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/*
 * I2C bus driver for the SH7760 I2C Interfaces.
 *
 * (c) 2005-2008 MSC Vertriebsges.m.b.H, Manuel Lauss <mlau@msc-ge.com>
 *
 * licensed under the terms outlined in the file COPYING.
 *
 */

#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/ioport.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/module.h>

#include <asm/clock.h>
#include <asm/i2c-sh7760.h>

/* register offsets */
#define I2CSCR		0x0		/* slave ctrl		*/
#define I2CMCR		0x4		/* master ctrl		*/
#define I2CSSR		0x8		/* slave status		*/
#define I2CMSR		0xC		/* master status	*/
#define I2CSIER		0x10		/* slave irq enable	*/
#define I2CMIER		0x14		/* master irq enable	*/
#define I2CCCR		0x18		/* clock dividers	*/
#define I2CSAR		0x1c		/* slave address	*/
#define I2CMAR		0x20		/* master address	*/
#define I2CRXTX		0x24		/* data port		*/
#define I2CFCR		0x28		/* fifo control		*/
#define I2CFSR		0x2C		/* fifo status		*/
#define I2CFIER		0x30		/* fifo irq enable	*/
#define I2CRFDR		0x34		/* rx fifo count	*/
#define I2CTFDR		0x38		/* tx fifo count	*/

#define REGSIZE		0x3C

#define MCR_MDBS	0x80		/* non-fifo mode switch	*/
#define MCR_FSCL	0x40		/* override SCL pin	*/
#define MCR_FSDA	0x20		/* override SDA pin	*/
#define MCR_OBPC	0x10		/* override pins	*/
#define MCR_MIE		0x08		/* master if enable	*/
#define MCR_TSBE	0x04
#define MCR_FSB		0x02		/* force stop bit	*/
#define MCR_ESG		0x01		/* en startbit gen.	*/

#define MSR_MNR		0x40		/* nack received	*/
#define MSR_MAL		0x20		/* arbitration lost	*/
#define MSR_MST		0x10		/* sent a stop		*/
#define MSR_MDE		0x08
#define MSR_MDT		0x04
#define MSR_MDR		0x02
#define MSR_MAT		0x01		/* slave addr xfer done	*/

#define MIE_MNRE	0x40		/* nack irq en		*/
#define MIE_MALE	0x20		/* arblos irq en	*/
#define MIE_MSTE	0x10		/* stop irq en		*/
#define MIE_MDEE	0x08
#define MIE_MDTE	0x04
#define MIE_MDRE	0x02
#define MIE_MATE	0x01		/* address sent irq en	*/

#define FCR_RFRST	0x02		/* reset rx fifo	*/
#define FCR_TFRST	0x01		/* reset tx fifo	*/

#define FSR_TEND	0x04		/* last byte sent	*/
#define FSR_RDF		0x02		/* rx fifo trigger	*/
#define FSR_TDFE	0x01		/* tx fifo empty	*/

#define FIER_TEIE	0x04		/* tx fifo empty irq en	*/
#define FIER_RXIE	0x02		/* rx fifo trig irq en	*/
#define FIER_TXIE	0x01		/* tx fifo trig irq en	*/

#define FIFO_SIZE	16

struct cami2c {
	void __iomem *iobase;
	struct i2c_adapter adap;

	/* message processing */
	struct i2c_msg	*msg;
#define IDF_SEND	1
#define IDF_RECV	2
#define IDF_STOP	4
	int		flags;

#define IDS_DONE	1
#define IDS_ARBLOST	2
#define IDS_NACK	4
	int		status;
	struct completion xfer_done;

	int irq;
	struct resource *ioarea;
};

static inline void OUT32(struct cami2c *cam, int reg, unsigned long val)
{
	__raw_writel(val, (unsigned long)cam->iobase + reg);
}

static inline unsigned long IN32(struct cami2c *cam, int reg)
{
	return __raw_readl((unsigned long)cam->iobase + reg);
}

static irqreturn_t sh7760_i2c_irq(int irq, void *ptr)
{
	struct cami2c *id = ptr;
	struct i2c_msg *msg = id->msg;
	char *data = msg->buf;
	unsigned long msr, fsr, fier, len;

	msr = IN32(id, I2CMSR);
	fsr = IN32(id, I2CFSR);

	/* arbitration lost */
	if (msr & MSR_MAL) {
		OUT32(id, I2CMCR, 0);
		OUT32(id, I2CSCR, 0);
		OUT32(id, I2CSAR, 0);
		id->status |= IDS_DONE | IDS_ARBLOST;
		goto out;
	}

	if (msr & MSR_MNR) {
		/* NACK handling is very screwed up.  After receiving a
		 * NAK IRQ one has to wait a bit  before writing to any
		 * registers, or the ctl will lock up. After that delay
		 * do a normal i2c stop. Then wait at least 1 ms before
		 * attempting another transfer or ctl will stop working
		 */
		udelay(100);	/* wait or risk ctl hang */
		OUT32(id, I2CFCR, FCR_RFRST | FCR_TFRST);
		OUT32(id, I2CMCR, MCR_MIE | MCR_FSB);
		OUT32(id, I2CFIER, 0);
		OUT32(id, I2CMIER, MIE_MSTE);
		OUT32(id, I2CSCR, 0);
		OUT32(id, I2CSAR, 0);
		id->status |= IDS_NACK;
		msr &= ~MSR_MAT;
		fsr = 0;
		/* In some cases the MST bit is also set. */
	}

	/* i2c-stop was sent */
	if (msr & MSR_MST) {
		id->status |= IDS_DONE;
		goto out;
	}

	/* i2c slave addr was sent; set to "normal" operation */
	if (msr & MSR_MAT)
		OUT32(id, I2CMCR, MCR_MIE);

	fier = IN32(id, I2CFIER);

	if (fsr & FSR_RDF) {
		len = IN32(id, I2CRFDR);
		if (msg->len <= len) {
			if (id->flags & IDF_STOP) {
				OUT32(id, I2CMCR, MCR_MIE | MCR_FSB);
				OUT32(id, I2CFIER, 0);
				/* manual says: wait >= 0.5 SCL times */
				udelay(5);
				/* next int should be MST */
			} else {
				id->status |= IDS_DONE;
				/* keep the RDF bit: ctrl holds SCL low
				 * until the setup for the next i2c_msg
				 * clears this bit.
				 */
				fsr &= ~FSR_RDF;
			}
		}
		while (msg->len && len) {
			*data++ = IN32(id, I2CRXTX);
			msg->len--;
			len--;
		}

		if (msg->len) {
			len = (msg->len >= FIFO_SIZE) ? FIFO_SIZE - 1
						      : msg->len - 1;

			OUT32(id, I2CFCR, FCR_TFRST | ((len & 0xf) << 4));
		}

	} else if (id->flags & IDF_SEND) {
		if ((fsr & FSR_TEND) && (msg->len < 1)) {
			if (id->flags & IDF_STOP) {
				OUT32(id, I2CMCR, MCR_MIE | MCR_FSB);
			} else {
				id->status |= IDS_DONE;
				/* keep the TEND bit: ctl holds SCL low
				 * until the setup for the next i2c_msg
				 * clears this bit.
				 */
				fsr &= ~FSR_TEND;
			}
		}
		if (fsr & FSR_TDFE) {
			while (msg->len && (IN32(id, I2CTFDR) < FIFO_SIZE)) {
				OUT32(id, I2CRXTX, *data++);
				msg->len--;
			}

			if (msg->len < 1) {
				fier &= ~FIER_TXIE;
				OUT32(id, I2CFIER, fier);
			} else {
				len = (msg->len >= FIFO_SIZE) ? 2 : 0;
				OUT32(id, I2CFCR,
					  FCR_RFRST | ((len & 3) << 2));
			}
		}
	}
out:
	if (id->status & IDS_DONE) {
		OUT32(id, I2CMIER, 0);
		OUT32(id, I2CFIER, 0);
		id->msg = NULL;
		complete(&id->xfer_done);
	}
	/* clear status flags and ctrl resumes work */
	OUT32(id, I2CMSR, ~msr);
	OUT32(id, I2CFSR, ~fsr);
	OUT32(id, I2CSSR, 0);

	return IRQ_HANDLED;
}


/* prepare and start a master receive operation */
static void sh7760_i2c_mrecv(struct cami2c *id)
{
	int len;

	id->flags |= IDF_RECV;

	/* set the slave addr reg; otherwise rcv wont work! */
	OUT32(id, I2CSAR, 0xfe);
	OUT32(id, I2CMAR, (id->msg->addr << 1) | 1);

	/* adjust rx fifo trigger */
	if (id->msg->len >= FIFO_SIZE)
		len = FIFO_SIZE - 1;	/* trigger at fifo full */
	else
		len = id->msg->len - 1;	/* trigger before all received */

	OUT32(id, I2CFCR, FCR_RFRST | FCR_TFRST);
	OUT32(id, I2CFCR, FCR_TFRST | ((len & 0xF) << 4));

	OUT32(id, I2CMSR, 0);
	OUT32(id, I2CMCR, MCR_MIE | MCR_ESG);
	OUT32(id, I2CMIER, MIE_MNRE | MIE_MALE | MIE_MSTE | MIE_MATE);
	OUT32(id, I2CFIER, FIER_RXIE);
}

/* prepare and start a master send operation */
static void sh7760_i2c_msend(struct cami2c *id)
{
	int len;

	id->flags |= IDF_SEND;

	/* set the slave addr reg; otherwise xmit wont work! */
	OUT32(id, I2CSAR, 0xfe);
	OUT32(id, I2CMAR, (id->msg->addr << 1) | 0);

	/* adjust tx fifo trigger */
	if (id->msg->len >= FIFO_SIZE)
		len = 2;	/* trig: 2 bytes left in TX fifo */
	else
		len = 0;	/* trig: 8 bytes left in TX fifo */

	OUT32(id, I2CFCR, FCR_RFRST | FCR_TFRST);
	OUT32(id, I2CFCR, FCR_RFRST | ((len & 3) << 2));

	while (id->msg->len && IN32(id, I2CTFDR) < FIFO_SIZE) {
		OUT32(id, I2CRXTX, *(id->msg->buf));
		(id->msg->len)--;
		(id->msg->buf)++;
	}

	OUT32(id, I2CMSR, 0);
	OUT32(id, I2CMCR, MCR_MIE | MCR_ESG);
	OUT32(id, I2CFSR, 0);
	OUT32(id, I2CMIER, MIE_MNRE | MIE_MALE | MIE_MSTE | MIE_MATE);
	OUT32(id, I2CFIER, FIER_TEIE | (id->msg->len ? FIER_TXIE : 0));
}

static inline int sh7760_i2c_busy_check(struct cami2c *id)
{
	return (IN32(id, I2CMCR) & MCR_FSDA);
}

static int sh7760_i2c_master_xfer(struct i2c_adapter *adap,
				  struct i2c_msg *msgs,
				  int num)
{
	struct cami2c *id = adap->algo_data;
	int i, retr;

	if (sh7760_i2c_busy_check(id)) {
		dev_err(&adap->dev, "sh7760-i2c%d: bus busy!\n", adap->nr);
		return -EBUSY;
	}

	i = 0;
	while (i < num) {
		retr = adap->retries;
retry:
		id->flags = ((i == (num-1)) ? IDF_STOP : 0);
		id->status = 0;
		id->msg = msgs;
		init_completion(&id->xfer_done);

		if (msgs->flags & I2C_M_RD)
			sh7760_i2c_mrecv(id);
		else
			sh7760_i2c_msend(id);

		wait_for_completion(&id->xfer_done);

		if (id->status == 0) {
			num = -EIO;
			break;
		}

		if (id->status & IDS_NACK) {
			/* wait a bit or i2c module stops working */
			mdelay(1);
			num = -EREMOTEIO;
			break;
		}

		if (id->status & IDS_ARBLOST) {
			if (retr--) {
				mdelay(2);
				goto retry;
			}
			num = -EREMOTEIO;
			break;
		}

		msgs++;
		i++;
	}

	id->msg = NULL;
	id->flags = 0;
	id->status = 0;

	OUT32(id, I2CMCR, 0);
	OUT32(id, I2CMSR, 0);
	OUT32(id, I2CMIER, 0);
	OUT32(id, I2CFIER, 0);

	/* reset slave module registers too: master mode enables slave
	 * module for receive ops (ack, data). Without this reset,
	 * eternal bus activity might be reported after NACK / ARBLOST.
	 */
	OUT32(id, I2CSCR, 0);
	OUT32(id, I2CSAR, 0);
	OUT32(id, I2CSSR, 0);

	return num;
}

static u32 sh7760_i2c_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
}

static const struct i2c_algorithm sh7760_i2c_algo = {
	.master_xfer	= sh7760_i2c_master_xfer,
	.functionality	= sh7760_i2c_func,
};

/* calculate CCR register setting for a desired scl clock.  SCL clock is
 * derived from I2C module clock  (iclk)  which in turn is derived from
 * peripheral module clock (mclk, usually around 33MHz):
 * iclk = mclk/(CDF + 1).  iclk must be < 20MHz.
 * scl = iclk/(SCGD*8 + 20).
 */
static int calc_CCR(unsigned long scl_hz)
{
	struct clk *mclk;
	unsigned long mck, m1, dff, odff, iclk;
	signed char cdf, cdfm;
	int scgd, scgdm, scgds;

	mclk = clk_get(NULL, "peripheral_clk");
	if (IS_ERR(mclk)) {
		return PTR_ERR(mclk);
	} else {
		mck = mclk->rate;
		clk_put(mclk);
	}

	odff = scl_hz;
	scgdm = cdfm = m1 = 0;
	for (cdf = 3; cdf >= 0; cdf--) {
		iclk = mck / (1 + cdf);
		if (iclk >= 20000000)
			continue;
		scgds = ((iclk / scl_hz) - 20) >> 3;
		for (scgd = scgds; (scgd < 63) && scgd <= scgds + 1; scgd++) {
			m1 = iclk / (20 + (scgd << 3));
			dff = abs(scl_hz - m1);
			if (dff < odff) {
				odff = dff;
				cdfm = cdf;
				scgdm = scgd;
			}
		}
	}
	/* fail if more than 25% off of requested SCL */
	if (odff > (scl_hz >> 2))
		return -EINVAL;

	/* create a CCR register value */
	return ((scgdm << 2) | cdfm);
}

static int sh7760_i2c_probe(struct platform_device *pdev)
{
	struct sh7760_i2c_platdata *pd;
	struct resource *res;
	struct cami2c *id;
	int ret;

	pd = dev_get_platdata(&pdev->dev);
	if (!pd) {
		dev_err(&pdev->dev, "no platform_data!\n");
		ret = -ENODEV;
		goto out0;
	}

	id = kzalloc(sizeof(struct cami2c), GFP_KERNEL);
	if (!id) {
		dev_err(&pdev->dev, "no mem for private data\n");
		ret = -ENOMEM;
		goto out0;
	}

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res) {
		dev_err(&pdev->dev, "no mmio resources\n");
		ret = -ENODEV;
		goto out1;
	}

	id->ioarea = request_mem_region(res->start, REGSIZE, pdev->name);
	if (!id->ioarea) {
		dev_err(&pdev->dev, "mmio already reserved\n");
		ret = -EBUSY;
		goto out1;
	}

	id->iobase = ioremap(res->start, REGSIZE);
	if (!id->iobase) {
		dev_err(&pdev->dev, "cannot ioremap\n");
		ret = -ENODEV;
		goto out2;
	}

	id->irq = platform_get_irq(pdev, 0);

	id->adap.nr = pdev->id;
	id->adap.algo = &sh7760_i2c_algo;
	id->adap.class = I2C_CLASS_HWMON | I2C_CLASS_SPD;
	id->adap.retries = 3;
	id->adap.algo_data = id;
	id->adap.dev.parent = &pdev->dev;
	snprintf(id->adap.name, sizeof(id->adap.name),
		"SH7760 I2C at %08lx", (unsigned long)res->start);

	OUT32(id, I2CMCR, 0);
	OUT32(id, I2CMSR, 0);
	OUT32(id, I2CMIER, 0);
	OUT32(id, I2CMAR, 0);
	OUT32(id, I2CSIER, 0);
	OUT32(id, I2CSAR, 0);
	OUT32(id, I2CSCR, 0);
	OUT32(id, I2CSSR, 0);
	OUT32(id, I2CFIER, 0);
	OUT32(id, I2CFCR, FCR_RFRST | FCR_TFRST);
	OUT32(id, I2CFSR, 0);

	ret = calc_CCR(pd->speed_khz * 1000);
	if (ret < 0) {
		dev_err(&pdev->dev, "invalid SCL clock: %dkHz\n",
			pd->speed_khz);
		goto out3;
	}
	OUT32(id, I2CCCR, ret);

	if (request_irq(id->irq, sh7760_i2c_irq, 0,
			SH7760_I2C_DEVNAME, id)) {
		dev_err(&pdev->dev, "cannot get irq %d\n", id->irq);
		ret = -EBUSY;
		goto out3;
	}

	ret = i2c_add_numbered_adapter(&id->adap);
	if (ret < 0)
		goto out4;

	platform_set_drvdata(pdev, id);

	dev_info(&pdev->dev, "%d kHz mmio %08x irq %d\n",
		 pd->speed_khz, res->start, id->irq);

	return 0;

out4:
	free_irq(id->irq, id);
out3:
	iounmap(id->iobase);
out2:
	release_resource(id->ioarea);
	kfree(id->ioarea);
out1:
	kfree(id);
out0:
	return ret;
}

static int sh7760_i2c_remove(struct platform_device *pdev)
{
	struct cami2c *id = platform_get_drvdata(pdev);

	i2c_del_adapter(&id->adap);
	free_irq(id->irq, id);
	iounmap(id->iobase);
	release_resource(id->ioarea);
	kfree(id->ioarea);
	kfree(id);

	return 0;
}

static struct platform_driver sh7760_i2c_drv = {
	.driver	= {
		.name	= SH7760_I2C_DEVNAME,
	},
	.probe		= sh7760_i2c_probe,
	.remove		= sh7760_i2c_remove,
};

module_platform_driver(sh7760_i2c_drv);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("SH7760 I2C bus driver");
MODULE_AUTHOR("Manuel Lauss <mano@roarinelk.homelinux.net>");