/*
    i2c Support for Atmel's AT91 Two-Wire Interface (TWI)

    Copyright (C) 2004 Rick Bronson
    Converted to 2.6 by Andrew Victor <andrew@sanpeople.com>

    Borrowed heavily from original work by:
    Copyright (C) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>

    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.
*/

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/clk.h>
#include <linux/platform_device.h>
#include <linux/io.h>

#include <mach/at91_twi.h>
#include <mach/board.h>
#include <mach/cpu.h>

#define TWI_CLOCK               100000          /* Hz. max 400 Kbits/sec */


static struct clk *twi_clk;
static void __iomem *twi_base;

#define at91_twi_read(reg)              __raw_readl(twi_base + (reg))
#define at91_twi_write(reg, val)        __raw_writel((val), twi_base + (reg))


/*
 * Initialize the TWI hardware registers.
 */
static void __devinit at91_twi_hwinit(void)
{
        unsigned long cdiv, ckdiv;

        at91_twi_write(AT91_TWI_IDR, 0xffffffff);       /* Disable all interrupts */
        at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST);    /* Reset peripheral */
        at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN);     /* Set Master mode */

        /* Calcuate clock dividers */
        cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3;
        cdiv = cdiv + 1;        /* round up */
        ckdiv = 0;
        while (cdiv > 255) {
                ckdiv++;
                cdiv = cdiv >> 1;
        }

        if (cpu_is_at91rm9200()) {                      /* AT91RM9200 Errata #22 */
                if (ckdiv > 5) {
                        printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n");
                        ckdiv = 5;
                }
        }

        at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
}

/*
 * Poll the i2c status register until the specified bit is set.
 * Returns 0 if timed out (100 msec).
 */
static short at91_poll_status(unsigned long bit)
{
        int loop_cntr = 10000;

        do {
                udelay(10);
        } while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0));

        return (loop_cntr > 0);
}

static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length)
{
        /* Send Start */
        at91_twi_write(AT91_TWI_CR, AT91_TWI_START);

        /* Read data */
        while (length--) {
                if (!length)    /* need to send Stop before reading last byte */
                        at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
                if (!at91_poll_status(AT91_TWI_RXRDY)) {
                        dev_dbg(&adap->dev, "RXRDY timeout\n");
                        return -ETIMEDOUT;
                }
                *buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff);
        }

        return 0;
}

static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length)
{
        /* Load first byte into transmitter */
        at91_twi_write(AT91_TWI_THR, *buf++);

        /* Send Start */
        at91_twi_write(AT91_TWI_CR, AT91_TWI_START);

        do {
                if (!at91_poll_status(AT91_TWI_TXRDY)) {
                        dev_dbg(&adap->dev, "TXRDY timeout\n");
                        return -ETIMEDOUT;
                }

                length--;       /* byte was transmitted */

                if (length > 0)         /* more data to send? */
                        at91_twi_write(AT91_TWI_THR, *buf++);
        } while (length);

        /* Send Stop */
        at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);

        return 0;
}

/*
 * Generic i2c master transfer entrypoint.
 *
 * Note: We do not use Atmel's feature of storing the "internal device address".
 * Instead the "internal device address" has to be written using a separate
 * i2c message.
 * http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
 */
static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num)
{
        int i, ret;

        dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);

        for (i = 0; i < num; i++) {
                dev_dbg(&adap->dev, " #%d: %sing %d byte%s %s 0x%02x\n", i,
                        pmsg->flags & I2C_M_RD ? "read" : "writ",
                        pmsg->len, pmsg->len > 1 ? "s" : "",
                        pmsg->flags & I2C_M_RD ? "from" : "to", pmsg->addr);

                at91_twi_write(AT91_TWI_MMR, (pmsg->addr << 16)
                        | ((pmsg->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));

                if (pmsg->len && pmsg->buf) {   /* sanity check */
                        if (pmsg->flags & I2C_M_RD)
                                ret = xfer_read(adap, pmsg->buf, pmsg->len);
                        else
                                ret = xfer_write(adap, pmsg->buf, pmsg->len);

                        if (ret)
                                return ret;

                        /* Wait until transfer is finished */
                        if (!at91_poll_status(AT91_TWI_TXCOMP)) {
                                dev_dbg(&adap->dev, "TXCOMP timeout\n");
                                return -ETIMEDOUT;
                        }
                }
                dev_dbg(&adap->dev, "transfer complete\n");
                pmsg++;         /* next message */
        }
        return i;
}

/*
 * Return list of supported functionality.
 */
static u32 at91_func(struct i2c_adapter *adapter)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static struct i2c_algorithm at91_algorithm = {
        .master_xfer    = at91_xfer,
        .functionality  = at91_func,
};

/*
 * Main initialization routine.
 */
static int __devinit at91_i2c_probe(struct platform_device *pdev)
{
        struct i2c_adapter *adapter;
        struct resource *res;
        int rc;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        if (!res)
                return -ENXIO;

        if (!request_mem_region(res->start, resource_size(res), "at91_i2c"))
                return -EBUSY;

        twi_base = ioremap(res->start, resource_size(res));
        if (!twi_base) {
                rc = -ENOMEM;
                goto fail0;
        }

        twi_clk = clk_get(NULL, "twi_clk");
        if (IS_ERR(twi_clk)) {
                dev_err(&pdev->dev, "no clock defined\n");
                rc = -ENODEV;
                goto fail1;
        }

        adapter = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
        if (adapter == NULL) {
                dev_err(&pdev->dev, "can't allocate inteface!\n");
                rc = -ENOMEM;
                goto fail2;
        }
        snprintf(adapter->name, sizeof(adapter->name), "AT91");
        adapter->algo = &at91_algorithm;
        adapter->class = I2C_CLASS_HWMON;
        adapter->dev.parent = &pdev->dev;
        /* adapter->id == 0 ... only one TWI controller for now */

        platform_set_drvdata(pdev, adapter);

        clk_enable(twi_clk);            /* enable peripheral clock */
        at91_twi_hwinit();              /* initialize TWI controller */

        rc = i2c_add_numbered_adapter(adapter);
        if (rc) {
                dev_err(&pdev->dev, "Adapter %s registration failed\n",
                                adapter->name);
                goto fail3;
        }

        dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
        return 0;

fail3:
        platform_set_drvdata(pdev, NULL);
        kfree(adapter);
        clk_disable(twi_clk);
fail2:
        clk_put(twi_clk);
fail1:
        iounmap(twi_base);
fail0:
        release_mem_region(res->start, resource_size(res));

        return rc;
}

static int __devexit at91_i2c_remove(struct platform_device *pdev)
{
        struct i2c_adapter *adapter = platform_get_drvdata(pdev);
        struct resource *res;
        int rc;

        rc = i2c_del_adapter(adapter);
        platform_set_drvdata(pdev, NULL);

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        iounmap(twi_base);
        release_mem_region(res->start, resource_size(res));

        clk_disable(twi_clk);           /* disable peripheral clock */
        clk_put(twi_clk);

        return rc;
}

#ifdef CONFIG_PM

/* NOTE: could save a few mA by keeping clock off outside of at91_xfer... */

static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
{
        clk_disable(twi_clk);
        return 0;
}

static int at91_i2c_resume(struct platform_device *pdev)
{
        return clk_enable(twi_clk);
}

#else
#define at91_i2c_suspend        NULL
#define at91_i2c_resume         NULL
#endif

/* work with "modprobe at91_i2c" from hotplugging or coldplugging */
MODULE_ALIAS("platform:at91_i2c");

static struct platform_driver at91_i2c_driver = {
        .probe          = at91_i2c_probe,
        .remove         = __devexit_p(at91_i2c_remove),
        .suspend        = at91_i2c_suspend,
        .resume         = at91_i2c_resume,
        .driver         = {
                .name   = "at91_i2c",
                .owner  = THIS_MODULE,
        },
};

static int __init at91_i2c_init(void)
{
        return platform_driver_register(&at91_i2c_driver);
}

static void __exit at91_i2c_exit(void)
{
        platform_driver_unregister(&at91_i2c_driver);
}

module_init(at91_i2c_init);
module_exit(at91_i2c_exit);

MODULE_AUTHOR("Rick Bronson");
MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
MODULE_LICENSE("GPL");