// SPDX-License-Identifier: GPL-2.0
/*
 * Renesas Solutions Highlander FPGA I2C/SMBus support.
 *
 * Supported devices: R0P7780LC0011RL, R0P7785LC0011RL
 *
 * Copyright (C) 2008  Paul Mundt
 * Copyright (C) 2008  Renesas Solutions Corp.
 * Copyright (C) 2008  Atom Create Engineering Co., Ltd.
 */
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/i2c.h>
#include <linux/platform_device.h>
#include <linux/completion.h>
#include <linux/io.h>
#include <linux/delay.h>
#include <linux/slab.h>

#define SMCR		0x00
#define SMCR_START	(1 << 0)
#define SMCR_IRIC	(1 << 1)
#define SMCR_BBSY	(1 << 2)
#define SMCR_ACKE	(1 << 3)
#define SMCR_RST	(1 << 4)
#define SMCR_IEIC	(1 << 6)

#define SMSMADR		0x02

#define SMMR		0x04
#define SMMR_MODE0	(1 << 0)
#define SMMR_MODE1	(1 << 1)
#define SMMR_CAP	(1 << 3)
#define SMMR_TMMD	(1 << 4)
#define SMMR_SP		(1 << 7)

#define SMSADR		0x06
#define SMTRDR		0x46

struct highlander_i2c_dev {
	struct device		*dev;
	void __iomem		*base;
	struct i2c_adapter	adapter;
	struct completion	cmd_complete;
	unsigned long		last_read_time;
	int			irq;
	u8			*buf;
	size_t			buf_len;
};

static bool iic_force_poll, iic_force_normal;
static int iic_timeout = 1000, iic_read_delay;

static inline void highlander_i2c_irq_enable(struct highlander_i2c_dev *dev)
{
	iowrite16(ioread16(dev->base + SMCR) | SMCR_IEIC, dev->base + SMCR);
}

static inline void highlander_i2c_irq_disable(struct highlander_i2c_dev *dev)
{
	iowrite16(ioread16(dev->base + SMCR) & ~SMCR_IEIC, dev->base + SMCR);
}

static inline void highlander_i2c_start(struct highlander_i2c_dev *dev)
{
	iowrite16(ioread16(dev->base + SMCR) | SMCR_START, dev->base + SMCR);
}

static inline void highlander_i2c_done(struct highlander_i2c_dev *dev)
{
	iowrite16(ioread16(dev->base + SMCR) | SMCR_IRIC, dev->base + SMCR);
}

static void highlander_i2c_setup(struct highlander_i2c_dev *dev)
{
	u16 smmr;

	smmr = ioread16(dev->base + SMMR);
	smmr |= SMMR_TMMD;

	if (iic_force_normal)
		smmr &= ~SMMR_SP;
	else
		smmr |= SMMR_SP;

	iowrite16(smmr, dev->base + SMMR);
}

static void smbus_write_data(u8 *src, u16 *dst, int len)
{
	for (; len > 1; len -= 2) {
		*dst++ = be16_to_cpup((__be16 *)src);
		src += 2;
	}

	if (len)
		*dst = *src << 8;
}

static void smbus_read_data(u16 *src, u8 *dst, int len)
{
	for (; len > 1; len -= 2) {
		*(__be16 *)dst = cpu_to_be16p(src++);
		dst += 2;
	}

	if (len)
		*dst = *src >> 8;
}

static void highlander_i2c_command(struct highlander_i2c_dev *dev,
				   u8 command, int len)
{
	unsigned int i;
	u16 cmd = (command << 8) | command;

	for (i = 0; i < len; i += 2) {
		if (len - i == 1)
			cmd = command << 8;
		iowrite16(cmd, dev->base + SMSADR + i);
		dev_dbg(dev->dev, "command data[%x] 0x%04x\n", i/2, cmd);
	}
}

static int highlander_i2c_wait_for_bbsy(struct highlander_i2c_dev *dev)
{
	unsigned long timeout;

	timeout = jiffies + msecs_to_jiffies(iic_timeout);
	while (ioread16(dev->base + SMCR) & SMCR_BBSY) {
		if (time_after(jiffies, timeout)) {
			dev_warn(dev->dev, "timeout waiting for bus ready\n");
			return -ETIMEDOUT;
		}

		msleep(1);
	}

	return 0;
}

static int highlander_i2c_reset(struct highlander_i2c_dev *dev)
{
	iowrite16(ioread16(dev->base + SMCR) | SMCR_RST, dev->base + SMCR);
	return highlander_i2c_wait_for_bbsy(dev);
}

static int highlander_i2c_wait_for_ack(struct highlander_i2c_dev *dev)
{
	u16 tmp = ioread16(dev->base + SMCR);

	if ((tmp & (SMCR_IRIC | SMCR_ACKE)) == SMCR_ACKE) {
		dev_warn(dev->dev, "ack abnormality\n");
		return highlander_i2c_reset(dev);
	}

	return 0;
}

static irqreturn_t highlander_i2c_irq(int irq, void *dev_id)
{
	struct highlander_i2c_dev *dev = dev_id;

	highlander_i2c_done(dev);
	complete(&dev->cmd_complete);

	return IRQ_HANDLED;
}

static void highlander_i2c_poll(struct highlander_i2c_dev *dev)
{
	unsigned long timeout;
	u16 smcr;

	timeout = jiffies + msecs_to_jiffies(iic_timeout);
	for (;;) {
		smcr = ioread16(dev->base + SMCR);

		/*
		 * Don't bother checking ACKE here, this and the reset
		 * are handled in highlander_i2c_wait_xfer_done() when
		 * waiting for the ACK.
		 */

		if (smcr & SMCR_IRIC)
			return;
		if (time_after(jiffies, timeout))
			break;

		cpu_relax();
		cond_resched();
	}

	dev_err(dev->dev, "polling timed out\n");
}

static inline int highlander_i2c_wait_xfer_done(struct highlander_i2c_dev *dev)
{
	if (dev->irq)
		wait_for_completion_timeout(&dev->cmd_complete,
					  msecs_to_jiffies(iic_timeout));
	else
		/* busy looping, the IRQ of champions */
		highlander_i2c_poll(dev);

	return highlander_i2c_wait_for_ack(dev);
}

static int highlander_i2c_read(struct highlander_i2c_dev *dev)
{
	int i, cnt;
	u16 data[16];

	if (highlander_i2c_wait_for_bbsy(dev))
		return -EAGAIN;

	highlander_i2c_start(dev);

	if (highlander_i2c_wait_xfer_done(dev)) {
		dev_err(dev->dev, "Arbitration loss\n");
		return -EAGAIN;
	}

	/*
	 * The R0P7780LC0011RL FPGA needs a significant delay between
	 * data read cycles, otherwise the transceiver gets confused and
	 * garbage is returned when the read is subsequently aborted.
	 *
	 * It is not sufficient to wait for BBSY.
	 *
	 * While this generally only applies to the older SH7780-based
	 * Highlanders, the same issue can be observed on SH7785 ones,
	 * albeit less frequently. SH7780-based Highlanders may need
	 * this to be as high as 1000 ms.
	 */
	if (iic_read_delay && time_before(jiffies, dev->last_read_time +
				 msecs_to_jiffies(iic_read_delay)))
		msleep(jiffies_to_msecs((dev->last_read_time +
				msecs_to_jiffies(iic_read_delay)) - jiffies));

	cnt = (dev->buf_len + 1) >> 1;
	for (i = 0; i < cnt; i++) {
		data[i] = ioread16(dev->base + SMTRDR + (i * sizeof(u16)));
		dev_dbg(dev->dev, "read data[%x] 0x%04x\n", i, data[i]);
	}

	smbus_read_data(data, dev->buf, dev->buf_len);

	dev->last_read_time = jiffies;

	return 0;
}

static int highlander_i2c_write(struct highlander_i2c_dev *dev)
{
	int i, cnt;
	u16 data[16];

	smbus_write_data(dev->buf, data, dev->buf_len);

	cnt = (dev->buf_len + 1) >> 1;
	for (i = 0; i < cnt; i++) {
		iowrite16(data[i], dev->base + SMTRDR + (i * sizeof(u16)));
		dev_dbg(dev->dev, "write data[%x] 0x%04x\n", i, data[i]);
	}

	if (highlander_i2c_wait_for_bbsy(dev))
		return -EAGAIN;

	highlander_i2c_start(dev);

	return highlander_i2c_wait_xfer_done(dev);
}

static int highlander_i2c_smbus_xfer(struct i2c_adapter *adap, u16 addr,
				  unsigned short flags, char read_write,
				  u8 command, int size,
				  union i2c_smbus_data *data)
{
	struct highlander_i2c_dev *dev = i2c_get_adapdata(adap);
	u16 tmp;

	init_completion(&dev->cmd_complete);

	dev_dbg(dev->dev, "addr %04x, command %02x, read_write %d, size %d\n",
		addr, command, read_write, size);

	/*
	 * Set up the buffer and transfer size
	 */
	switch (size) {
	case I2C_SMBUS_BYTE_DATA:
		dev->buf = &data->byte;
		dev->buf_len = 1;
		break;
	case I2C_SMBUS_I2C_BLOCK_DATA:
		dev->buf = &data->block[1];
		dev->buf_len = data->block[0];
		break;
	default:
		dev_err(dev->dev, "unsupported command %d\n", size);
		return -EINVAL;
	}

	/*
	 * Encode the mode setting
	 */
	tmp = ioread16(dev->base + SMMR);
	tmp &= ~(SMMR_MODE0 | SMMR_MODE1);

	switch (dev->buf_len) {
	case 1:
		/* default */
		break;
	case 8:
		tmp |= SMMR_MODE0;
		break;
	case 16:
		tmp |= SMMR_MODE1;
		break;
	case 32:
		tmp |= (SMMR_MODE0 | SMMR_MODE1);
		break;
	default:
		dev_err(dev->dev, "unsupported xfer size %zu\n", dev->buf_len);
		return -EINVAL;
	}

	iowrite16(tmp, dev->base + SMMR);

	/* Ensure we're in a sane state */
	highlander_i2c_done(dev);

	/* Set slave address */
	iowrite16((addr << 1) | read_write, dev->base + SMSMADR);

	highlander_i2c_command(dev, command, dev->buf_len);

	if (read_write == I2C_SMBUS_READ)
		return highlander_i2c_read(dev);
	else
		return highlander_i2c_write(dev);
}

static u32 highlander_i2c_func(struct i2c_adapter *adapter)
{
	return I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_I2C_BLOCK;
}

static const struct i2c_algorithm highlander_i2c_algo = {
	.smbus_xfer	= highlander_i2c_smbus_xfer,
	.functionality	= highlander_i2c_func,
};

static int highlander_i2c_probe(struct platform_device *pdev)
{
	struct highlander_i2c_dev *dev;
	struct i2c_adapter *adap;
	struct resource *res;
	int ret;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (unlikely(!res)) {
		dev_err(&pdev->dev, "no mem resource\n");
		return -ENODEV;
	}

	dev = kzalloc(sizeof(struct highlander_i2c_dev), GFP_KERNEL);
	if (unlikely(!dev))
		return -ENOMEM;

	dev->base = ioremap(res->start, resource_size(res));
	if (unlikely(!dev->base)) {
		ret = -ENXIO;
		goto err;
	}

	dev->dev = &pdev->dev;
	platform_set_drvdata(pdev, dev);

	dev->irq = platform_get_irq(pdev, 0);
	if (iic_force_poll)
		dev->irq = 0;

	if (dev->irq) {
		ret = request_irq(dev->irq, highlander_i2c_irq, 0,
				  pdev->name, dev);
		if (unlikely(ret))
			goto err_unmap;

		highlander_i2c_irq_enable(dev);
	} else {
		dev_notice(&pdev->dev, "no IRQ, using polling mode\n");
		highlander_i2c_irq_disable(dev);
	}

	dev->last_read_time = jiffies;	/* initial read jiffies */

	highlander_i2c_setup(dev);

	adap = &dev->adapter;
	i2c_set_adapdata(adap, dev);
	adap->owner = THIS_MODULE;
	adap->class = I2C_CLASS_HWMON;
	strlcpy(adap->name, "HL FPGA I2C adapter", sizeof(adap->name));
	adap->algo = &highlander_i2c_algo;
	adap->dev.parent = &pdev->dev;
	adap->nr = pdev->id;

	/*
	 * Reset the adapter
	 */
	ret = highlander_i2c_reset(dev);
	if (unlikely(ret)) {
		dev_err(&pdev->dev, "controller didn't come up\n");
		goto err_free_irq;
	}

	ret = i2c_add_numbered_adapter(adap);
	if (unlikely(ret)) {
		dev_err(&pdev->dev, "failure adding adapter\n");
		goto err_free_irq;
	}

	return 0;

err_free_irq:
	if (dev->irq)
		free_irq(dev->irq, dev);
err_unmap:
	iounmap(dev->base);
err:
	kfree(dev);

	return ret;
}

static int highlander_i2c_remove(struct platform_device *pdev)
{
	struct highlander_i2c_dev *dev = platform_get_drvdata(pdev);

	i2c_del_adapter(&dev->adapter);

	if (dev->irq)
		free_irq(dev->irq, dev);

	iounmap(dev->base);
	kfree(dev);

	return 0;
}

static struct platform_driver highlander_i2c_driver = {
	.driver		= {
		.name	= "i2c-highlander",
	},

	.probe		= highlander_i2c_probe,
	.remove		= highlander_i2c_remove,
};

module_platform_driver(highlander_i2c_driver);

MODULE_AUTHOR("Paul Mundt");
MODULE_DESCRIPTION("Renesas Highlander FPGA I2C/SMBus adapter");
MODULE_LICENSE("GPL v2");

module_param(iic_force_poll, bool, 0);
module_param(iic_force_normal, bool, 0);
module_param(iic_timeout, int, 0);
module_param(iic_read_delay, int, 0);

MODULE_PARM_DESC(iic_force_poll, "Force polling mode");
MODULE_PARM_DESC(iic_force_normal,
		 "Force normal mode (100 kHz), default is fast mode (400 kHz)");
MODULE_PARM_DESC(iic_timeout, "Set timeout value in msecs (default 1000 ms)");
MODULE_PARM_DESC(iic_read_delay,
		 "Delay between data read cycles (default 0 ms)");