--- /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 1.1 2002-05-27 18:57:25 charles Exp $
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 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.
+ *
+ *
+ * Slightly hacked to fit in with YAFFS by Charles Manning.
+ */
+#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);
+#endif
+
projects / yaffs / .git / blobdiff