1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
|
/*
* This file contains an ECC algorithm from Toshiba that detects and
* corrects 1 bit errors in a 256 byte block of data.
*
* drivers/mtd/nand/nand_ecc.c
*
* Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
* Toshiba America Electronics Components, Inc.
*
* $Id: nand_ecc.c,v 1.15 2005/11/07 11:14:30 gleixner Exp $
*
* This file is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 or (at your option) any
* later version.
*
* This file is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with this file; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*
* As a special exception, if other files instantiate templates or use
* macros or inline functions from these files, or you compile these
* files and link them with other works to produce a work based on these
* files, these files do not by themselves cause the resulting work to be
* covered by the GNU General Public License. However the source code for
* these files must still be made available in accordance with section (3)
* of the GNU General Public License.
*
* This exception does not invalidate any other reasons why a work based on
* this file might be covered by the GNU General Public License.
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mtd/nand_ecc.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
};
/**
* nand_trans_result - [GENERIC] create non-inverted ECC
* @reg2: line parity reg 2
* @reg3: line parity reg 3
* @ecc_code: ecc
*
* 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;
}
/**
* nand_calculate_ecc - [NAND Interface] Calculate 3 byte ECC code for 256 byte block
* @mtd: MTD block structure
* @dat: raw data
* @ecc_code: buffer for ECC
*/
int nand_calculate_ecc(struct mtd_info *mtd, 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;
return 0;
}
/**
* nand_correct_data - [NAND Interface] Detect and correct bit error(s)
* @mtd: MTD block structure
* @dat: raw data read from the chip
* @read_ecc: ECC from the chip
* @calc_ecc: the ECC calculated from raw data
*
* Detect and correct a 1 bit error for 256 byte block
*/
int nand_correct_data(struct mtd_info *mtd, 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;
}
EXPORT_SYMBOL(nand_calculate_ecc);
EXPORT_SYMBOL(nand_correct_data);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
MODULE_DESCRIPTION("Generic NAND ECC support");
|
