hw/ecc.c

   1 /*
   2  * Calculate Error-correcting Codes. Used by NAND Flash controllers
   3  * (not by NAND chips).
   4  *
   5  * Copyright (c) 2006 Openedhand Ltd.
   6  * Written by Andrzej Zaborowski <balrog@zabor.org>
   7  *
   8  * This code is licensed under the GNU GPL v2.
   9  */
  10
  11 #include "hw.h"
  12 #include "flash.h"
  13
  14 /*
  15  * Pre-calculated 256-way 1 byte column parity.  Table borrowed from Linux.
  16  */
  17 static const uint8_t nand_ecc_precalc_table[] = {
  18     0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a,
  19     0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  20     0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f,
  21     0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  22     0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c,
  23     0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  24     0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59,
  25     0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  26     0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33,
  27     0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  28     0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56,
  29     0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  30     0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55,
  31     0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  32     0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30,
  33     0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  34     0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30,
  35     0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  36     0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55,
  37     0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  38     0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56,
  39     0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  40     0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33,
  41     0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  42     0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59,
  43     0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  44     0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c,
  45     0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  46     0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f,
  47     0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  48     0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a,
  49     0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  50 };
  51
  52 /* Update ECC parity count.  */
  53 uint8_t ecc_digest(ECCState *s, uint8_t sample)
  54 {
  55     uint8_t idx = nand_ecc_precalc_table[sample];
  56
  57     s->cp ^= idx & 0x3f;
  58     if (idx & 0x40) {
  59         s->lp[0] ^= ~s->count;
  60         s->lp[1] ^= s->count;
  61     }
  62     s->count ++;
  63
  64     return sample;
  65 }
  66
  67 /* Reinitialise the counters.  */
  68 void ecc_reset(ECCState *s)
  69 {
  70     s->lp[0] = 0x0000;
  71     s->lp[1] = 0x0000;
  72     s->cp = 0x00;
  73     s->count = 0;
  74 }
  75
  76 /* Save/restore */
  77 VMStateDescription vmstate_ecc_state = {
  78     .name = "ecc-state",
  79     .version_id = 0,
  80     .minimum_version_id = 0,
  81     .minimum_version_id_old = 0,
  82     .fields = (VMStateField []) {
  83         VMSTATE_UINT8(cp, ECCState),
  84         VMSTATE_UINT16_ARRAY(lp, ECCState, 2),
  85         VMSTATE_UINT16(count, ECCState),
  86         VMSTATE_END_OF_LIST(),
  87     },
  88 };