arch/arm/mach-mxs/ocotp.c

   1 /*
   2  * Copyright 2010 Freescale Semiconductor, Inc. All Rights Reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #include <linux/delay.h>
  16 #include <linux/err.h>
  17 #include <linux/mutex.h>
  18
  19 #include <asm/processor.h>      /* for cpu_relax() */
  20
  21 #include <mach/mxs.h>
  22
  23 #define OCOTP_WORD_OFFSET               0x20
  24 #define OCOTP_WORD_COUNT                0x20
  25
  26 #define BM_OCOTP_CTRL_BUSY              (1 << 8)
  27 #define BM_OCOTP_CTRL_ERROR             (1 << 9)
  28 #define BM_OCOTP_CTRL_RD_BANK_OPEN      (1 << 12)
  29
  30 static DEFINE_MUTEX(ocotp_mutex);
  31 static u32 ocotp_words[OCOTP_WORD_COUNT];
  32
  33 const u32 *mxs_get_ocotp(void)
  34 {
  35         void __iomem *ocotp_base = MXS_IO_ADDRESS(MXS_OCOTP_BASE_ADDR);
  36         int timeout = 0x400;
  37         size_t i;
  38         static int once = 0;
  39
  40         if (once)
  41                 return ocotp_words;
  42
  43         mutex_lock(&ocotp_mutex);
  44
  45         /*
  46          * clk_enable(hbus_clk) for ocotp can be skipped
  47          * as it must be on when system is running.
  48          */
  49
  50         /* try to clear ERROR bit */
  51         __mxs_clrl(BM_OCOTP_CTRL_ERROR, ocotp_base);
  52
  53         /* check both BUSY and ERROR cleared */
  54         while ((__raw_readl(ocotp_base) &
  55                 (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR)) && --timeout)
  56                 cpu_relax();
  57
  58         if (unlikely(!timeout))
  59                 goto error_unlock;
  60
  61         /* open OCOTP banks for read */
  62         __mxs_setl(BM_OCOTP_CTRL_RD_BANK_OPEN, ocotp_base);
  63
  64         /* approximately wait 32 hclk cycles */
  65         udelay(1);
  66
  67         /* poll BUSY bit becoming cleared */
  68         timeout = 0x400;
  69         while ((__raw_readl(ocotp_base) & BM_OCOTP_CTRL_BUSY) && --timeout)
  70                 cpu_relax();
  71
  72         if (unlikely(!timeout))
  73                 goto error_unlock;
  74
  75         for (i = 0; i < OCOTP_WORD_COUNT; i++)
  76                 ocotp_words[i] = __raw_readl(ocotp_base + OCOTP_WORD_OFFSET +
  77                                                 i * 0x10);
  78
  79         /* close banks for power saving */
  80         __mxs_clrl(BM_OCOTP_CTRL_RD_BANK_OPEN, ocotp_base);
  81
  82         once = 1;
  83
  84         mutex_unlock(&ocotp_mutex);
  85
  86         return ocotp_words;
  87
  88 error_unlock:
  89         mutex_unlock(&ocotp_mutex);
  90         pr_err("%s: timeout in reading OCOTP\n", __func__);
  91         return NULL;
  92 }