/* S3C2410 I2C Controller
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/i2c-id.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/device.h>

#include <asm/hardware.h>
#include <asm/irq.h>

#include <asm/hardware/clock.h>
#include <asm/arch/regs-gpio.h>
#include <asm/arch/regs-iic.h>
#include <asm/arch/iic.h>

static int debug_info;
static int debug_norm = 1;

enum s3c24xx_i2c_state {
	STATE_IDLE,
	STATE_START,
	STATE_READ,
	STATE_WRITE,
	STATE_STOP
};

struct s3c24xx_i2c {
	spinlock_t		lock;
	wait_queue_head_t	wait;

	struct i2c_msg		*msg;
	unsigned int		msg_num;
	unsigned int		msg_idx;
	unsigned int		msg_ptr;

	enum s3c24xx_i2c_state	state;

	void __iomem		*regs;
	struct clk		*clk;
	struct device		*dev;
	struct resource		*irq;
	struct resource		*ioarea;
	struct i2c_adapter	adap;
};

/* default platform data to use if the user does not supply
 * any 
*/

static struct s3c2410_platform_i2c s3c24xx_i2c_default_platform = {
	.flags		= 0,
	.slave_addr	= 0x10,
	.bus_freq	= 100*1000,
	.max_freq	= 400*1000,
};

/* Debug */

#define DBG(lev, msg...) do {
	if (lev < debug_info) 	dev_info(i2c->dev, msg);
	if (lev < debug_norm ) dev_dbg(i2c->dev, msg); 
	} while(0)


/* s3c24xx_i2c_get_platformdata
 *
 * get the platform data associated with the given device, or return
 * the default if there is none
*/

static inline struct s3c2410_platform_i2c *s3c24xx_i2c_get_platformdata(struct device *dev)
{
	if (dev->platform_data != NULL)
		return (struct s3c2410_platform_i2c *)dev->platform_data;

	return &s3c24xx_i2c_default_platform;
}

/* s3c24xx_i2c_master_complete
 *
 * complete the message and wake up the caller, using the given return code,
 * or zero to mean ok.
*/

static inline void s3c24xx_i2c_master_complete(struct s3c24xx_i2c *i2c, int ret)
{
	DBG(2, "s3c24xx_i2c_master_complete, code %d\n", ret);

	i2c->msg_ptr = 0;
	i2c->msg = NULL;
	i2c->msg_idx ++;
	i2c->msg_num = 0;
	if (ret)
		i2c->msg_idx = ret;

	wake_up(&i2c->wait);
}

static inline void s3c24xx_i2c_disable_ack(struct s3c24xx_i2c *i2c)
{
	unsigned long tmp;
	
	DBG(3, "s3c24xx_i2c_disable_ack:\n");

	tmp = readl(i2c->regs + S3C2410_IICCON);
	writel(tmp & ~S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);

}

static inline void s3c24xx_i2c_enable_ack(struct s3c24xx_i2c *i2c)
{
	unsigned long tmp;
	
	tmp = readl(i2c->regs + S3C2410_IICCON);
	writel(tmp | S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);

}

/* irq enable/disable functions */

static inline void s3c24xx_i2c_disable_irq(struct s3c24xx_i2c *i2c)
{
	unsigned long tmp;
	
	tmp = readl(i2c->regs + S3C2410_IICCON);
	writel(tmp & ~S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}

static inline void s3c24xx_i2c_enable_irq(struct s3c24xx_i2c *i2c)
{
	unsigned long tmp;
	
	tmp = readl(i2c->regs + S3C2410_IICCON);
	writel(tmp | S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}


/* s3c24xx_i2c_message_start
 *
 * put the start of a message onto the bus 
*/

static void s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c, 
				      struct i2c_msg *msg)
{
	unsigned int addr = (msg->addr & 0x7f) << 1;
	unsigned long stat;

	stat = readl(i2c->regs + S3C2410_IICSTAT);
	stat &= ~S3C2410_IICSTAT_MODEMASK;
	stat |=  S3C2410_IICSTAT_START;
	stat |=  S3C2410_IICSTAT_TXRXEN;

	if (msg->flags & I2C_M_RD) {
		stat |= S3C2410_IICSTAT_MASTER_RX;
		addr |= 1;
	} else
		stat |= S3C2410_IICSTAT_MASTER_TX;

	// todo - check for wether ack wanted or not
	s3c24xx_i2c_enable_ack(i2c);

	DBG(3, "START Written %08lx to IICSTAT, %02x to DS\n", stat, addr);
	writeb(addr, i2c->regs + S3C2410_IICDS);
	writel(stat, i2c->regs + S3C2410_IICSTAT);
}

static inline void s3c24xx_i2c_stop(struct s3c24xx_i2c *i2c, int ret)
{
	unsigned long iicstat = readl(i2c->regs + S3C2410_IICSTAT);

	DBG(2, "s3c24xx_i2c_msg_stop:\n");

	/* stop the transfer */
	iicstat &= ~ S3C2410_IICSTAT_START;
	writel(iicstat, i2c->regs + S3C2410_IICSTAT);
	
	i2c->state = STATE_STOP;
	
	s3c24xx_i2c_master_complete(i2c, ret);
	s3c24xx_i2c_disable_irq(i2c);
}

/* helper functions to determine the current state in the set of
 * messages we are sending */

/* is_lastmsg()
 *
 * returns TRUE if the current message is the last in the set 
*/

static inline int is_lastmsg(struct s3c24xx_i2c *i2c)
{
	return i2c->msg_idx >= (i2c->msg_num - 1);
}

/* is_msglast
 *
 * returns TRUE if we this is the last byte in the current message
*/

static inline int is_msglast(struct s3c24xx_i2c *i2c)
{
	return i2c->msg_ptr == i2c->msg->len-1;
}

/* is_msgend
 *
 * returns TRUE if we reached the end of the current message
*/

static inline int is_msgend(struct s3c24xx_i2c *i2c)
{
	return i2c->msg_ptr >= i2c->msg->len;
}

static int i2s_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
{
	unsigned long tmp;
	unsigned char byte;
	int ret = 0;

	DBG(3, "nextbyte: msg %p, num=%d, idx=%d, ptr=%d, state=%d\n",
	    i2c->msg, i2c->msg_num, i2c->msg_idx, i2c->msg_ptr, i2c->state);

	switch (i2c->state) {

	case STATE_IDLE:
		dev_err(i2c->dev, "%s: called in STATE_IDLE\n", __FUNCTION__);
		goto out;
		break;

	case STATE_STOP:
		dev_err(i2c->dev, "%s: called in STATE_STOP\n", __FUNCTION__);
		s3c24xx_i2c_disable_irq(i2c);		
		goto out_ack;

	case STATE_START:
		/* last thing we did was send a start condition on the
		 * bus, or started a new i2c message
		 */
		
		DBG(3, "STATE_START: iicstat=%lx\n", iicstat);

		if (iicstat  & S3C2410_IICSTAT_LASTBIT &&
		    !(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
			/* ack was not received... */
			DBG(2, "ACK not received from slave\n");

			s3c24xx_i2c_stop(i2c, -EREMOTEIO);
			goto out_ack;
		}

		if (i2c->msg->flags & I2C_M_RD)
			i2c->state = STATE_READ;
		else
			i2c->state = STATE_WRITE;

		/* terminate the transfer if there is nothing to do
		 * (used by the i2c probe to find devices */

		if (is_lastmsg(i2c) && i2c->msg->len == 0) {
			DBG(3, "START: Looks like probe\n");
			s3c24xx_i2c_stop(i2c, 0);
			goto out_ack;
		}

		if (i2c->state == STATE_READ)
			goto prepare_read;

		/* fall through to the write state, as we will need to 
		 * send a byte as well */

	case STATE_WRITE:
		/* we are writing data to the device... check for the
		 * end of the message, and if so, work out what to do
		 */

		if (!is_msgend(i2c)) {
			byte = i2c->msg->buf[i2c->msg_ptr++];

			DBG(3, "WRITE byte %02x\n", byte);
			writeb(byte, i2c->regs + S3C2410_IICDS);
			
		} else if (!is_lastmsg(i2c)) {
			/* we need to go to the next i2c message */

			DBG(3, "WRITE: Next Message\n");

			i2c->msg_ptr = 0;
			i2c->msg_idx ++;
			i2c->msg++;
			
			/* check to see if we need to do another message */
			if (i2c->msg->flags & I2C_M_NOSTART) {
				// todo //
				DBG(1, "WRITE: Error I2C_M_NOSTART\n");
			}
			
			/* send the new start */
			s3c24xx_i2c_message_start(i2c, i2c->msg);
			i2c->state = STATE_START;
		} else {
			/* send stop */
			DBG(3, "WRITE: Send Stop\n");

			s3c24xx_i2c_stop(i2c, 0);
		}
		break;

	case STATE_READ:
		/* we have a byte of data in the data register, do 
		 * something with it, and then work out wether we are
		 * going to do any more read/write
		 */

		if (!(i2c->msg->flags & I2C_M_IGNORE_NAK) &&
		    !(is_msglast(i2c) && is_lastmsg(i2c))) {

			if (iicstat & S3C2410_IICSTAT_LASTBIT) {
				DBG(2, "READ: No Ack\n");

				s3c24xx_i2c_stop(i2c, -ECONNREFUSED);
				goto out_ack;
			}
		}

		i2c->msg->buf[i2c->msg_ptr++] = readb(i2c->regs + S3C2410_IICDS);

		DBG(3, "READ: Read %02x\n", i2c->msg->buf[i2c->msg_ptr-1]);

	prepare_read:
		if (is_msglast(i2c)) {
			/* last byte of buffer */

			if (is_lastmsg(i2c))
				s3c24xx_i2c_disable_ack(i2c);
			
		} else if (is_msgend(i2c)) {
			/* ok, we've read the entire buffer, see if there
			 * is anything else we need to do */

			if (is_lastmsg(i2c)) {
				/* last message, send stop and complete */
				DBG(3, "READ: Send Stop\n");

				s3c24xx_i2c_stop(i2c, 0);
			} else {
				/* go to the next transfer */
				DBG(3, "READ: Next Transfer\n");

				i2c->msg_ptr = 0;
				i2c->msg_idx ++;
				i2c->msg++;
			}
		}

		break;
	}

	/* acknowlegde the IRQ and get back on with the work */

 out_ack:
	DBG(3, "out_ack:\n");
	tmp = readl(i2c->regs + S3C2410_IICCON);	
	tmp &= ~S3C2410_IICCON_IRQPEND;
	writel(tmp, i2c->regs + S3C2410_IICCON);
 out:
	return ret;
}
/* s3c24xx_i2c_irq
 *
 * top level IRQ servicing routine
*/

static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id,
			   struct pt_regs *regs)
{
	struct s3c24xx_i2c *i2c = dev_id;
	unsigned long status;
	unsigned long tmp;

	status = readl(i2c->regs + S3C2410_IICSTAT);

	DBG(3, "s3c24xx_i2c_irq: status %08lx\n", status);

	if (status & S3C2410_IICSTAT_ARBITR) {
		// deal with arbitration loss
	}

	if (i2c->state == STATE_IDLE) {
		DBG(3, "IRQ: error i2c->state == IDLE\n");

		tmp = readl(i2c->regs + S3C2410_IICCON);	
		tmp &= ~S3C2410_IICCON_IRQPEND;
		writel(tmp, i2c->regs +  S3C2410_IICCON);
		goto out;
	}
	
	// pretty much this leaves us with the fact that we've
	// transmitted or received whatever byte we last sent

	i2s_s3c_irq_nextbyte(i2c, status);

 out:
	return IRQ_HANDLED;
}


/* s3c24xx_i2c_set_master
 *