fba7b1c60e4bbdf8539f94be636847736214c66e
[openocd.git] / src / flash / nand / ecc.c
1 /*
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.
4 *
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. ]
8 *
9 * Copyright (C) 2000-2004 Steven J. Hill (sjhill at realitydiluted.com)
10 * Toshiba America Electronics Components, Inc.
11 *
12 * Copyright (C) 2006 Thomas Gleixner <tglx at linutronix.de>
13 *
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
17 * later version.
18 *
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
22 * for more details.
23 *
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 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
27 *
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.
35 *
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.
38 */
39
40 #ifdef HAVE_CONFIG_H
41 #include "config.h"
42 #endif
43
44 #include "core.h"
45
46 /*
47 * Pre-calculated 256-way 1 byte column parity
48 */
49 static const uint8_t nand_ecc_precalc_table[] = {
50 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00,
51 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
52 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
53 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
54 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
55 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
56 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
57 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
58 0x6a, 0x3f, 0x3c, 0x69, 0x33, 0x66, 0x65, 0x30, 0x30, 0x65, 0x66, 0x33, 0x69, 0x3c, 0x3f, 0x6a,
59 0x0f, 0x5a, 0x59, 0x0c, 0x56, 0x03, 0x00, 0x55, 0x55, 0x00, 0x03, 0x56, 0x0c, 0x59, 0x5a, 0x0f,
60 0x0c, 0x59, 0x5a, 0x0f, 0x55, 0x00, 0x03, 0x56, 0x56, 0x03, 0x00, 0x55, 0x0f, 0x5a, 0x59, 0x0c,
61 0x69, 0x3c, 0x3f, 0x6a, 0x30, 0x65, 0x66, 0x33, 0x33, 0x66, 0x65, 0x30, 0x6a, 0x3f, 0x3c, 0x69,
62 0x03, 0x56, 0x55, 0x00, 0x5a, 0x0f, 0x0c, 0x59, 0x59, 0x0c, 0x0f, 0x5a, 0x00, 0x55, 0x56, 0x03,
63 0x66, 0x33, 0x30, 0x65, 0x3f, 0x6a, 0x69, 0x3c, 0x3c, 0x69, 0x6a, 0x3f, 0x65, 0x30, 0x33, 0x66,
64 0x65, 0x30, 0x33, 0x66, 0x3c, 0x69, 0x6a, 0x3f, 0x3f, 0x6a, 0x69, 0x3c, 0x66, 0x33, 0x30, 0x65,
65 0x00, 0x55, 0x56, 0x03, 0x59, 0x0c, 0x0f, 0x5a, 0x5a, 0x0f, 0x0c, 0x59, 0x03, 0x56, 0x55, 0x00
66 };
67
68 /*
69 * nand_calculate_ecc - Calculate 3-byte ECC for 256-byte block
70 */
71 int nand_calculate_ecc(struct nand_device *nand, const uint8_t *dat, uint8_t *ecc_code)
72 {
73 uint8_t idx, reg1, reg2, reg3, tmp1, tmp2;
74 int i;
75
76 /* Initialize variables */
77 reg1 = reg2 = reg3 = 0;
78
79 /* Build up column parity */
80 for (i = 0; i < 256; i++) {
81 /* Get CP0 - CP5 from table */
82 idx = nand_ecc_precalc_table[*dat++];
83 reg1 ^= (idx & 0x3f);
84
85 /* All bit XOR = 1 ? */
86 if (idx & 0x40) {
87 reg3 ^= (uint8_t) i;
88 reg2 ^= ~((uint8_t) i);
89 }
90 }
91
92 /* Create non-inverted ECC code from line parity */
93 tmp1 = (reg3 & 0x80) >> 0; /* B7 -> B7 */
94 tmp1 |= (reg2 & 0x80) >> 1; /* B7 -> B6 */
95 tmp1 |= (reg3 & 0x40) >> 1; /* B6 -> B5 */
96 tmp1 |= (reg2 & 0x40) >> 2; /* B6 -> B4 */
97 tmp1 |= (reg3 & 0x20) >> 2; /* B5 -> B3 */
98 tmp1 |= (reg2 & 0x20) >> 3; /* B5 -> B2 */
99 tmp1 |= (reg3 & 0x10) >> 3; /* B4 -> B1 */
100 tmp1 |= (reg2 & 0x10) >> 4; /* B4 -> B0 */
101
102 tmp2 = (reg3 & 0x08) << 4; /* B3 -> B7 */
103 tmp2 |= (reg2 & 0x08) << 3; /* B3 -> B6 */
104 tmp2 |= (reg3 & 0x04) << 3; /* B2 -> B5 */
105 tmp2 |= (reg2 & 0x04) << 2; /* B2 -> B4 */
106 tmp2 |= (reg3 & 0x02) << 2; /* B1 -> B3 */
107 tmp2 |= (reg2 & 0x02) << 1; /* B1 -> B2 */
108 tmp2 |= (reg3 & 0x01) << 1; /* B0 -> B1 */
109 tmp2 |= (reg2 & 0x01) << 0; /* B7 -> B0 */
110
111 /* Calculate final ECC code */
112 #ifdef NAND_ECC_SMC
113 ecc_code[0] = ~tmp2;
114 ecc_code[1] = ~tmp1;
115 #else
116 ecc_code[0] = ~tmp1;
117 ecc_code[1] = ~tmp2;
118 #endif
119 ecc_code[2] = ((~reg1) << 2) | 0x03;
120
121 return 0;
122 }
123
124 static inline int countbits(uint32_t b)
125 {
126 int res = 0;
127
128 for (; b; b >>= 1)
129 res += b & 0x01;
130 return res;
131 }
132
133 /**
134 * nand_correct_data - Detect and correct a 1 bit error for 256 byte block
135 */
136 int nand_correct_data(struct nand_device *nand, u_char *dat,
137 u_char *read_ecc, u_char *calc_ecc)
138 {
139 uint8_t s0, s1, s2;
140
141 #ifdef NAND_ECC_SMC
142 s0 = calc_ecc[0] ^ read_ecc[0];
143 s1 = calc_ecc[1] ^ read_ecc[1];
144 s2 = calc_ecc[2] ^ read_ecc[2];
145 #else
146 s1 = calc_ecc[0] ^ read_ecc[0];
147 s0 = calc_ecc[1] ^ read_ecc[1];
148 s2 = calc_ecc[2] ^ read_ecc[2];
149 #endif
150 if ((s0 | s1 | s2) == 0)
151 return 0;
152
153 /* Check for a single bit error */
154 if (((s0 ^ (s0 >> 1)) & 0x55) == 0x55 &&
155 ((s1 ^ (s1 >> 1)) & 0x55) == 0x55 &&
156 ((s2 ^ (s2 >> 1)) & 0x54) == 0x54) {
157
158 uint32_t byteoffs, bitnum;
159
160 byteoffs = (s1 << 0) & 0x80;
161 byteoffs |= (s1 << 1) & 0x40;
162 byteoffs |= (s1 << 2) & 0x20;
163 byteoffs |= (s1 << 3) & 0x10;
164
165 byteoffs |= (s0 >> 4) & 0x08;
166 byteoffs |= (s0 >> 3) & 0x04;
167 byteoffs |= (s0 >> 2) & 0x02;
168 byteoffs |= (s0 >> 1) & 0x01;
169
170 bitnum = (s2 >> 5) & 0x04;
171 bitnum |= (s2 >> 4) & 0x02;
172 bitnum |= (s2 >> 3) & 0x01;
173
174 dat[byteoffs] ^= (1 << bitnum);
175
176 return 1;
177 }
178
179 if (countbits(s0 | ((uint32_t)s1 << 8) | ((uint32_t)s2 << 16)) == 1)
180 return 1;
181
182 return -1;
183 }