+++ /dev/null
-/*
- * drivers/mtd/nand_ecc.c
- *
- * Copyright (C) 2000 Steven J. Hill (sjhill@cotw.com)
- * Toshiba America Electronics Components, Inc.
- *
- * $Id: nand_ecc.c,v 1.3 2002-09-27 20:50:50 charles Exp $
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public License
- * version 2.1 as published by the Free Software Foundation.
- *
- * This file contains an ECC algorithm from Toshiba that detects and
- * corrects 1 bit errors in a 256 byte block of data.
- */
- // Minor tweak by Charles Manning to prevent exporting symbols
- // when compiled in with yaffs.
-
-const char *nand_ecc_c_version = "$Id: nand_ecc.c,v 1.3 2002-09-27 20:50:50 charles Exp $";
-
-#if 0
-#include <linux/types.h>
-#include <linux/kernel.h>
-#include <linux/module.h>
-#endif
-
-#include "yportenv.h"
-
-/*
- * Pre-calculated 256-way 1 byte column parity
- */
-static const u_char 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
-};
-
-
-/*
- * Creates non-inverted ECC code from line parity
- */
-static void nand_trans_result(u_char reg2, u_char reg3,
- u_char *ecc_code)
-{
- u_char a, b, i, tmp1, tmp2;
-
- /* Initialize variables */
- a = b = 0x80;
- tmp1 = tmp2 = 0;
-
- /* Calculate first ECC byte */
- for (i = 0; i < 4; i++) {
- if (reg3 & a) /* LP15,13,11,9 --> ecc_code[0] */
- tmp1 |= b;
- b >>= 1;
- if (reg2 & a) /* LP14,12,10,8 --> ecc_code[0] */
- tmp1 |= b;
- b >>= 1;
- a >>= 1;
- }
-
- /* Calculate second ECC byte */
- b = 0x80;
- for (i = 0; i < 4; i++) {
- if (reg3 & a) /* LP7,5,3,1 --> ecc_code[1] */
- tmp2 |= b;
- b >>= 1;
- if (reg2 & a) /* LP6,4,2,0 --> ecc_code[1] */
- tmp2 |= b;
- b >>= 1;
- a >>= 1;
- }
-
- /* Store two of the ECC bytes */
- ecc_code[0] = tmp1;
- ecc_code[1] = tmp2;
-}
-
-/*
- * Calculate 3 byte ECC code for 256 byte block
- */
-void nand_calculate_ecc (const u_char *dat, u_char *ecc_code)
-{
- u_char idx, reg1, reg2, reg3;
- int j;
-
- /* Initialize variables */
- reg1 = reg2 = reg3 = 0;
- ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
-
- /* Build up column parity */
- for(j = 0; j < 256; j++) {
-
- /* Get CP0 - CP5 from table */
- idx = nand_ecc_precalc_table[dat[j]];
- reg1 ^= (idx & 0x3f);
-
- /* All bit XOR = 1 ? */
- if (idx & 0x40) {
- reg3 ^= (u_char) j;
- reg2 ^= ~((u_char) j);
- }
- }
-
- /* Create non-inverted ECC code from line parity */
- nand_trans_result(reg2, reg3, ecc_code);
-
- /* Calculate final ECC code */
- ecc_code[0] = ~ecc_code[0];
- ecc_code[1] = ~ecc_code[1];
- ecc_code[2] = ((~reg1) << 2) | 0x03;
-}
-
-/*
- * Detect and correct a 1 bit error for 256 byte block
- */
-int nand_correct_data (u_char *dat, u_char *read_ecc, u_char *calc_ecc)
-{
- u_char a, b, c, d1, d2, d3, add, bit, i;
-
- /* Do error detection */
- d1 = calc_ecc[0] ^ read_ecc[0];
- d2 = calc_ecc[1] ^ read_ecc[1];
- d3 = calc_ecc[2] ^ read_ecc[2];
-
- if ((d1 | d2 | d3) == 0) {
- /* No errors */
- return 0;
- }
- else {
- a = (d1 ^ (d1 >> 1)) & 0x55;
- b = (d2 ^ (d2 >> 1)) & 0x55;
- c = (d3 ^ (d3 >> 1)) & 0x54;
-
- /* Found and will correct single bit error in the data */
- if ((a == 0x55) && (b == 0x55) && (c == 0x54)) {
- c = 0x80;
- add = 0;
- a = 0x80;
- for (i=0; i<4; i++) {
- if (d1 & c)
- add |= a;
- c >>= 2;
- a >>= 1;
- }
- c = 0x80;
- for (i=0; i<4; i++) {
- if (d2 & c)
- add |= a;
- c >>= 2;
- a >>= 1;
- }
- bit = 0;
- b = 0x04;
- c = 0x80;
- for (i=0; i<3; i++) {
- if (d3 & c)
- bit |= b;
- c >>= 2;
- b >>= 1;
- }
- b = 0x01;
- a = dat[add];
- a ^= (b << bit);
- dat[add] = a;
- return 1;
- }
- else {
- i = 0;
- while (d1) {
- if (d1 & 0x01)
- ++i;
- d1 >>= 1;
- }
- while (d2) {
- if (d2 & 0x01)
- ++i;
- d2 >>= 1;
- }
- while (d3) {
- if (d3 & 0x01)
- ++i;
- d3 >>= 1;
- }
- if (i == 1) {
- /* ECC Code Error Correction */
- read_ecc[0] = calc_ecc[0];
- read_ecc[1] = calc_ecc[1];
- read_ecc[2] = calc_ecc[2];
- return 2;
- }
- else {
- /* Uncorrectable Error */
- return -1;
- }
- }
- }
-
- /* Should never happen */
- return -1;
-}
-
-#if 0
-EXPORT_SYMBOL(nand_calculate_ecc);
-EXPORT_SYMBOL(nand_correct_data);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Steven J. Hill <sjhill@cotw.com>");
-MODULE_DESCRIPTION("Generic NAND ECC support");
-#endif
projects / yaffs / .git / blobdiff