/*
 * 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\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);
}

/* 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\n");

        /* 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\n", __func__);
                break;

        case STATE_STOP:
                dev_err(i2c->dev, "%s: called in STATE_STOP\n", __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\n");
                        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\n");

                                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\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) {

                                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\n");

                                nuc900_i2c_stop(i2c, 0);
                        } else {
                                /* go to the next transfer */
                                dev_dbg(i2c->dev, "READ: Next Transfer\n");

                                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\n");
                goto out;
        }

        if (i2c->state == STATE_IDLE) {
                dev_dbg(i2c->dev, "IRQ: error i2c->state == IDLE\n");
                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)\n", 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\n");
        else if (ret != num)
                dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);

        /* ensure the stop has been through the bus */

        dev_dbg(i2c->dev, "waiting for bus idle\n");

        /* 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\n");

 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)\n", 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 = pdev->dev.platform_data;
        if (!pdata) {
                dev_err(&pdev->dev, "no platform data\n");
                return -EINVAL;
        }

        i2c = kzalloc(sizeof(struct nuc900_i2c), GFP_KERNEL);
        if (!i2c) {
                dev_err(&pdev->dev, "no memory for state\n");
                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\n");
                ret = -ENOENT;
                goto err_noclk;
        }

        dev_dbg(&pdev->dev, "clock source %p\n", 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\n");
                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\n");
                ret = -ENXIO;
                goto err_clk;
        }

        i2c->regs = ioremap(res->start, resource_size(res));

        if (i2c->regs == NULL) {
                dev_err(&pdev->dev, "cannot map IO\n");
                ret = -ENXIO;
                goto err_ioarea;
        }

        dev_dbg(&pdev->dev, "registers %p (%p, %p)\n",
                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\n");
                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\n", 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\n");
                goto err_irq;
        }

        platform_set_drvdata(pdev, i2c);

        dev_info(&pdev->dev, "%s: NUC900 I2C adapter\n",
                                                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");