blob: 2e341b75437ae2e15fb7b3dc54bb8b578bf5a308 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * This file contains an ECC algorithm from Toshiba that detects and
3 * corrects 1 bit errors in a 256 byte block of data.
4 *
5 * drivers/mtd/nand/nand_ecc.c
6 *
7 * Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
8 * Toshiba America Electronics Components, Inc.
9 *
10 * $Id: nand_ecc.c,v 1.14 2004/06/16 15:34:37 gleixner Exp $
11 *
12 * This file is free software; you can redistribute it and/or modify it
13 * under the terms of the GNU General Public License as published by the
14 * Free Software Foundation; either version 2 or (at your option) any
15 * later version.
16 *
17 * This file is distributed in the hope that it will be useful, but WITHOUT
18 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
19 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
20 * for more details.
21 *
22 * You should have received a copy of the GNU General Public License along
23 * with this file; if not, write to the Free Software Foundation, Inc.,
24 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
25 *
26 * As a special exception, if other files instantiate templates or use
27 * macros or inline functions from these files, or you compile these
28 * files and link them with other works to produce a work based on these
29 * files, these files do not by themselves cause the resulting work to be
30 * covered by the GNU General Public License. However the source code for
31 * these files must still be made available in accordance with section (3)
32 * of the GNU General Public License.
33 *
34 * This exception does not invalidate any other reasons why a work based on
35 * this file might be covered by the GNU General Public License.
36 */
37
38#include <linux/types.h>
39#include <linux/kernel.h>
40#include <linux/module.h>
41#include <linux/mtd/nand_ecc.h>
42
43/*
44 * Pre-calculated 256-way 1 byte column parity
45 */
46static const u_char nand_ecc_precalc_table[] = {
47 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
48 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
49 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
50 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
51 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
52 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
53 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
54 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
55 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
56 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
57 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
58 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
59 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
60 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
61 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
62 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
63};
64
65
66/**
67 * nand_trans_result - [GENERIC] create non-inverted ECC
68 * @reg2: line parity reg 2
69 * @reg3: line parity reg 3
70 * @ecc_code: ecc
71 *
72 * Creates non-inverted ECC code from line parity
73 */
74static void nand_trans_result(u_char reg2, u_char reg3,
75 u_char *ecc_code)
76{
77 u_char a, b, i, tmp1, tmp2;
78
79 /* Initialize variables */
80 a = b = 0x80;
81 tmp1 = tmp2 = 0;
82
83 /* Calculate first ECC byte */
84 for (i = 0; i < 4; i++) {
85 if (reg3 & a) /* LP15,13,11,9 --> ecc_code[0] */
86 tmp1 |= b;
87 b >>= 1;
88 if (reg2 & a) /* LP14,12,10,8 --> ecc_code[0] */
89 tmp1 |= b;
90 b >>= 1;
91 a >>= 1;
92 }
93
94 /* Calculate second ECC byte */
95 b = 0x80;
96 for (i = 0; i < 4; i++) {
97 if (reg3 & a) /* LP7,5,3,1 --> ecc_code[1] */
98 tmp2 |= b;
99 b >>= 1;
100 if (reg2 & a) /* LP6,4,2,0 --> ecc_code[1] */
101 tmp2 |= b;
102 b >>= 1;
103 a >>= 1;
104 }
105
106 /* Store two of the ECC bytes */
107 ecc_code[0] = tmp1;
108 ecc_code[1] = tmp2;
109}
110
111/**
112 * nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code for 256 byte block
113 * @mtd: MTD block structure
114 * @dat: raw data
115 * @ecc_code: buffer for ECC
116 */
117int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code)
118{
119 u_char idx, reg1, reg2, reg3;
120 int j;
121
122 /* Initialize variables */
123 reg1 = reg2 = reg3 = 0;
124 ecc_code[0] = ecc_code[1] = ecc_code[2] = 0;
125
126 /* Build up column parity */
127 for(j = 0; j < 256; j++) {
128
129 /* Get CP0 - CP5 from table */
130 idx = nand_ecc_precalc_table[dat[j]];
131 reg1 ^= (idx & 0x3f);
132
133 /* All bit XOR = 1 ? */
134 if (idx & 0x40) {
135 reg3 ^= (u_char) j;
136 reg2 ^= ~((u_char) j);
137 }
138 }
139
140 /* Create non-inverted ECC code from line parity */
141 nand_trans_result(reg2, reg3, ecc_code);
142
143 /* Calculate final ECC code */
144 ecc_code[0] = ~ecc_code[0];
145 ecc_code[1] = ~ecc_code[1];
146 ecc_code[2] = ((~reg1) << 2) | 0x03;
147 return 0;
148}
149
150/**
151 * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
152 * @mtd: MTD block structure
153 * @dat: raw data read from the chip
154 * @read_ecc: ECC from the chip
155 * @calc_ecc: the ECC calculated from raw data
156 *
157 * Detect and correct a 1 bit error for 256 byte block
158 */
159int nand_correct_data(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc)
160{
161 u_char a, b, c, d1, d2, d3, add, bit, i;
162
163 /* Do error detection */
164 d1 = calc_ecc[0] ^ read_ecc[0];
165 d2 = calc_ecc[1] ^ read_ecc[1];
166 d3 = calc_ecc[2] ^ read_ecc[2];
167
168 if ((d1 | d2 | d3) == 0) {
169 /* No errors */
170 return 0;
171 }
172 else {
173 a = (d1 ^ (d1 >> 1)) & 0x55;
174 b = (d2 ^ (d2 >> 1)) & 0x55;
175 c = (d3 ^ (d3 >> 1)) & 0x54;
176
177 /* Found and will correct single bit error in the data */
178 if ((a == 0x55) && (b == 0x55) && (c == 0x54)) {
179 c = 0x80;
180 add = 0;
181 a = 0x80;
182 for (i=0; i<4; i++) {
183 if (d1 & c)
184 add |= a;
185 c >>= 2;
186 a >>= 1;
187 }
188 c = 0x80;
189 for (i=0; i<4; i++) {
190 if (d2 & c)
191 add |= a;
192 c >>= 2;
193 a >>= 1;
194 }
195 bit = 0;
196 b = 0x04;
197 c = 0x80;
198 for (i=0; i<3; i++) {
199 if (d3 & c)
200 bit |= b;
201 c >>= 2;
202 b >>= 1;
203 }
204 b = 0x01;
205 a = dat[add];
206 a ^= (b << bit);
207 dat[add] = a;
208 return 1;
209 }
210 else {
211 i = 0;
212 while (d1) {
213 if (d1 & 0x01)
214 ++i;
215 d1 >>= 1;
216 }
217 while (d2) {
218 if (d2 & 0x01)
219 ++i;
220 d2 >>= 1;
221 }
222 while (d3) {
223 if (d3 & 0x01)
224 ++i;
225 d3 >>= 1;
226 }
227 if (i == 1) {
228 /* ECC Code Error Correction */
229 read_ecc[0] = calc_ecc[0];
230 read_ecc[1] = calc_ecc[1];
231 read_ecc[2] = calc_ecc[2];
232 return 2;
233 }
234 else {
235 /* Uncorrectable Error */
236 return -1;
237 }
238 }
239 }
240
241 /* Should never happen */
242 return -1;
243}
244
245EXPORT_SYMBOL(nand_calculate_ecc);
246EXPORT_SYMBOL(nand_correct_data);
247
248MODULE_LICENSE("GPL");
249MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
250MODULE_DESCRIPTION("Generic NAND ECC support");