ocotp.c

Go to the documentation of this file.

/*
 * Copyright 2010 Freescale Semiconductor, Inc. All Rights Reserved.
 *
 * 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.
 */

#include <linux/delay.h>
#include <linux/err.h>
#include <linux/mutex.h>

#include <asm/processor.h>  /* for cpu_relax() */

#include <mach/mxs.h>

#define OCOTP_WORD_OFFSET       0x20
#define OCOTP_WORD_COUNT        0x20

#define BM_OCOTP_CTRL_BUSY      (1 << 8)
#define BM_OCOTP_CTRL_ERROR     (1 << 9)
#define BM_OCOTP_CTRL_RD_BANK_OPEN  (1 << 12)

static DEFINE_MUTEX(ocotp_mutex);
static u32 ocotp_words[OCOTP_WORD_COUNT];

const u32 *mxs_get_ocotp(void)
{
    void __iomem *ocotp_base = MXS_IO_ADDRESS(MXS_OCOTP_BASE_ADDR);
    int timeout = 0x400;
    size_t i;
    static int once = 0;

    if (once)
        return ocotp_words;

    mutex_lock(&ocotp_mutex);

    /*
     * clk_enable(hbus_clk) for ocotp can be skipped
     * as it must be on when system is running.
     */

    /* try to clear ERROR bit */
    __mxs_clrl(BM_OCOTP_CTRL_ERROR, ocotp_base);

    /* check both BUSY and ERROR cleared */
    while ((__raw_readl(ocotp_base) &
        (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR)) && --timeout)
        cpu_relax();

    if (unlikely(!timeout))
        goto error_unlock;

    /* open OCOTP banks for read */
    __mxs_setl(BM_OCOTP_CTRL_RD_BANK_OPEN, ocotp_base);

    /* approximately wait 32 hclk cycles */
    udelay(1);

    /* poll BUSY bit becoming cleared */
    timeout = 0x400;
    while ((__raw_readl(ocotp_base) & BM_OCOTP_CTRL_BUSY) && --timeout)
        cpu_relax();

    if (unlikely(!timeout))
        goto error_unlock;

    for (i = 0; i < OCOTP_WORD_COUNT; i++)
        ocotp_words[i] = __raw_readl(ocotp_base + OCOTP_WORD_OFFSET +
                        i * 0x10);

    /* close banks for power saving */
    __mxs_clrl(BM_OCOTP_CTRL_RD_BANK_OPEN, ocotp_base);

    once = 1;

    mutex_unlock(&ocotp_mutex);

    return ocotp_words;

error_unlock:
    mutex_unlock(&ocotp_mutex);
    pr_err("%s: timeout in reading OCOTP\n", __func__);
    return NULL;
}