/*
 * Blackfin On-Chip OTP Memory Interface
 *
 * Copyright 2007-2009 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 <mtd/mtd-abi.h>

#include <asm/blackfin.h>
#include <asm/bfrom.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);

/**
 *      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 (0x%x:%s)", page, flags,
                        (flags & OTP_UPPER_HALF ? "upper" : "lower"));
                ret = bfrom_OtpRead(page, flags, &content);
                if (ret & OTP_MASTER_ERROR) {
                        stamp("error from otp: 0x%x", ret);
                        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
static bool allow_writes;

/**
 *      bfin_otp_init_timing - setup OTP timing parameters
 *
 *      Required before doing any write operation.  Algorithms from HRM.
 */
static u32 bfin_otp_init_timing(void)
{
        u32 tp1, tp2, tp3, timing;

        tp1 = get_sclk() / 1000000;
        tp2 = (2 * get_sclk() / 10000000) << 8;
        tp3 = (0x1401) << 15;
        timing = tp1 | tp2 | tp3;
        if (bfrom_OtpCommand(OTP_INIT, timing))
                return 0;

        return timing;
}

/**
 *      bfin_otp_deinit_timing - set timings to only allow reads
 *
 *      Should be called after all writes are done.
 */
static void bfin_otp_deinit_timing(u32 timing)
{
        /* mask bits [31:15] so that any attempts to write fail */
        bfrom_OtpCommand(OTP_CLOSE, 0);
        bfrom_OtpCommand(OTP_INIT, timing & ~(-1 << 15));
        bfrom_OtpCommand(OTP_CLOSE, 0);
}

/**
 *      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)
{
        ssize_t bytes_done;
        u32 timing, page, base_flags, flags, ret;
        u64 content;

        if (!allow_writes)
                return -EACCES;

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

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

        stampit();

        timing = bfin_otp_init_timing();
        if (timing == 0) {
                mutex_unlock(&bfin_otp_lock);
                return -EIO;
        }

        base_flags = OTP_CHECK_FOR_PREV_WRITE;

        bytes_done = 0;
        page = *pos / (sizeof(u64) * 2);
        while (bytes_done < count) {
                flags = base_flags | (*pos % (sizeof(u64) * 2) ? OTP_UPPER_HALF : OTP_LOWER_HALF);
                stamp("processing page %i (0x%x:%s) from %p", page, flags,
                        (flags & OTP_UPPER_HALF ? "upper" : "lower"), buff + bytes_done);
                if (copy_from_user(&content, buff + bytes_done, sizeof(content))) {
                        bytes_done = -EFAULT;
                        break;
                }
                ret = bfrom_OtpWrite(page, flags, &content);
                if (ret & OTP_MASTER_ERROR) {
                        stamp("error from otp: 0x%x", ret);
                        bytes_done = -EIO;
                        break;
                }
                if (flags & OTP_UPPER_HALF)
                        ++page;
                bytes_done += sizeof(content);
                *pos += sizeof(content);
        }

        bfin_otp_deinit_timing(timing);

        mutex_unlock(&bfin_otp_lock);

        return bytes_done;
}

static long bfin_otp_ioctl(struct file *filp, unsigned cmd, unsigned long arg)
{
        stampit();

        switch (cmd) {
        case OTPLOCK: {
                u32 timing;
                int ret = -EIO;

                if (!allow_writes)
                        return -EACCES;

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

                timing = bfin_otp_init_timing();
                if (timing) {
                        u32 otp_result = bfrom_OtpWrite(arg, OTP_LOCK, NULL);
                        stamp("locking page %lu resulted in 0x%x", arg, otp_result);
                        if (!(otp_result & OTP_MASTER_ERROR))
                                ret = 0;

                        bfin_otp_deinit_timing(timing);
                }

                mutex_unlock(&bfin_otp_lock);

                return ret;
        }

        case MEMLOCK:
                allow_writes = false;
                return 0;

        case MEMUNLOCK:
                allow_writes = true;
                return 0;
        }

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

static const struct file_operations bfin_otp_fops = {
        .owner          = THIS_MODULE,
        .unlocked_ioctl = bfin_otp_ioctl,
        .read           = bfin_otp_read,
        .write          = bfin_otp_write,
        .llseek         = default_llseek,
};

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");