i2c-nuc900.c

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/*
 * 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/[email protected]>.
 * Written by Wan ZongShun <[email protected]>
 *
 * 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 wether 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 __devinit 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 __devexit 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     = __devexit_p(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, <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:nuc900-i2c0");