bfin-otp.c

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/*
 * 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);

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;

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;
}

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);
}

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,
};

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;
}

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 <[email protected]>");
MODULE_DESCRIPTION("Blackfin OTP Memory Interface");
MODULE_LICENSE("GPL");