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(struct ecc_state_s *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(struct ecc_state_s *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: void ecc_put(QEMUFile *f, struct ecc_state_s *s)
   78: {
   79:     qemu_put_8s(f, &s->cp);
   80:     qemu_put_be16s(f, &s->lp[0]);
   81:     qemu_put_be16s(f, &s->lp[1]);
   82:     qemu_put_be16s(f, &s->count);
   83: }
   84: 
   85: void ecc_get(QEMUFile *f, struct ecc_state_s *s)
   86: {
   87:     qemu_get_8s(f, &s->cp);
   88:     qemu_get_be16s(f, &s->lp[0]);
   89:     qemu_get_be16s(f, &s->lp[1]);
   90:     qemu_get_be16s(f, &s->count);
   91: }