/*
 * Blackfin On-Chip OTP Memory Interface
 *  Supports BF52x/BF54x
 *
 * Copyright 2007-2008 Analog Devices Inc.
 *
 * Enter bugs at http://blackfin.uclinux.org/
 *
 * Licensed under the GPL-2 or later.
 */

#include <linux/device.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/types.h>

#include <asm/blackfin.h>
#include <asm/uaccess.h>

#define stamp(fmt, args...) pr_debug("%s:%i: " fmt "\n", __func__, __LINE__, ## args)
#define stampit() stamp("here i am")
#define pr_init(fmt, args...) ({ static const __initconst char __fmt[] = fmt; printk(__fmt, ## args); })

#define DRIVER_NAME "bfin-otp"
#define PFX DRIVER_NAME ": "

static DEFINE_MUTEX(bfin_otp_lock);

/* OTP Boot ROM functions */
#define _BOOTROM_OTP_COMMAND           0xEF000018
#define _BOOTROM_OTP_READ              0xEF00001A
#define _BOOTROM_OTP_WRITE             0xEF00001C

static u32 (* const otp_command)(u32 command, u32 value) = (void *)_BOOTROM_OTP_COMMAND;
static u32 (* const otp_read)(u32 page, u32 flags, u64 *page_content) = (void *)_BOOTROM_OTP_READ;
static u32 (* const otp_write)(u32 page, u32 flags, u64 *page_content) = (void *)_BOOTROM_OTP_WRITE;

/* otp_command(): defines for "command" */
#define OTP_INIT             0x00000001
#define OTP_CLOSE            0x00000002

/* otp_{read,write}(): defines for "flags" */
#define OTP_LOWER_HALF       0x00000000 /* select upper/lower 64-bit half (bit 0) */
#define OTP_UPPER_HALF       0x00000001
#define OTP_NO_ECC           0x00000010 /* do not use ECC */
#define OTP_LOCK             0x00000020 /* sets page protection bit for page */
#define OTP_ACCESS_READ      0x00001000
#define OTP_ACCESS_READWRITE 0x00002000

/* Return values for all functions */
#define OTP_SUCCESS          0x00000000
#define OTP_MASTER_ERROR     0x001
#define OTP_WRITE_ERROR      0x003
#define OTP_READ_ERROR       0x005
#define OTP_ACC_VIO_ERROR    0x009
#define OTP_DATA_MULT_ERROR  0x011
#define OTP_ECC_MULT_ERROR   0x021
#define OTP_PREV_WR_ERROR    0x041
#define OTP_DATA_SB_WARN     0x100
#define OTP_ECC_SB_WARN      0x200

/**
 *	bfin_otp_read - Read OTP pages
 *
 *	All reads must be in half page chunks (half page == 64 bits).
 */
static ssize_t bfin_otp_read(struct file *file, char __user *buff, size_t count, loff_t *pos)
{
	ssize_t bytes_done;
	u32 page, flags, ret;
	u64 content;

	stampit();

	if (count % sizeof(u64))
		return -EMSGSIZE;

	if (mutex_lock_interruptible(&bfin_otp_lock))
		return -ERESTARTSYS;

	bytes_done = 0;
	page = *pos / (sizeof(u64) * 2);
	while (bytes_done < count) {
		flags = (*pos % (sizeof(u64) * 2) ? OTP_UPPER_HALF : OTP_LOWER_HALF);
		stamp("processing page %i (%s)", page, (flags == OTP_UPPER_HALF ? "upper" : "lower"));
		ret = otp_read(page, flags, &content);
		if (ret & OTP_MASTER_ERROR) {
			bytes_done = -EIO;
			break;
		}
		if (copy_to_user(buff + bytes_done, &content, sizeof(content))) {
			bytes_done = -EFAULT;
			break;
		}
		if (flags == OTP_UPPER_HALF)
			++page;
		bytes_done += sizeof(content);
		*pos += sizeof(content);
	}

	mutex_unlock(&bfin_otp_lock);

	return bytes_done;
}

#ifdef CONFIG_BFIN_OTP_WRITE_ENABLE
/**
 *	bfin_otp_write - Write OTP pages
 *
 *	All writes must be in half page chunks (half page == 64 bits).
 */
static ssize_t bfin_otp_write(struct file *filp, const char __user *buff, size_t count, loff_t *pos)
{
	stampit();

	if (count % sizeof(u64))
		return -EMSGSIZE;

	if (mutex_lock_interruptible(&bfin_otp_lock))
		return -ERESTARTSYS;

	/* need otp_init() documentation before this can be implemented */

	mutex_unlock(&bfin_otp_lock);

	return -EINVAL;
}
#else
# define bfin_otp_write NULL
#endif

static struct file_operations bfin_otp_fops = {
	.owner    = THIS_MODULE,
	.read     = bfin_otp_read,
	.write    = bfin_otp_write,
};

static struct miscdevice bfin_otp_misc_device = {
	.minor    = MISC_DYNAMIC_MINOR,
	.name     = DRIVER_NAME,
	.fops     = &bfin_otp_fops,
};

/**
 *	bfin_otp_init - Initialize module
 *
 *	Registers the device and notifier handler. Actual device
 *	initialization is handled by bfin_otp_open().
 */
static int __init bfin_otp_init(void)
{
	int ret;

	stampit();

	ret = misc_register(&bfin_otp_misc_device);
	if (ret) {
		pr_init(KERN_ERR PFX "unable to register a misc device\n");
		return ret;
	}

	pr_init(KERN_INFO PFX "initialized\n");

	return 0;
}

/**
 *	bfin_otp_exit - Deinitialize module
 *
 *	Unregisters the device and notifier handler. Actual device
 *	deinitialization is handled by bfin_otp_close().
 */
static void __exit bfin_otp_exit(void)
{
	stampit();

	misc_deregister(&bfin_otp_misc_device);
}

module_init(bfin_otp_init);
module_exit(bfin_otp_exit);

MODULE_AUTHOR("Mike Frysinger <vapier@gentoo.org>");
MODULE_DESCRIPTION("Blackfin OTP Memory Interface");
MODULE_LICENSE("GPL");