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i2c-at91.c

/*
    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/version.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 <asm/io.h>

#include <asm/arch/at91_twi.h>
#include <asm/arch/board.h>
#include <asm/arch/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, res->end - res->start + 1, "at91_i2c"))
            return -EBUSY;

      twi_base = ioremap(res->start, res->end - res->start + 1);
      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;
      }
      sprintf(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, res->end - res->start + 1);

      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, res->end - res->start + 1);

      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("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");

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