1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * This file contains an ECC algorithm from Toshiba that detects and
4 * corrects 1 bit errors in a 256 byte block of data.
5 *
6 * drivers/mtd/nand/raw/nand_ecc.c
7 *
8 * Copyright (C) 2000-2004 Steven J. Hill (sjhill@realitydiluted.com)
9 * Toshiba America Electronics Components, Inc.
10 *
11 * Copyright (C) 2006 Thomas Gleixner <tglx@linutronix.de>
12 *
13 * As a special exception, if other files instantiate templates or use
14 * macros or inline functions from these files, or you compile these
15 * files and link them with other works to produce a work based on these
16 * files, these files do not by themselves cause the resulting work to be
17 * covered by the GNU General Public License. However the source code for
18 * these files must still be made available in accordance with section (3)
19 * of the GNU General Public License.
20 *
21 * This exception does not invalidate any other reasons why a work based on
22 * this file might be covered by the GNU General Public License.
23 */
24
25 #include <common.h>
26
27 #include <linux/errno.h>
28 #include <linux/mtd/mtd.h>
29 #include <linux/mtd/nand_ecc.h>
30
31 /*
32 * NAND-SPL has no sofware ECC for now, so don't include nand_calculate_ecc(),
33 * only nand_correct_data() is needed
34 */
35
36 #if !defined(CONFIG_NAND_SPL) || defined(CONFIG_SPL_NAND_SOFTECC)
37 /*
38 * Pre-calculated 256-way 1 byte column parity
39 */
40 static const u_char nand_ecc_precalc_table[] = {
41 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
42 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
43 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
44 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
45 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
46 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
47 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
48 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
49 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
50 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
51 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
52 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
53 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
54 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
55 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
56 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
57 };
58
59 /**
60 * nand_calculate_ecc - [NAND Interface] Calculate 3-byte ECC for 256-byte block
61 * @mtd: MTD block structure
62 * @dat: raw data
63 * @ecc_code: buffer for ECC
64 */
nand_calculate_ecc(struct mtd_info * mtd,const u_char * dat,u_char * ecc_code)65 int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat,
66 u_char *ecc_code)
67 {
68 uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
69 int i;
70
71 /* Initialize variables */
72 reg1 = reg2 = reg3 = 0;
73
74 /* Build up column parity */
75 for(i = 0; i < 256; i++) {
76 /* Get CP0 - CP5 from table */
77 idx = nand_ecc_precalc_table[*dat++];
78 reg1 ^= (idx & 0x3f);
79
80 /* All bit XOR = 1 ? */
81 if (idx & 0x40) {
82 reg3 ^= (uint8_t) i;
83 reg2 ^= ~((uint8_t) i);
84 }
85 }
86
87 /* Create non-inverted ECC code from line parity */
88 tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */
89 tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
90 tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
91 tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
92 tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
93 tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
94 tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
95 tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
96
97 tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */
98 tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
99 tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
100 tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
101 tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
102 tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
103 tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
104 tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
105
106 /* Calculate final ECC code */
107 ecc_code[0] = ~tmp1;
108 ecc_code[1] = ~tmp2;
109 ecc_code[2] = ((~reg1) << 2) | 0x03;
110
111 return 0;
112 }
113 #endif /* CONFIG_NAND_SPL */
114
countbits(uint32_t byte)115 static inline int countbits(uint32_t byte)
116 {
117 int res = 0;
118
119 for (;byte; byte >>= 1)
120 res += byte & 0x01;
121 return res;
122 }
123
124 /**
125 * nand_correct_data - [NAND Interface] Detect and correct bit error(s)
126 * @mtd: MTD block structure
127 * @dat: raw data read from the chip
128 * @read_ecc: ECC from the chip
129 * @calc_ecc: the ECC calculated from raw data
130 *
131 * Detect and correct a 1 bit error for 256 byte block
132 */
nand_correct_data(struct mtd_info * mtd,u_char * dat,u_char * read_ecc,u_char * calc_ecc)133 int nand_correct_data(struct mtd_info *mtd, u_char *dat,
134 u_char *read_ecc, u_char *calc_ecc)
135 {
136 uint8_t s0, s1, s2;
137
138 s1 = calc_ecc[0] ^ read_ecc[0];
139 s0 = calc_ecc[1] ^ read_ecc[1];
140 s2 = calc_ecc[2] ^ read_ecc[2];
141 if ((s0 | s1 | s2) == 0)
142 return 0;
143
144 /* Check for a single bit error */
145 if( ((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
146 ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
147 ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
148
149 uint32_t byteoffs, bitnum;
150
151 byteoffs = (s1 << 0) & 0x80;
152 byteoffs |= (s1 << 1) & 0x40;
153 byteoffs |= (s1 << 2) & 0x20;
154 byteoffs |= (s1 << 3) & 0x10;
155
156 byteoffs |= (s0 >> 4) & 0x08;
157 byteoffs |= (s0 >> 3) & 0x04;
158 byteoffs |= (s0 >> 2) & 0x02;
159 byteoffs |= (s0 >> 1) & 0x01;
160
161 bitnum = (s2 >> 5) & 0x04;
162 bitnum |= (s2 >> 4) & 0x02;
163 bitnum |= (s2 >> 3) & 0x01;
164
165 dat[byteoffs] ^= (1 << bitnum);
166
167 return 1;
168 }
169
170 if(countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 <<16)) == 1)
171 return 1;
172
173 return -EBADMSG;
174 }
175