/*
 * i2c-ocores.c: I2C bus driver for OpenCores I2C controller
 * (http://www.opencores.org/projects.cgi/web/i2c/overview).
 *
 * Peter Korsgaard <jacmet@sunsite.dk>
 *
 * 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/config.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/wait.h>
#include <linux/i2c-ocores.h>
#include <asm/io.h>

struct ocores_i2c {
	void __iomem *base;
	int regstep;
	wait_queue_head_t wait;
	struct i2c_adapter adap;
	struct i2c_msg *msg;
	int pos;
	int nmsgs;
	int state; /* see STATE_ */
};

/* registers */
#define OCI2C_PRELOW		0
#define OCI2C_PREHIGH		1
#define OCI2C_CONTROL		2
#define OCI2C_DATA		3
#define OCI2C_CMD		4 /* write only */
#define OCI2C_STATUS		4 /* read only, same address as OCI2C_CMD */

#define OCI2C_CTRL_IEN		0x40
#define OCI2C_CTRL_EN		0x80

#define OCI2C_CMD_START		0x91
#define OCI2C_CMD_STOP		0x41
#define OCI2C_CMD_READ		0x21
#define OCI2C_CMD_WRITE		0x11
#define OCI2C_CMD_READ_ACK	0x21
#define OCI2C_CMD_READ_NACK	0x29
#define OCI2C_CMD_IACK		0x01

#define OCI2C_STAT_IF		0x01
#define OCI2C_STAT_TIP		0x02
#define OCI2C_STAT_ARBLOST	0x20
#define OCI2C_STAT_BUSY		0x40
#define OCI2C_STAT_NACK		0x80

#define STATE_DONE		0
#define STATE_START		1
#define STATE_WRITE		2
#define STATE_READ		3
#define STATE_ERROR		4

static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
{
	iowrite8(value, i2c->base + reg * i2c->regstep);
}

static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
{
	return ioread8(i2c->base + reg * i2c->regstep);
}

static void ocores_process(struct ocores_i2c *i2c)
{
	struct i2c_msg *msg = i2c->msg;
	u8 stat = oc_getreg(i2c, OCI2C_STATUS);

	if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
		/* stop has been sent */
		oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
		wake_up(&i2c->wait);
		return;
	}

	/* error? */
	if (stat & OCI2C_STAT_ARBLOST) {
		i2c->state = STATE_ERROR;
		oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
		return;
	}

	if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
		i2c->state =
			(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;

		if (stat & OCI2C_STAT_NACK) {
			i2c->state = STATE_ERROR;
			oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
			return;
		}
	} else
		msg->buf[i2c->pos++] = oc_getreg(i2c, OCI2C_DATA);

	/* end of msg? */
	if (i2c->pos == msg->len) {
		i2c->nmsgs--;
		i2c->msg++;
		i2c->pos = 0;
		msg = i2c->msg;

		if (i2c->nmsgs) {	/* end? */
			/* send start? */
			if (!(msg->flags & I2C_M_NOSTART)) {
				u8 addr = (msg->addr << 1);

				if (msg->flags & I2C_M_RD)
					addr |= 1;

				i2c->state = STATE_START;

				oc_setreg(i2c, OCI2C_DATA, addr);
				oc_setreg(i2c, OCI2C_CMD,  OCI2C_CMD_START);
				return;
			} else
				i2c->state = (msg->flags & I2C_M_RD)
					? STATE_READ : STATE_WRITE;
		} else {
			i2c->state = STATE_DONE;
			oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
			return;
		}
	}

	if (i2c->state == STATE_READ) {
		oc_setreg(i2c, OCI2C_CMD, i2c->pos == (msg->len-1) ?
			  OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
	} else {
		oc_setreg(i2c, OCI2C_DATA, msg->buf[i2c->pos++]);
		oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_WRITE);
	}
}

static irqreturn_t ocores_isr(int irq, void *dev_id, struct pt_regs *regs)
{
	struct ocores_i2c *i2c = dev_id;

	ocores_process(i2c);

	return IRQ_HANDLED;
}

static int ocores_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
	struct ocores_i2c *i2c = i2c_get_adapdata(adap);

	i2c->msg = msgs;
	i2c->pos = 0;
	i2c->nmsgs = num;
	i2c->state = STATE_START;

	oc_setreg(i2c, OCI2C_DATA,
			(i2c->msg->addr << 1) |
			((i2c->msg->flags & I2C_M_RD) ? 1:0));

	oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);

	if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
			       (i2c->state == STATE_DONE), HZ))
		return (i2c->state == STATE_DONE) ? num : -EIO;
	else
		return -ETIMEDOUT;
}

static void ocores_init(struct ocores_i2c *i2c,
			struct ocores_i2c_platform_data *pdata)
{
	int prescale;
	u8 ctrl = oc_getreg(i2c, OCI2C_CONTROL);

	/* make sure the device is disabled */
	oc_setreg(i2c, OCI2C_CONTROL, ctrl & ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));

	prescale = (pdata->clock_khz / (5*100)) - 1;
	oc_setreg(i2c, OCI2C_PRELOW, prescale & 0xff);
	oc_setreg(i2c, OCI2C_PREHIGH, prescale >> 8);

	/* Init the device */
	oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
	oc_setreg(i2c, OCI2C_CONTROL, ctrl | OCI2C_CTRL_IEN | OCI2C_CTRL_EN);
}


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

static struct i2c_algorithm ocores_algorithm = {
	.master_xfer	= ocores_xfer,
	.functionality	= ocores_func,
};

static struct i2c_adapter ocores_adapter = {
	.owner		= THIS_MODULE,
	.name		= "i2c-ocores",
	.class		= I2C_CLASS_HWMON,
	.algo		= &ocores_algorithm,
};


static int __devinit ocores_i2c_probe(struct platform_device *pdev)
{
	struct ocores_i2c *i2c;
	struct ocores_i2c_platform_data *pdata;
	struct resource *res, *res2;
	int ret;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
		return -ENODEV;

	res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	if (!res2)
		return -ENODEV;

	pdata = (struct ocores_i2c_platform_data*) pdev->dev.platform_data;
	if (!pdata)
		return -ENODEV;

	i2c = kzalloc(sizeof(*i2c), GFP_KERNEL);
	if (!i2c)
		return -ENOMEM;

	if (!request_mem_region(res->start, res->end - res->start + 1,
				pdev->name)) {
		dev_err(&pdev->dev, "Memory region busy\n");
		ret = -EBUSY;
		goto request_mem_failed;
	}

	i2c->base = ioremap(res->start, res->end - res->start + 1);
	if (!i2c->base) {
		dev_err(&pdev->dev, "Unable to map registers\n");
		ret = -EIO;
		goto map_failed;
	}

	i2c->regstep = pdata->regstep;
	ocores_init(i2c, pdata);

	init_waitqueue_head(&i2c->wait);
	ret = request_irq(res2->start, ocores_isr, 0, pdev->name, i2c);
	if (ret) {
		dev_err(&pdev->dev, "Cannot claim IRQ\n");
		goto request_irq_failed;
	}

	/* hook up driver to tree */
	platform_set_drvdata(pdev, i2c);
	i2c->adap = ocores_adapter;
	i2c_set_adapdata(&i2c->adap, i2c);
	i2c->adap.dev.parent = &pdev->dev;

	/* add i2c adapter to i2c tree */
	ret = i2c_add_adapter(&i2c->adap);
	if (ret) {
		dev_err(&pdev->dev, "Failed to add adapter\n");
		goto add_adapter_failed;
	}

	return 0;

add_adapter_failed:
	free_irq(res2->start, i2c);
request_irq_failed:
	iounmap(i2c->base);
map_failed:
	release_mem_region(res->start, res->end - res->start + 1);
request_mem_failed:
	kfree(i2c);

	return ret;
}

static int __devexit ocores_i2c_remove(struct platform_device* pdev)
{
	struct ocores_i2c *i2c = platform_get_drvdata(pdev);
	struct resource *res;

	/* disable i2c logic */
	oc_setreg(i2c, OCI2C_CONTROL, oc_getreg(i2c, OCI2C_CONTROL)
		  & ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));

	/* remove adapter & data */
	i2c_del_adapter(&i2c->adap);
	platform_set_drvdata(pdev, NULL);

	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
	if (res)
		free_irq(res->start, i2c);

	iounmap(i2c->base);

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (res)
		release_mem_region(res->start, res->end - res->start + 1);

	kfree(i2c);

	return 0;
}

static struct platform_driver ocores_i2c_driver = {
	.probe  = ocores_i2c_probe,
	.remove = __devexit_p(ocores_i2c_remove),
	.driver = {
		.owner = THIS_MODULE,
		.name = "ocores-i2c",
	},
};

static int __init ocores_i2c_init(void)
{
	return platform_driver_register(&ocores_i2c_driver);
}

static void __exit ocores_i2c_exit(void)
{
	platform_driver_unregister(&ocores_i2c_driver);
}

module_init(ocores_i2c_init);
module_exit(ocores_i2c_exit);

MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
MODULE_DESCRIPTION("OpenCores I2C bus driver");
MODULE_LICENSE("GPL");