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 "vl.h"
  12
  13 /*
  14  * Pre-calculated 256-way 1 byte column parity.  Table borrowed from Linux.
  15  */
  16 static const uint8_t nand_ecc_precalc_table[] = {
  17     0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a,
  18     0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  19     0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f,
  20     0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  21     0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c,
  22     0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  23     0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59,
  24     0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  25     0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33,
  26     0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  27     0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56,
  28     0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  29     0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55,
  30     0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  31     0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30,
  32     0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  33     0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30,
  34     0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
  35     0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55,
  36     0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
  37     0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56,
  38     0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
  39     0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33,
  40     0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
  41     0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59,
  42     0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
  43     0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c,
  44     0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
  45     0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f,
  46     0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
  47     0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a,
  48     0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
  49 };
  50
  51 /* Update ECC parity count.  */
  52 uint8_t ecc_digest(struct ecc_state_s *s, uint8_t sample)
  53 {
  54     uint8_t idx = nand_ecc_precalc_table[sample];
  55
  56     s->cp ^= idx & 0x3f;
  57     if (idx & 0x40) {
  58         s->lp[0] ^= ~s->count;
  59         s->lp[1] ^= s->count;
  60     }
  61     s->count ++;
  62
  63     return sample;
  64 }
  65
  66 /* Reinitialise the counters.  */
  67 void ecc_reset(struct ecc_state_s *s)
  68 {
  69     s->lp[0] = 0x0000;
  70     s->lp[1] = 0x0000;
  71     s->cp = 0x00;
  72     s->count = 0;
  73 }
  74
  75 /* Save/restore */
  76 void ecc_put(QEMUFile *f, struct ecc_state_s *s)
  77 {
  78     qemu_put_8s(f, &s->cp);
  79     qemu_put_be16s(f, &s->lp[0]);
  80     qemu_put_be16s(f, &s->lp[1]);
  81     qemu_put_be16s(f, &s->count);
  82 }
  83
  84 void ecc_get(QEMUFile *f, struct ecc_state_s *s)
  85 {
  86     qemu_get_8s(f, &s->cp);
  87     qemu_get_be16s(f, &s->lp[0]);
  88     qemu_get_be16s(f, &s->lp[1]);
  89     qemu_get_be16s(f, &s->count);
  90 }