/*
 *  mx21_gpio.c
 *
 *  author: Tarun Tuli <tarun@virtualcogs.com>
 *  Created: Sept 22, 2007
 *  Copyright: 2007 Virtual Cogs Embedded Systems Inc.
 *
 *  Provides access to the GPIO space on the i.MX21 from userspace thru IOCTL
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/version.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <linux/vmalloc.h>
#include <linux/mman.h>
#include <linux/slab.h>
#include <linux/ioport.h>

#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
#include <linux/wrapper.h>
#endif

#define mx21gpio_MAJOR 240
#define mx21gpio_NAME "gpio"

#define GPIO_BASE 0x10015000
#define GPIO_MASK 0x00000fff
#define GPIO_SIZE 0x600
#define COMMAND_MASK 0x80000000

#undef DEBUG

volatile unsigned int *gpio_ptr;
unsigned int offset;

DECLARE_WAIT_QUEUE_HEAD(mx21gpio_wait);

static int mx21gpio_open1 (struct inode *inode, struct file *file) {

	return 0;
}

static int mx21gpio_release1 (struct inode *inode, struct file *file) {

	return 0;
}

static int mx21gpio_ioctl1(struct inode *inode, struct file *file,
		unsigned int cmd, unsigned long arg) {

	int retval = 0;
	unsigned int *access_addr;
	unsigned int command_type;
	unsigned int offset;
	
	command_type = 0x80000000ul;
	
	// Set the offset for register accesses
	command_type = COMMAND_MASK & cmd;

	offset = ~COMMAND_MASK & cmd & GPIO_MASK;
	if(offset > GPIO_SIZE)
		retval=-EINVAL;

	offset = offset >> 2;	// adjust to 32bit boundary
	access_addr = (unsigned int *)(gpio_ptr + offset);

#ifdef DEBUG
	printk("GPIO:  Command Type: %d\n       Access Address: 0x%.4x (GPIO_PTR: 0x%.4x, Offset: 0x%.4x)\n       Arg: 0x%.4x\n       Cmd: 0x%.4x    \n", command_type, access_addr, gpio_ptr, offset, arg, cmd);
#endif

	switch(command_type)
	{
		case 0:
			//read
			if(!access_ok(VERIFY_READ, (unsigned int *)arg, sizeof(int)))
				return -EFAULT;

			*(unsigned int *)arg = readl((volatile unsigned int *)&gpio_ptr[offset]);
			break;
		case COMMAND_MASK:
			//write
			if(!access_ok(VERIFY_WRITE, (unsigned int *)arg, sizeof(int)))
				return -EFAULT;

			writel(*(unsigned int *)arg,(volatile unsigned int *)&gpio_ptr[offset]); 
			break;
		default:
			retval = -EINVAL;
	}

	return retval;
}

// define which file operations are supported
struct file_operations mx21gpio_fops = {
	.owner	=	THIS_MODULE,
	.llseek	=	NULL,
	.read		=	NULL,
	.write	=	NULL,
	.readdir	=	NULL,
	.poll		=	NULL,
	.ioctl	=	mx21gpio_ioctl1,
	.mmap		=	NULL,
	.open		=	mx21gpio_open1,
	.flush	=	NULL,
	.release	=	mx21gpio_release1,
	.fsync	=	NULL,
	.fasync	=	NULL,
	.lock		=	NULL,
	.readv	=	NULL,
	.writev	=	NULL,
};

// initialize module
static int __init mx21gpio_init_module (void) {
	printk("i.MX21 GPIO Interface Module\n");
	printk(KERN_INFO "\nGPIO: i.MX21 GPIO Driver Loading.\n");
	printk(KERN_INFO "GPIO: Using Major Number %d on %s\n", mx21gpio_MAJOR, mx21gpio_NAME); 
	if (register_chrdev(mx21gpio_MAJOR, mx21gpio_NAME, &mx21gpio_fops)) {
		printk("GPIO: unable to get major %d. ABORTING!\n", mx21gpio_MAJOR);
		return -EBUSY;
	}

	// Perform Memory REMAP
	if (check_mem_region(GPIO_BASE, GPIO_SIZE))
	{
		printk(KERN_ERR "GPIO: Unable to acquire GPIO address.\n");
		return -EBUSY;
	}

	request_mem_region(GPIO_BASE, GPIO_SIZE, mx21gpio_NAME);
	gpio_ptr = (volatile unsigned int *)__ioremap(GPIO_BASE, GPIO_SIZE, 0);


	if (!gpio_ptr)
	{
		printk(KERN_ERR "GPIO: Unable to map GPIO.\n");
		release_mem_region(GPIO_BASE, GPIO_SIZE);
		return -EBUSY;
	}

	printk("GPIO: 0x%.4x size 0x%.4x mapped to 0x%.4x\n", GPIO_BASE, GPIO_SIZE, (unsigned int)gpio_ptr);

	return 0;
}

static void __exit mx21gpio_cleanup_module (void) {
	iounmap((void *)gpio_ptr);
	release_mem_region(GPIO_BASE, GPIO_SIZE);
	printk("GPIO: Device released.\n");
	unregister_chrdev (mx21gpio_MAJOR, mx21gpio_NAME);
}

module_init(mx21gpio_init_module);
module_exit(mx21gpio_cleanup_module);
MODULE_AUTHOR("tarun@virtualcogs.com");
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("iMX21 GPIO Device Driver");