/*

 * Calculate Error-correcting Codes. Used by NAND Flash controllers

 * (not by NAND chips).

 *

 * Copyright (c) 2006 Openedhand Ltd.

 * Written by Andrzej Zaborowski <balrog@zabor.org>

 *

 * This code is licensed under the GNU GPL v2.

 */

#include "hw.h"

#include "flash.h"

/*

 * Pre-calculated 256-way 1 byte column parity.  Table borrowed from Linux.

 */

static const uint8_t nand_ecc_precalc_table[] = {

    0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a,

    0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,

    0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f,

    0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,

    0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c,

    0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,

    0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59,

    0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,

    0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33,

    0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,

    0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56,

    0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,

    0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55,

    0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,

    0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30,

    0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,

    0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30,

    0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,

    0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55,

    0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,

    0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56,

    0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,

    0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33,

    0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,

    0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59,

    0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,

    0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c,

    0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,

    0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f,

    0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,

    0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a,

    0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,

};

/* Update ECC parity count.  */

uint8_t ecc_digest(struct ecc_state_s *s, uint8_t sample)

{

    uint8_t idx = nand_ecc_precalc_table[sample];

    s->cp ^= idx & 0x3f;

    if (idx & 0x40) {

        s->lp[0] ^= ~s->count;

        s->lp[1] ^= s->count;

    }

    s->count ++;

    return sample;

}

/* Reinitialise the counters.  */

void ecc_reset(struct ecc_state_s *s)

{

    s->lp[0] = 0x0000;

    s->lp[1] = 0x0000;

    s->cp = 0x00;

    s->count = 0;

}

/* Save/restore */

void ecc_put(QEMUFile *f, struct ecc_state_s *s)

{

    qemu_put_8s(f, &s->cp);

    qemu_put_be16s(f, &s->lp[0]);

    qemu_put_be16s(f, &s->lp[1]);

    qemu_put_be16s(f, &s->count);

}

void ecc_get(QEMUFile *f, struct ecc_state_s *s)

{

    qemu_get_8s(f, &s->cp);

    qemu_get_be16s(f, &s->lp[0]);

    qemu_get_be16s(f, &s->lp[1]);

    qemu_get_be16s(f, &s->count);

}