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i2c-ixp2000.c

/*
 * drivers/i2c/busses/i2c-ixp2000.c
 *
 * I2C adapter for IXP2000 systems using GPIOs for I2C bus
 *
 * Author: Deepak Saxena <dsaxena@plexity.net>
 * Based on IXDP2400 code by: Naeem M. Afzal <naeem.m.afzal@intel.com>
 * Made generic by: Jeff Daly <jeffrey.daly@intel.com>
 *
 * Copyright (c) 2003-2004 MontaVista Software Inc.
 *
 * This file is licensed under  the terms of the GNU General Public 
 * License version 2. This program is licensed "as is" without any 
 * warranty of any kind, whether express or implied.
 *
 * From Jeff Daly:
 *
 * I2C adapter driver for Intel IXDP2xxx platforms. This should work for any
 * IXP2000 platform if it uses the HW GPIO in the same manner.  Basically, 
 * SDA and SCL GPIOs have external pullups.  Setting the respective GPIO to 
 * an input will make the signal a '1' via the pullup.  Setting them to 
 * outputs will pull them down. 
 *
 * The GPIOs are open drain signals and are used as configuration strap inputs
 * during power-up so there's generally a buffer on the board that needs to be 
 * 'enabled' to drive the GPIOs.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>

#include <asm/hardware.h>     /* Pick up IXP2000-specific bits */
#include <asm/arch/gpio.h>

static inline int ixp2000_scl_pin(void *data)
{
      return ((struct ixp2000_i2c_pins*)data)->scl_pin;
}

static inline int ixp2000_sda_pin(void *data)
{
      return ((struct ixp2000_i2c_pins*)data)->sda_pin;
}


static void ixp2000_bit_setscl(void *data, int val)
{
      int i = 5000;

      if (val) {
            gpio_line_config(ixp2000_scl_pin(data), GPIO_IN);
            while(!gpio_line_get(ixp2000_scl_pin(data)) && i--);
      } else {
            gpio_line_config(ixp2000_scl_pin(data), GPIO_OUT);
      }
}

static void ixp2000_bit_setsda(void *data, int val)
{
      if (val) {
            gpio_line_config(ixp2000_sda_pin(data), GPIO_IN);
      } else {
            gpio_line_config(ixp2000_sda_pin(data), GPIO_OUT);
      }
}

static int ixp2000_bit_getscl(void *data)
{
      return gpio_line_get(ixp2000_scl_pin(data));
}

static int ixp2000_bit_getsda(void *data)
{
      return gpio_line_get(ixp2000_sda_pin(data));
}

struct ixp2000_i2c_data {
      struct ixp2000_i2c_pins *gpio_pins;
      struct i2c_adapter adapter;
      struct i2c_algo_bit_data algo_data;
};

static int ixp2000_i2c_remove(struct platform_device *plat_dev)
{
      struct ixp2000_i2c_data *drv_data = platform_get_drvdata(plat_dev);

      platform_set_drvdata(plat_dev, NULL);

      i2c_del_adapter(&drv_data->adapter);

      kfree(drv_data);

      return 0;
}

static int ixp2000_i2c_probe(struct platform_device *plat_dev)
{
      int err;
      struct ixp2000_i2c_pins *gpio = plat_dev->dev.platform_data;
      struct ixp2000_i2c_data *drv_data = 
            kzalloc(sizeof(struct ixp2000_i2c_data), GFP_KERNEL);

      if (!drv_data)
            return -ENOMEM;
      drv_data->gpio_pins = gpio;

      drv_data->algo_data.data = gpio;
      drv_data->algo_data.setsda = ixp2000_bit_setsda;
      drv_data->algo_data.setscl = ixp2000_bit_setscl;
      drv_data->algo_data.getsda = ixp2000_bit_getsda;
      drv_data->algo_data.getscl = ixp2000_bit_getscl;
      drv_data->algo_data.udelay = 6;
      drv_data->algo_data.timeout = 100;

      drv_data->adapter.id = I2C_HW_B_IXP2000,
      strlcpy(drv_data->adapter.name, plat_dev->dev.driver->name,
            sizeof(drv_data->adapter.name));
      drv_data->adapter.algo_data = &drv_data->algo_data,

      drv_data->adapter.dev.parent = &plat_dev->dev;

      gpio_line_config(gpio->sda_pin, GPIO_IN);
      gpio_line_config(gpio->scl_pin, GPIO_IN);
      gpio_line_set(gpio->scl_pin, 0);
      gpio_line_set(gpio->sda_pin, 0);

      if ((err = i2c_bit_add_bus(&drv_data->adapter)) != 0) {
            dev_err(&plat_dev->dev, "Could not install, error %d\n", err);
            kfree(drv_data);
            return err;
      } 

      platform_set_drvdata(plat_dev, drv_data);

      return 0;
}

static struct platform_driver ixp2000_i2c_driver = {
      .probe            = ixp2000_i2c_probe,
      .remove           = ixp2000_i2c_remove,
      .driver           = {
            .name = "IXP2000-I2C",
            .owner      = THIS_MODULE,
      },
};

static int __init ixp2000_i2c_init(void)
{
      return platform_driver_register(&ixp2000_i2c_driver);
}

static void __exit ixp2000_i2c_exit(void)
{
      platform_driver_unregister(&ixp2000_i2c_driver);
}

module_init(ixp2000_i2c_init);
module_exit(ixp2000_i2c_exit);

MODULE_AUTHOR ("Deepak Saxena <dsaxena@plexity.net>");
MODULE_DESCRIPTION("IXP2000 GPIO-based I2C bus driver");
MODULE_LICENSE("GPL");


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