static const struct i2c_algorithm em_i2c_algo = {
	.master_xfer = em_i2c_xfer,
	.functionality = em_i2c_func,
	.reg_slave      = em_i2c_reg_slave,
	.unreg_slave    = em_i2c_unreg_slave,
};

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\n", 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);