2 * This file contains an ECC algorithm from Toshiba that allows for detection
3 * and correction of 1-bit errors in a 256 byte block of data.
5 * [ Extracted from the initial code found in some early Linux versions.
6 * The current Linux code is bigger while being faster, but this is of
7 * no real benefit when the bottleneck largely remains the JTAG link. ]
9 * Copyright (C) 2000-2004 Steven J. Hill (sjhill at realitydiluted.com)
10 * Toshiba America Electronics Components, Inc.
12 * Copyright (C) 2006 Thomas Gleixner <tglx at linutronix.de>
14 * This file is free software; you can redistribute it and/or modify it
15 * under the terms of the GNU General Public License as published by the
16 * Free Software Foundation; either version 2 or (at your option) any
19 * This file is distributed in the hope that it will be useful, but WITHOUT
20 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
21 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
24 * You should have received a copy of the GNU General Public License
25 * along with this program. If not, see <http://www.gnu.org/licenses/>.
27 * As a special exception, if other files instantiate templates or use
28 * macros or inline functions from these files, or you compile these
29 * files and link them with other works to produce a work based on these
30 * files, these files do not by themselves cause the resulting work to be
31 * covered by the GNU General Public License. However the source code for
32 * these files must still be made available in accordance with section (3)
33 * of the GNU General Public License.
35 * This exception does not invalidate any other reasons why a work based on
36 * this file might be covered by the GNU General Public License.
46 * Pre-calculated 256-way 1 byte column parity
48 static const uint8_t nand_ecc_precalc_table
[] = {
49 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
50 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
51 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
52 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
53 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
54 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
55 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
56 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
57 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
58 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
59 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
60 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
61 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
62 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
63 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
64 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
68 * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
70 int nand_calculate_ecc(struct nand_device
*nand
, const uint8_t *dat
, uint8_t *ecc_code
)
72 uint8_t idx
, reg1
, reg2
, reg3
, tmp1
, tmp2
;
75 /* Initialize variables */
76 reg1
= reg2
= reg3
= 0;
78 /* Build up column parity */
79 for (i
= 0; i
< 256; i
++) {
80 /* Get CP0 - CP5 from table */
81 idx
= nand_ecc_precalc_table
[*dat
++];
84 /* All bit XOR = 1 ? */
87 reg2
^= ~((uint8_t) i
);
91 /* Create non-inverted ECC code from line parity */
92 tmp1
= (reg3
& 0x80) >> 0; /* B7 -> B7 */
93 tmp1
|= (reg2
& 0x80) >> 1; /* B7 -> B6 */
94 tmp1
|= (reg3
& 0x40) >> 1; /* B6 -> B5 */
95 tmp1
|= (reg2
& 0x40) >> 2; /* B6 -> B4 */
96 tmp1
|= (reg3
& 0x20) >> 2; /* B5 -> B3 */
97 tmp1
|= (reg2
& 0x20) >> 3; /* B5 -> B2 */
98 tmp1
|= (reg3
& 0x10) >> 3; /* B4 -> B1 */
99 tmp1
|= (reg2
& 0x10) >> 4; /* B4 -> B0 */
101 tmp2
= (reg3
& 0x08) << 4; /* B3 -> B7 */
102 tmp2
|= (reg2
& 0x08) << 3; /* B3 -> B6 */
103 tmp2
|= (reg3
& 0x04) << 3; /* B2 -> B5 */
104 tmp2
|= (reg2
& 0x04) << 2; /* B2 -> B4 */
105 tmp2
|= (reg3
& 0x02) << 2; /* B1 -> B3 */
106 tmp2
|= (reg2
& 0x02) << 1; /* B1 -> B2 */
107 tmp2
|= (reg3
& 0x01) << 1; /* B0 -> B1 */
108 tmp2
|= (reg2
& 0x01) << 0; /* B7 -> B0 */
110 /* Calculate final ECC code */
118 ecc_code
[2] = ((~reg1
) << 2) | 0x03;
123 static inline int countbits(uint32_t b
)
133 * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
135 int nand_correct_data(struct nand_device
*nand
, u_char
*dat
,
136 u_char
*read_ecc
, u_char
*calc_ecc
)
141 s0
= calc_ecc
[0] ^ read_ecc
[0];
142 s1
= calc_ecc
[1] ^ read_ecc
[1];
143 s2
= calc_ecc
[2] ^ read_ecc
[2];
145 s1
= calc_ecc
[0] ^ read_ecc
[0];
146 s0
= calc_ecc
[1] ^ read_ecc
[1];
147 s2
= calc_ecc
[2] ^ read_ecc
[2];
149 if ((s0
| s1
| s2
) == 0)
152 /* Check for a single bit error */
153 if (((s0
^ (s0
>> 1)) & 0x55) == 0x55 &&
154 ((s1
^ (s1
>> 1)) & 0x55) == 0x55 &&
155 ((s2
^ (s2
>> 1)) & 0x54) == 0x54) {
157 uint32_t byteoffs
, bitnum
;
159 byteoffs
= (s1
<< 0) & 0x80;
160 byteoffs
|= (s1
<< 1) & 0x40;
161 byteoffs
|= (s1
<< 2) & 0x20;
162 byteoffs
|= (s1
<< 3) & 0x10;
164 byteoffs
|= (s0
>> 4) & 0x08;
165 byteoffs
|= (s0
>> 3) & 0x04;
166 byteoffs
|= (s0
>> 2) & 0x02;
167 byteoffs
|= (s0
>> 1) & 0x01;
169 bitnum
= (s2
>> 5) & 0x04;
170 bitnum
|= (s2
>> 4) & 0x02;
171 bitnum
|= (s2
>> 3) & 0x01;
173 dat
[byteoffs
] ^= (1 << bitnum
);
178 if (countbits(s0
| ((uint32_t)s1
<< 8) | ((uint32_t)s2
<< 16)) == 1)