/*
   * linux/drivers/i2c/busses/i2c-nuc900.c
   *
   * Copyright (c) 2010 Nuvoton technology corporation.
   *
   * This driver based on S3C2410 I2C driver of Ben Dooks <ben-Y5A6D6n0/KfQXOPxS62xeg@public.gmane.org>.
   * Written by Wan ZongShun <mcuos.com-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
   *
   * 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;version 2 of the License.
   *
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  
  #include <linux/i2c.h>
  #include <linux/init.h>
  #include <linux/time.h>
  #include <linux/interrupt.h>
  #include <linux/delay.h>
  #include <linux/errno.h>
  #include <linux/err.h>
  #include <linux/platform_device.h>
  #include <linux/clk.h>
  #include <linux/cpufreq.h>
  #include <linux/slab.h>
  #include <linux/io.h>
  
  #include <mach/mfp.h>
  #include <linux/platform_data/i2c-nuc900.h>
  
  /* nuc900 i2c registers offset */
  
  #define CSR		0x00
  #define DIVIDER		0x04
  #define CMDR		0x08
  #define SWR		0x0C
  #define RXR		0x10
  #define TXR		0x14
  
  /* nuc900 i2c CSR register bits */
  
  #define IRQEN		0x003
  #define I2CBUSY		0x400
  #define I2CSTART	0x018
  #define IRQFLAG		0x004
  #define ARBIT_LOST	0x200
  #define SLAVE_ACK	0x800
  
  /* nuc900 i2c CMDR register bits */
  
  #define I2C_CMD_START	0x10
  #define I2C_CMD_STOP	0x08
  #define I2C_CMD_READ	0x04
  #define I2C_CMD_WRITE	0x02
  #define I2C_CMD_NACK	0x01
  
  /* i2c controller state */
  
  enum nuc900_i2c_state {
  	STATE_IDLE,
  	STATE_START,
  	STATE_READ,
  	STATE_WRITE,
  	STATE_STOP
  };
  
  /* i2c controller private data */
  
  struct nuc900_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;
  	unsigned int		irq;
  
  	enum nuc900_i2c_state	state;
  
  	void __iomem		*regs;
  	struct clk		*clk;
  	struct device		*dev;
  	struct resource		*ioarea;
  	struct i2c_adapter	adap;
  };
  
  /* nuc900_i2c_master_complete
   *
   * complete the message and wake up the caller, using the given return code,
   * or zero to mean ok.
  */
  
  static inline void nuc900_i2c_master_complete(struct nuc900_i2c *i2c, int ret)
  {
  	dev_dbg(i2c->dev, "master_complete %d
  ", 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);
  }
  
  /* irq enable/disable functions */
  
  static inline void nuc900_i2c_disable_irq(struct nuc900_i2c *i2c)
  {
  	unsigned long tmp;
  
  	tmp = readl(i2c->regs + CSR);
  	writel(tmp & ~IRQEN, i2c->regs + CSR);
  }
  
  static inline void nuc900_i2c_enable_irq(struct nuc900_i2c *i2c)
  {
  	unsigned long tmp;
  
  	tmp = readl(i2c->regs + CSR);
  	writel(tmp | IRQEN, i2c->regs + CSR);
  }
  
  
  /* nuc900_i2c_message_start
   *
   * put the start of a message onto the bus
  */
  
  static void nuc900_i2c_message_start(struct nuc900_i2c *i2c,
  				      struct i2c_msg *msg)
  {
  	unsigned int addr = (msg->addr & 0x7f) << 1;
  
  	if (msg->flags & I2C_M_RD)
  		addr |= 0x1;
  	writel(addr & 0xff, i2c->regs + TXR);
  	writel(I2C_CMD_START | I2C_CMD_WRITE, i2c->regs + CMDR);
  }
  
  static inline void nuc900_i2c_stop(struct nuc900_i2c *i2c, int ret)
  {
  
  	dev_dbg(i2c->dev, "STOP
  ");
  
  	/* stop the transfer */
  	i2c->state = STATE_STOP;
  	writel(I2C_CMD_STOP, i2c->regs + CMDR);
  
  	nuc900_i2c_master_complete(i2c, ret);
  	nuc900_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 nuc900_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 nuc900_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 nuc900_i2c *i2c)
  {
  	return i2c->msg_ptr >= i2c->msg->len;
  }
  
  /* i2c_nuc900_irq_nextbyte
   *
   * process an interrupt and work out what to do
   */
  
  static void i2c_nuc900_irq_nextbyte(struct nuc900_i2c *i2c,
  							unsigned long iicstat)
  {
  	unsigned char byte;
  
  	switch (i2c->state) {
  
  	case STATE_IDLE:
  		dev_err(i2c->dev, "%s: called in STATE_IDLE
  ", __func__);
  		break;
  
  	case STATE_STOP:
  		dev_err(i2c->dev, "%s: called in STATE_STOP
  ", __func__);
  		nuc900_i2c_disable_irq(i2c);
  		break;
  
  	case STATE_START:
  		/* last thing we did was send a start condition on the
  		 * bus, or started a new i2c message
  		 */
  
  		if (iicstat & SLAVE_ACK &&
  		    !(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
  			/* ack was not received... */
  
  			dev_dbg(i2c->dev, "ack was not received
  ");
  			nuc900_i2c_stop(i2c, -ENXIO);
  			break;
  		}
  
  		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
  		 * as this is used by the i2c probe to find devices.
  		*/
  
  		if (is_lastmsg(i2c) && i2c->msg->len == 0) {
  			nuc900_i2c_stop(i2c, 0);
  			break;
  		}
  
  		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 (!(i2c->msg->flags & I2C_M_IGNORE_NAK)) {
  			if (iicstat & SLAVE_ACK) {
  				dev_dbg(i2c->dev, "WRITE: No Ack
  ");
  
  				nuc900_i2c_stop(i2c, -ECONNREFUSED);
  				break;
  			}
  		}
  
  retry_write:
  
  		if (!is_msgend(i2c)) {
  			byte = i2c->msg->buf[i2c->msg_ptr++];
  			writeb(byte, i2c->regs + TXR);
  			writel(I2C_CMD_WRITE, i2c->regs + CMDR);
  
  		} else if (!is_lastmsg(i2c)) {
  			/* we need to go to the next i2c message */
  
  			dev_dbg(i2c->dev, "WRITE: Next Message
  ");
  
  			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) {
  
  				if (i2c->msg->flags & I2C_M_RD) {
  					/* cannot do this, the controller
  					 * forces us to send a new START
  					 * when we change direction
  					*/
  
  					nuc900_i2c_stop(i2c, -EINVAL);
  				}
  
  				goto retry_write;
  			} else {
  				/* send the new start */
  				nuc900_i2c_message_start(i2c, i2c->msg);
  				i2c->state = STATE_START;
  			}
  
  		} else {
  			/* send stop */
  
  			nuc900_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 whether we are
  		 * going to do any more read/write
  		 */
  
  		byte = readb(i2c->regs + RXR);
  		i2c->msg->buf[i2c->msg_ptr++] = byte;
  
  prepare_read:
  		if (is_msglast(i2c)) {
  			/* last byte of buffer */
  
  			if (is_lastmsg(i2c))
  				writel(I2C_CMD_READ | I2C_CMD_NACK,
  							i2c->regs + CMDR);
  
  		} 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 */
  				dev_dbg(i2c->dev, "READ: Send Stop
  ");
  
  				nuc900_i2c_stop(i2c, 0);
  			} else {
  				/* go to the next transfer */
  				dev_dbg(i2c->dev, "READ: Next Transfer
  ");
  
  				i2c->msg_ptr = 0;
  				i2c->msg_idx++;
  				i2c->msg++;
  
  				writel(I2C_CMD_READ, i2c->regs + CMDR);
  			}
  
  		} else {
  			writel(I2C_CMD_READ, i2c->regs + CMDR);
  		}
  
  		break;
  	}
  }
  
  /* nuc900_i2c_irq
   *
   * top level IRQ servicing routine
  */
  
  static irqreturn_t nuc900_i2c_irq(int irqno, void *dev_id)
  {
  	struct nuc900_i2c *i2c = dev_id;
  	unsigned long status;
  
  	status = readl(i2c->regs + CSR);
  	writel(status | IRQFLAG, i2c->regs + CSR);
  
  	if (status & ARBIT_LOST) {
  		/* deal with arbitration loss */
  		dev_err(i2c->dev, "deal with arbitration loss
  ");
  		goto out;
  	}
  
  	if (i2c->state == STATE_IDLE) {
  		dev_dbg(i2c->dev, "IRQ: error i2c->state == IDLE
  ");
  		goto out;
  	}
  
  	/* pretty much this leaves us with the fact that we've
  	 * transmitted or received whatever byte we last sent
  	*/
  
  	i2c_nuc900_irq_nextbyte(i2c, status);
  
   out:
  	return IRQ_HANDLED;
  }
  
  
  /* nuc900_i2c_set_master
   *
   * get the i2c bus for a master transaction
  */
  
  static int nuc900_i2c_set_master(struct nuc900_i2c *i2c)
  {
  	int timeout = 400;
  
  	while (timeout-- > 0) {
  		if (((readl(i2c->regs + SWR) & I2CSTART) == I2CSTART) &&
  				((readl(i2c->regs + CSR) & I2CBUSY) == 0)) {
  			return 0;
  		}
  
  		msleep(1);
  	}
  
  	return -ETIMEDOUT;
  }
  
  /* nuc900_i2c_doxfer
   *
   * this starts an i2c transfer
  */
  
  static int nuc900_i2c_doxfer(struct nuc900_i2c *i2c,
  			      struct i2c_msg *msgs, int num)
  {
  	unsigned long iicstat, timeout;
  	int spins = 20;
  	int ret;
  
  	ret = nuc900_i2c_set_master(i2c);
  	if (ret != 0) {
  		dev_err(i2c->dev, "cannot get bus (error %d)
  ", ret);
  		ret = -EAGAIN;
  		goto out;
  	}
  
  	spin_lock_irq(&i2c->lock);
  
  	i2c->msg     = msgs;
  	i2c->msg_num = num;
  	i2c->msg_ptr = 0;
  	i2c->msg_idx = 0;
  	i2c->state   = STATE_START;
  
  	nuc900_i2c_message_start(i2c, msgs);
  	spin_unlock_irq(&i2c->lock);
  
  	timeout = wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ * 5);
  
  	ret = i2c->msg_idx;
  
  	/* having these next two as dev_err() makes life very
  	 * noisy when doing an i2cdetect
  	*/
  
  	if (timeout == 0)
  		dev_dbg(i2c->dev, "timeout
  ");
  	else if (ret != num)
  		dev_dbg(i2c->dev, "incomplete xfer (%d)
  ", ret);
  
  	/* ensure the stop has been through the bus */
  
  	dev_dbg(i2c->dev, "waiting for bus idle
  ");
  
  	/* first, try busy waiting briefly */
  	do {
  		iicstat = readl(i2c->regs + CSR);
  	} while ((iicstat & I2CBUSY) && --spins);
  
  	/* if that timed out sleep */
  	if (!spins) {
  		msleep(1);
  		iicstat = readl(i2c->regs + CSR);
  	}
  
  	if (iicstat & I2CBUSY)
  		dev_warn(i2c->dev, "timeout waiting for bus idle
  ");
  
   out:
  	return ret;
  }
  
  /* nuc900_i2c_xfer
   *
   * first port of call from the i2c bus code when an message needs
   * transferring across the i2c bus.
  */
  
  static int nuc900_i2c_xfer(struct i2c_adapter *adap,
  			struct i2c_msg *msgs, int num)
  {
  	struct nuc900_i2c *i2c = (struct nuc900_i2c *)adap->algo_data;
  	int retry;
  	int ret;
  
  	nuc900_i2c_enable_irq(i2c);
  
  	for (retry = 0; retry < adap->retries; retry++) {
  
  		ret = nuc900_i2c_doxfer(i2c, msgs, num);
  
  		if (ret != -EAGAIN)
  			return ret;
  
  		dev_dbg(i2c->dev, "Retrying transmission (%d)
  ", retry);
  
  		udelay(100);
  	}
  
  	return -EREMOTEIO;
  }
  
  /* declare our i2c functionality */
  static u32 nuc900_i2c_func(struct i2c_adapter *adap)
  {
  	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_NOSTART |
  		I2C_FUNC_PROTOCOL_MANGLING;
  }
  
  /* i2c bus registration info */
  
  static const struct i2c_algorithm nuc900_i2c_algorithm = {
  	.master_xfer		= nuc900_i2c_xfer,
  	.functionality		= nuc900_i2c_func,
  };
  
  /* nuc900_i2c_probe
   *
   * called by the bus driver when a suitable device is found
  */
  
  static int nuc900_i2c_probe(struct platform_device *pdev)
  {
  	struct nuc900_i2c *i2c;
  	struct nuc900_platform_i2c *pdata;
  	struct resource *res;
  	int ret;
  
  	pdata = dev_get_platdata(&pdev->dev);
  	if (!pdata) {
  		dev_err(&pdev->dev, "no platform data
  ");
  		return -EINVAL;
  	}
  
  	i2c = kzalloc(sizeof(struct nuc900_i2c), GFP_KERNEL);
  	if (!i2c) {
  		dev_err(&pdev->dev, "no memory for state
  ");
  		return -ENOMEM;
  	}
  
  	strlcpy(i2c->adap.name, "nuc900-i2c0", sizeof(i2c->adap.name));
  	i2c->adap.owner   = THIS_MODULE;
  	i2c->adap.algo    = &nuc900_i2c_algorithm;
  	i2c->adap.retries = 2;
  	i2c->adap.class   = I2C_CLASS_HWMON | I2C_CLASS_SPD;
  
  	spin_lock_init(&i2c->lock);
  	init_waitqueue_head(&i2c->wait);
  
  	/* find the clock and enable it */
  
  	i2c->dev = &pdev->dev;
  	i2c->clk = clk_get(&pdev->dev, NULL);
  	if (IS_ERR(i2c->clk)) {
  		dev_err(&pdev->dev, "cannot get clock
  ");
  		ret = -ENOENT;
  		goto err_noclk;
  	}
  
  	dev_dbg(&pdev->dev, "clock source %p
  ", i2c->clk);
  
  	clk_enable(i2c->clk);
  
  	/* map the registers */
  
  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  	if (res == NULL) {
  		dev_err(&pdev->dev, "cannot find IO resource
  ");
  		ret = -ENOENT;
  		goto err_clk;
  	}
  
  	i2c->ioarea = request_mem_region(res->start, resource_size(res),
  					 pdev->name);
  
  	if (i2c->ioarea == NULL) {
  		dev_err(&pdev->dev, "cannot request IO
  ");
  		ret = -ENXIO;
  		goto err_clk;
  	}
  
  	i2c->regs = ioremap(res->start, resource_size(res));
  
  	if (i2c->regs == NULL) {
  		dev_err(&pdev->dev, "cannot map IO
  ");
  		ret = -ENXIO;
  		goto err_ioarea;
  	}
  
  	dev_dbg(&pdev->dev, "registers %p (%p, %p)
  ",
  		i2c->regs, i2c->ioarea, res);
  
  	/* setup info block for the i2c core */
  
  	i2c->adap.algo_data = i2c;
  	i2c->adap.dev.parent = &pdev->dev;
  
  	mfp_set_groupg(&pdev->dev, NULL);
  
  	clk_get_rate(i2c->clk);
  
  	ret = (i2c->clk.apbfreq)/(pdata->bus_freq * 5) - 1;
  	writel(ret & 0xffff, i2c->regs + DIVIDER);
  
  	/* find the IRQ for this unit (note, this relies on the init call to
  	 * ensure no current IRQs pending
  	 */
  
  	i2c->irq = ret = platform_get_irq(pdev, 0);
  	if (ret <= 0) {
  		dev_err(&pdev->dev, "cannot find IRQ
  ");
  		goto err_iomap;
  	}
  
  	ret = request_irq(i2c->irq, nuc900_i2c_irq, IRQF_SHARED,
  			  dev_name(&pdev->dev), i2c);
  
  	if (ret != 0) {
  		dev_err(&pdev->dev, "cannot claim IRQ %d
  ", i2c->irq);
  		goto err_iomap;
  	}
  
  	/* Note, previous versions of the driver used i2c_add_adapter()
  	 * to add the bus at any number. We now pass the bus number via
  	 * the platform data, so if unset it will now default to always
  	 * being bus 0.
  	 */
  
  	i2c->adap.nr = pdata->bus_num;
  
  	ret = i2c_add_numbered_adapter(&i2c->adap);
  	if (ret < 0) {
  		dev_err(&pdev->dev, "failed to add bus to i2c core
  ");
  		goto err_irq;
  	}
  
  	platform_set_drvdata(pdev, i2c);
  
  	dev_info(&pdev->dev, "%s: NUC900 I2C adapter
  ",
  						dev_name(&i2c->adap.dev));
  	return 0;
  
   err_irq:
  	free_irq(i2c->irq, i2c);
  
   err_iomap:
  	iounmap(i2c->regs);
  
   err_ioarea:
  	release_resource(i2c->ioarea);
  	kfree(i2c->ioarea);
  
   err_clk:
  	clk_disable(i2c->clk);
  	clk_put(i2c->clk);
  
   err_noclk:
  	kfree(i2c);
  	return ret;
  }
  
  /* nuc900_i2c_remove
   *
   * called when device is removed from the bus
  */
  
  static int nuc900_i2c_remove(struct platform_device *pdev)
  {
  	struct nuc900_i2c *i2c = platform_get_drvdata(pdev);
  
  	i2c_del_adapter(&i2c->adap);
  	free_irq(i2c->irq, i2c);
  
  	clk_disable(i2c->clk);
  	clk_put(i2c->clk);
  
  	iounmap(i2c->regs);
  
  	release_resource(i2c->ioarea);
  	kfree(i2c->ioarea);
  	kfree(i2c);
  
  	return 0;
  }
  
  static struct platform_driver nuc900_i2c_driver = {
  	.probe		= nuc900_i2c_probe,
  	.remove		= nuc900_i2c_remove,
  	.driver		= {
  		.owner	= THIS_MODULE,
  		.name	= "nuc900-i2c0",
  	},
  };
  
  static int __init i2c_adap_nuc900_init(void)
  {
  	return platform_driver_register(&nuc900_i2c_driver);
  }
  
  static void __exit i2c_adap_nuc900_exit(void)
  {
  	platform_driver_unregister(&nuc900_i2c_driver);
  }
  subsys_initcall(i2c_adap_nuc900_init);
  module_exit(i2c_adap_nuc900_exit);
  
  MODULE_DESCRIPTION("NUC900 I2C Bus driver");
  MODULE_AUTHOR("Wan ZongShun, <mcuos.com-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:nuc900-i2c0");