2 * This file contains an ECC algorithm from Toshiba that detects and
3 * corrects 1 bit errors in a 256 byte block of data.
5 * drivers/mtd/nand/nand_ecc.c
7 * Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
8 * Toshiba America Electronics Components, Inc.
10 * Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de>
12 * $Id: nand_ecc.c,v 1.15 2005/11/07 11:14:30 gleixner Exp $
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 along
25 * with this file; if not, write to the Free Software Foundation, Inc.,
26 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
28 * As a special exception, if other files instantiate templates or use
29 * macros or inline functions from these files, or you compile these
30 * files and link them with other works to produce a work based on these
31 * files, these files do not by themselves cause the resulting work to be
32 * covered by the GNU General Public License. However the source code for
33 * these files must still be made available in accordance with section (3)
34 * of the GNU General Public License.
36 * This exception does not invalidate any other reasons why a work based on
37 * this file might be covered by the GNU General Public License.
40 #include <linux/types.h>
41 #include <linux/kernel.h>
42 #include <linux/module.h>
43 #include <linux/mtd/nand_ecc.h>
46 * Pre-calculated 256-way 1 byte column parity
48 static const u_char 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 - [NAND Interface] Calculate 3 byte ECC code
70 * @mtd: MTD block structure
72 * @ecc_code: buffer for ECC
74 int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
77 uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
80 /* Initialize variables */
81 reg1 = reg2 = reg3 = 0;
83 /* Build up column parity */
84 for(i = 0; i < 256; i++) {
85 /* Get CP0 - CP5 from table */
86 idx = nand_ecc_precalc_table[*dat++];
89 /* All bit XOR = 1 ? */
92 reg2 ^= ~((uint8_t) i);
96 /* Create non-inverted ECC code from line parity */
97 tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */
98 tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
99 tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
100 tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
101 tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
102 tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
103 tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
104 tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
106 tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */
107 tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
108 tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
109 tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
110 tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
111 tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
112 tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
113 tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
115 /* Calculate final ECC code */
116 #ifdef CONFIG_NAND_ECC_SMC
123 ecc_code[2] = ((~reg1) << 2) | 0x03;
127 EXPORT_SYMBOL(nand_calculate_ecc);
129 static inline int countbits(uint32_t byte)
133 for (;byte; byte >>= 1)
139 * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
140 * @mtd: MTD block structure
141 * @dat: raw data read from the chip
142 * @read_ecc: ECC from the chip
143 * @calc_ecc: the ECC calculated from raw data
145 * Detect and correct a 1 bit error for 256 byte block
147 int nand_correct_data(struct mtd_info *mtd, u_char *dat,
148 u_char *read_ecc, u_char *calc_ecc)
152 #ifdef CONFIG_NAND_ECC_SMC
153 s0 = calc_ecc[0] ^ read_ecc[0];
154 s1 = calc_ecc[1] ^ read_ecc[1];
155 s2 = calc_ecc[2] ^ read_ecc[2];
157 s1 = calc_ecc[0] ^ read_ecc[0];
158 s0 = calc_ecc[1] ^ read_ecc[1];
159 s2 = calc_ecc[2] ^ read_ecc[2];
161 if ((s0 | s1 | s2) == 0)
164 /* Check for a single bit error */
165 if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
166 ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
167 ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
169 uint32_t byteoffs, bitnum;
171 byteoffs = (s1 << 0) & 0x80;
172 byteoffs |= (s1 << 1) & 0x40;
173 byteoffs |= (s1 << 2) & 0x20;
174 byteoffs |= (s1 << 3) & 0x10;
176 byteoffs |= (s0 >> 4) & 0x08;
177 byteoffs |= (s0 >> 3) & 0x04;
178 byteoffs |= (s0 >> 2) & 0x02;
179 byteoffs |= (s0 >> 1) & 0x01;
181 bitnum = (s2 >> 5) & 0x04;
182 bitnum |= (s2 >> 4) & 0x02;
183 bitnum |= (s2 >> 3) & 0x01;
185 dat[byteoffs] ^= (1 << bitnum);
190 if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
195 EXPORT_SYMBOL(nand_correct_data);
197 MODULE_LICENSE("GPL");
198 MODULE_AUTHOR("Steven J. Hill <sjhill@realitydiluted.com>");
199 MODULE_DESCRIPTION("Generic NAND ECC support");